sc;persll,inci dawcl is mar 1978 military specifical ion

SC;PERSLL,INCiDOD-X43577/‘, (USAF)Dawcl IS MAR 1978

MILITARY SPECIFICAl ION

ASSEMBLIES, MOVING MECHANICAL, FOR SPACE A N D L A U N C H V E H I C L E S,

G E N E R A L S P E C I F I C A T I O N F O R

This specification is approved for use by the Department of the Air Force.and is available for USC by all Dcpartmcnts and Agencies of the Dcpartmcnt of Dcfcnsc.

1A. SCOPE

1.1 m. This specification sets forth the generalrequirements for the design, manufacture, quality control, andtesting of moving mechanical assemblies to be used on space andlaunch vehicles.

.1 . 2 ADD~~c~reference in vehicle'or

This specification is intended forequipment specifications, to incorporate

those requirements which are common to most moving mechanicalassemblies for space and launch vehicles. The requirements

Rcncfkial comments (I-ccommcndations, additions. deletions). and any pcrtincnt Jatawhich may hc of USC in improving this document should bc addrcsscd to:

USAF Space Di\Qsion, SD,ALMP. 0. Box 92960Worldway Postal CenterLos Angclcs, CA 90009-2960

Llw the wlf-addrcsscd Standardization Document Impro~xmcn~ Plopohal ( DD Fwm1426) sppcaring at the end of this document or comment by Icttcr.

L

AMSC N/A FS(’ 1820

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MIL-A-83577B (USAF)01 FEB 1988

stated are a composite of those that have been found to be costeffective for high reliability space and launch vehicleapplications. The requirements covered by this specificationare applicable to the mechanical or electromechanical devicesthat control the movement of a mechanical part of a space oriaunch vehicle relative to another part. They include, but arenot limited to, deployment mechanisms, sensor mechanisms,pointing mechanisms, drive mechanisms, despin mechanisms,separation mechanisms, momentum and reaction wheels, controlmoment gyros, gimbals, and other mechanisms required to performspecific functions. The requirements apply to the overallmoving mechanical assembly as well as to the actuators, motors,springs, dampers, linkages, latches, bearings, clutches, cams,booms, gimbals, slip rings, gears, and instrumentation that arean integral part of these mechanical assemblies. When thisspecification is used as a reference document to specify generalrequirements for moving mechanical assemblies to be used onlaunch vehicles, injection stages, reentry vehicles, or othervehicles, the term "space vehicle" is to be interpreted as theapplicable vehicle.

2. APPLICABLE DOCUMEloTS

2.1 Ggvernment Documents. .2.1.1 Soeclflcations. Stmdards. and Handbooks. The

following specifications, standards, and handbooks form a partof this specification to the extent specified herein. Unlessotherwise specified, the issues of these documents shall bethose listed in the issue of the Department of Defense Index ofSpecifications and Standards (DoDISS) and supplement thereto,cited in the solicitation.

SPECIFICATIONS:

Federal

QQ-N-290 Nickel Plating (Electrodeposited)

QQ-C-320 Chromium Plating (Electrodeposited)

Q Q - S - 7 6 3 Steel Bars, Shapes, and Forgings,Corrosion Resisting

Military

-

MIL-M-3171 Magnesium Alloy, Processes for Pretreatment -and Prevention of Corrosion on

2


MIL-C-5541

MIL-H-5606

MIL-H-6083

MIL-H-6088

MIL-I-6868

MIL-H-6875

MIL-F-7179


Chemical Conversion Coatings on Aluminumand Aluminum Alloys

Hydraulic Fluid, Petroleum Base; AircraftMissile and Ordnance

Hydraulic Fluid; Petroleum Base:For Preservation & Operation

Heat Treatment of Aluminum Alloys

Inspection Process, Magnetic Particle

Heat Treatment of Steel (Aircraft Practice),Process for

Finishes and Coatings, General Specificationfor Protection of Aerospace Weapons Systems,Structures and Parts

MIL-S-7742 Screw Threads, Standard, Optimum SelectedSeries, General Specification for

MIL-M-8609 Motors, Direct Current, 28V System, Aircraft,General Specification F o r

MIL-A-8625 Anodic Coatings, for Aluminum and AluminumA l l a y s

MIL-S-8879 Screw Threads, Controlled Radius Root withIncreased Minor Diameter, GeneralSpecification f o r

DOD-E-8983 Electronic Equipment, Aerospace, ExtendedSpace Environment, General Specification for

MIL-S-13572 Spring, Helical, Compression and Extension

MIL-M-13786 Motors, Fractional Horsepower, Direct Currentand Universal (For Communication and OtherElectronic and Special Military Applications)

MIL-M-13787 Motors, Alternating Current, FractionalHorsepower, Squirrel Cage (For Communicationand Other Electronic and Special MilitaryApplications)

MI&C-26074 Coatings, Electroless Nickel, Requirements

MIL-M-45202 Magnesium Alloys, Anodic Treatment of

3



MIL-H-81200 Heat Treatment of Titanium and Titanium Alloys

MIL-B-81793 Bearing, Ball, Precision, for Instrumentsand Rotating Components

DOD-W-83575 Wiring Harness, Space Vehicle, Designand Testing, General Specification for

DOD-E-83578 Explosive Ordnance for Space Vehicles,General Specification for

STANDARDS:

FED-STD-209 Clean Room and Work Station Requirements,Controlled Environment

MIL-STD-29 Springs, Mechanical: Drawing Requirements for

MIL-STD-453 Radiographic Inspection Methods

MIL-STD-889 Dissimilar Metals

MIL-STD-1246 Product Cleanliness Levels and ContaminationControl Program

MIL-STD-1515 Fasteners for Use in the Design andConstruction of Aerospace Mechanical Systems

MIL-STD-1522 Standard General Requirements for Safe Designand Operation of Pressurized Missile andSpace Systems

MIL-STD-1540 Test Requirements for Space Vehicles

MIL-STD-1547 Electronic Parts, Materials and Processesfor Space and Launch Vehicles

MIL-STD-1568 Materials and Processes for CorrosionPrevention and Control in Aerospace Systems

MIL-STD-6866 Inspection, Liquid Penetrant

MS-33540 Safety Wiring and Cotter Pinning, GeneralPractices for

4


MXL-A-835778 (USAF)01 FEB 1988

HANDBOOKS:

MIL-HDBK-5

MIL-HDBK-17

MIL-HDBK-23

MIL-HDBK-217

DOD-HDBK-263

Metallic Materials and Elements fo r AerospaceVehicle Structures

Plastics for Aerospace Vehicles - Part 1,Reinforced Plastics; - Part II, TransparentGlazing Materials

Structural Sandwich Composites

Reliability Prediction of Electronic Equipment

Electrostatic Discharge Control Handbook forProtection of Electrical b Electronic Parts,Assemblies and Equipment

.2.1.2 Qther Go emment Documents. Dra inas. and. The hollowing other governs&t documents,drawings, and publications form a part of this specification tothe extent specified herein. Unless otherwise specified, theissues shall be those i n e ff e c t o n the clat!e of the solicitation.

SP-R-0022 Vacuum Stability Requirements of PolymericMaterials for Spacecraft Applications(NASA JSC)

MSFC-SPEC-522 Stress Corrosion Cracking Control(NASA M S F C )

NHB 1700.7 Safety Policy and Requirements for PayloadsUsing the Space Transportation System (STS)(NASA)

(Copies of specifications, standards, handbooks, drawings,publications, and other government documents required bycontractors in connection with specific acquisition functionsshould be obtained from the contracting activity or as directedby the contracting officer.)

.2.2 Other htblic4tuura The following document(s), form apart of this specification to the extent specified herein.Unless otherwise specified, the issues of the documents whichare DOD adopted shall be those listed in the issue of the DoDISSspecified in the solicitation. Unless otherwise specified, theissues of documents not listed in the DoDISS shall be the issueof the nongovernment documents which is current on the date ofthe solicitation.

5


MIL-A-835778 (USAF)01 FEB 1988

AMERICAN GEAR MANUFACTURER'S ASSOCIATION (AGMA)

AGMA Handbook American Gear Manufacturer's AssociationHandbook

(Application for copies should be addressed to AGMA, 1500 KingSt., Suite 201, Alexandria, VA 22314)

ANTI-FRICTION BEARING MANUFACTURERS ASSOCIATION (AFBMA)

AFBMA Standards AFBMA Standards for Ball and RollerBearings and Balls

(Application for copies should be addressed to AFBMA, Suite 700,1101 Connecticut Ave.N.W., Washington, D.C. 20036)

(Industry association specifications and standards are normallyavailable for reference from libraries. They are alsodistributed among technical groups and using Federal agencies)

2.3 Qrder of Prem In the event of a conflictbetween the text of this specification and the references citedherein, the text of this specification shall take precedence. -Nothing in this specification, however, shall supersedeapplicable laws and regulations unless a specific exemption hasbeen obtained.

3. REQUIREMENTS. . .3.1 vnt Wpiqhfi;na Factorg . The requirements

stated herein are a composite of the designs, items, andpractices found to be cost effective for high reliability movingmechanical assemblies used in space vehicles. Because of the,broad scope of the requirements stated herein and the wide rangeof applications, all requirements stated are not of equalimportance or weight. They have been divided into fourcategories of importance, ranging from requirements that areimposed on all applications to examples of acceptable designs,items, and practices. The relative weighting of requirements isan important consideration when tailoring the specification tospecific applications and in making trade studies ofalternatives (see 6.1). The weighting factors that areincorporated in the specification are:

I I)a. Weichtina factor a "Shall" designates the mostimportant weighting ievel, the mandatoryrequirements. Unless specifically tailored out or -modified by the contract, they constitute the firmcontractual compliance requirements. Any

6


MIL-A-83577B (USAF)01 PEB 1988

deviations from the contractually imposedmandatory requirements requires the approval ofthe contracting officer (see 6.2.3).

I b. Weiahtina factor b “Shall, wherepracticable, - desig;ates the second weightinglevel. Alternative designs, items, or practicesmay be used for specific applications when the useof the alternative is substantiated by documentedtechnical trade studies. These trade studiesshall be made available for review when requestedor provided to the government in accordance withthe contract provisions. Unless required by othercontract provisions, deviations, from the “shall,where practicable” requirements do not requireapproval of the contracting officer.

C . I ”WeMhUtm factor c “Preferred” or ‘ should”designates the third’weighting level. Unlessrequired by other contract provisions, deviationsfrom these preferred requirements do not requireapproval of the contracting officer and do notrequire documented technical substantiation.

* ”d . Wm factor d “May” designates the lowestweighting level. In’some cases these "may'requirements are stated as examples of acceptabledesigns, items, and practices. Unless required byother contract provisions, deviations from the‘may” requirements do not require approval of thecontracting officer and do not require documentedtechnical substantiation.

. .3-2 -al Desian Rem .

.3.2.1 w of Pw. mterisls. md Processes .Unless otherwise specified in the contract, the parts,materials, and processes shall be selected and controlled inaccordance with contractor established and documented proceduresto satisfy the requirements specified herein. The selection andcontrol procedures shall emphasize quality and reliability tomeet the mission requirements and to minimize total life cyclecosts for the applicable system. Electronic parts shall be JANClass S‘or in accordance with ML-STD-1547. An additionalobjective in the selection of parts, materials, and processesshall be to marimize commonality and thereby minimize thevariety of parts, related tools, and test equipment required inthe fabrication, installation, and maintenance of the vehicle.However, identical electrical connectors, identical fluidf itt ings, or other identical parts shall not be used on a space

7



vehicle where inadvertent interchange of the items orinterconnections could cause possible malfunction.mater ia ls ,

The parts,and processes selected shall be of suff icient proven

quality to allow the space equipment to meet the functionalp e r f o r m a n c e , r e l i a b i l i t y ,l i f e c y c l e ,

and strength requirements during itsincluding all environmental degradation effects.

Parts, mater ia ls , and processes shall be selected to ensure thatany damage or deterioration from the space environment, or theoutgassing effects in the space environment, will not reduce theperformance of the space vehicle beyond the specif ied l imits.

.3.2.1.1 pfaterxals Materials shall , where practicable, bese lected that have deminstrated their suitability for theintended application. Inherently fungus-inert materials shall beused, where practicable. Combustible materials or materials thatcan generate toxic outgassing or toxic products of combustionshal l not be used i f cost -e f fect ive a l ternat ives ex ist .

Materials shall , where practicable, be selected f o r l o woutgassing in accordance with SP-R-0022 (NASA JSC). The totalmass loss in 24 hours shall be less than 1 percent, and thecollected volatile condensable material shall be less than 0.1percent when heated in vacuum (0.0001 Torr) to 125 deg C (257deg F) and collected at 23 deg C (73 deg F ) . T h e hygroscopicnature of many materials such as ester lubricants, composites,electroformed nickel, and anodic coatings for aluminum should berecognized i f they are used, since they emit water in a vacuumand therefore may be unsuitable for some applications.Analytical contamination models shall be used to evaluateperformance impacts of outgassing on adjacent criticalequipment. Swelling and shrinkage characteristics of materialsshall be shown to be within acceptable tolerances under worstcase humidity and temperature cycling.

Metals shal l be corros ion res is tant , or shal l be suitablytreated to resist corrosion when subjected to the specif iedenvironments. Protection of dissimilar metal combinations shallbe in accordance with MIL-STD-889. Care shall be exercised inthe selection of materials and processes in accordance withMSFC-SPEC-522 and MIL-STD-1568 to avoid stress corrosioncracking and brittle fracture failure modes, and to precludefailures induced by hydrogen embrittlement. For example,aluminum alloys 2020-T6, 7079-T6, and 7178-T6 shall not be usedfor s tructural appl i cat ions . The use of 7075-T6, 2024-T3,2024-T4, and 2014-T6 sheet material less than 6.3 millimeters(0.25 inches) thick is allowed, provided short transversestresses (design, attachment, assembly, thermal, and residual)are below acceptable stress corrosion l imits and corrosionprotection systems are provided. Other forms of 7075 shall beheat treated to the -T73 or -T76 t e m p e r .

8



The following alloys and heat treatments shall not be usedin applications where the temperature exceeds 65 deg C (149 degF): 5083-H32; 5083-H38; 5086-H34; 5086-H38; 5456-H32; and5456-H38. Heat treatment of aluminum alloy parts shall be inaccordance with MIL-H-6088. Heat treatment of steel parts shallbe in accordance with MIL-H-6875. Heat treatment of titaniumand titanium alloys shall be in accordance with MIL-H-81200.All high strength steel parts heat treated at or above 1241megapascals (180,000 pounds per square inch) ultimate tensilestrength shall include appropriate test specimens from the sameheat of material as the part. These test specimens shallaccompany the parts through the entire fabrication cycle toensure that the desired properties are obtained. When acidcleaning baths or plating processes are used on high strengthsteel parts, the parts shall be baked at 190 deg C (374 deg F)for not less than 23 hours following such processes to alleviatehydrogen embrittlement problems.

Materials with low fracture toughness in the predictedoperating environment, such as that exhibited by some plastics,shall not be used. Materials which are susceptible to crackingdue to shock loads, or shock loads combined with lowtemperatures, shall not be utilized near any pyrotechnicallyactuated devices.

To minimize possible interactions with experiments or withthe earth's magnetic field, magnetic materials shall be usedonly where necessary for equipment operation. For spacevehicles that will operate at altitudes above 1000 kilometers(621 nautical miles), insulating materials or finishes having aresistivity greater than 10 megohm-meters shall not be usedexcept in applications where charge buildup will not beexcessive. Except for honeycomb panels, wall thickness of sheetmetal and wall thickness on composite parts shall, wherepracticable, be greater than 0.5 millimeters (.020 inches) tominimize the possibility of handling damage. Honeycomb shall bevented to prevent excessive blow-off forces in vacuum.

3.2.1.2 me Trm. Any surface treatments orcoatings used shall be such that completed components shall beresistant to corrosion. The design goal should be that therewould be no harmful corrosion of the completed components orassemblies when exposed to moderately humid or mildly corrosiveenvironments while unprotected during manufacture or handling,such as possible industrial environments or sea coast fog thatcould be expected prior to launch. Harmful corrosion shall beconstrued as being any type of corrosion which interferes withmeeting the specified performance o f the equipment or itsassociated parts. Protective methods and materials forcleaning, surface treatment, and applications of protective

9


MIL-A-83577B (USAF)01 F E B 1 9 8 8

coatings shall be in accordance with MIL-F-7179. Cadmium andzinc coatings shall not be used. Chromium plating shall be inaccordance with QQ-C-320. Nickel plating shall be in accordancewith QQ-N-290 or MIL-C-26074. Anodic treatment of aluminum andaluminum alloys shall be in accordance with MIL-A-8625. Anodictreatment of magnesium shall be in accordance with MIL-M-45202.Corrosion protection of magnesium shall be in accordance withMIL-M-3171. Chemical films for aluminum and aluminum alloysshall be in accordance with MIL-C-5541.

3 . 2 . 2 DePlovablw Deployables (see 6.2.6) shall , wherepracticable, be designid so that they are self supporting whenplaced in any orientation relative to gravity, while in eitherthe stowed or deployed configuration. Deployable5 shall bedesigned with sufficient motive force to permit full operationduring ground testing without depending upon the assistance ofgravity to demonstrate deployment. Of f - loading devices tosimulate a zero-g condition are allowed so that the deployabledoes not have to act against the force of gravity. Thedeployables shall util ize redundancy, where practicable, in thedesign to improve the reliability of d e p l o y m e n t . Techniquessuch as redundant springs or the use of a back up deploymentdevice shall be considered to satisfy this requirement. Where a -device rotates after deployment, as in sun tracking solararrays, the design shall be, where practicable, such that thecenter of gravity of the device is coincident with the axis ofrotation to preclude the need for counterbalancing duringfunct ional test ing . For a l l deployables , the deployment motions h a l l , where practicable, be controlled or restrained for theful l range o f t ravel . A controlled deployment may be providedby a motor and gear drive mechanism or other suitable means. Arestrained deployment may be provided by a spring and damperdrive mechanism or other suitable means . For al 1 deployables,rebound of the deployable after contacting the stops should beminimized. Kick-off springs or other suitable devices shall ,where practicable, be used to initiate deployment motion. Thesesprings shall have a stroke long enough to ensure completedisengagement o f the deployable from its retention mechanism.Field joints shall be provided, where practicable, to permitdisassembly of all deplcyables from the space vehicle and topermit disassembly of rotating or translating elements from theremainder of the deployable to facil itate testing or replacementof parts . Deployables which require discrete sequentialmotions, each initiated by separate pyrotechnic events , shal lhave either the primary initiation of each event separatelyground commanded or shall have a backup ground command for eache v e n t . Where cables (nonelectrical) are used in the deploymentmechanism, they shall be adequately guided and supported by -f a i r l e a d s . All pulleys shall util ize pulley guards which extendto the tangency points of the cable. Where operational

10



acceleration loads are applied to a deployed assembly, such asthose generated by space vehicle spin or propulsion forces, t h edesign should preferably be such that the accelerations tend todrive the deployable into its deployed latched position.

.3 . 2 . 2 . 1 -ial DeDlOYIWnf Where two or moredeployables are used on a space vehicle, the deployment of o n eshall not be dependent upon the successful deployment of theother , unless this sequential method of operation isunavoidable. Where this sequential dependency cannot beavoided, and the deployable that could be obstructed is missionc r i t i c a l ( s e e 6.2.41, a fully redundant release device and fullyredundant or backup deployment mechanism shall be provided forthe deployable which, by its failure (see 6.2.8) could p r e v e n tsuccessful deployment of the mission critical deployable.

3 .2 .2 .2 Retention and R e l e a s e D e v i c e s .

3 . 2 . 2 . 2 - l General. Pos i t ive retent ion provis ions shal lbe.provided for deployables in the stowed and in the deployedp o s i t i o n s . The effects of deflections such as those induced bycentrifugal forces or differential thermal growth of a n ydeployable with respect to its space vehicle attachments shallbe considered in the design of the attachments. Devices thatmay be subject to binding due to misalignment, adverseto lerances , or contamination shall not be used. S l i p j o i n t sshall be avoided, where practicable. Flexures, four barl inkages , or other types of pivotal l inkage are preferred.S e l f - a l i g n i n g f e a t u r e s , such as self-aligning bearings and rodends, shall be used, where practicable, to preclude binding ofpivoting elements. Continuous hinges, such as piano hinges,shall not be used for large deployable panels . Pyrotechnical lyactuated devices, motor driven devices, or other suitabletechniques may be used to retain the deployable in the stowedp o s i t i o n . Release mechanisms which permit ejection of partsaway from the space vehicle shall be avoided, wherep r a c t i c a b l e . The design of latching devices shall be such thatpeaking of resistance near the end of travel of the deployableis minimized. Leaf spring latches which become the primaryelement for reacting deployment or deployment rebound loadsshall be avoided, where practicable. Catches using a permanentmagnet as the holding element shall be avoided, wherep r a c t i c a b l e . The design and materials used for the retentiondevices shall be such that the stresses are maintainedsufficiently below the fatigue endurance l imit to avoid fatiguefailures due to cyclic design load levels and environmentalexposure. Retention and release devices shall be designed topreclude cold welding and friction welding (see 6.2.2). Forsurfaces that sl ide or separate during operational use, t h econtact pressures at the interfaces shall b e m i n i m i z e d

11



consistent with providing adequate ascent stiffness. Thesesurfaces shall be fabricated from appropriate materials andlubricated so as to prevent gall ing or seizure. Where contactareas may be reduced from the nominal as a result of tolerancebuild-up, the minimum area which could occur shall be used indetermining contact pressure.

3.2.2.2.2 Pin Pullers Where pin pullers are used, suchas cartridge actuated or &explosive pin pullers, they shall bedesigned to be in double shear. The design, installation, andcheckout procedures for pin pullers shall ensure that loads dueto misalignment of the pin are within design limits. A minimumretraction force margin of safety of 100 percent at worst caseenvironmental conditions and under worst case tolerances shallbe maintained for all nonexplosive pin pullers. Functionalmargins of cartridge actuated pin pullers shall comply withDOD-E-83578. Where the force margin of safety cannot be metwith a release device, such as a pin puller, in the direct pathof the primary load, designs which utilize the mechanicaladvantage of a linkage to reduce the loads on the device may beused. Release devices, such as pin pullers, shall havesufficient stroke so that complete release is attained underworst case tolerances and environmental conditions. As aminimum, pin pullers shall rolrirct at least 2 millimeters (.08inches) beyond the point of release calculated under worst casedimensional tolerances and environmental conditions. Redundantrelease devices shall be used, where practicable. An example isa toggle release mechanism where activation of either pin pullerpermits release.

I .3.2.2.3 w Actueed De lcegdevice designs and their applicatizn shill

Cartridge actuatedcomply with

DOD-EL83578. Redundant pyrotechnic devices shall be used, wherep r a c t i c a b l e .

.3 . 2 . 2 . 4 Test Fm The fixtures to be used to assistin the fabrication and tesiing of the deployables shall bedesigned in conjunction with the deployable device to ensurecompatibility. Where it is impractical to design the deployableto support itself in a one “g” field, supplemental supports maybe employed for test purposes. These supplemental supportsshall be designed so that their influence on the operation ofthe mechanism is minimized. The test f ixtures shal lincorporate , where practicable, provisions to measure torque vsangle and time vs angle, or equivalent linear measurements forl inear devices . Where practicable, test f ixtures shal l haveinterlocks or other safety features incorporated to precludedamage to the moving mechanical assembly or deployable in theevent of testing malfunctions. Tethers and supports shall beincorporated as backup features to preclude damage in the evento f f a i l u r e .

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12



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3 .2 .3 Beatinqs For deployables, hinges, and linkages,self-aligning beariigs shall be used, where practicable, topreclude binding due to misalignments. Bearings shall not beused for ground current return paths or to carry electricalcurrent. All ferrous material bearings shall employ, wherepracticable, a corrosion-resistant steel that is in accordancewith QQ-S-763. Rolling element bearings shall, wherepracticable, be of 44OC stainless steel; however, 52100 or MS0steels may be employed providing they are suitably protectedfrom corrosion (see 3.2.4). Rolling element bearings shall havea minimum hardness of Rockwell C58. Ball bearings used inapplications where low torque ripple is required or wherefatigue life is critical shall, where practicable, be fabricatedof consumable electrode vacuum melted (CEVM) material.

.3.2.3.1 Bal l Bm Bearings used in criticalapplications such as reaction wheels, control moment gyros,gimbals, de-spin mechanisms, and pointing devices shall meetABEC 7, 7P or 7T tolerance or better in accordance with theAFBMA Standards. Nonstandard bearings or thin sectionedbearings where AFBMA tolerances do not apply shall have themanufacturers precision level most nearly equivalent to ABEC 7.Bearings used in noncritical applications such as one time usedeployables, shall, where practicable, meet ABEC 5 or better.Stainless steel bearings shall, where practicable, also be inaccordance with MIL-B-81793.

3.2.3.1.1 Desian and Selectiog Ball bearing selection,mounting, and preloading shall be b;sed on the following designconsiderations:

a.

b.

C .

d.

e.

f .

9*

h.

Maximum combined axial, radial, and moment loadssustained during ground handling, launch, onorbit, or other operational modes

Stiffness requirements

Effects of temperature, temperature gradients,fits, tolerances, and initial preload on torque,stiffness, and life

Lubrication

Wear

Smoothness of operation (torque ripple)

Friction torques, considering breakaway andrunning, in the installed state

Reliability and life

13



The design of each ball bearing installation shall besubstant iated by analysis and either development tests or previoususage. The mater ia ls , s tresses , s t i f fness , fat igue l i fe , pre load ,and possible binding under normal, as well as the most severecombined loading conditions, and other expected environmentalconditions shall be considered. Al ignments , f i t s , to lerances ,thermal and load induced distortions, and other conditions shallbe considered in determining preload variations. An analysis ofthe effects of fits and temperatures shall be performed where thepre load value i s cr i t i ca l to meet e i ther l i fe , f r i c t ion , orst i f fness requirements . Bearing fat igue l i fe ca lculat ions shal lbe based on a survival probability of 99.95 percent when subjectedto maximum time varying loads. Appropr iate correct ion factorsshall be included to account for the selected bearing materialsand lubrication parameters. Bearing retainer design s h a l lprovide an acceptable contribution to bearing friction t o r q u e a n dtorque v a r i a t i o n . For noncritical applications, such as mostdeployables , if nonquite running is acceptable, the mean Hertziancontact stress shall not exceed 2758 megapascals (400,000 psi)when subjected to the yield load. During operation, the meanHertzian stress shall not exceed 2310 megapascalj (335,000 psi) .The bearings shall be designed.to withstand the ultimate loadwithout f racture . The yield and ultimate factors of safety shall5e a s s p e c i f i e d i n 3 . 4 . 1 . 5 .

3 . 2 . 3 . 1 . 2 Bearina ADnlications R e a u i t i n a Quiet One.L o Toraue Rlnole

rat ion QIEFor these applications, in addition to the

rezuirements of Piragraph 3 . 2 . 3 . 1 . 1 bearing races and ballsshall be designed so that stress lecels are below the levels thatwould cause unacceptable permanent deformation during applicationof ascent loads . Where ball bearing deformation is required tocarry a portion or all of the space vehic le ascent loads , andwhere smoothness of operation is required on orbit, the meanHertzian stress levels of the bearing steel shall not exceed 2310megapascals (335,000 pounds per square inch) when subjected tothe y ie ld load . The upper and lower extremes of the contactell ipses shall be contained by the raceways. The stress andshoulder height requirements of the races shall be analyzed forboth nominal and off-nominal bearing tolerances.analysis and for quality control,

For subsequentthese bearings shall be

serialized and measurements critical to their operation shall berecorded. Depending on the application and its requirements,consideration shall be given to recording preload, low speedtorque, inside diameter, outside diameter,angle,

radial play or c o n t r o lcurvatures, raceway roundness, ball size and roundness,

raceway surface finishes, and hardness.

-

.3 . 2 . 3 . 1 . 3 me o f B e a r - . The design of bearings thatare to be used for a number of f l ights shall be substantiated byanalysis and either development tests or previous usage.

14


MIL-A-835778 (USAF)01 FEB 1988

3 . 2 . 3 . 1 . 4 B e a r i n a Alianment . Run-out tolerances on shaftand housing diameters and shoulders shall be established inaccordance with the needs of the application and the sensitivityof the bearing to misalignment. Bearings requiring stringentcontrol of al ignment inc lude :

a. Thin section, large diameter bearings

b. Preloaded bearings

C . Bearings operating continuously at speed

d . Bearings requiring low torque ripple

e . Bear ings that osc i l late

Overall misalignment of inner plus outer rings of thesebear ings shal l , where practicable, not exceed 0.3 m i l l i r a d i a n s .Other bearings shall , where practicable, have overallmisalignment not exceeding 1 milliradian.

.3 . 2 . 3 . 2 Wer Beulna Tvoes Selection of other bearingtypes such as ro l ler , needle , or ’ j ournal , shall be based on thefo l lowing des ign cons iderat ions :

a.

b.

C .

d .

e .

f .

g*

h.

Maximum combined axial, radial, a n d moment loadssustained during ground handling, launch, ono r b i t , or other operational modes

Temperature excursions and thermal gradients

Effects of temperature on f its and tolerances

S t i f f n e s s

Lubricat ion

Smoothness of operation

Fric t ion torques

Rel iabi l i ty over the des ign l i fe

The design of each bearing installation shall besubstantiated by analysis and either development tests orprevious usage. The mater ia ls , s t resses , s t i f fness , fa t iguel i f e , p r e l o a d , and possible binding under normal, as well as tmost severe combined loading conditions, and other expectedenvironmental conditions shall be considered.

he

15



-

3 . 2 . 4 bubricants. Lubrication shall be provided byg r e a s e s , l i q u i d s , solid f i lm lubricants, or a combination ofe i ther grease or l iquid with so l id f i lm lubr icants , so f t metal l i cf i lms, or sacrifical cages (for ball bearings) for all contactingsurfaces having relative motion. The selection of lubricants formoving mechanical assemblies shall be based on the followingcons iderat ions :

a.

b.

C .

d.

e.

f .

g.

h.

i .

L

k.

1.

m.

n.

0 .

P*

C o e f f i c i e n t o f f r i c t i o n

Lubrication property changes in storage or in avacuum environment

Depletion and wear out

Operating temperature limits

Creep properties

viscosity vs temperature properties

Pressure coefficient of viscosity (ball bearings)

Outgassing that could cause contamination such ason optical or thermal control surfaces (see 3.2.1.1)

Corrosion protection

Poss ib i l i ty o f po lymerizat ion , part icular ly due tohigh contact pressures or contaminants.

Protection against cold welding and friction welding

Cleanl iness

Run-in requirements such as rate of speed, load,and time duration

Any requirements for demonstration of thesuitability of the lubricant in a simulatedenvironment

Any requirements of other environments suchhumidity and salt spray

Compatibility of the lubricant with o t h e rmater ia ls , part icular ly other lubr icants i f

space

as

used -The lubricant chosen shall not cause detrimental effects on

the moving mechanical assembly during or after operation at

16


MIL-A-835778 (USAF)01 FEB 1968

-

ambient conditions. The vent paths from all l iquid lubricantsshall be designed such that the outgassing products do n o timpinge d irect ly on cr i t i ca l sur faces . The selection of thelubricant for use in the critical moving mechanical assemblyshall be based upon development tests of the lubricant thatdemonstrate the abil ity of the lubricant system to provideadequate lubrication under all specif ied operating conditionsover the des ign l i fe t ime. The lubricant selected, and theprocesses used in cleaning parts and applying the lubricantshal l be de l ineated . Lubricants used with M50 or 52100 gearmaterials shall include corrosion inhibitors which preventcorrosion when the assembly is humidity tested in accordancewith Paragraph 6.4.9 of MIL-STD-1540.

. .3 . 2 . 4 . 2 Pallina mnt Bearin- In moving mechanicalassembl ies ut i l i z ing grease or l iquid ’ lubr icat ion in ro l l ingelement bearings, the lubricant f i lm thickness shall bemaximized consistent with the following:

a. The lubricant selected

b. The range of operating conditions including load,torque, speed, and temperature

C . Bearing parameters such as size, number of balls,and ball size as they relate to weight and volumeconstraints.

Bearings operating in the boundary lubrication regime, i .e . ,contact o f asper i t ies , shal l be avo ided , where pract i cable . I fbearings must be operated in the boundary lubrication regime, aboundary lubricant with good anti-wear characteristics shall beused. Perflourinated polyether and sil icone lubricants shouldbe avoided in this regime except where light loads and l i m i t e dtrave l are expected . Where bearing lubricant reservoirs areused, the reservoir shall be attached, where practicable, to anarea of relatively high temperature to enhance molecular andsurface f low into the bearing. Barrier f i lms or shielding orboth may be used to separate the bearing from the reservoirs tominimize surface migration such as that caused by loss oflubr icant due to wicking action of the reservoir. Incorporationof the above techniques d ic tates that the lubr icant transfermechanism be primarily by molecular flow. The preferredapproach to lubrication of bear ings involves p lac ing thereservoirs in intimate contact with the bearing races and addinga larger amount of lubricant than would be ordinarily requiredto provide acceptable lubr icant f i lms . The above method oflubrication is preferred providing that any increase in churningtorques can be tolerated. The design adequacy of the lubricanttransfer mechanism shall be substantiated by analysis and either

17



development tests or previous usage. This analysis shall takeinto account the test results and, as applicable, the effects of*zero g ” , position and surface area of the reservoir,temperature gradients, venting, reservoir material , amount oflubricant stored in the reservoir, surface migration, pressure,free molecular f low, material surface roughness, porosity, andc a p i l l a r y a c t i o n . Bearing lubrication tests and supportinganalyses shall be used to show that the chosen lubricanttransport mechanisms such as surface migration, vaporization,and wick action provide effective lubricant f i lms over theexpected operating temperatures, thermal gradients, and internalenvironments. If providing adequate life of bearings depends ontheir operating in an elastohydrodynamic (EHD) lubricationregime (see 6.2.7) and not in the boundary lubrication regime,and it can not be clearly shown by analysis that the bearingoperating range is well within the regime, then a test method,such as contact resistance measurements, shall be used toestablish that an EHD film is being generated. In general, thelubrication system variables that should be substantiated bycomponent development tests include, as appropriate, amount oflubr icant , retainer design, reservo ir des ign , and the reservoirproximity to the areas requiring lubrication. When liquidlubr icat ion is used , the design shall ensure that migration ofthe lubricant through the seals is not excessive or detrimentalto the space vehicle.

.3 . 2 . 4 . 3 Prv F i l m wcaticm Applicat ion o f dry f i lmlubricants to the surfaces of beaiings, V-band c lamps, coi 1spr ings , leaf spr ings , clock springs, constant force springs,gears, or other items shall be by an appropriate process.Bonding, peening, sputtering, vacuum depositing, ion plating, orany other process that provides a predictable, uniform, andrepeatable lubricant f i lm may be appropriate. Compositematerials containing dry f i lm lubricant in their composition maybe used in appropriate applications. Where appropriate, dryfilm lubricants should be burnished to provide a uniform filmthat reduces the coe f f i c ient o f f r i c t ion f rom the *as a p p l i e d ”condition and minimizes the generation of lubricant p ow d e r .Corrosion resistant materials shall be used in bearingsemploying dry fi lm lubricants. Consideration shall be given toprotection of molybdenum disulfide dry f i lm lubricants fromadverse affects due to exposure to atmospheric humidity.Testing in a humid environment shall, where practicable, eitherbe avoided or minimized.

.3 . 2 . 4 . 4 H a r d C o -carbide , t i tanium nitr ide ,*

I-lard coatings such as titaniumand chromium may be used to extend

l i f e , reduce wear, prevent welding, reduce friction, and toprevent corrosion either with or without a l iquid or dry f i lmlubr icant . These coatings shall be applied by an appropriate

18


MIL-A-835778 (USAF)01 FEE 1988

-

process, such as ion implantation or chemical vapor deposition,that assures that the coating will not flake off under maximumstress.

3.2.4.5 Hydraulic FluiQS Fluids used in hydraulicsystems shall be in conformance with MIL-H-6083 or MIL-H-5605.

.3.2.5 BrushandRi . Electrical brushesand slip ring assemblies shall utilize inierface geometry andmaterials that have demonstrated satisfactory performance inground testing or space applications with similar requirements.Brushes that are nominally all carbon shall not be used.Electrical brushes shall be lubricated either by dry filmlubricant that is a composite with the brush material or by aliquid lubricant that is impregnated into the brush material orretained in the area of the brush. Electrical brush and slipring design shall be based on, but not limited to, the followingconsiderations:

a.

b.

c.

d.

e.

f .

g*

h.

i.

j.

k.

1.

m.

n.

0.

Brush and slip ring interface geometry

Contact forces

Wear rate of brushes and rings

Contact force control over the service life

Zero Lg* effects

Materials used for the brushes and the rings

Surface speeds

Outgassing

Sealing provisions

Control or containment of wear debris

Debris barriers or traps to prevent ring-to-ringor ring-to-case shorts

Electrical current density

Voltage level

Brush-to-ring contact resistance

Brush-to-ring electrical noise

19


MIL-A-835778 (USAF)01 FEB 1988

P* Temperature

q. Contact area

r. Lubrication

S . Prevention of corrosion between the rinq and brush

t. The ability to conduct accelerated testing

Design verification testing of brushes and commutator orslip ring assemblies shall be conducted to demonstrate that thelubricant is not significantly deteriorated or driven from theareas requiring lubrication by adverse thermal, gravity forces,or other conditions; and that wear rates, wear debris,electrical noise level, friction torque, and lubricant loss arecompatible with design requirements.

. .3.2.6 -al and Electra Gshall be in accordance with DOD-En89i3

Electronic equipmentWiring external to

equipment enclosures shall be in accordance with DOD-W-83575.Where wiring harnesses cross a moving or rotating interface, the _installation drawings shall define dimensions including loopsizes an3 distances to attachments, if applicable. Attachmentclamps shall be provided sufficiently close to any loops so thatmovement of the harness into the path of motion of the movingmechanical assembly cannot occur under any conditions. Wirebundles crossing a moving or rotating interface shall notcontain strain-energy elements specifically added to assistdeployment. All metal parts of the movinq mechanical assemblyshall be appropriately grounded to vehicle structure so thatcharge build-up in space and shock hazards on the ground can beminimized. The total current drawn from the power source duringeach mode of operation shall be determined to precludeinadvertent electrical overloads. These determinations ormeasurements shall be made at the minimum, nominal, and maximumvoltage of the power source, and under the most severeenvironmental conditions. Overload protection, when required,shall be a part of the space vehicle electrical power controlsubsystem. A capability shall be provided to reset powerdisconnects by ground command.

3.2.7 &l_e&.ric Motprs Alternating current motors shallconform to MIL-M-13787. ’Direct current motors shall conform toMIL-M-8609 or MIL-M-13786. For long term space application,brushless motors are preferred for their durability.Applications for conventional brush commutated motors shallconsider lubrication, wear, input voltage range, andelectromagnetic interference compatibility. Where applicable,the motor and its controller should be designed to provide

-



-

adequate position and rate feedback for a local closed loopcontrol system.

For applications where the motor performance is crit ical tothe mission success, the design shall be based on a completemotor character izat ion . The motor characterization shallinc lude rotor inert ia , friction and damping parameters, back-EMFconstant or torque constant , t ime constant , torquec h a r a c t e r i s t i c s , speed versus torque curves, thermald i s s i p a t i o n , temperature effects, and, where a p p l i c a b l e ,analysis to demonstrate adequate margin against back driving.For applications where the motor is integrated into a higherassembly, the motor characterization shall be performed at themotor level prior to the integration.

Where motors are operated at high duty cycles, the design ofthe motor mount shall accommodate the heat transfer from themotor case to surrounding structure.

3 . 2 . 7 . 1 Sm. For applications where l imitedspeed, inherent holding capability, or discrete step motion i srequired, brushless permanent magnet stepper motors arep r e f e r r e d . In cases where the magnetic holding capability ofthe motor is used to hold the load in position, the design shallbe based on the detent torque at each discrete rotor positionfor both the clockwise and counterclockwise direction. I f themagnetic detent torque of the stepper motor is marginal to holdthe load, trickle current may be applied to the motor windingwhen it is not energized. The trickle current should bedisconnected when the motor is energized to reduce its effect onrunning torque. Detent torque margin may be assessed byconsider ing the approximately s inusoidal ly varying e lectr ica ltorque over a 4 step interval. Detent torque should change onlyif there is a change in shaft position.c o n d i t i o n s ,

Under dynamicstep integrity rather than torque margin should be

the design criteria used to accommodate the range of c o n d i t i o n sdes ired ( load inert ia , compl iance , and res is t ive torque) . Wherestepper motors are used to drive a load, pulsing the steppermotor at a repetition rate that is at or near the naturalfrequency of the load shall be avoided. Variable rate steppingshould be avoided due to the diff iculties in analyzing anddemonstrating performance. Where other methods are practicable,stepper motor detent torque should not be used as holding torqueto prevent backdriving of redundant drives.

3 . 2 . 7 . 2 m Motorg. For applications where smoothoperation, precise position control , high speed, or high torqueis r e q u i r e d , permanent magnet, brushless, direct current torquemotors are pre ferred for the ir e f f i c iency . For brushless torquemotors, electronic commutators such as the Hall effect sensor,

21



-

r e s o l v e r , and optical encoder have been successfully used forspace appl i cat ions . Where smooth operation is required, coggingtorque should be minimized. When a redundant motor is mountedon a common shaft with the primary motor, the effect of onemotor failure on the other motor should be minimized.

3 . 2 . 7 . 3 meet Currmt Bruh Motou Direct currentbrush motors may require special design &d brush selection toavoid arcing or dust generation in both partial and high vacuum,as well as during ground testing. In part i cular , se lect ion o fbrush motors should be avoided where operation at very lowtemperatures is required or where service is other thanintermittent . Care should be taken to avoid use of motors withinsufficient commutation segments which usually result in highbrush wear. Guidelines and requirements for brush assembliesare provided in Paragraph 3.2.5.

3.2.7.4 Q;tber Motor Tvoep. Other motor types are not tobe excluded, but their applicability for space use may bel imited . For example, reluctance motors have a high weight totorque or power ratio, series wound direct current motors havel o w e f f i c i e n c y , and shunt direct current motors have lowstart ing torque .

3.2.8 a Helical springs shall be in accordancewith ML-S-13572 a:d MIL-STD-29. Helical compression springsare preferred to helical tension springs.spr ings shal l ,

Helical compressionwhere practicable, be enclosed or otherwise

captivated to prevent buckling,i f broken.

and to provide motive power evenThe attachments for retaining leaf springs shall be

designed to reduce stress concentrations by such features asrounding of sharp corners or keeping mounting holes away fromhighly stressed areas. Spring design shall consider fatiguelife and the effects of temperature on spr ing per formance . Toreduce the possibil ity of a reduction of potential energy due tocreep , springs which are stored in a stressed condition shall bedesigned to maintain stress levels below the materialproport ional l imit . Redundant springs,independently,

capable of workingshall be used in all applications, where

p r a c t i c a b l e . When minimum friction is desirable, springs shallbe dry fi lm lubricated. The dry fi lm lubricant shall bese lec ted to avo id corros ion , and shall not contain carbon orpowdered metal.

3.2.9 Dampers. Dampers may be utilized to absorb energyof impact of deployable devices at th8 extremes of travel or tolimit the rate of travel during the entire travel per iod .Deformable material, viscous dampers, or eddy current dampersare preferred to coulomb friction type dampers, which accomplishenergy dissipation by the rubbing of two surfaces. Redundant

-

22


MIL-A-835778 (USAF)01 FEB 1988

dampers should be incorporated or a backup mechanism provided,to prevent a damper from becoming a single point failure mode.

.3 . 2 . 9 . 1 Deformterm Dm The use ofcrushable mater ia l or the p last i c deformition of soft metals toabsorb energy is limited to single use applications. The designshall permit inspection and replacement of the deformablematerial following ground tests. The design shall consider theeffect of the deformable material tolerances on the f inalposition of the mechanism with respect to its desired position.

3 . 2 . 9 . 2 V i s c o u s Damera Viscous damper fluids shall bemaintained to at least a cleinliness of Level 200 as defined inMIL-STD-1246. All viscous dampers shall be vacuum filled topreclude entrapment of a i r . Filters shall be used in viscousdampers unless they are incompatible with the viscosity of thefluid being used or the design of the d a m p e r . The calculationof the force or torque margin in assemblies with viscous dampersshall include, but not be limited to, the seal friction due tomechanical compression of elastomers, fluid pressure on theelastomers, and possible changes in static and dynamic frictiondue to storage time. The design shall make appropriateprovisions for changes in fluiil vr,lt~me and viscosity withtemperature. As a minimum, dampers shall either incorporateredundant seals or be hermetically enclosed to prevent leakageduring the ent ire on-orb i t l i fe o f the space vehic le . In rotarydamper applications, the loads should be balanced around thedamper output shaft to minimize radial loads. When dampers areused on deployables, it may be necessary to provide thermalcontro ls to achieve the des ired damping character is t i cs . Insuch cases, the damper may be mounted within a thermallycontrolled portion of the space vehicle or damper-mountedheaters may be used. Dampers used on deployables should bedesigned to provide less damping at the beginning of deploymentthan toward the end of the deployment cycle. Preference shouldbe given to designs util izing large orif ices or clearances andhigh viscosity f luids to minimize f low restriction due tocontaminants or particulate matter.

3 . 2 . 9 . 3 Eddv Current Dam. Eddy c u r r e n t d a m p e r s s h a l lbe designed to provide the required damping over the designtemperature range. Where practicable, redundant rotatingsurfaces should be provided. Depending on the design andsubstant iat ing test data , it may be necessary to control thedamper temperature to maintain its damping rate within thedesired range. In that case, the damper may be mounted within athermally controlled portion of the space vehicle ordamper-mounted thermal control heaters may be used. Eddycurrent dampers may be designed to provide different dampingrates by misaligning the magnets. If the damper is designed to

23



provide an adjustable damping rate, it should be designed with apositive lock for launch conditions to prevent the damping ratefrom drift ing out of the selected position.

3 . 2 . 1 0 Gear&. All gears used in moving mechanicalassemblies shall be in accordance with the standards of t h eAmerican Gear Manufacturers Association. The lubricationrequirements of Paragraph 3.2.4 are applicable to gears.Hunting tooth (see 6.2.10) gear ratios shall be used, where theappl icat ion is appropr iate , to d istr ibute wear . For betterprotect ion of the gear teeth , the through hardness or surfacehardness or both may be increased, and the surface finish of theteeth improved through grinding, honing, lapping, a n dpre-run- in . The through hardness may be increased by materialor heat treatment changes. The surface hardness may beincreased by nitriding, carburizing, induction hardening, oranodizing. Undercutting of spur gear pinions should beavoided. Spur gear designs which have greater recess actionthan approach action are preferred. Spur gear contact ratiosshould be greater than 1.4 for power transmission gearing.Cantilever gear shaft mounting should be avoided in order t oreduce nonuniform tooth face load distribution.are not recommended,

A l u m i n u m g e a r s _except for l ight duty , l imited l i fe

application where tooth wear and the coefficient of thermalexpansion can be accommodated, and where compatibility with theselected lubricant can be established. An anodization processmay be used to improve wear resistance for acceptable aluminumgear appl icat ions , provided that contact stresses will not causethe coating to crack. Gear tooth patterns should be checked onfirst assembly to establish that the pattern is well centeredover the tooth f lank, and that edge loading is not present.

.3.2.10.1 wand S e l e c t i o n Gearing design andselection shall be based on the foilowing design considerations:

a.

b.

C .

d.

e .

f .

Tooth p i t t ing , Br inel l ing , and bending stresses undernominal and peak operating loads

Impact tooth loads from maximum combined axial, radial,and moment loads sustained during ground handling,launch, on orbit, or other modes

Backlash

Precision including position errors and transmissionerrors (smoothness of motion) (see 3 .2 .10 .3 )

S t i f f n e s s

I n e r t i a

24



-

9.

h.

i .

j.

k.

1.

m.

n.

Lubricat ion

Effects of temperature and temperature gradients onquality of lubrication and gear contact pattern

Effects of tooth geometry on specif ic sl iding and wear

Frict ion and fr i c t ion var iat ion ( torque r ipple )

Undercutting and tooth profi le modifications

Gear mounting, misalignment, face load d istr ibut ion ,and variation in operating center distance

Mater ia ls , manufacturing and heat treatment processes,and finish coatings

Service l i fe , duty cyc le , fa i lure modes , and re l iabi l i ty. .3 . 2 . 1 0 . 2 Harmanlc_Drlves . A harmonic drive is a unique

form of gear transmission that provides high gear ratio andtorque capability in a compact configuration with minimump o s i t i o n e r r o r . Typically, a h a rm on i c drive consists of ac i r c u l a r e p l i n e , a wave genera tor bear i ng , a n d f l e r s p l i n e . Theharmonic drive shall be designed so it is not subjected to loadsthat cause ratcheting. Each element shall meet the applicablerequirements stated herein. For example, the wave generatorbearing shall meet the requirements of Paragraph 3 .2 .3 . Forl o n g l i f e a p p l i c a t i o n s , suf f i c ient lubr icant shal l be providedto the bearings and to the gear teeth to ensure proper operationthroughout the l i fe cyc le .

3.2.10.3 mn Get-. F o r p r e c i s i o n g e a r s , s u c h a sin f i n e po i n t i ng m e chan i sm s ,pract i cable , be used .

an t i -back l a sh gear i ng shal l , w h e r eFor critical applications, A G M A q u a l i t y

level 12 or better should be considered (see AGMA H a n d b o o k ) .Where gears are required to be matched sets, they shall beident i f ied and marked as such .

.3 . 2 . 1 1 Faste ers a d Locklna,in accordance with: ML&D-l515

Fastening systems shall beThreaded parts shall be in

accordance with ML-S-7742 or &L-S-8879. A minimum engagementof f ive full threads is required for threaded attachments; orfor through bolts, the threaded ends shall protrude a minimum oftwo full threads beyond the end of the nut. Screw sizes smallerthan 3.6 mill imeters (No. 8) in diameter shall be avoided, wherep r a c t i c a b l e . Where there are areas which may be sensitive todebris generated during assembly of threaded parts, blind holesshould be considered. Tolerances shall be controlled to preventthreaded parts from bottoming in blind holes. The types, sizes,

25



and quantities of fasteners used should be minimized.Consideration should be given to the frequency of access or usewhen selecting the type of fastener.

3.2.11.1 Lockina Deviw Positive locking devices shallbe used on all fasteners. Preferred positive locking devicesare bent tab washers, cotter pins, safety wire, self-lockingthreads, or self-locking provisions by means of plastic materialcontained in the nut, bolt, or screw. Self-locking nuts arepreferred to.bolts or screws that contain plastic material foruse as a locking device. Where other locking devices arepracticable, locking compounds shall not be used on fasteners toprovide locking. Also, locking compounds shall not be used inareas where excess compound could migrate to surfaces which mustremain free to move. Self-locking devices which depend upon aninterference fit between metallic threads shall be avoided,where practicable, in applications where particulatecontamination may cause damage or degradation to the equipmentor vehicle. Where preload in fasteners is critical, straingauges, crush washers, or equivalent techniques shall be used,where practicable, in lieu of torque wrench setting of thepreload. Safety wiring and cotter pins shall be in accordancewith MS-33540. Drawings shall clearly depict the safety wirinqmethod and configuration used. Through bolts or screws withlocknuts are preferred to threaded inserts. Threaded insertsshall be used in applications that require tapped holes inaluminum, magnesium, plastic, or other materials that aresusceptible to galling or thread damage. When self-lockingfeatures are used, the screw length shall be sufficient to fullyengage the locking device with a minimum of two turns underworst case tolerances. When self-locking features are used, anallowable range of run-in torque, or the maximum number ofreuses that would still ensure an adequate lock, shall bespecified. Spring type or star type lock washers shall not beused. Adjustable fittings or mounting plates which useoversized holes or slotted holes to provide adjustment shall notbe dependent upon friction between the fitting or mounting plateand the mounting surface to provide locking. Diamond typeserrations shall not be used.

3.2.11.2 Pivots, When the shaft of a bolt is used as arotating element in a rotating joint, a castle nut with cotterpin, or a locknut with deformed threads shall be used forretention of the bolt. The grip length of the rotating boltshall ensure that sufficient end play is provided to precludebinding. When the shaft of a bolt is used as a fixed pivotalelement in a rotating joint, the bolt shall either be a shoulderbolt or the bolt shall pass through a spacer. The grip lengthof the shoulder bolt or the length of the spacer shall ensurethat sufficient end play is provided to preclude binding when

26


-1

MIL-A-83577B (USAF)01 FEE 1988

the se l f - locking nut i s t ightened. S p l i t o r r o l l e dspring-action pins shall not be used as pivots for rotatingj o i n t s . Where split or rolled spring-action pins are used inother appl i cat ions , a positive means of retaining the pin, suchas s taking the edges of the ho le , shal l be ut i l i zed . Lockingcompounds shall not be used as the retention method for pivotp ins .

3 . 2 . 1 1 . 3 Snap Rinas. Snap rings shall be avoided where amore positive means of retention can be u s e d . Snap rings shallnot be used to retain pins in l inkages or other applicationswhere there is a possibility that moment loads may be imposed onthe snap ring. Where snap rings are used in the presence of dryf i l m l u b r i c a t i o n , care shall be taken to ensure that no dry f i l mlubricant is deposited in the groove for the snap ring. Newsnap rings shall be used each time the assembly, or portionthereof which includes the snap ring, is disassembled andreassembled.

-_

3.2.12 Stooa. Mechanical stops or shoulders andassociated attachments shall be designed to a structural yieldfactor of safety , based on stat i c analys is , of at least 2.0 formaximum impact loads that occur upon full extension, actuation,or stopping of moving mechanical assemblies. IIUpaCt iodds shdll

account for uncertainties in model parameters, analysismethodology, and any other effects such as ampl i f ied inert ialoads that may be transmitted through gear trains. If it can beshown-that the dynamic analysis inherently accounts for dynamicload amplification as a result of the impact, ordinary factorsof safety as specified elsewhere in this document may be used.The design shall ensure that the stop transients do notoverstress gear teeth or drive mechanisms. A snubbingarrangement which dissipates energy may be provided wherenecessary to reduce the impact forces. Adjustments shall beprovided in linkages and stops to ensure that the travel of themoving mechanical assembly is not restricted before contact w i t hthe stop b y tolerance buildups, thermal distortions, and otheru n c e r t a i n t i e s .

3.2.12 Struck. Structural design of each movingmechanical assembly shall be based upon a load analysis, stressanalysis, fatigue analysis, and the substantiating testprogram. Fracture mechanics analysis shall be performed if thebrittle failure mode cannot be avoided in the design. Thestress analys is shal l inc lude cons iderat ions o f s tructurals t i f f n e s s , elastic or plastic deformations, and thermald i s t o r t i o n s . The design shall possess sufficient strength,r i g i d i t y , and other necessary characteristics required t osurvive all loads and environmental conditions that exist withinthe envelope of mission requirements, and to meet any alignment

27



constraints or pointing accuracy requirements that may beimposed for successful performance of the system. The assemblyshall survive these loads and environments in a manner that doesnot reduce the probability of the successful completion of themission. The structure shall be designed to have sufficientstrength to withstand simultaneously the yield loads (see6.2.17), applied temperature, and other environmentalconditions, without experiencing gross yielding or detrimentaldeformation. The structure shall be designed to withstandsimultaneously the ultimate loads (see 6.2.16), appliedtemperature, and other environmental conditions withoutcollapse. Refer to Paragraph 3.4.1.5 for acceleration levels,yield and ultimate factors of safety, and margins of safety, andto Paragraph 3.6.3 for fitting factors. Material strength andother mechanical and physical properties shall be selected fromMIL-HDBK-5 and NIL-HDBK-17 or from contractor test values,where appropriate. When contractor test values are used, theyshall be based on a sufficient number of tests to establish themechanical properties on a statistical basis. Allowablematerial strengths used in the design shall reflect the effectsof load, temperature, and time associated with the designenvironment. The following material strength allowable valuesshall be used:

a. For single load path primary structures, the Avalues in MIL-HDBK-5 shall used.

b. For multiple load path and secondary structures,the B values in MIL-HDBK-5 may be used.

The loads shall be derived by considering all worst caseoperational conditions such as lift-off, ascent, ignition,shutdown, deployment, reentry, and vibration conditions whichmay be induced by the launch vehicle or injection stage. Inaddition, orbital loads which may be induced by thermalconditions, spin up, separation, impulsive forces, propulsivevariations, nutation, wobble motions, or other control systemassociated conditions shall be included.

. .3.2.12.1 Ronmetallx Structural MaterlabS,

3.2.12.1.1 .Fiber-reiwd Comnofite Mararlal.leg Composite material strengths, and other mechanical

or physical properties, shall be selected from reliable sources,such as MIL-HDBK-17 or data determined in approved contractordevelopment test programs.

The anisotropy of typical laminated composite structuralelements shall be accounted for when establishing laminatematerial properties and failure modes. The laminate s t rength

-

28



-

and other mechanical properties used shall be appropriate forthe critical structural modes of failure and environmentalconditions.

For cases where applicable material properties do not exist,testing is required to establish such values. The variabilityof small coupon specimen properties and the scaling to full-sizecomposite structure shall be addressed to establish realisticdesign properties. In particular, the potential effects of lowinterlaminar strength, the lack of ductility, local yielding,and sensitivity to impact and handling damage shall be addressedin the critical regions of the structure. Composite primarystructures shall be acceptance proof tested at minimum loads of1.1 times the design limit loads.

3.2.12.1.2 Adhesives and Polvmgx2 . Mechanical andphysical properties of adhesives and polymers shall be selectedfrom authorized sources of reference such as MIL-HDBK-23 or datadetermined in approved contractor development test programs.Nonmetallic structural material shall be selected from JSC-07572or verified for acceptability by methods of SPEC-SP-R-0022.

.3 . 2 . 1 2 . 1 . 3 Ulowables for lRmm&aUlc Mater ialE_ The

design allowables basis for primary and secondary nonmetallicstructure shall correspond with ‘A’ and “B” levels,respectively, as defined in MIL-HDBK-5, wherever possible. Forfail-safe primary structure, the “B” values may be used. Inspecial circumstances where design data at the requisitestatistical level are not available, the contractor may, withDOD approval, conduct special limited data acquisition tests toestablish S-basis (test basis) allowables. Under thesecircumstances, an acceptance proof test is mandatory.

3.2.13 med Cpmwnentr. Pressurized componentsshall be in accordance with MIL-STD-1522.

.3.2.14 mtr- . Sufficient diagnosticinstrumentation shall be developed and provided, wherepracticable, as part of the moving mechanical assembly todetermine the mode of failure should an on-orbit failure occur.These may be such devices as strain gauges, temperature sensors,pressure transducers, position indicators, potentiometers,switches, tachometers, accelerometers, or current monitors.When an electrical motor, other than a stepper motor, is used,the motor current shall be instrumented so that torque can bedetermined during development, acceptance, and qualificationtest ing. Deployables shall, where practicable, have stowed anddeployed position switches to indicate both release of t h edeployable from its restraining mechanism and end of travel or*latching position. Potentiometers may be used to provide data

29


MIL-A-83577B (USAF)01 F E B 1 9 8 8

-

on intermediate pos i t ions . Where switches are used as indicatingdevices for deployables , the design of the switch mounting a n dthe switch orientation shall be such that maladjustment of theswitch shal l not prevent full travel of the deployable to i t sdeployment stop. In no case shall the direction of actuation ofa switch be the same as the direction of motion of themechanism, i .e . , motion directly into the switch so that theswitch can be damaged by misadjustment. Cam operated switchesusing ramps are preferred where the final position of the switchon the ramp is incapable of depressing the switch further thanits normal operating range. Where switches are used, levers orother suitable devices shall be provided to decrease thesensitivity to adjustment of the switch and to ensure thatsuf f i c ient overtravel i s provided a f ter actuat ion o f theswitch. Switches shall be hermetically sealed. S u f f i c i e n ton-orbit instrumentat ion shall be provided to measure criticaltemperatures and to detect off-nominal thermal conditions.

.3 . 2 . 1 5 T e s t Pow and mt Pamter8 Test p o i n t sshall be provided to accommodate a continuity of critical testparameter measurements from component acceptance tests throughsubsystem tests, vehicle acceptance tests, prelaunch checkout,and on-orbit test measurements. Test points shall be provided,where practicable, as telemetry points on connector pins. Thetest parameters shall be chosen to provide assurance o fsatisfactory equipment performance and to isolate faults shouldthey occur. The parameter test limits shall be established s u c hthat the measurements are made to an expanding accuracytolerance that avoids the possible rejection of equipment whichhas passed tests conducted at lower levels of assembly. Theon-orbit instrumentation and measurement techniques shall beused during ground tests to provide a data base that wouldpermit parameter traceability with respect to variations inenvironmental conditions.

3 . 3 PerfpUgdnce.. . .3 . 3 . 1 Bror B-et f o r Prem Control Ass@alx~ . For

moving mechanical assemblies used in pointing applications whereprec is ion contro l i s necessary , the error budget shall includeperformance errors due to misalignments, deflections, dynamicloads, thermal d is tort ions , control system transients, steadys t a t e e r r o r s , f r i c t i o n , f r i c t i o n n o i s e ( f r i c t i o n o r t o r q u ev a r i a t i o n s ) , f r i c t i o n h y s t e r e s i s , structural and mechanicalh y s t e r e s i s , backlash, drive motor ripple, and other errorsources as applicable.

3.3.2 Failure Modes and Effects Required performanceand reliability shall be ensured basid upon a failure modes,e f f e c t s , a n d c r i t i c a l i t y a n a l y s i s ( s e e 6 . 2 . 9 ) . The failures to

‘30


MIL-A-835778 (USAF)01 FEB 1988

be considered shall include, but are not limited to, poweroutage, low voltage conditions, damper leakage, binding orexcessive frictional loads, increase in friction noise,overtemperature conditions, excessive temperature gradients,failure of limit switches, partial or complete deploymentfai lure, and structural failure in the moving mechanicalassembly. During the preliminary design phase, an initialfailure mode analysis shall consider providing redundancy in thedesign to achieve the required reliability. Failure modesestablished for the moving mechanical assemblies shall be usedas a basis for selecting in-flight telemetry monitoring pointsto be used for ground diagnostic analysis should an anomalouscondition occur.

3.3.3 Binale Point Failurea Single point failure modesfor moving mechanical assemblies*and their component parts shallbe avoided, where practicable. This requirement may beimplemented by such means as use of redundant springs or motorsin deployment mechanisms so that failure of one spring or motordoes not prevent full deployment and latching. Where redundancyis provided, the redundant portion of the moving mechanicalassembly shall be in accordance with all the requirements ofthis specification. Where single point failure modes areunavoidable, or their avoidance is not practicable, thecontractor shall ensure a satisfactory design based on anassessment of the mishap risk, and appropriate substantiatinganalyses and tests. The assessment and analyses shall include:

a. An estimate of the reliability for the design l i feof the mechanical assembly.

b. An assessment of the risk involved should themoving mechanical assembly fail.

C . An assessment of the penalty to the space vehicleby incorporation of redundancy or backup modes ofoperation. The assessment shall includeconsideration of complexity, safety, reliability,weight, volume, and electrical power.

3.3.4 .mic P e r - Adequate servo stabilitymargins, acceptable structural’rigidity including resonantfrequency and damping characteristics, and acceptableinteractions with the spacecraft control system shall be ensuredfor each moving mechanical assembly by appropriate dynamicanalysis. The analysis shall include dynamic loading effectsand any effects due to changes in mass properties, momentumbalance, or transient torques during operation of the movingmechanical assembly or operation of the space vehicle.

31


MIL-A-835778 (USAF)01 FEB 1988

3.3 .5 Qf f -nominal Operat ion . The sensi t iv i ty of t h e d e s i g nand operational performance to changes in various parameters shallbe considered and minimized in the design. The design sensitivityshould be substantiated by analysis or tests conducted todetermine the effects of various off-nominal parameters which arebeyond design requirements. These off-nominal parameters shallinclude, but not be l imited to, such items as higher dynamicresponse of surrounding structure, higher and lower speed o fmotors, higher and lower velocities o f deployables , varying dutyc y c l e s , misalignments, friction due to contamination, overload andheating of motors due to stall ing, inadvertent spin up of t h edespun portion of dual spin space vehicles, inadvertent spin-up of3 ax is contro l led space vehic les , higher and lower spin speeds ofspinning space vehicles, higher and lower nutation frequenciesassociated with spinning space vehicles, unsymmetrical deploymentof so lar arrays , trans ient overvo l tage , high and low bus vo l tage ,power down modes, and off-nominal environmental conditionsincluding such changes in environmental conditions as those causedby a delay in deployment of a device until a subsequent groundstat ion contact .

3 . 3 . 6 m. Moving mechanical assemblies shall bedesigned with the highest practicable torque margin or, for l ineard e v i c e s , the highest practicable force margin. Two components ofmargin shall be considered: (a) the static torque or force marginwhich. applies to the torque or force required to overcome driveresistance and (b) the kinetic margin which applies to the torqueo r force required to impart acceleration.

Deployable devices shall have torque or force marginsconsistent with the requirements of Paragraphs 3.3.6.1 and 3.3.6.2at any-position of the deployment range. Minimum availabledriving capability and maximum load determination shall beverified through an appropriate test program; each element o fresistance shall be characterized in this test program. Wheremoving mechanical assemblies are driven by electrical motors,(except stepper motors) a torque versus current relationship foreach motor under minimum, maximum, and ambient thermal conditionsshal l be establ ished. The performance sensitivity of movingmechanical assemblies to environmental variations such astemperature , pressure , acce lerat ion , v ibrat ion , and radiat ion , i fappropriate, shall be evaluated and the torque or force marginsver i f ied for the most cr i t i ca l reg ions o f operat ion .

In spring driven mechanisms where redundant springs are usedinstead of a backup deployment mechanism, the mechanism shall havea positive torque or force margin for a one-spring-out case basedon combining worst case conditions. In the event of a brokenspring, the remaining system margin estimate shall includeresistive forces or torques which could be generated by the brokenspring.

32



.3.3.6.1 mtlc Torgue or Force Marain. The static margin(see 6.2.14) depends on the minimum driving torque or force andmaximum static resisting torques or forces. Minimum availabledriving capability shall be determined by including the worstcase combination of such items as supply voltage, temperature,motor and controller parameters, and minimum available drivetorque or force, all of which act so as to minimize the driveoutput capability. Maximum static resistance determination shallinclude the worst case combination of such items as staticfriction, alignment effects, latching forces, wire harness loads,damper drag, and variations in lubricity, including degradationor depletion of lubricant under vacuum and worst case thermalconditions. To avoid operational problems and to account foruncertainties, the initial design minimum acceptable statictorque or force margin, based on combining worst case conditions,shall be higher than actually required as a final value, asindicated in Table I. For those cases where high confidence doesnot exist in the determination of worst case load or drivingcapability, a margin considerably higher than that requiredTable I may be appropriate.

--TABLE I. Required Static Torque or Force Margin

Verses Program Phases

PROGRAM PHASE

Conceptual Design Review

Preliminary Design Review

Critical Design Review

Acceptance/Qualification Test

REQUIRED TORQUEOR FORCE MARGIN

175 percent

150 percent

125 percent

100 percent

in

3.3.6.2 Kinetic Toraue or Force Marain. The kinetictorque or force margin (see 6.2.11) depends on the minimum drivecapability available to accelerate a specified inertia or massat a specified rate. The kinetic torque or force margin shal lbe greater than 25 percent, where practicable. However, itshould be recognized also that excessive margin requirements maybe detrimental in the design of some systems. The minimum drivecapability shall be based on that portion of the drive outputavailable after overcoming the maximum friction, wire bundle,

33



and other resistance in the system. The drive system shall besized to accelerate the inertia or mass specified in the designspecification. Typically, values of inertia and mass specifiedin design specifications include allowances for system growthover the duration of a program. In those cases where inertia ormass growth exceed the initially estimated values, considerationshould be given to reducing the acceleration requirements.

3.3.7 Toleranw Tolerances on all parts used in movingmechanical assemblies'shall be established to ensure thatadequate clearances are maintained under all environmentallyinduced conditions, including thermally induced distortions.

. .3.4 EDvirowtal wan s To provide adesign f a c t o r o f safety or margin, the moving mechanicalassemblies shall be designed to function within performancespecifications when exposed to environmental levels that exceedthe maximum levels predicted during its service life by thespecified margins. The maximum predicted environments shall bedetermined in accordance with the definitions in MIL-STD-1540.

.3.4.1 Launchironment . The equipment shall bedesigned to function within performance specifications afterexposure in the launch configuration to the maximum iaunch orother nonorbital service environments. These environmentsinclude temperature, vibration, acoustic noise, shock,acceleration, atmospheric pressure, humidity, and electricalstorms with associated radiation.

3.4.1.1 j&B@D. The design shall be capable ofwithstanding thermal environments during launch preparations andlaunch which are between 10 deg C (18 deg F) above the maximumpredicted temperature and 10 deg C (18 deg F) below the minimumpredicted temperature.

. . . .3.4.1.2 Random Vibm or AC-C Boise A randomvibration environment that is 6 decibels (dB) above the maximumpredicted levels shall b e used to provide the required designmargin of safety. This design environment shall be consideredto persist for three tires the exposure duration associated withenvironmental amplitudes that are greater than one half themaximum predicted environmental amplitudes, but for not lessthan three minutes, along each of the three orthogonal axes. Anacoustic design environment that is 6 dB above the maximumpredicted levels shall be used instead of the mechanicalvibration environment for components where mechanical vibrationwould not simulate imposition of the service environment. Thesecomponents are characterized by large ratios of surface area tovolume.

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-MIL-A-83577B (USAF)

01 FEB 1988

3.4.1.3 Sinusoidal Vibration. In some cases higherfrequency sinusoidal vibration may be present, caused, forexample, by unstable combustion or imbalances in rotatingequipment. In those cases the design levels shall be 6 dB abovethe maximum predicted levels in order to provide the requireddesign margin of safety.

3.4.1.4 Shock. The design shock spectrum shall be atleast 6 dB over the maximum predicted pyrotechnic shock levels.

I3.4.1.5 meleration The design acceleration levelshall be the maximum predicted level multiplied by an ultimatefactor of safety that includes a 10 percent test measurementtolerance. The launch design acceleration ultimate factor ofsafety shall be at least 1.38 (1.25 + 10 percent) for unmannedspace vehicles and 1.54 (1.40 + 10 percent) for manned spacevehicles. Unless otherwise specified, the yield factor ofsafety shall be 1.0. All yield and ultimate strength margins ofsafety shall be positive (see 6.2.15). When applicable, thecross axis design acceleration shall include the accelerationdue to rotation.

.3.4.1.6 Atmospherrc Pressure . The design shall becapable of sustaining ambient pressures thatschange from sea

level to 0.0133 pascals (1.929 x 10-6 pounds per square inch)in 3 minutes.

3.4.1.7 witv and Salt SDrgp The design shall, wherepracticable, be capable of sustaining exposures up to 12 hoursin duration to moderately humid or mildly corrosive environmentswhile unprotected during manufacture or handling, such aspossible industrial environments or sea coast fog that could beexpected prior to launch. Approval of the contracting officeris required if it is necessary to provide special environmentalcontrols due to the possible degradation of the lubricatingproperties of many dry film lubricants in high humidityenvironments, or to degradation of other lubricants in lowhumidity environments, or for other reasons. The effect ofhumidity, salt spray, or industrial environments on the movingmechanical assembly may be determined by nonoperatingdevelopment tests to identify fabrication, storage,transportation, and launch environment constraints or controlsthat may be necessary.

-,

3 . 4 . 2 On_otbit The equipment shall bedesigned to function within periormance specifications followingor, if appropriate, during exposure to environmental levels thatexceed the maximum predicted on-orbit environments by the designfactor of safety or design margin. These environments includethermal, vacuum, radiation exposure, shock, random vibration,and acceleration.

35



3 . 4 . 2 . 1 T h e r m a l gnd VW The moving mechanicalassemblies shall operate at any-temperature within their thermaldesign range, at an ambient pressure less than 133 micropascals(1 .93 x low7 p s i ) . The thermal design range is from 10 deg C(18 deg F) above the maximum predicted temperature to 10 deg C (18deg F) below the minimum predicted temperature.. In addition, thethermal design range shall not be less than from +71 deg C to -34deg C (160 deg F to -29 deg F) unless attainment of this capabilitywould not be practicable or would adversely influence the design,such as necessitating the use of a less desirable lubricant.

3 . 4 . 2 . 2 R a d i a t i o n . The moving mechanical assemblies shallbe designed to operate within performance specif ications afterexposure to on-orbit level radiation environments for the servicelife o f t h e a s s e m b l y . The time l ine of the on-orbi t leve ls shal linclude a representative number of time perlods at the maximumpredicted radiation levels to ensure a satisfactory design margin.

3 . 4 . 2 . 3 sboch. The design level pyrotechnic shock spectrumshall be at least 6 dB over the maximum predicted levels occurringduring on-orbit operation.

. .3 . 4 . 2 . 4 Randam Vlbw . The on-orbit random vibration -design level shall be at least 6 dB above the maximum predictedo n - o r b i t l e v e l s .

.3 . 4 . 2 . 5 B The on-orbit acceleration designlevel shall be the maxim& predicted on-orbi t leve ls mult ip l iedby a factor of safety that includes a 10 percent test measurementto lerance . The on-orb i t des ign acce lerat ion factor o f sa fetyshall be at least two. When applicable, the acce lerat ion shal linclude that which is due to space vehicle rotation.

. .3 . 4 . 3 mnl Svortation. a n d Hm. Fabrication and handling of moving mechanicalassemblies skall be accomplished in a clean room environmentwith an air cleanliness that is in accordance with metric systemclass 3500 (English system class 100,000) or better as specif iedin FED-STD-209. Environmental conditions during processing andduring storage, prior to acceptance testing, shall be within thef o l l o w i n g l i m i t s :

a. Temperature: 21 deg C 2 20 deg C(70 deg F f 36 deg F)

b. Humidity: 50 percent f 40 percent

Storage, handling, and transportation conditions to which -items are to be subjected subsequent to acceptance testing, andpr ior to f l ight , shal l be contro l led to environmental condit ions

36



which do not exceed the maximum predicted requirements imposedby launch, flight, or the specified acceptance tests.

Critical bearing surfaces employing molybdenum dry filmlubricants shall be protected by a dry nitrogen purge or othersuitable means of excluding humidity during the storage andpre-launch environment.

.3 . 5 wiflca_fion anO H a r k in g Each moving mechanicalassembly and interchangeable subass&nbly shall be identified bya nameplate. The nameplate identification may be attached to,etched in, or marked directly on the item where size and non-interference of operation permits. The nameplate shall utilizesuitable letter size and contrasting colors, ,contrasting surfacef i n i s h e s , or other techniques to provide identification that isreadily legible. The nameplate shall be capable of withstandingcleaning procedures and environmental exposures anticipatedduring the service life of the item without becoming illegible.Metal foil nameplates may be applied if they can be placed in anarea where they cannot interfere with proper operation shouldthey inadvertently become detached. Metal stamping shall not beused. Where practicable, identification nameplates oncomponents and subassemblies shall be in locations which permitobservation of the marking at the next higher level ofassembly. Nameplates shall contain, as a minimum, the following:

a. Item identification number

b, Serial number

C . Lot number

d. Manufacturer

e . Nomenclature

The marking of any two or more items intended for spaceapplications with the same item number or identification shallindicate that they may be capable of being changed, one foranother, without alteration of the items themselves or ofadjoining equipment if the items also meet the specified flightaccreditation requirements.

3.5.1 Data Car-. When size limitations, cost, or otherconsiderations preclude marking all applicable information on anitem, the nameplate may simply provide a reference key to cardsor documents where the omitted nameplate information may befound. A copy of the referenced nameplate information or cardshall accompany the item or assembly containing the item duringground tests and ground operations.

37


ML-A-83577B (USAF)01 FEB 1988

3.5.2 ‘NOT FOR -SIT" .Maw Items which by intent orby mater ia l d ispos i t ion are not suiiable for use in flight, andwhich could be acc idental ly subst i tuted for f l ight or f l ightspare hardware, shall be red tagged or striped with red paint,or both, to prevent such substitution. The red tag shall beconspicuous and marked “NOT FOR FLIGHT.” The red paint shall bematerial compatible and the stripes unmistakable.

.3 . 6 lneerface Re-

3 . 6 . 1 Clearancg . The clearance requirements between themoving mechanical assembly or deployable and any other structureor component shall be established and maintained. Themanufacturing, assembly, and alignment tolerances as well asenvironmental conditions such as temperature, temperaturegradients , v ibrat ion , d i s t o r t i o n d u e to- relaxation of the *g”f ie ld , e f fects o f centr i fugal forces , and acce lerat ion dur ingthe critical periods of launch and on-orbit operations shall betaken into consideration for establishing clearance adequacy.The established clearances shall be maintained duringtransportation and all operational modes o f the space vehicle.Obscuration of the operational f ields of view of v e h i c l e s e n s o r sby the moving mechanical assemblies shall be avoided except -where obscuration is a design requirement of the sensor system.Interface control drawings or layouts shall indicate the stowed,extended, and critical intermediate positions of the movingmechanica l assembl ies and deployable8 with respect to fields ofview and surrounding structure or components.

3 . 6 . 2 Migm,_~alignment and adjustmdnt

Provisions shall be included to permitof moving mechanical assemblies with

respect to the space vehicle and other subsystem elements whereappropr iate . A shimming-type alignment technique may be usedtihere additional surface area is necessary to provide a bearingsurface or where electrical bonding is required. Where anadjustable-type alignment technique is used, locking provisionsas specif ied herein shall be provided. Installation o falignment pins is permissible i f the pins are positivelyretained with the moving mechanical assembly mounting facestructure and permit the moving mechanical assembly to be easilyremoved from the vehicle.

3 . 6 . 3 Strum. In selecting the design for thestructural interface of the moving mechanical assembly with thespace vehicle, preference shall be given to simple approachesthat minimize the complexity of the interface. The movingmechanical assembly shall , where practicable, be easily installedand readily accessible for inspection or removal. Standard wrench -clearances shall be provided. The use of special tools shall beminimized. In addition, where complex connections and structural

38


MIL-A-835778 (USAF)01 FEB 1988

--

--

assembly interfaces are employed, the design of fittings shallbe based on a minimum fitting factor of 1.15 at ultimate load.

.3 . 6 . 4 -1 Interfaq8B Where practicable, a commoninterface drill template shall b; used to ensure correctmechanical mating, particularly for interfaces external to themoving mechanical assembly.

.3.6.5 Ipterchaaw A n y two or more movingmechanical assemblies beating’the same part number oridentification shall possess such functional and physicalcharacteristics as to be equivalent in performance anddurability and shall be capable of being changed, one foranother, without alterations of the items themselves or ofadjoining items except for alignment adjustments.

3.7 QDera

3.7.1 Beliability The reliability allocations to themoving mechanical asse;blies and the assigned designrequirements shall ensure that the overall vehicle reliabilityrequirements are met under the severe extremes of acceptancetesting, storage, transportation, preflight testing, andoperational environments. Highly reliable assemblies areusually obtained by elimination of single point failure modesunless it can be shown that the addition of redundancy actuallyreduces overall reliability due to added complexity. Theincorporation of redundancy is usually an acceptable techniquefor meeting the reliability requirements. For designs thatswitch redundant subassemblies or units autonomously, or byground command, the failure rates for the switching circuits,and for the redundant equipment while in the off line mode,shall be appropriately included in the reliabilitydetermination. The reliability of each moving mechanicalassembly shall be analytically determined using piece part orcomponent failure rates obtained from actual usage data whereavailable, or evaluated at anticipated operating temperaturesfrom standard data sources such as MIL-HDBK-217. The assemblyreliability shall be evaluated in terms of events and usagecycles that occur in operation. The design margins shallpreclude wear out o f components within the service life of thespace vehicle at the programmed duty cycle, including the wearassociated with all preflight testing.

3 .7 .2 silitp Except for possible relubricationafter extended storage, or’at prescribed intervals in multiplereuse applications, the moving mechanical assemblies shall,where practicable, be designed so as not to require anyscheduled maintenance or repair during their service life.Suitable development tests and inspections at appropriate

39



intervals shall validate that scheduled maintenance is notrequired. However, access shall be provided for replacement o fage-dated elastomeric materials which may have “expiration ofu s e f u l l i f e ” dates that can occur before scheduled f l ight.

. .3 . 7 . 3 Human Throughout the design anddevelopment of the moving meihanical assemblies, c r i t e r i a s h a l lbe judic ious ly appl ied to obtain e f fect ive , compat ib le , and safeman-equipment interactions. The design of all moving mechanicalassemblies shall be such that they may be tested or inspected toensure that they are assembled and installed correctly.Provisions such as tabs, shoulders, and different thread sizesshall be employed to prevent assembly in any incorrect mannerwhich may impair the intended functions of the moving mechanicalassembly.

.3 . 7 . 4 w Lib The combined operational and:lonoperational s e r v i c e iife of the moving mechanical assembliesshall exceed the service l i fe of the space vehic le in which theyare mounted. The serv ice l i fe inc ludes a l l operat ional andnonoperational t ime required or allowed after successfulcompletion of acceptance tests.

-3.7.5 Liafety

3 . 7 . 5 . 1 G e n e r a l Safetu. The design shall be such that asafety hazard to personnel and surrounding equipment shall notbe created during installation, maintenance, ground test, andtransportation of moving mechanical assemblies and deployables.;Yoving mechanical assemblies, particularly those associated withdeployables , shall be protected from damage which may occur atany stage of the fabrication, assembly, testing, ortransportat ion . When deployables are in their deployedp o s i t i o n s , special precautions such as restrictions on theactivities of personnel in the immediate area and exclusion ofothers by means of personnel barriers shall be used. Duringinstallation, maintenance, ground test, and transportation,precautions shall be taken to preclude the dropping of tools orother items that might injure personnel or damage sensitiveequipment. Tethering of tools to the person or clothing i srecommended. In addition, protect ive covers or o t h e r p r o t e c t i v edevices shall be incorporated, where appropriate. Requiredsafety procedures for handling, storing, and testing explosiveordnance shall be documented and implemented where applicable.

3 . 7 . 5 . 2 Svace TransDortation Sv&&m Payloads For allmoving mechanical assemblies and deployables that’are inpayloads which are to be launched by the Space TransportationSystem (STS), the safety requirements shall also be inaccordance with Chapter 2 of NHB 1700.7 (NASA). For these

,40



-

payloads, it is required that the payload must tolerate aminimum number of failures and operator errors determined by theconsequence of any hazardous functions. For catastrophichazards or hazards that would result in personnel injury, losso f the orb i ter , or loss of STS facil it ies and equipment, thehazard shall be controlled such that no combination of twof a i l u r e s , operator errors , or radio frequency signals wouldunleash the hazard. For critical hazards or hazards that wouldresult in damage to STS equipment or in the use of contingencyor emergency procedures, the hazard needs to be controlled suchthat no single failure, or operator error, would unleash thehazard. Hazardous functions are thereby controlled with eithertwo or three inhib i ts for cr i t i ca l or catastrophic hazards ,r e s p e c t i v e l y . These requirements are not applicable tononcredible failures where extensive analysis and test programsassure high re l iabi l i ty in the des ign. In part icular ,structural failures and the failure of spring elements whichmeet all structural design and design verif ication requirementsare considered such noncredible failures.

For the structural elements in moving mechanical assembliesand deployables, Chapter 2 of NHB 1700.7 (NASA) defines safetyrequirements for space equipment structural design, stressc o r r o s i o n , pressure vesse ls , sealed containers, elecLrica1subsystems, radiation, hazardous materials, destruct subsystems,pyrotechnics , flammable atmospheres, and reflown hardware.

.3 . 0 nanufacturlna

3.8.1 ms and Contrab. Acceptance and flightcertification of space equipment is based primarily on anevaluation of data from the manufacturing process. Handling andstorage of parts and materials for space applications shall becontrolled consistent with the criticality of the end use ofeach item. Controlled environment and controlled access shall,be used to the extent required to avoid degradation o f t h equal i ty and re l iabi l i ty o f the parts , mater ia ls , andassemblies. The manufacturing process shall be accomplished inaccordance with documented procedures and process controls whichensure the reliabil ity and quality required for the mission.These manufacturing procedures and process controls shall bedocumented to give visibil ity to the procedures andspec i f i cat ions by which a l l processes , operat ions , inspect ions ,and tests are to be accomplished by the contractor. Thisinternal contractor documentation shall include the name of e a c hpart or component, each material required, the point it entersthe manufacturing flow, and the contro l l ing spec i f i cat ion ordrawing. The documentation shall indicate required tooling,f a c i l i t i e s , and test equipment; the manufacturing check pointsand pertinent process control thresholds; the quality assurance

41



v e r i f i c a t i o n p o i n t s ; and the verif ication procedurescorresponding to each applicable process or material l isted.The specif ications, procedures, drawings, and supportingdocumentat ion shal l re f lect the spec i f i c rev is ions in e f fect atthe time the items were produced. These flow charts and thereferenced specif ications, procedures, drawings, and supportingdocumentation become the manufacturing process control baselineand shall be retained by the contractor for reference. I t i srecognized that many factors may warrant making changes to thisdocumented baseline; however, all changes to the baselineprocesses used, or the baseline documents used, shall berecorded by the contractor fol lowing establishment of themanufacturing baseline or following the manufacture of the f irstitem or lot of items. These changes provide the basis f o rfl ight accreditation of the items manufactured or of subsequentf l i g h t i t e m s .

The manufacturing process and control documents shallprovide a contractor-controlled baseline that ensures that anysubsequent failure or discrepancy analysis that may be requiredcan identify the specif ic manufacturing materials and processesthat were used for each item. In this way, changes can beincorporated into a known baseline item to correct problems. .-

3 . 8 . 2 Production Lots. To the extent practicable, partsfor use in space equipment shall.be grouped together inindividual production lots during the various stages of theirmanufacture to ensure that all devices assembled during the sametime period use the same materials, tools, methods, andc o n t r o l s . Parts and devices for space equipment that cannot beadequately tested after assembly without destruction of thei t em., such as explosive ordnance devices, shall have lotcontrols implemented during their manufacture to ensure auni form qual i ty and re l iabi l i ty leve l o f the ent ire lo t . Eachlot shall be manufactured, tested, and stored as a singlebatch. Sequential lot numbers that indicate the date ofmanufacture shall be assigned to each production lot.( T y p i c a l l y , use three digits for the day of the year and t w odig i ts for the year . )

. .3 . 8 . 3 Contsrg;Lnatiog.3.8.3.1 Fabricatiud Handling Fabr ica t ion and

handl ing of space equipment shall be &complished in a cleanenvironment. Attent ion sha l l be g iven to avoid ingn o n p a r t i c u l a t e ( c h e m i c a l ) a s w e l l a s p a r t i c u l a t e a i rcontaminat ion . To avoid safety and contamination problems, theuse of l iqu ids sha l l be min imized in a reas where in i t i a tors ,e x p l o s i v e b o l t s , or any loaded explosive devices are exposed.

42



3.8.3.2 Device Cleanliness. The particulate cleanlinessof internal moving subassemblies shall be maintained to at leastlevel 500 as defined in MIL-STD-1246. External surfaces shallbe visibly clean. The allowable product nonvolatile residue(NVR) level shall be maintained to at least level "G", asdefined in MIL-STD-1246. Specific cleanliness requirementsshall be determined for each moving mechanical assembly based onan analysis of overall system cleanliness requirements.

.3.8 .3 .3 Putawsina, Items that might otherwise produce

deleterious outgassing while on orbit shall, where practicable,be baked for a sufficient time to drive out all but anacceptable level of outgassing products prior to installation i nthe assembly. Where baking is not practicable, exposure tovacuum within the operating temperature of the item shall beemployed.

.3.8.4 ElectrastatrC Discharae Appropriate provisionsstated in DOD-HDBK-263 shall be u&d to avoid and to protectagainst the effects of static electricity generation anddischarge in areas containing electrostatic sensitive devicessuch as microcircuits, initiators, explosive bolts, or any .loaded explosive device. Both equipment and personnel shall begrounded.

.3.8.5 Q8m

be manufactured, processid,Moving mechanical assemblies shall

tested, handled, and installed suchthat the finished items are of sufficient quality to ensurereliable operation, safety, and service life. The items shallbe free of defects that would interfere with operational usesuch as excessive scratches, nicks, burrs, loose material,contamination, and corrosion.

. . .3.9 Wae and Provlslons Storage, handling,

and transportation conditions to which moving mechanicalassemblies are to be subjected prior to flight shall becontrolled to the limits of Paragraph 3.4.3. The items shall becapable of meeting the operational requirements withoutrefurbishment, other than relubrication, after nonoperationalstorage of four years in a controlled environment (see 3.4.3).The orientation or storage environment or both shall be chosento minimize oil flow within the assembly. Storage shallpreferably be in a "no-load" condition with springs in a relaxedstate and pressure vessels unpressurized. The storage,relubrication, and retesting of all moving mechanical assembliesshall be in accordance with documented procedures.

Cleanliness shall be maintained during processing, storage,and transportation using appropriate protective containers orc o v e r s . Electrostat i c sens i t ive i tems, such as most e lec tronic

43



assemblies and components containing explosives, shall be storedand transported in sealed packages using antistatic wrappingmater ia l . The antistatic wrapping material used should notproduce nonvolati le residues. The antistatic wrapping materialshall be grounded through a resistor prior to removal. Thegrounding resistor shall have a value between 100,000 ohms and1 meqohm.

Temperature and humidity conditions and transportation shockexposure shall be monitored subsequent to manufacture, and themeasured levels shall be evaluated against the acceptance testl i m i t s .

4. QUALITY ASSURANCE PROVISIONS

4 . 1 ReSDOnSibilitV for -Dections and Tern Unlessotherwise specified in the contract, the contractir isresponsible for the performance of all inspection and testrequirements as specif ied herein. Except as otherwise specif iedin the contract , the contractor may use his own or any other

facil it ies suitable for the performance of the i n spec t i on and -test requirements specified herein, unless disapproved by thegovernment. The government reserves the right to perform any ofthe inspections set forth in the specification where s u c hinspections are deemed necessary to assure that supplies andservices conform to prescribed requirements.

. . .4.1.1 ResPanslbilitv for Corqpliancemeet all requirements of Sections 3 and 4.

All items shallThe inspections set

forth in this specif ication shall become a part of thecontractor ’s overall inspection system or quality program. Theabsence of any inspection requirements in the spec i f i cat ionshall not relieve the contractor of the responsib i l i ty o fassuring that all products or supplies submitted to theGovernment for acceptance comply with all requirements of thec o n t r a c t .

I .4 . 1 . 2 vnt & Iwertion FaciJitia Themanufacturer shall ensure that test and inspection iacilities ofsufficient accuracy, quality, and quantity are established andmaintained to permit performance of required inspections.

. . . .4 . 2 Classlficatlon of Insusctwns a n d Tw The testsand inspect ions spec i f ied here in are c lass i f ied is f o l l o w s :

a. Parts, mater ia ls , and process controls (see 4.3) _

b. Development tests (See 4.4)

44



C. First assembly inspection (see 4.5)

-

a. Component and subsystem level acceptance tests(see 4.6)

e . Qualification tests (see 4.7)

f. Vehicle level acceptance tests (see 4.8)

9* Prelaunch validation tests and inspections(see 4.9)

4.3 Parts. Materials. and Process Controb To ensurethat a reliable moving mechanical assembly is fibricated, allparts and materials shall be adequately controlled and inspectedprior to assembly. During fabrication, the tools and processes,as well as parts and materials, shall be adequately controlledand inspected to ensure compliance with the approvedmanufacturing processes and controls.

4.3.1 Recorbs. Records documenting the accreditationstatus of the moving mechanical assemblies shall be maintainedfollowing assignment of serial numbers. Each moving mechanicalassembly shall have inspection records and test recordsmaintained by serial number to provide traceability from systemusage to production lot data for the device. Complete recordsshall be maintained and shall be available for review during theservice life of the system. The records shall indicate allrelevant test data, all rework or modifications, and allinstallation and removals for whatever reason.

4.3.2 Banufactv. Each moving mechanicalassembly and each critical subassembly shall be subjected toin-process manufacturing and assembly screens to ensurecompliance with the specified requirements to the extentpracticable. Compliance with the documented process controls,documented screening requirements, required hardwareconfiguration, and general workmanship requirements shall beverified. At each level of assembly, each completed unit shallbe subjected to visual inspection to ensure that it is free ofobvious defects and is within Specified physical limits.

. .4.3.3 flonconformlna Mate- Nonconforming material,components, or assemblies that do-not meet the establishedtolerance limits set for the acceptance limits in the in-processscreens shall be rejected for use. Any rejected material,component, or assembly may be reworked and rescreened inaccordance with established procedures if system reliability isnot jeopardized, and if the rework is not so extensive as tojeopardize the lot identity of the material or assembled unit.

. 45



If reworked material or an assembled unit that was lotcontrolled subsequently pass the in-process screens, it canagain be considered part of the lot. Reassignment of units thatwere lot controlled to a different lot shall not be made.Nonconforming material or assembled units that do not satisfythese rework criteria shall be considered scrap.

4.3.4 -Dection oC_. As a minimum, all castings,fusion welds, fibre composite or honeycomb parts and surfaces ofstressed parts shall be inspected as follows:

a. I n t e r n a l . All castings and all fusionwelds shall be inspected for the presence ofinternal defects by radiographic methods inaccordance with MIL-STD-453. Plastic compositestructural elements shall be inspected for thepresence of internal defects by an appropriatetest method.

b. Surface defects. The surfaces of stressed partsshall be inspected in accordance with MIL-X-6868(magnetic particle inspection method), inaccordance with MIL-STD-6866 (liquid penetl-antinspection method), or in accordance with otherinspection methods, as appropriate. Heat-treatedsteel parts with tensile strength above 1,790megapascals (259,617 pounds per square inch)ultimate that require a grinding operation afterfinal heat treatment shall be inspected by nitaletch on all surfaces subject to grinding.

All parts used in critical moving mechanical assemblies orparts comprising single point failures shall be completelyinspected to ensure that no defects exist which could lead to'degraded performance or failure.

. 4.3.5 Bon of Assemhbm The dimensions, weight,finish, identification markings, and cleanliness of each movingmechanical assembly shall be inspected, as appropriate, prior toacceptance testing and prior to installation on the vehicle.Inspection of the assembly shall be made to ensure that aminimum thread engagement of five full threads exists for allthreaded attachments; or where through bolts are used, that aminimum of two full threads protrude beyond the end of the nut.Fasteners shall be inspected for compliance with required torquelevels. These inspections shall be made concurrently with theassembly of the parts. Pin pullers shall be inspected at thevehicle test level to verify adequate travel and travel margin.All moving mechanical assemblies shall be inspected before andafter exposure to environmental tests at the component test

46


MIL-A-835778 (USAF)01 FEB 1988

*-

level, at the vehicle test level, and at the launch site. I naddition, the inspections should be conducted at intermediatetest points. These inspection processes shall include, but arenot limited to, the following:

a.

b.

C .

6.

8.

f .

h.

Scratchefi or dammed surfaces . If surface damageis sufficient to affect the intended function ofthe assembly, or the performance is degraded (e.g.,damaged thermal control surfaces, increasedfriction of contacting surfaces or contaminationdue to debris), the moving mechanical assemblyshall be rejected.

.Rust or corrosion Any parts exhibiting rust orcorros ion sha l l b; r e j ec ted .

tener toraue, Fasteners shall be visuallyinspected for looseness. In addition, the torqueshall be checked on preselected fasteners beforeand after exposure to each environmental testcondition.

Handlina. Graphite epoxy and other compositeparts shall be visually inspected for damage. Wheretubular composite members are used, the internalsurfaces shall, where practicable, be visuallyinspected for damage, by means o f a borescope or byother appropriate means.

.in- Product particulate cleanliness shallnot exceed ieve 500 as defined in MIL-STD-1246.Product nonvolatile residue (NVR) shall be incompliance with the applicable requirementsspecified for each assembly.

Wirina harness-. Wiring harnesses shall beinspected to verify that they are properly securedand to verify that the proper configuration i smaintained, particularly in the area of rotatingparts or joints.

ectotd Dust caps shallbe installed on unused connectois during shipmentor test. Although unnecessary disconnecting andreconnecting of connectors shall be avoided,inspection for connector out-of-round and broken orloose electrical pins shall be made, wherepracticable.

. .tiluer lnsulatloD Multilayer insulation

should be inspected a; the vehicle test level and

47



-

after vehicle shipment for adequate clearance withrespect to adjacent moving mechanical assembliesto ensure that movement of the assemblies will notbe impeded during operation. In addition, whereswitches are used for indicating purposes, theclearance between the multilayer insulation andthe switch shall be verified to ensure that properoperation of the switch can occur.

.1. Safety wire Fasteners utilizing safety wire

shall be inipected to ensure that the wire isproperly installed and that such wire cannotresult in interference with other parts of themoving mechanical assembly.

j. Alianmentappropriaie.

Alignment shall be inspectec! asAlignment mirrors shall be inspected

to verify freedom from damage or displacement.Alignments of deployables shall, wherepracticable, be checked in their deployedpositions.

k. Switch= Indicating switches shall be inspectedto ensur;! that they operate satisfactorily andthat adequate overtravel exists. Switch wiresshall be inspected to verify that they are freefrom damage or sharp bends. Switch actuationshall, where practicable, be verified by means ofelectrical continuity.

1. Brinel;Ligg. Highly loaded surfaces such aspreload fittings or overcenter latches shall beinspected for evidence of Brinelling damage tosurfaces in contact.

m. Sor* Where accessibility permits, thefollowing inspections and measurements shall bemade on springs: inspection for broken coils orother damage and measurement of spring force ortorque and spring rate on the fully assembledmoving mechanical assembly. The spring load atthe installed position and the spring rate shallbe measured before assembly, recorded, and thesprings properly serialized. The spring load andthe spring rate shall also be measured andrecorded after spring assembly or installation, asappropriate. The location of each serializedspring on the moving mechanical assembly shall berecorded. On all springs comprising single pointfailures, the heat treat shall be checked, where

-

-

48



n .

0 .

Pm

p r a c t i c a b l e , using an unstressed portion of eachspring, such as on the ground flats on the ends o fcompression springs. Where there is a danger ofcausing damage as a result of the heat treat test,a lot sampling technique may be used if approvedby the contracting officer. Where practicable,actual spring position and deflected shape duringthe entire range of travel shall be checked toavoid off-nominal loading due to coil displacementand tang movement

DamPers Viscous dampers shall be performance andleak chicked. Deformable material dampers shall beinspected to ensure that the material is notdeformed or damaged.

B* Clearances shall be inspected toensure compliance with the specified requirements.

E l e c t r i c = Where accessibility permits, thefollowing inspections and measurements shall bemade on electric motors:

1. Verification of the part number.

2. Identification of special precautions (ifany) such as use of keepers during armatureremoval, and observation of lead color codefor polarity where suppression diodes areused.

3. Inspection for adequate lead length andclearance from other leads to which motornoise might introduce electromagneticinterference.

4. Adequate mount heat sinking.

5. Inspection of freedom of motion withoutbinding or misalignment problems.

Operationally the input current may be monitoredto verify brush and motor performance.

.4.3.6 Lubricant Processina Procedures Lubr icant

p r o c e s s i n g p r o c e d u r e s s h a l l b e e s t a b l i s h e d ’ t o c o n t r o l t h eu n i f o r m i t y , r e p e a t a b i l i t y , c l e a n l i n e s s , a c c o u n t a b i l i t y , a n damount of lubricant in the moving mechanical assemblies. Theseprocedures shall also delineate the processes of removal ofbearingishipping l u b r i c a n t s . Shipping lubr icants sha l l be

49



analyzed for compatibil ity with the applied lubricant. Porousball bearing retainers and lubricant reservoirs which haveshipping lubricants in them shall be replaced before processingwith the f l ight lubr icant . Each bearing to be processed with al iquid lubr icant shal l be tested for wetabi l i ty pr ior toappl icat ion o f the f l ight lubr icant . The wetability test methodshall be approved by the contracting off icer.

4.4 De elonmt Te&& . Development test ing may beperformed 0: moving mechanical assemblies to supplementanalytical techniques in the quantification of d e s i g n p a r a m e t e r sand to promote the evolution of new design concepts.Developmental testing shall be used to validate new designconcepts for critical components and assemblies as a prelude toq u a l i f i c a t i o n t e s t i n g . The nature and extent of developmentaltesting on components, subsystems, and complete moving mechanicalassembl ies shal l be suf f i c ient to ensure that qual i f i cat iontesting of new designs will produce minimal failures which wouldthen require redesign. Developmental testing shall be conductedusing MIL-STD-1540 as a guide. Critical components requiringdevelopment tests should be identified early in the design anddevelopment program, and a l ist of tests and items so identif iedshould be documented. The adequacy of the development testing isa contractor responsibil ity; however, 8ome contracts may allowthe contracting off icer to delay approval to proceed withqualif ication testing pending a review of the development testr e s u l t s . In that case, a particular test should not beconsidered completed until a minimum of 30 days after the testresults have been presented to the contracting off icer. Unlessthe design is substantiated by previous usage, developmentaltest ing shal l inc lude the fo l lowing, as appl icable :

a. Tests to substantiate the design of each bearinginsta l lat ion with respect to mater ia ls , s tresses ,s t i f f n e s s , fat ique l i fe . pre load, and poss ib lebinding under normal, as well as the most severecombined loading conditions, and the expectedenvironmental conditions.

b. For bearings that are reused, tests to characterizethe wear and lubrication changes resulting frombearing reuse, and the effects these changes haveon torque margin.

C . Where practicable, tests to substantiate theeffects of temperature gradients on bearing preloadand st i f fness .

d. For critical moving mechanical assemblies, tests ofthe lubricant that demonstrate the abil ity of the

50


MIL-A-835778 (USAF)01 FEB 1988

-

e.

f .

g*

h.

i .

j.

lubricant system to provide adequate lubricationunder all specified operating conditions over thedesign lifetime.

Where contact pressure is sufficiently high, suchthat friction welding might be possible, design andprocess verification tests shall be conducted atthe piece part or subassembly level to verify theselection of materials and lubricants in theproposed application.

F or brushes and commutator or slip ring assemblies,tests to demonstrate that the lubricant is notsignificantly deteriorated or driven from the areasrequiring lubrication by adverse thermal, gravityforces, or other conditions; and that wear rates,wear debris, electrical noise level, frictiontorque, and lubricant loss are compatible withdesign requirements.

For deployable devices, minimum available drivingcapability and maximum load determination shall beverified through an appropriate test program; eachelement of resistance shall be characterized inthis test program.

For moving mechanical assemblies driven byelectrical motors, a torque versus currentrelationship for each motor under minimum, maximum,and ambient thermal and vacuum conditions shall beestablished.

Where practicable, tests to substantiate thatscheduled maintenance is not required.

Eddy current dampers shall be tested forrepeatability of damping rate and torque values fortwice its expected operational life cycle. Theeddy current damper shall be tested at temperatureextremes to determine its damping rate over thetemperature range.

4.5 First -1~ s An inspection of the firstof each of the moving mechanical aisemblies produced withproduction equipment and procedures shall be conducted at a timeand location acceptable to the contracting officer. There shallbe no discrepancies among the equipment, the fabrication toolingused, the released drawings, the test data, the inspectionrecords, and the specification requirements, First assemblyapproval is valid only on the contract or purchase order under

51


MIL-A-83577B (USAF)01 FED 1988

-

which it is granted, unless extended by the contracting officerto other contracts or purchase orders.

4.6 Component and Subs-tern Level meotance Testi. Theconfiguration and workmanship of the completed hardware shall beverified by inspection prior to the start of acceptance testing.Acceptance tests shall be conducted on each moving mechanicalassembly in accordance with the acceptance test requirements ofMIL-STD-1540. The acceptance tests shall incorporate the run-in,functional, and environmental test requirements stated herein.The acceptance tests shall be structured to detect workmanshipdefects that could affect operational performance. Componentsfabricated from fiber composite material or of honeycombconstruction shall be subjected to acceptance proof testing. Theacceptance testing of moving mechanical assemblies that are partof a deployable device shall, where practicable, be conductedwith the moving mechanical assembly attached to the deployabledevice. In some cases, such as solar array drives, despin bearingassemblies, or pointing devices, dummy loads may be substitutedfor the driven member. The dummy loads shall provide a reasonablerepresentation of the dynamic characteristics (such as inertia,stiffness, free play, and natural frequencies) of the actualdriven member. The effect of friction due to the additionalweight of the dummy load on the drive unit shall be accounted forin evaluating the test results. Dummy loads are also permittedto minimize the effects of air damping where large panels aredeployed under ambient conditions. Appropriate quantitativemeasurements such as torque vs angle measurements and time vsangle measurements, or equivalent linear measurements for lineardevices, shall be made during run-in, functional, andenvironmental acceptance testing of all moving mechanicalassemblies. For spring driven devices, torque vs anglemeasurements shall be made during restowing .as well as duringdeployment in order to generate a torque vs angle hysteresiscurve to determine torque mArgin F?r l;near devices, equivalent_a.._linear measurements shall be made to determine force margin. Asa minimum, these measurements shall be made under ambient andacceptance level hot and cold temperatures. When an assembly istoo large or complex to be tested, results of component orsubassembly torque or force margin testing may be added to obtainthe assembly torque margin. Moving mechanical assemblies thatcontain redundancy in their design shall, where practicable,demonstrate performance to their requirements in each redundantmode of operation. Functional operation and alignment of eachmoving mechanical assembly, including instrumentation that is anintegral part of the assembly, shall be tested and checked, wherepracticable, before and after exposure to each environmentalacceptance test. All swaged ends on rods or cables shall be 100 -percent tested with a load equal to twice the limit load (see6.2.12). (Note: the proof factor of safety shall be 2.0 forswaged ends on rods or cables.)

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- MIL-A-83577B (USAF)01 F E B 1988

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4 .6 .1 Run_in After initial functional testing, arun-in test shall be p&formed on each moving mechanical assemblybefore it is subjected to further acceptance testing, unless i tcan be shown that this procedure would be detrimental toperformance and would result in reduced reliability. The primarypurpose o f the run-in test is to detect material and workmanshipdefects which occur early in the component l i f e . Another purposeof the run-in test is to wear-in parts o f the moving mechanicalassembly so that they perform in a consistent and controlledmanner. Satisfactory wear-in may be manifested by a reduction inrunning friction to a constant low level. The run-in test shallbe conducted for a minimum of 50 hours except for items where thenumber o f cycles of operation, rather than hours of operation, i sa more appropriate measure of the capability to perform in aconsistent and controlled manner. For these units, the run-intest shall be for at least 15 cycles or 5 percent of the totalexpected service life cycles, whichever is greater. The run-intest conditions should be representative of the operationalloads, speed, and environment; however, operation o f the assemblyat ambient conditions may be conducted if the test objectives canbe met and the ambient environment will not degrade reliabilityor cause unacceptable changes to occur within the equipment such'as the g e n e rrr t io n of excessive debris. During the run-in test,sufficient periodic measurements shall be made to indicate whatconditions may be changing with time and what w e a r ratecharacteristics exist. Test procedures, test time, and criteriafor performance adequacy shall be in accordance with a test planthat has been approved by the contracting officer. All geartrains using solid film lubricants shall, where practicable, beinspected and cleaned following the run-in test.

. .4.6.2 Functional and Environmenfel Accevtance Each movingmechanical assembly shall be subjected to function;1 andenvironmental tests that are in accordance with the applicableacceptance test requirements of MfL-STD-1540. Functional testsshall be structured to demonstrate that the moving mechanicalassembly is capable of operating in such a manner that allperformance requirements are satisfied. Functional tests arerequired before and after exposure to environmental test conditionsin order to establish whether damage or degradation in performancehas occurred. These tests shall be sufficiently comprehensive andshall include sufficient measurements to determine whetherperformance specifications are met. The functional tests areusually conducted at room ambient conditions, with the initialfunctional testing used as a baseline against which subsequentperformance is compared. Where a device is designed to operate inextreme heat or cold or in some other environmental extreme, and afunctional test at ambient conditions would not be significant,the functional tests shall be conducted in the appropriateenvironment that would demonstrate performance. Al l cormnand

53


!41L-A-835778 ( U S A F )0 1 F E i3 1 9 8 8

functions should be exercised during functional testing. Themoving mechanical assemblies shall be tested in their launch or i ntheir on-orbit configurations corresponding to the environmentbeing simulated. They shall be passive or operating correspondingto their state during the launch or on-orbit operational phases.Fully assembled deployables shall , where practicable, have torquevs angle and time vs angle measurements, or equivalent linearmeasurements for linear devices, made during thermal vacuumt e s t i n g . When a harmonic drive is used for precision pointinga p p l i c a t i o n s , full functional testing should be performed toverify the harmonic drive characteristics at each level o fassembly. Funct ional tests should inc lude tors ional s t i f fness ,damping, a n d f r i c t i o n c h a r a c t e r i s t i c s . A f t e r a harmonic drive isassembled into the parent assembly, it shall be inspected for thededoidal condit ion (see 6 .2 .5 ) . When operation of a deployable ina vacuum chamber or measurements in a vacuum chamber areimpract ica l , the fully assembled deployable shall have deploymentt e s t s , including torque vs angle and time vs angle measurements,or equivalent l inear measurements for l inear devices, made.in ahot or cold box. When the fully assembled deployable is so largethat it cannot be completely enclosed within a hot or cold box,the moving mechanical assemblies themselves may be separatelyenclosed within several smaller hot or cold boxes which surrrrrln?lonly the moving mechanical assembly portion of the d e p l o y a b l ed e v i c e . Test procedures, test t ime, and cr i ter ia for per formanceadequacy shal l be as approved by , the contract ing o f f i cer . IUodisassembly, adjustments, or repair shall be made on movingmechanical assemblies during functional and environmentalacceptance testing or after completion of testing unless approvedby the contracting officer.

4 . 7 Qualificafion Tw The qual i f i cat ion tests o f themoving mechanical assemblies.shall be conducted in accordancewith the qualification test requirements of MXL-STD-1540. The 6dB, 10 deg C (18 deg F ) , or other design factors o f safety ormargins specif ied herein include test condition tolerances thatare those allowed in MIL-STD-1540. When the actual qualif icationor acceptance test tolerances can be shown to be less than thoses p e c i f i e d i n MfL-STD-1540, the qualif ication test levels may beappropriately reduced in accordance with provisions specif ied inMXL-STD-1540. The qualification tests shall incorporate thedesign life verification test, functional test, and environmentaltest requirements stated herein. Moving mechanical assemblieswhich are required to operate more than once during theiron-orbi t l i fe shal l be tested us ing dedicated qual i f i cat ionitems. Where a moving mechanical assembly is required to operateonly once during i ts on-orbi t l i fe , consideration may be given t oflight use of the qual i f i cat ion art i c le based on the requirementsof Section 8 of MIL-STD-1540. However, any fl ight use of aqual i f i cat ion art ic le shal l have pr ior approval by the

54



--

contracting officer. The qualification tests shall be structuredto demonstrate the design adequacy and design margins. Anacceptance test shall precede the qualification tests. Torque vsangle measurements and time vs angle measurements, or equivalentlinear measurements for linear devices, shall be made duringqualification testing of all moving mechanical assemblies.Satisfactory completion of these tests or equivalent proven spacevehicle operational performance is required for flightcertification or qualification. Compliance with all or portionsof the qualification requirements based upon tests of similaritems or upon equivalent space vehicle operational performanceshall require approval of the contracting officer. The generaltest measurements and test configurations used for qualificationtests shall be similar to those used for acceptance tests.Moving mechanical assemblies that contain redundancy in theirdesign shall, where practicable, demonstrate performance to theirrequirements in each redundant mode of operation during thequalification test. Functional operation and alignment of eachmoving mechanical assembly, including instrumentation that is anintegral part of the assembly, shall, where practicable, betested and checked, before and after exposure to eachqualification test.

4.7.1 - .pesiun Life VeWon Te&s . The design lifeverification tests are intended to evaluate lubricantsuitabi l ity, release and deployment life cycle margins, wearlife, and avoidance of fatigue. One or more items of each of themoving mechanical assemblies, produced with production equipmentand procedures, shall be subjected to a design life verificationtest. The number of units to be tested should be sufficient toachieve the desired confidence level for the test results. Thesetests shall be conducted to simulate operational use within therange of the worst predicted operational environments. The itemsshall be subjected to tests which demonstrate the capability toperform the full operational life cycle. Masses, loads, andstiffness of support structure shall be actual or simulatedoperational values, and any interfacing equipment such as thermalheaters, cabling, or hoses shall be in place so that operationalconditions are simulated. The test and criteria for performanceadequacy shall be approved by the contracting officer. F or itemshaving a relatively low percentage duty cycle, it shall beacceptable to compress the operational cycle into a tolerabletotal test duration. For assemblies which operate continuouslyon-orbit, or at very high percentage duty cycles, acceleratedtest techniques may be employed if such an approach can be shownto be valid. For such assemblies, tests shall be under properenvironmental conditions, of varying duration, followed bydisassembly and inspection. A single item may be used providedthat periodic disassembly and inspection does not influence thetest conditions sufficiently to invalidate the test resu l ts .

55


MIL-A-835778 (USAF)01 FEB 1988

Detailed analyses of lubricant consumption, debris accumulation,wear, or other critical parameters may be used to provide basesfor forecasting the expected life of the assembly. The movingmechanical assemblies used for life test shall be essentiallyidentical with the flight items. The only differences betweenthe test items and the flight items shall be those changesnecessary for incorporation of test instrumentation. Thesedifferences shall not jeopardize the validity of the tests withrespect to the flight hardware. Sufficient instrumentation shallbe used to provide knowledge of the operating conditions withinthe assemblies during life testing such as internal pressures,temperatures, and temperature gradients. Where liquidlubrication is used, consideration shall be given to measuringlubricant loss, degradation, distribution, quantity, andoutgassing constituents over the duration of the test. Theinstrumentation shall be similar to that employed in other testphases to provide a basis for comparison of the design life testconditions with those of other selected ground tests and withthose during orbital operations. The design life test movingmechanical assembly shall be operated as expected in flight withequipment operating in accordance with the predicted duty cycle.The tests shall include variations of the expected flight usage,such as power down modes to check low temperature operation of

._

the system, to the degree practicable without exceeding thethermal limits of the equipment. All electrical slip ring andcommutator assembly tests shall be conducted with representativelevels of electrical current at the rated voltage across theinterface. All moving mechanical assemblies shall be tested forat least twice the number of duty cycles expected in operationaluse, plus twice the number of duty cycles expected duringcomponent and vehicle functional and environmental tests. stopsshall be tested by intentionally running the moving mechanicalassembly into the stops whether or not the moving mechanicalassembly has limit switches to prevent contacting the stops innormal operation. The stops shall be tested for at least twicethe number of duty cycles expected in operational use, plus twicethe number of duty cycles expected during component and vehiclefunctional and environmental tests. For moving mechanicalassemblies which employ limit switches and do not normallycontact the stops, the qualification tests o f the stops may beconducted as a separate subassembly level test with the switchinactive. A functional test shall be conducted after the designlife verification test has been completed and the assembly shallbe disassembled and inspected for anomalous conditions. Thecritical areas of parts which may be subject to fatigue failureshall be inspected to determine if failure has occurred.

4.7.2 Functional and Environmental Qualification. Oneitem of each of the moving mechanical assemblies, produced withproduction equipment and procedures, shall be subjected to

56



environmental qualification testing to verify satisfactoryperformance at the design environmental levels. Tests shall bein accordance with the applicable qualification test requirementsof MIL-STD-1540. The moving mechanical assemblies shall betested in their launch or in their on-orbit configurationscorresponding to the environment being simulated. They shall bepassive or operating corresponding to their state during thelaunch or on-orbit operational phases. Test procedures, testtime, and criteria for performance adequacy shall be as approvedby the contracting officer. Qualification testing of deployablesshall include tests to simulate the lowest motive force combinedwith the highest resistance under the most a d v e r s e environmentalconditions to provide the worst case torque margin. In addition,the highest motive force combined with the lowest resistanceunder the most aiding environmental conditions. shall be tested toprovide the worst case loading including the loads against thestops. Sufficient measurements shall be made to show that therequirements of this specification are met under both of theabove conditions. Measurements shall include torque vs angle andtime vs angle, or equivalent linear measurements for lineardevices. For deployables, time correlated video recording, ormotion picture film coverage, and potentiometers, accelerometers,or other appropriate instrumentation shall be utilized for allfunctional and environmental qualification tests to enable thedynamics of the deployment to be determined and to establish timevs angle or time vs distance acceptance test criteria limits. Aone-time release test of pyrotechnic devices shall be conductedin the fully assembled configuration using a worst case lowestexplosive charge loading of 80%. This release test shall beconducted using worst case tolerances and worst caseenvironmental conditions. To evaluate the possibility ofstructural damage to moving mechanical assemblies actuated bypyrotechnic devices, a one-time test shall also be conductedunder worst case highest explosive charge loading. A 120 percentexplosive charge load shall, where practicable, be used for thistest. Instrumentation shall be provided on adjacent equipmentduring release tests to assess the transmitted shock loads. Astatic load test to demonstrate the required strength, safetyfactors, and margins shall be conducted. Following the staticload test, the assemblies shall be completely disassembled andreinspected for possible damage.

4.0 yehicle Level A c w t a n c e Testa The vehicle levelacceptance tests shall be conducted in kordance with therequirements of MIL-STD-1540. After assembly of the deployableon the space vehicle, a time correlated video recording or motionpicture film of deployment shall be utilized to ensure that thedynamics of deployment are within specified time vs angle or t imevs distance pass-fail criteria. Where deployment is impracticalafter assembly on the space vehicle, this recording of the

57



dynamics of deployment shall be made during the last ‘functionaldeployment prior to mounting of the deployable on the spacevehicle. A first motion cold test of all deployables shall beincluded, where practicable, as part of the space vehicle thermaltesting to verify release of the deployables at the acceptanceievel cold temperature.

. . .4 . 9 Prelwch Vawon Teatlnq_9Ddd‘.QD. Theprelaunch validation tests shall be conducted in accordance withthe requirements of MIL-STD-1540.

4.9-l -ace Tests. Where practicable, a completedeployment of deployable flight hardware in the flightconfiguration shall be conducted after attachment of thedeployable to the space vehicle. A hand held walkout, ifappropriate, is sufficient to satisfy this requirement. Thistest should be conducted at the latest possible time prior tof l ight. Where a complete deployment is not practical due to thesize of the deployable, lack of a “one-g’ supporting fixture, orrisk of damage associated with a hand held walkout, an alignmentcheck and an initial motion release test shall be conducted inlieu of the above requirements. A measurement of the minimumbreakaway force shall be made to ensure that no binding of thettriuasa mechanism or excessive friction due to distortions ofpivot support brackets is present.

-

.4.9.2 InsPectlon Where practicable, the inspectionslisted in Paragraph 413.5 shall be repeated at the launch siteafter assembly of the vehicle in the flight configuration.Deployments such as hand-held walkouts, or other deployments suchas those required to provide access to nearby equipment, or aspart of pre-flight checks, should not be performed without thepresence of an inspector to witness, approve, and sign-offacceptability of the handling, deployment, and restowingprocedures.

.4 . 9 . 3 Prelaunch Vam Prelaunchvalidation exercises shall include contingency cases involvinganomalous operation of moving mechanical assemblies. Forexample, partial deployment of space vehicle devices may causeadditional effects on the space vehicle such as changes to thethermal control of the space vehicle, changes to the inertialproperties of the space vehicle, degradation of communicationsystems, and possible blocking of sensors. In some cases theeffects of the failure may be circumvented by operation of thespace vehicle in a different mode, such as increasing the spacevehicle spin speed to aid in deployment of a deployable devicewhich has experienced a hang-up. These contingency plans should _be formulated and exercised to the extent practicable.

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ML-A-83577B (USAF)01 FEB 1988

. .4.9 .4 Prebunch Dn ofB e a r inas that are Reused.Bearings that are to be used for a number of flights shall beinspected and retested after the initial flight. Individualbearing tests shall be conducted to determine if the resistivetorques are within acceptable limits. If the mechanism torqueor force margins are less than the minimum acceptancerequirements, the bearings shall be completely inspected,refurbished, and retested as necessary after each flight. Ifthe mechanism torque or force margins are considerably higherthan minimum acceptance requirements, the bearings tests andinspections following subsequent flights may be relaxed.

. .4 . 1 0 nodif ications. Rewor)t._and R e t e s t - Completedmoving mechanical assemblies shall be modified’and reworked withthe same high quality assurance provisions and criteria as theoriginal assembly. Inspection and retesting shall be inaccordance with XIL-STD-1540 and the requirements stated herein,or as directed by the contracting officer. Moving mechanicalassemblies that have successfully completed the run-in test andare subsequently repaired, reworked, modified, or reacceptancetested shall not be given another run-in test unless the reworkis so extensive as to invalidate the initial run-in. Movingmechanical assemblies that are not assembled on a space vehiclebut are placed in storage for more than one year shall beretested in accordance with the established thermal or thermalv a c u u m acceptance teat procedure6 prior to use. After two yearsof storage and every year thereafter, the liquid lubricants usedin these moving mechanical assemblies shall, where practicable,be sample tested to evaluate degradation. If there is evidenceof lubricant degradation, the cause of the degradation shall beeliminated and

5. PACKAGIl.IG

6. BOTES

the assembly relubricated.

(Not Applicable)

.6 . 1 -red AD D- Where possible, therequirements in the specification are stated in terms that areself-tailoring to each application. However, additional tailoringof the requirements should be considered throughout theacquisition process within the constraints of the major programelements. These elements typically include performance, testing,reliability, schedules, production costs, operating costs,maintenance costs, and other high cost drivers in the projectedlife cycle. Contractors are encouraged to identify to thecontracting officer, for program office review andreconsideration, any requirements imposed by this specificationthat are believed excessive. However, contractors are reminded

59



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that deviations from contractually imposed requirements can begranted only by the contracting officer. The use of the weightingfactors in the specification (see 3.1) is intended to assist inthe tailoring of requirements to specific applications and toassist contractors in the design process. Because theimplications of the weighting factors vary with the type ofcontract and with other contract provisions, it is important toprovide clear contractual language, particularly regarding designreviews and the resolution of any subsequent actions.

6.2 Befinitions. Definitions are in accordance withMIL-STD-1540 and as indicated in the following paragraphs:

.6.2.1 Cartridae Actuated Device A cartridge actuateddevice is a mechanism which employs ihe energy produced by anexplosive charge to perform or initiate a mechanical action. Acartridge actuated device is one type of explosive ordnancedevice.

. .6.2.2 m id Weldina and Friction Welding Where interfacecontact pressures are high, 'such as on V-ban; clamp assemblies orpreloaded .release devices for deployablea, the parts may tend toadhere to each other due to cold welding'or friction welding. -Cold welding may occur where a device is held under load for longperiods of time in vacuum conditions. Friction welding may occurwhere small motions are induced at the preloaded interfaces as aresult of vibration excitation.

.6.2.3 Contractina Off- A contracting officer is aperson with the authority to e;ter into, administer, or terminatecontracts and make related determinations and findings. The termincludes authorized representatives of the contracting officeracting within the limits of their authority as delegated by thecontracting officer.

6.2.4 Critical Comuonent or As- . A critical componentor assembly is one which is not backed up by a redundant unit orfunction, and whose failure could cause complete loss of the spacevehicle or the loss of a primary portion of the mission. Anexample is the despin bearing assembly on a dual spin spacecraft.

.6.2.5 Qedoldal ConditiQa A dedoidal condition applies toharmonic drives and is the coidition where the flerspline is notconcentrically engaged with the circular spline.

6.2.6 DeDlovable A deployable is a device which is movedby a moving mechanical assembly (e.g., a drive mechanism) from astowed position on the space vehicle to an extended position -adjacent to the vehicle. Solar arrays, antennas, experimentbooms, or sun shields are classified as deployables where they

60



meet the above description. The term deployable should beinterpreted as inclusive of all devices which are deployed,retracted, or restowed.

. . .6.2.7 EXastohvdrodvnamic won Rem . Anelastohydrodynamic (EHD) lubrication regime is one in which thereis a sufficient liquid lubricant film thickness in the contactregion between the rolling element and the race to precludemetallic asperity contact.

6.2.8 Failure A failure of a device or system is an eventor condition which'causes the device or system to perform outsideof its specification limits. The failure modes include thoseassociated with functional performance, premature operation,failure to operate at a prescribed time, failure to ceaseoperation at 8 prescribed time, and others that are unique to thedevice or system.

. . .6.2.9 Fail-, Effects. and C&icalitv Ana lvsisFailure mode, effects, and criticality analysis (FMECA) is'adesign evaluation procedure which (8) documents 811 crediblepotential failures in 8 system or component design, (b) determinesby single point failure rrnalysi8 the effect of each failure onsystem operation, (c) identifies failures critical to operationalsuccess or personnel safety, or system damage, and (d) ranks eachpotential failure according to the combined influence of failureeffect, severity, and probability of occurrence.

.6.2.10 -tina Tooth A hunting tooth design describescondition where the numbe; of teeth on the driven and driving

a

gears are selected so that the same two teeth do not mesh witheach revolution of the larger of the two gears. The number ofteeth on each gear should be selected, within the limits of thegear ratio requirement, to maximize the number of revolutionsbefore meshing of the same two teeth.

. .6 . 2 . 1 1 Kinetic Torw o r P a r - The kinetic torquemargin is defined as the ratio of the driv; torque less resistingtorque (torque required to overcome friction and wire harnessbending) divided by torque required for acceleration, minus one.

The kinetic torque margin expressed in percentage is as follows:

Drive Torque - Resisting Torque 1t 1

i__Torque Required for Acceleration J

61



For linear devices, “Force” replaces ‘Torque” in thedefinition so that the kinetic force margin is defined as therat io o f the dr ive force less the res is t ing forces d iv ided bythe f o r c e required for acceleration, minus one.

The kinetic force margin expressed in percentage is as follows:

r Drive Force - Resisting Force -1= 100

I_

- 1F o r c e Required for Acceleration

J

6.2 .12 wt Los-maximum expected operating

Limit loads are defined as theloads including dispersions.

. .6 . 2 . 1 3 male Point Fw The failure of an elementin a device (or system) represenis a single point failure modeif its failure would cause the device (or system) to fail. Asingle point failure mode within a redundant device of a systemis therefore typically not a single point failure mode of thatsystem. If it is, the devices are not completely redundant.

-

.6.2.14 WC Toraue or Force naraig The static torquemargin is defined as the ratio of the dri;e torque less thetorques required for acceleration divided by the resisting torque(torque required to overcome friction and wire harness bending),minus one.

The static torque margin expressed in percentage is as follows:

rDrive Torque - Drive Torque Required for Acceleration 1f 100 I- - 1

Resisting Torque1

For linear devices, ‘Force” replaces “Torque” in thedefinition so that the static force margin is defined as the ratioof the drive force less the force required for a c c e l e r a t i o ndivided by the resisting force, minus o n e .

The static force margin expressed in percentage is as follows:

r Drive Force - Force Required for Acceleration= 100 1 - 1

1 _ Resisting Force

62

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.6.2.15 Gtrenath of Saf&y The strength marginof safety is the increment by which th; yield or ultimate loadcapability of the structure exceeds the yield or ultimateapplied load for a specific condition, expressed as a fractionof the applied load.

6.2.16 yltimate Londa Ultimate loads are the product oflimit loads (see 6.2.12) a:d the ultimate factor of safety.

6.2.13 Yield. Yield loads are the product of limitloads and the yield factor of safety.

6.3 mst Plans and Prom The test requirementsstated herein are intended to be eipanded in the qualityassurance section of the detailed specifications that may beprepared for each moving mechanical assembly. In any case, thetest requirements are the basis for preparing detailed testplans and test procedures that are required. Pass-fail criteriashould be established for all tests, and should be included inthe test plans and procedures.

The functional test sufficiency to demonstrate operationwithin all the performance requirements should be described inthe test plans. The test plans should also specify the testsequence planned for each level of assembly. In general, theextensive testing of items at the lowest level of assembly hasbeen found to be extremely cost effective. The more reliancethat is placed on vehicle or system levels of testing, thehigher the risk of not finding problems that may exist, and thehigher the cost of repairs, schedule delays, and retests thatmay be necessary if problems are found.

For each item, a cost effective acceptance test sequenceshould be determined before the start of testing. Generally,the test sequence should parallel the exposure to theenvironments in the expected flight sequence. However,following the run-in test, it is permissible to run the mostperceptive tests next and the most costly tests last, providingthat this sequence of testing does not cast doubt on theadequacy of the teat program. The qualification teat sequenceshould generally be the same as the acceptance teat sequence foreach level of assembly. Although completion of all acceptanceteats may be desirable at the component level of assembly, insome instances it may not be coat effective.some electronic devices,

For example, forthe thermal test may be a more

effective acceptance test screen than the required thermalvacuum test. In that case, the teat plan should indicate theintention to conditionally accept the component based on thethermal test, with the thermal vacuum acceptance testrequirements.being satisfied during tests at higher levels of

63


MIL-A-835778 (USAF)01 FEB 1988

assembly. In addition, some moving mechanical assemblies cannotbe completely tested at the component level because retentionlatches, mechanical stops, installation attachments or otherspace vehicle interfaces that are critical for the properperformance of the device are not present. In these cases, aconditional acceptance at the component level may berecommended. The test items still open would be listed to avoidwhat might otherwise become an oversight in conducting the spacevehicle level acceptance tests or in accepting sparecomponents. Test flow diagrams should be included which showall functional, acceptance, and qualification tests with areference to the applicable paragraph of the test plan whichdescribes the pass-fail criteria. Test plans and the criteriafor successful compliance with the test requirements should beprepared on a schedule so that they may be submitted to thecontracting officer at least 90 days before initiation of thetests. Test procedures should be approved by the contractingofficer at least 30 days before initiation of the tests.

. I6.4 Subiect Term (Key Word1 w

BearingsBrushesCold weldingDampersDeformable materialsDeployablesDry film lubricationElastohydrodynamic lubricationForce marginFriction weldingGearsHunting toothKinetic force marginKinetic torque marginLiquid lubricationLocking devicesLubricantsMoving mechanical assembliesRedundancyRelease devicesRetention devicesRun-inSequential deploymentSlip ringsSnap ringsSpringsStatic force marginStatic torque marginstops

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Torque marginViscous dampers

6.5 Sunersession Data . This issue of MIL-A-83577 is acomplete revision that supersedes all previous issues ofDOD-A-83577 for new designs. The previous issues of DOD-A-83577remain in effect to cover the procurement of previously designedequipment.

Custodian: Preparing Activity:Air Force - 19 Air Force - 19

(Project No. 1820-F015)Dot. 1557b, Arch 1234b

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MIL-A-83577B (USAF)01 FE5 1988

INDEX

--

Subiect Pacle

Acceptance tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52,53,57Alignment .......................................... 15,38,48Applicable documents ................................. 2Application .......................................... 1Assembly inspection .................................. 46,51Ball bearings ........................................ 13Bearing applications requiring low torque ripple ..... 14Bearing alignment ..................................... 15Bearings ............................................. 13Brushes ..................................... ......... 19Classification of inspections and tests .............. 44Cleanliness ................................. 16,23,36,43,47Clearance ................................ 23,34,38,47,48,49Cold welding ......................................... 16,60Commonality .......................................... 7Commutators .......................................... 20Contact rings (slip rings) ........................... 19Contamination ......................................... 42Corrosion ......................................... 8,9,13,47Craftsmanship ......................................... 43Critical component or assembly ......... 17,21,25,45,46,50,60Dampers .............................................. 22,49Data cards ............................................ 37Direct current brush motors ........................... 22Dedoidal condition .................................... 60Definitions .......................................... 60Deformable materials for damping ..................... 23Deployables .......................................... lo,60Design requirements ................................... 7Design life verification test ........................ 55Development tests ..................................... 50Dry film lubrication ................................. 18Dynamic performance .................................. 31Eddy current dampers .................................. 23Elastohydradynamic lubrication ....................... 18,61Electric motors ....................................... 20,49Electrical brushes and slip ring assemblies .......... 19Electrical and electronic equipment .................. 20Electrical wiring .................................... 20,47Electrostatic discharge ............................... 43Environmental acceptance tests ....................... 53Environmental design requirements .................... 34Environmental storage requirements ................... 36Environmental qualification tests .................... 56Equipment safety ..................................... 40

67



INDEX (Continued)

Subiect

-

Pase

Error budget ......................................... 30Fabrication environment .............................. 36Failure ............................. 8,11,12,29,31,41,58,61Failure modes and effects ....................... 23,30,39,61Fasteners ............................................ 25,46Finishes ............................................. 9First assembly inspection ............................ 51Force margin ...................................... 12,33,61Friction welding ..................................... 16,60Functional acceptance test ........................... 53Functional and environmental qualification ........... 56Gears ................................................ 24Handling .............................................. 42Handling environment ................................. 36Harmonic Drives ....................................... 25Human engineering .................................... 40Humidity and salt spray .............................. 35Hunting tooth ........................................ 24,61 -Identification and marking ........................... 37Inspection .................................. 44,45,46,51,56Inspection of assemblies .......................... 45,46,51Inspection of parts ................................... 45,46Instrumentation ...................................... 29Interchangeability ................................... 39Interface requirements ............................... 38Interface tests ...................................... 58Internal defects ..................................... 46Kinetic force margin .................................. 33,61Kinetic torque margin ................................. 33,61Launch environments .................................. 34Limit loads .......................................... 45,62Liquid lubrication ................................... 17,18Locking devices ...................................... 26Lubricant processing procedures ...................... 49Lubricants ........................................... 16Maintainability ...................................... 39Manufacturing ......................................... 41Margins ..... 12,21,23,28,31-36,39,46,50,52,54,55,57,59,61-63Materials allowables ................................. 29Materials and process selection ...................... 7,8Mechanical interfaces ................................. 39Modifications ........................................ 59Noncomforming materials ............................... 45 INotes ................................................ 59Not for Flight ........................................ 38

68



INDEX (Continued)

Subi ect PaaeOff-nominal operation ................................ 32On-orbit environments ................................ 35Operability .......................................... 39Order of precedence .................................. 6Outgassing ............................................ 43Packaging ............................................ 59Parts, materials, and process controls ............... 41,45Performance .......................................... 30Piece part inspection ................................ 46Pin puller ............................................ 12Potentiometers ....................................... 29,57Precision Gears ....................................... 25Prelaunch validation exercises ....................... 58Prelaunch validation tests ........................... 58Pressurized components ............................... 29Production lots ....................................... 42Program phases ........................................ 33Pyrotechnic devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l-' E7 60-.,dI,Qualification tests .................................. 54Quality assurance provisions ......................... 44Records ............................................... 45Redundancy ...................... lo-12,21-23,31,32,39,52,55Release devices ...................................... 11Reliability .......................................... 39Repair ............................................... 59Requirement weighting factors ........................ 6Requirements ......................................... 6Responsibility for compliance ........................ 44Reuse of bearings ..................................... 14,59Retention devices .................................... 10R e t e s t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Run-in test .......................................... 53Safety ............................................... 40Safety wiring ........................................ 26,48Scope ................................................ 1Screw threads ........................................ 25Selection of parts, materials, and processes ......... 7Sequential deployment ................................ 11Service life ......................................... 40Single point failures ................. 23,31,39,41,46,48,62Sinusoidal vibration ................................. 35Slip rings ........................................... 19Snap rings ........................................... 27Space transportation payloads ......................... 40Springs .............................................. 22,48

69



INDEX (Continued)

Subim UQS

Static torque or force margin ........................ 33,62Stepper motors ........................................ 21stops ................................................ 27Storage .............................................. 36,43Strength margins ............................... 27-29,35,63Structural interface ................................. 38Structure ............................................ 27Supplemental supports ................................ 12Surface defects ...................................... 46Switches .......................................... 29-31,48Table I ............................................... 33Tailored application ................................. 59Test fixtures ........................................ 12,58Test points and test parameters ...................... 30Test plans ........................................... 63Test sequence ........................................ 63Tolerances ........................................... 34Torque margin .................................. 21,22,30.61Torque motors ......................................... 21Torque vs angle measurement .......................... 12Transportation environment ........................... 36Ultimate loads .................................... 28,39,63Vehicle level acceptance tests ....................... 57Viscous dampers ...................................... 23,49Weighting factors .................................... 6Yield loads ....................................... 27,28,63

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