lat-pr-01967section 8.3 – structural design1 glast lat project cdr/cd-3 review may 12-16 2003 23...
Post on 02-Jan-2016
218 Views
Preview:
TRANSCRIPT
LAT-PR-01967 Section 8.3 – Structural Design 1
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003
23 Apr 2003
Martin Nordby nordby@slac.stanford.edu
With contributions from:
Youssef Ismail John Ku
Mike Foss Rich Bielawski
Michael Lovelette Jim Haughton
Eric Gawehn Larry Wai
Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope
LAT Structural SystemsLAT Structural Systems
LAT-PR-01967 Section 8.3 – Structural Design 2
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 AgendaAgenda
• Design Overview
– LAT design
– Design and interface changes since Delta PDR
– CCB actions, trade studies, and open issues
• Peer Review RFA’s and requirements
• Structural analysis model development
• Structural analysis results
– LAT modal analysis
– Distortion analysis
– Interface loads extraction
• Environmental test plans
– Integration and test flow
– Modal survey testing
– Sine vibe and sine burst testing
– Acoustic testing
– Optical and muon surveying
• Summary and conclusions
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 3
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Mechanical Design OverviewMechanical Design Overview
LAT OverviewLAT Overview
Anticoincidence Detector (ACD)
Mass 270.1 kg (Mar 2003 est)Size 1806 mm w x 1081.5 mm hInterfaces Grid bolted joint, shear pins
Electronics
Mass 199.3 kg (Mar 2003 est)Size 1417 mm sq x 222 mm hInterfaces Stand-off to CAL; thermal joint
to X-LAT Plate
Grid/X-LAT Plate/Radiators
Mass 329.3 kg (Mar 2003 est)Size 1580 mm sq x 236 mm hInterfaces Four-point mount to SC
flexures
LAT Structural Design Parameters
Design Spec
Mass 2679.4 kg <3000 kg
Center of Gravity 149.3 mm <185 mm
Width 1806 mm <1820 mm
Height 1081.5 mm 1100 mm
LAT Mass Budget and Current Estimates (kg)
Estimate Budget
TKR 504.9 510.0
CAL 1375.8 1440.0
ACD 270.1 280.0
Mech 329.3 345.0
Elec 199.3 220.0
LAT Total 2679.4 3000Source: LAT-TD-00564-6 “LAT Mass Status Report Mass Estimates for Mar 2003”
Calorimeter (CAL)
Mass 1375.8 kg (Mar 2003 est)Size 364 mm sq x 224 mm hInterfaces Grid bolted friction joint
Tracker (TKR)
Mass 504.9 kg (Mar 2003 est)Size 372 mm sq x 640 hInterfaces Grid Ti flexure mount and
Cu strap
LAT-PR-01967 Section 8.3 – Structural Design 4
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 System Block DiagramSystem Block Diagram
TKR ModuleCFC tray, side walls
Gridmonolithic alum structure
CAL Modulesalum bottom plate
Elec. Boxesalum electronics box
MLI InsulationMLI surrounding underside of LAT
ACDBase Elec Ass’y alum frame
LAT Radiatorson +/- Y sides of LAT Grid
SpacecraftLAT mounting structure
SpacecraftSC bus structure
Solar ArraysS.A. mount
MLISurrounding ACD
LAT Block DiagramLAT Block Diagram
X-LAT Platemonolithic alum structure
Radiator Mnt BktSupport Radiators at corners of Grid
EMI SkirtShields E-Boxes, supports X-LAT Pl
Htr Switch BoxesOperate Radiator heaters
Anticoincidence Detector
Tracker
Mechanical Systems
Spacecraft
Trigger and Data Flow Electronics
Calorimeter
Legend
LAT-PR-01967 Section 8.3 – Structural Design 5
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Design DetailsLAT Design Details
Grid corner detail showing heat pipes and purge grooves; corner chamfer and bottom flange
Radiator Mount at Grid corners. Note mid-side Grid Wing
Reverse-angle view of VCHP S-bends and DSHP connection TKR mid-side and corner flexures
Copper thermal straps
LAT-PR-01967 Section 8.3 – Structural Design 6
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Interface DetailsLAT Interface Details
Grid Wing with SC mount bracket
EMI Skirt push-back around SC stay-clear
LV fairing static stay-clear
PAF, per Boeing PPG
Flexure on top of octagonal SC volume
LAT-PR-01967 Section 8.3 – Structural Design 7
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Underside Design DetailsLAT Underside Design Details
Upside-down view of a Grid Y side, showing DSHP’s, Grid Wing, X-LAT Plate, and EMI Skirt
Detail of TEM, TPS, and EPU box stack
Empty boxes
EPU boxes
PDU box
GASU box
SIU boxes
TEM/TPS (16x)
LAT Underside View of LAT Underside View of Electronics BoxesElectronics Boxes
LAT-PR-01967 Section 8.3 – Structural Design 8
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Design Changes Since Delta-PDRLAT Design Changes Since Delta-PDR
• Subsystem changes affecting system performance
– Re-designed TKR bottom tray: added titanium and CFC reinforcement to CC tray
– Modified TKR flexure: accommodated updated bottom tray design and provided for stiffer cantilever mode for TKR
– Increased ACD mass: accommodated larger tile overlaps and an increase in structural stiffness/strength
• LAT internal interface changes
– Integrated Grid Wing into bottom flange• Incorporated Wing into machined Grid (no longer a bolt-on part)• Tapered the Wing into a full bottom flange around Grid perimeter to reduce stress concentrations
at SC mount, heat pipe cut-outs, and CAL-Grid tab joints
– Changed TKR thermal interface to thermal straps• Copper straps provided an improved compliant joint to the Grid
– Stiffened TKR flexure connection to Grid by eliminating the shimmed “diving board”• This was part of TKR bottom tray re-design• Effect was to increase TKR first-mode natural frequency
– Moved Electronics Box structural mount to CAL back plate• Boxes are now hard-mounted to CAL plate by way of moment-bearing stand-offs• Cleaner structural design simplified analysis and test plans for CAL and Electronics groups• Forces on the X-LAT Plate are reduced to just the inertial loads of the plate
– X-LAT plate thermal connection changed to V-Therm cloth• Test program underway
– CAL-Grid bolted joint modified to include pins• Development program underway to finalize pinned joint design• Design incorporated into CDR analysis
LAT-PR-01967 Section 8.3 – Structural Design 9
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT External Interface Changes Since Delta-PDRLAT External Interface Changes Since Delta-PDR
• Finalized Radiator dimensions and interface
– Modified Radiator aspect ratio at request of Spectrum
– Agreed on final width, based on reduction in spacing between Radiators that was requested by Spectrum
– Agreed on final height, based on Spectrum’s positioning of the LAT and PAF stay-clear agreements with Boeing
– Resulting radiator area has increased to 2.78 m2, although its efficiency has decreased
• Finalized Radiator mount location to SC
– Moved strut mounting location down at request of Spectrum
– This reduced Radiator first-mode natural frequency, but margin to 50 Hz requirements is still large
• Modified LAT-SC mount region
– Finalized bolt pattern and pad size to accommodate Spectrum’s flexure design
– Agreed to final LAT and SC stay-clear geometry around flexure
• Increased LAT envelope around ACD
– Increased enveloped by 10 mm around the base of the ACD to accommodate the lower ACD tile and connectors
– Change was approved by GLAST PO and Spectrum, and is part of the LAT baseline
LAT-PR-01967 Section 8.3 – Structural Design 10
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Design Changes Since Delta PDR (cont)Design Changes Since Delta PDR (cont)
LAT Delta PDR Design LAT Delta PDR Design July 2002July 2002
LAT CDR Design LAT CDR Design May 2003May 2003
Radiator panels widened and shortened, reducing thermal efficiencyPanels cut-out
locations fixed
SC-LAT mount region finalized
VCHP S-bends
LAT-PR-01967 Section 8.3 – Structural Design 11
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Change Control Board Changes Since Delta-PDRChange Control Board Changes Since Delta-PDR
• ACD mass growth (LAT-XR-01200-01)
– Added structural mass to increase design margins
– Added mass in scintillating tiles to increase size of tiles and overlap between tiles
• Mechanical Systems mass growth (LAT-XR-01621-01)
– Added mass for Grid box additions: Grid Wing, bottom flange, EMI Skirt stiffening, X-LAT thermal straps
– Added mass for slightly increased Radiator area
• Calorimeter mass de-allocation (LAT-XR-01642-01)
– Decreased mass allocation to reflect reduction in size of CsI logs
– Log size was reduced to accommodate tolerance stack-up within CFC box structure
• Power allocation update (LAT-XR-01998-02)
– Updated power allocations based on current measured values
– New allocations and hot-/cold-case bounds flowed to LAT-TD-00225-05, “A Summary of LAT Dissipated Power for Use in Thermal Design.”
– Updated allocations and bounds have been used for CDR thermal analysis
LAT-PR-01967 Section 8.3 – Structural Design 12
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Mechanical System Schematic DiagramLAT Mechanical System Schematic Diagram
Rad
iato
rRad
iato
rGrid Base Ass’y
CAL
TKR
ACD
X-LAT Plate
EM
I S
kir
t
RadMntBkt
Electronics
Htr SwBox
Spacecraft
LV Payload Attach Fitting
EM
I Skirt
RadMntBkt
Htr SwBox
SolarArray
SolarArray
Thermal
Structural
EMI/Grounding
Accommodation
Direction of arrow signifiesdirection of reliance, structuralsupport or heat flow
LAT Schematic DiagramLAT Schematic Diagram
Anticoincidence Detector
Tracker
Mechanical Systems
Spacecraft
Trigger and Data Flow Electronics
Calorimeter
Legend
LAT-PR-01967 Section 8.3 – Structural Design 13
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Trade Studies Since Delta PDRTrade Studies Since Delta PDR
• Moved Electronics Box structural mount to CAL back plate
– Trade issues• Hard-mounting the Electronics Boxes to the X-LAT Plates vastly increases the complexity of the
structural design, and makes verification testing of the CAL difficult• De-coupling the Electronics Boxes produces a stiffer, more testable structural design, at the cost
of a lower-conductance thermal design
– Trade conclusion• Boxes now hard-mounted to CAL plate by way of moment-bearing stand-offs• The cleaner structural design simplifies analysis and test plans for CAL and Electronics groups• Forces on the X-LAT Plate are reduced to just inertial loads of the plate
– Open issues• X-LAT Plate to Electronics Box thermal interface is still under development• V-Therm is the baseline design, but its implementation is still under development• More on this during the Mechanical Subsystem talk
• Radiator panel top profile
– Trade issue• Prior to spacecraft selection, and rectangular hole was baselined at the top of the Radiator, to
allow for integrating the VCHP’s and accessing the LAT-SC bolted joint• This design was structurally adequate, but afforded poor access to the CDR VCHP connection
design and limited access to the SC-LAT bolted joint
– Trade conclusion• Modified the Radiator panel design to include a stepped top profile• Radiator area is only marginally impacted• The stepped design allows good access along the entire top of the Radiator, under the bottom of
the ACD
LAT-PR-01967 Section 8.3 – Structural Design 14
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Structural Interface Open IssuesStructural Interface Open Issues
• CAL-Grid structural joint
– Issue: joint has recently been changed from an all-friction joint to a pinned joint, but analysis and development testing are not yet complete
– Closure plan• Structural analysis underway CDR analysis results will be used to finalize joint limit loads• Joint testing is underway Coupon tests will establish joint allowables• Process development work underway Pinned liquid-shim application processes (and the
impact on the joint design) are understood; final process qualification is underway
• X-LAT Plate to Electronics box thermal joint
– Issue: thermal strap design was recently abandoned in favor of V-Therm carbon fiber cloth, with much testing yet to be done
– Closure plan• Materials testing• Contamination studies and testing• Thermal properties testing• Joint design and tolerance study
• Radiator-SC strut angle
– Issue: Spectrum has proposed to change the IRD baseline and angle support struts holding the bottom of the Radiator
– Closure plan
LAT-PR-01967 Section 8.3 – Structural Design 15
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Structural RFA’s from Peer ReviewStructural RFA’s from Peer Review
ID # Status RFA Description RFA Response/Closure Plan
Mech-2
Subm itted for closure (21 Apr 2003)
Provide details of the TKR-Grid s tructural interface and fabrication plans
A TKR m odule is m ounted to the Grid by way of 8 flexures , They extend down through the bay cut-out in the Grid top flange, and bolt to the s ide of the top flange with 12 shoulder bolts—1 bolt per corner flexure and 2 bolts per m id-s ide flexure. These m ounts provide the sole m eans of both TKR m odule alignm ent and s tructural support.
On the TKR s ide of the interface, the holes in the flexure are es tablished during assem bly of the bottom tray. The tray close-out is assem bled us ing a jig which accurately locates the 4 titanium corner bosses and close-out s ide pieces . The jig also holds these in place during curing of the s tructural adhes ive which holds the pieces together. As part of this assem bly process , the corner flexures are pinned and bonded to the titanium corner bosses). Once the tray is cured, holes are m achined in the corner flexures us ing drill bushing that are m achined into the assem bly jig. Likewise, the m id-s ide flexures are accurately located on the close-out and bonded in place, us ing the jig for alignm ent.
The result of this process is 12 flexure holes which are 25 m icrons overs ized, located to an absolute accuracy of 12 m icrons (TBD) with respect to the bottom tray. During m odule s tacking, and wall bolt-up, the perpendicularity of the s idewalls is es tablished by the bottom tray. Thus , the overall alignm ent of a m odule is held very tightly, with little tolerance build-up, with respect to the holes in the flexures .
On the Grid s ide of the interface, the m ating hole features for m ounting the flexures are counterbored holes and tapped holes for locating the shoulder bolt and carrying shear, and a for locking the bolt in place. The holes are pos itioned and drilled us ing a jig . This jig is fabricated with the bottom tray assem bly jig, and the m ating holes are m atch-drilled. This ensures that the flexure and Grid holes line up exactly, to the degree of repeatability of the hole drilling process . On the Grid s ide of the interface, the counterbored holes are expected to be aligned to within 25 m icrons (TBR) with respect to true pos ition. The jig will be pos itioned in the Grid bay by two pins located on the top flange of the Grid. Vertical pos ition and pitch/yaw attitude of the jig will be es tablished with respect to the Grid prim ary datum feature (the bottom of the Grid at the corners ) and not the local surface of the top flange. This elim inates the tipping error associated with the planarity tolerance of the Grid top surface.
A secondary issue associated with TKR m odule pos itioning is assuring that the flexures can provide adequate range of flexing in their as -ins talled pos ition. This is determ ined by the tolerance of pos ition and perpendicularity of the Grid top flange s idewall with respect to the flexures on the orthogonal s idewalls . To accom m odate this need, the Grid top flange s idewalls will be toleranced with respect to the sam e pin holes in the bay that are used to pos ition flexure holes . This elim inates tolerance build-up which would lim it the flexure range-of-travel. TKR flexures requirem ents are that they be pos itioned to within +/- 0.2 m m (TBR) of their true pos ition. Current plans for Grid m achining include m achining the s idewalls to a profile tolerance of 0.25 m m (double-s ided), which provides 0.15 m m of m argin.
LAT-PR-01967 Section 8.3 – Structural Design 16
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Structural RFA’s from Peer Review (cont 1)Structural RFA’s from Peer Review (cont 1)
ID # Status RFA Description RFA Response/Closure Plan
Mech-3
Subm itted for closure (21 Apr 2003)
Conduct fail-safe analys is of fas teners at all bolted interfaces
Stress analys is of all bolted interfaces has (or will) show pos itive m argins for all joints and bolting hardware. Furtherm ore, qualification tes ting at the subsys tem level will dem onstrate that the des ign can endure loads and s tresses associated with protoflight or qualification environm ents . Finally, all bolted joints will be subjected to verification tes ting at either the subsys tem or LAT level (or both) to verify workm anship. The GLAST PO and LAT cons ider this adequate for m itigating the risk of fas tener problem s during launch.
Mech-4
Subm itted for closure (21 Apr 2003)
Evaluate effect of over-cons traint at the LAT-SC interface on pointing error
This is one of m any load cases planned to be analyzed in evaluating the coupling of the LAT and SC as it relates to pointing knowledge error. The LAT plans to run these analyses following com pletion of the CDR des ign load case analyses .
Mech-5
Subm itted for closure (21 Apr 2003)
Static load cases should include a 0 g or tens ion load in the thrus t direction with lateral loads
Tens ion/negative thrus t accelerations have been added to the lis t of LAT load cases , for com pleteness . Results of these load cases will be part of the CDR s tructural results .
Mech-6
Subm itted for closure (21 Apr 2003)
Incorporate updated X-LAT, E-Box, and interface des igns into CDR s tructural and therm al-m echanical analyses
The Peer Review s tructural m odel did not include the recent changes to the electronics box s tructural m ounting to the CAL and X-LAT Plates . These changes have now been incorporated into the m odel, and interface loads presented at the CDR will include these interfaces . Furtherm ore, s tructural load cases for extrem e qualification-level therm al environm ents have been m odified to adequately bound these extrem es (see also Mech RFA #24).
Mech-7
Subm itted for closure (21 Apr 2003)
Add to LAT Environm ental Spec a loads recovery section for the X-LAT to E-Box interface loads .
The LAT-SS-00778 “LAT Environm ental Specification” already includes interface s tructural requirem ents at the E-Box to X-LAT interface. This is specified in the form of peak transverse m isalignm ent that m ust be accom m odated by either s ide of the interface. This will be updated as part of the CDR analys is , and peak loads at this interface will be added.
Mech-8
Subm itted for closure (21 Apr 2003)
Provide delivery date for full-up LAT FEM dynam ic m odel
Current plans are to deliver the LAT CDR FEA m odel 4 weeks after the close of the CDR, assum ing there are no CDR RFA’s which im pact the FEA m odeling.
LAT-PR-01967 Section 8.3 – Structural Design 17
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Structural RFA’s from Peer Review (cont 2)Structural RFA’s from Peer Review (cont 2)
ID # Status RFA Description RFA Response/Closure Plan
Mech-9
Subm itted for closure (21 Apr 2003)
Perform subsys tem and LAT FEA m odel quality checks
Verification of subsys tem m odels and m odel integration into the LAT FEA m odel is planned. Results of this will be part of the CDR m aterial. Verification tes ts that are being run on all subsys tem m odels :
Subsys tem m odel evaluationReview m odel—units , orientation/coordinate sys tem , s ize, m esh resolutionReview delivery report—do the report and m odel agree
FEA m odel check-runsFree-free m odal analys is—check m odel for m echanism sTrans lation check—check m odel for inadvertent groundingGravity check—check that inertial loads are reacted only at boundariesTem perature check—check that s tructure is free to expand/contract
Analys is com parison runsMass—com pare m odel m ass with subsys tem es tim ateCenter of m ass—com pare m odel center of m ass with subsys tem es tim ateModal analys is—check agains t subsys tem detailed m odel and report
Mech-11
Subm itted for closure (21 Apr 2003)
Com plete LAT internal ICDs, IDDs and lis t any open issues at CDR
The following is a lis t of ICD’s and IDD’s within the LAT, and their s tatus as of the response date lis ted:
LAT-DS-00040-09: LAT Ins trum ent Layout—released (14 Apr 03)LAT-DS-00038-4: LAT Ins trum ent Layout—firs t draft being checked (14 Apr 03)LAT-DS-00233-3: CAL-LAT IDD—final check prior to release (14 Apr 03)LAT-SS-00238-4: CAL-LAT Mech, Therm , Elec ICD--releasedLAT-DS-00309-1: ACD-LAT IDD—final check prior to release (14 Apr 03)LAT-SS-00363-4: ACD-LAT Mech, Therm , Elec ICD--releasedLAT-DS-00851-1: TKR-LAT IDD—firs t draft underway (14 Apr 03)LAT-SS-00138-5: TKR-LAT Mech, Therm ICD—releasedLAT-DS-01630-1: Electronics -LAT IDD—firs t draft underway (14 Apr 03)LAT-SS-01794-1: Elec-LAT Mech, Therm ICD—firs t draft underway (14 Apr 03)
Mech-17 21-Apr-03Detail required acous tic tes t M-GSE des ign inform ation needed from Spectrum
LAT-PR-01967 Section 8.3 – Structural Design 18
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Structural RFA’s from Peer Review (cont 3)Structural RFA’s from Peer Review (cont 3)
ID # Status RFA Description RFA Response/Closure Plan
Mech-18
Subm itted for closure (21 Apr 2003)
Cons ider reques ting a set of S/C flexures to use during dynam ic tes ting of LAT
SC flexures have been cons idered for use during LAT environm ental tes ting, but their use has not been baselined. While the use of the SC flexures is conceptually appealing, the logis tics and com plications of im plem enting them into the LAT tes t planning was deem ed not worth the additional cos t (dollars and risk) associated with us ing them . (See also RFA #Mech-35)
Mech-19
Subm itted for closure (21 Apr 2003)
Conduct cross-orthogonality check of tes t ins trum entation with full FEA m odel
Pre-tes t analys is is planned for all LAT dynam ics tes ts , but will not be com pleted until after CDR.
Mech-20 21-Apr-03For all ins trum entation that flies , update relevant m ass report entries for these item s
Mech-24Approved (21 Apr 2003)
Use QT’s for therm al load cases chosen for s tructural analys is
The therm al soak s tructural load case has been m odified to reflect wors t-case hot and cold survival soak tem peratures for subsys tem s. Results of this load case will be part of the CDR m aterial
Mech-35Response written (22 Apr 2003)
Evaluate perform ing LAT m odal survey and s ine vibe tes ting us ing spacecraft flexures
SC flexures have been cons idered for use during LAT environm ental tes ting, but their use has not been baselined. While the use of the SC flexures is conceptually appealing, the logis tics and com plications of im plem enting them into the LAT tes t planning was deem ed not worth the additional cos t (dollars and risk) associated with us ing them . (See also RFA #Mech-18)
LAT-PR-01967 Section 8.3 – Structural Design 19
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Requirements Flow-DownLAT Requirements Flow-Down
M AR
EM I R qm ts. D oc.
LATEnvironm enta lSpecification
LAT-SS-00778
M ission SystemSpecification
433-SPEC -0001
ScienceR equirem ents
D ocum ent433-SR D -0001
LAT-SC InterfaceR equirem ents
D ocum ent433-IR D -0001
LAT Perform anceSpecification
LAT-SS-00010
LAT IO CPerform anceSpecification
LAT-SS-00015
AC D SubsystemSpecification
LAT-SS-00016
TKR SubsystemSpecification
LAT-SS-00017
C AL SubsystemSpecification
LAT-SS-00018
Trigger &D ataflow Subsys.
SpecificationLAT-SS-00019
SASSubsystem
SpecificationLAT-SS-00020
LO FSubsystem
SpecificationLAT-SS-00021
Pow erSubsystem
SpecificationLAT-SS-00136
M echanicalSubsystem
SpecificationLAT-SS-00115
Mis
sio
nL
eve
l 2a
LA
TL
eve
l 2b
LA
T S
ub
syst
emL
eve
l 3
ScienceR qm ts
M issionR qm ts
Interface R qm ts
Interface R qm ts
TC S Perform anceSpecification
LAT-SS-00715
SAS D esignSpecification
LAT-SS-00505
C AL D esignSpecification
LAT-SS-00210
LAT TriggerSpecification
LAT-SS-00284
LAT TKR D esignSpecification
LAT-SS-00134
LAT O perationsFacility
SpecificationLAT-SS-01783
Tow er Pow erSupplies
SpecificationLAT-SS-01537
AC D D esignSpecification
LAT-SS-00352
Des
ign
Sp
ec
ific
ati
on
Lev
el 4
LAT D ataflowSpecification
LAT-SS-00285
LAT F light SWSpecification
LAT-SS-00399
LAT R eadoutE lectronic
SpecificationLAT-SS-00152
R adiator D esignSpecification
LAT-SS-00394
X-LAT P lateD esign
SpecificationLAT-SS-01240
G rid Box D esignSpecification
LAT-SS-00775
1553 D efin ition
LAT-SC InterfaceC ontro l D ocum ent
M ission G roundSystem
R equirem entD ocum ents
LAT IO C /M O C /SSC Interface
C ontro lD ocum ents
LAT-G BMInterface C ontro l
D ocum ent
In Developm ent
LAT-PR-01967 Section 8.3 – Structural Design 20
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Key LAT Configuration and Structural RequirementsKey LAT Configuration and Structural Requirements
Parameter Req. Design Margin Comply Ver Driving Req.LAT Configuration
LAT mass allocation < 3000 kg 2679.4 kg 320.6 kg Y MIRD 3.2.2.4/ MSS 3.3.1.9.3
LAT vertical center of mass above LIP < 185 mm 149.3 mm 35.7 mm Y M IRD 3.2.2.5LAT lateral center of mass off Z-axis < 20 mm 1.26 mm 18.74 mm Y M IRD 3.2.2.5LAT moment of inertia about X-, Y-axes < 1500 kg-m2 1058 kg-m^2 442 kg-m^2 Y A IRD 3.2.2.7LAT moment of inertia about Z-axis < 2000 kg-m2 1340 kg-m^2 660 kg-m^2 Y A IRD 3.2.2.7LAT stay-clear envelope as shown in IRD Appendix A
OK IRD 3.2.2.2
LAT mount to SC as shown in IRD Appendix A
1550 mm separation
OK IRD 3.2.2.3
Max Radiator area < 5.88 m^2 5.57 m^2 0.31 m^2 Y I IRD 3.2.3.4.1Configured as 2 separate Radiators OK Y I IRD 3.2.3.4.1Radiator max width < 1.903 m 1.896 m 7 mm Y I IRD 3.2.3.4.1Positioned according to IRD App. A > 1.84 m sep 1.863 m 22.6 mm Y I IRD 3.2.3.4.2Mount point for Radiator support as shown in IRD Appendix A
1.177 m below LIP
OK Y I IRD 3.2.3.4.3
Structural, LoadsFixed-base first-mode > 50 Hz 11% Y T IRD 3.2.2.8.1.2
TKR alignment during normal LAT operation< 7arc-sec 1s
radial4.1 arc-sec
peak-to-peak2.9 arc-sec +
5sY T, A
MSS 3.3.1.11.1.2
Static-equivalent launch loads per MSS OK Y T, A IRD 3.2.2.8.2Sinusoidal vibration launch loads per MSS OK Y T IRD 3.2.2.8.9Acoustic launch loads per MSS OK Y T IRD 3.2.2.8.5
Notes: IRD: LAT-SC Interface Requirements Document (433-IRD-0001) M: MeasureMSS: Mission Systems Specif ication (433-SPEC-0001) A: AnalysisOK: design incorporates requirement I: InspectY: Yes, design has been show n to meet req T: TestN: No, design does not meet reqP: Planned--design likely meets req, but has not been demonstrated yet
LAT-PR-01967 Section 8.3 – Structural Design 21
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Integrated Structural FEA ModelLAT Integrated Structural FEA Model
• LAT structural model moved to NASTRAN
– Changed FEA software from ANSYS to NASTRAN to make it more compatible with GLAST project office
– Re-built model to improve dynamic analysis capabilities
– Model is used to generate system structural response and interface limit loads
• Subsystem models updated
– New TKR model from Hytec—including bottom tray and flexure design modifications
– Updated ACD model from GSFC—with new mass baseline
– Incorporated reduced CAL model from NRL
– New Radiator model from LM—including size and mount point modifications
– Re-built electronics—new model based on current E-Box and interface designs
– Grid Box model modified—integrated Wing and X-LAT Plate modifications have been included
LAT Finite Element ModelLAT Finite Element Model
NEW Picture
LAT-PR-01967 Section 8.3 – Structural Design 22
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003
Subsystem Check TKR CAL ACD Elec Rad XLAT Grid Comments Evaluation CriteriaSubsystem FEA reviewUnits check ü metric used; units consistent yes/noOrientation/coord sys correctly oriented in LCS yes/noMesh size size suitable for LAT modelMesh resolution, qlty resolution error is acceptable est mesh density error < 20%Review report report and model agree yes/noSubsystem FEA check runsFree-free evaluate mechanisms, DOF's no mechanisms; 6 DOF'sTranslation check unit translation, rotation no groundingGravity check reaction force check forces sum to mass
Temperature checktemp increase to check for grounding, conductivity
no grounding; thermally conductive
Mass compare to mass estimate FEA mass within 5% of estCenter of mass compare to mass estimate FEA c.g within 5 mm of est
Modal analysischeck against subsystem detailed model and report
Mode shapes, freq's agree with subsystem report to 2 Hz
Subsystem FEA Model Quality ChecksSubsystem FEA Model Quality Checks
• Subsystem model evaluation
– Review model—units, orientation/coordinate system, size, mesh resolution
– Review delivery report—do the report and model agree
• FEA model check-runs
– Free-free modal analysis—check model for mechanisms
– Translation check—check model for inadvertent grounding
– Gravity check—check that inertial loads are reacted only at boundaries
– Temperature check—check that structure is free to expand/contract
• Analysis comparison runs
– Mass, center of mass—compare with subsystem estimate
– Modal analysis—check against subsystem detailed model and report
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 23
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT FEA Model Boundary ConditionsLAT FEA Model Boundary Conditions
• Accelerations
– Used LAT center-of-mass accelerations from LAT Environmental Spec. for structural load cases
• SC mount boundary condition mimics flexure-type connection
– X-Side SC mount• Restrained in the Y- and Z-directions• Free in all 3 rotational DOF’s and X
– Y-Side SC mount• Restrained in the X- and Z-directions• Free in all 3 rotational DOF’s and Y
• Radiator mounting
– Radiators mounted to Grid through Radiator Mount Bracket
– SC boundary condition fixed in Y-direction (out-of-plane) only
LAT F.E.A. Properties and Current LAT EstimatesLAT F.E.A. Properties and Current LAT Estimates
Source: LAT-TD-00564-06 “LAT Mass Status Report, Mass Estimates for Mar 2003,” 7 Mar 2003
LAT Static-Equivalent Design AccelerationsLAT Static-Equivalent Design Accelerations
Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003
LAT F.E.A. Model MetricsLAT F.E.A. Model Metrics
LAT F.E.A. Current LAT Est.Subsystem Mass
(kg)Center of
Gravity (m)Mass (kg)
Center of Gravity (m)
TKR 1 1.00 505 230.0CAL 1376 -148.8ACD 270 318.2Radiators 77 -1368.6Grid Box 253 -218.0Elec. Boxes 199 -352.9Total 1 1.00 2679 -86.9
Model Feature Quantity
NodesTotal elementsPoint elementsShell elementsBeam elements
LAT Design Unit
Launch EventLift-Off/ Airloads
MECO
Lateral 5.1 0.2 gAxial (Z) +4.1/-1.4 +6.8 g
UPDATE
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 24
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT FEA Model Quality ChecksLAT FEA Model Quality Checks
• FEA model check-runs
– Free-free modal analysis—check model for mechanisms
– Translation check—check model for inadvertent grounding
– Gravity check—check that inertial loads are reacted only at boundaries
– Temperature check—check that structure is free to expand/contract
• Analysis comparison runs
– Mass—compare model mass with LAT estimate
– Center of mass—compare model center of mass with LAT estimate
– Modal analysis—compare subsystem modes in LAT model against fixed-base results
LAT Model Check TKR CAL ACD Elec Rad XLAT Grid Comments Evaluation CriteriaFree-free ü evaluate mechanisms, DOF's no mechanisms; 6 DOF'sTranslation check unit translation, rotation no groundingGravity check reaction force check forces sum to mass
Temperature checktemp increase to check for grounding, conductivity
no grounding; thermally conductive
Mass compare to mass estimate FEA mass within 5% of estCenter of mass compare to mass estimate FEA c.g within 5 mm of est
Modal analyisiscompare subsystem modes to fixed-base results
Modes, freq's consistent w/ subsystem results
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 25
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Launch and On-Orbit Load Case DefinitionsLaunch and On-Orbit Load Case Definitions
Launch Structural Load CasesLaunch Structural Load Cases
Launch X Y Z Configuration/CommentsStatic-Equiv.Modal on SC Mount Flight config. Supports fixed in Z and hoop, free radially
ð Lift-Off/Airloads 1 +5.1g 0 g +4.1g Flight config. LAT is +X/-X symmetricð Lift-Off/Airloads 2 0 g +5.1g +4.1g Flight config. LAT is +Y/-Y symmetricð Lift-Off/Airloads 3 +3.6 g +3.6 g +4.1 g Flight config. Diagonal lateral acceleration
Lift-Off/Airloads 4 -3.6 g +3.6 g +4.1 g Flight config. Diagonal lateral accelerationð Lift-Off/Airloads 5 +5.1g 0 g -1.4 g Flight config. ð Lift-Off/Airloads 6 0 g +5.1g -1.4 g Flight config. ð Lift-Off/Airloads 7 +3.6 g +3.6 g -1.4 g Flight config. Diagonal lateral acceleration
Lift-Off/Airloads 8 -3.6 g +3.6 g -1.4 g Flight config. Diagonal lateral accelerationð MECO 1 +0.2 g 0 g +6.8g Flight config.
MECO 2 0 g +0.2 g +6.8g Flight config. MECO 3 + 0.14 g + 0.14 g +6.8g Flight config. Diagonal lateral acceleration
Subsystem TemperatureOn-Orbit Thermal TKR CAL ACD Elec Rad XLAT Grid Configuration/Comments
ð Cold survival soak -30 -30 -40 -40 -67 -40 -40 Cold surv temp's imposed on struc modelð Hot survival soak 50 50 45 60 60 40 40 Hot surv temp's imposed on struc model
Hot-case Temps mapped from thermal model resultsCold-case Temps mapped from thermal model resultsThermal transient Temps mapped from thermal model results +/- 3C/95 min period
On-Orbit Thermal Load CasesOn-Orbit Thermal Load Cases
LAT-PR-01967 Section 8.3 – Structural Design 26
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Integration and Test Load Case DefinitionsIntegration and Test Load Case Definitions
I&T Load Case X Y Z Configuration/Comments
Integration, TransportIntegration 1 0 g 0 g +1 g 4 corner mounts in GPR. No Rad, X-LAT, or ACDIntegration 2 +1 g 0 g 0 g 4 corner mounts in GPR, rotated 90 deg. No Rad, X-LAT, or ACDIntegration 3 0 g 0 g -1 g 4 corner mounts in GPR, upside down. No Rad, X-LAT, or ACD
ð Integration 4 0 g 0 g +1 g 4 corner mounts in GPR. No Rad, with X-LAT, ACDð Integration 5 +1 g 0 g 0 g 4 corner mounts in GPR, rotated 90 deg. No Rad, with X-LAT, ACD
Integration 6 0 g 0 g -1 g 4 corner mounts in GPR, upside down. No Rad, with X-LAT, ACDð Crane lift 1 +1 g 2 GPR corner supports carrying entire load. No Rad
Transport 1 M 4 corner mounts in GPR on transport stand. No RadTransport 2 +1 g 4 corner mounts in GPR on transport stand. No RadTest ConfigurationsSurvey 1 0 g 0 g -1 g 3-pt mid-side support, in GPR. No Rad
ð Survey 2 +1 g 0 g 0 g 3-pt mid-side support, rotated 90 deg in GPR. No RadModal survey M 4-pt mid-side support on modal survey stand. No RadSine vibe 1 Flight interface to vibe test stand. No RadAcoustic 1 1 g Flight interface to acoustic test stand. With RadT-Vac 1 1 g 3-pt mid-side flight mount to T-Vac stand. Sideways. With Rad
Subsystem TemperatureI&T Thermal TKR CAL ACD Elec Rad XLAT Grid Configuration/Comments
Chill-bar cooled 3-pt mid-side mount; chill bars on X-sidesð 40C bake-out soak 40 40 40 40 40 40 40 Bake-out temp's imposed on struc model
T-Vac cold-case Temps mapped from thermal model results 3-pt mid-side mount on T-Vac standT-Vac hot-case Temps mapped from thermal model results 3-pt mid-side mount on T-Vac stand
Integration and Test Structural Load CasesIntegration and Test Structural Load Cases
Integration and Test Thermal Load CasesIntegration and Test Thermal Load Cases
LAT-PR-01967 Section 8.3 – Structural Design 27
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Modal Analysis ResultsModal Analysis Results
• 10 modes below 75 Hz
– 1 significant LAT modes
– Multiple ACD panel, BEA vibration modes
– Multiple Radiator modes and mode combinations
• LAT drumhead mode
– Hz at 2679 kg estimate
– Hz at 3000 kg allocation
Significant LAT ModesSignificant LAT Modes
LAT Drumhead ModeLAT Drumhead Mode
# Freq. Effective Mass Fraction Mode Description
123456789
10CAL shearing modeTKR cantilever tipping modeCAL z-axis drumhead mode
Parameter Req Design Margin Comply
LAT natural frequency > 50 Hz Y
UPDATE
UPDATE
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 28
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Summary of Key Deflections Due to Launch LoadsSummary of Key Deflections Due to Launch Loads
• Grid Deflection
– 6.8 g thrust load at MECO produces maximum Grid bowing
– Grid max deflections• Center: mm• Corner: mm
• TKR Gap closing
– Dishing of the Grid tends to tip TKR modules together
• Max gap closing: mm• Budget: mm
• Radiator distortion
– In-plane max motion: mm
– Out-of-plane max bowing: mm
LAT Deflected Shape PlotLAT Deflected Shape Plot
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 29
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Interface DeflectionsInterface Deflections
• Deflections and relative motions extracted directly from integrated FEA model
• Relative motions at interfaces are part of LAT Environmental Spec interface loads definition
LAT Deflections Static-Equiv Acceleration LAT Internal Deflections and Relative Motions
X Y Z
Gri
d c
ente
r ax
ial
Gri
d c
orn
er
axia
l
Gri
d c
ente
r X
TK
R la
tera
l gap
cl
osi
ng
AC
D-T
KR
gap
cl
osi
ng
Rad
iato
r U
x
Rad
iato
r o
ut-
of-
pla
ne
Eb
ox-
XL
AT
re
lati
ve m
oti
on
Delta PDR Predict
CDR Max PredictLaunch StaticLift-Off/Airloads 1 +5.1g 0 g +4.1gLift-Off/Airloads 2 0 g +5.1g +4.1gLift-Off/Airloads 3 +3.6 g +3.6 g +4.1 gLift-Off/Airloads 5 +5.1g 0 g -1.4 gLift-Off/Airloads 6 0 g +5.1g -1.4 gLift-Off/Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit ThermalCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Thermal40C bake-out soak
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 30
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Interface Load RecoveryInterface Load Recovery
• The LAT Environmental Specification is the collection point for interface loads for subsystem design and test
• Current load tables in the LAT Environmental Specification contain results from the Delta-PDR structural model (also being used for the current CLA cycle)
– Some interface limit loads were generated by LAT static-equivalent analyses
– Some limit loads were gleaned from the preliminary CLA, completed in December, 2001
• The goal of CDR analysis is to generate updated loads, based on the CDR design, and compare with Delta-PDR design values
– Include results for all load cases to assure that worst-case loads have been captured
– Identify interfaces and load cases where CDR analysis shows higher predicts than earlier analysis develop action plan to resolve these issues
– Identify interfaces where loads have come down considerably investigate reducing limit loads in the Environmental Specification, to increase design margin
LAT Mech PDR Structural AnalysisAug, 2001
LAT PDR Structural AnalysisJan, 2002
Prelim CLA Results OutDec 2001-Mar, 2002
Deliver Mech PDR LAT FEA (Sep,
2001)
LAT Delta-PDR Structural AnalysisAug, 2002
Deliver Delta- PDR LAT FEA (Sep,
2002)
LAT CDR Structural AnalysisMay, 2003
LAT Env SpecMar, 2003
SC Study II Struc Models
Deliver CDR LAT FEA
(Jun, 2003)
Spectrum Proposal
Struc Model
Mission PDR CLA Results OutMay, 2003
LAT Env SpecJun, 2003
Spectrum PDR Struc
Model
Mission CDR CLA Results OutSep, 2003
LAT Env SpecOct, 2003
LAT Structural Analysis Flow-down ScheduleLAT Structural Analysis Flow-down Schedule
LAT-PR-01967 Section 8.3 – Structural Design 31
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003SC-LAT Interface Load RecoverySC-LAT Interface Load Recovery
• Loads shown are the maxima for all 4 mount points, for the static-equivalent load cases shown
• Environmental Spec loads are the result of the preliminary CLA
SC-LAT Loads Static-Equiv Acceleration Forces Along Axes Mom ents About Axes
X Y Z R (N)Theta
(N) Z (N)R (N-m )
Theta (N-m )
Z (N-m )
Env Spec loads 29 23778 29625 270 160 222
MaxLaunch StaticLif t-Of f /Airloads 1 +5.1g 0 g +4.1gLif t-Of f /Airloads 2 0 g +5.1g +4.1gLif t-Of f /Airloads 3 +3.6 g +3.6 g +4.1 gLif t-Of f /Airloads 5 +5.1g 0 g -1.4 gLif t-Of f /Airloads 6 0 g +5.1g -1.4 gLif t-Of f /Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit Therm alCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Therm al40C bake-out soakUPDATE
LAT-PR-01967 Section 8.3 – Structural Design 32
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Radiator Interface Load Recovery Radiator Interface Load Recovery
• Loads are derived from the LAT static-equivalent analysis, using LAT center-of-gravity accelerations
• The preliminary CLA of the LAT/Radiators on a generic spacecraft predicted a maximum strut load of only 365 N, so the CLA does not produce the limit load for this interface
• Acoustic analysis predictions could alter these limit loads for the interface to the SC mount struts
Rad-Rad Mnt Bkt Static-Equiv Acceleration
X Y ZIn-Plane
Lateral (N)Norm al to Plane (N) Z-Axis (N)
Env Spec loads 795 266 1336
MaxLaunch StaticLif t-Of f /Airloads 1 +5.1g 0 g +4.1gLif t-Of f /Airloads 2 0 g +5.1g +4.1gLif t-Of f /Airloads 3 +3.6 g +3.6 g +4.1 gLif t-Of f /Airloads 5 +5.1g 0 g -1.4 gLif t-Of f /Airloads 6 0 g +5.1g -1.4 gLif t-Of f /Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit Therm alCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Therm al40C bake-out soak
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 33
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003TKR Interface Load RecoveryTKR Interface Load Recovery
• TKR Flexure joint
– Flexures isolate the carbon-fiber TKR structure from thermal strains of the Grid
– All flexure normals point to the center of a TKR module
– The 8 flexures are not a kinematic mount
• TKR Flexure force recovery
– Nodal forces are retrieved by isolating nodal forces at the TKR Flexure beam elements
– Design limit loads are the maximaof the TKR module loads
• Limit loads identified for peak compressive, tensile, and shear load
• Peak loads all occur in corner bays
TKR-Grid Flexures Static-Equiv Accleration Mid-Side Flexures Corner Flexures
X Y ZShear
(N)Radial
(N)Tens/
Comp (N)Shear
(N)Radial
(N)Tens/
Comp (N)
Env Spec loads 2266 391 1003 1277
MaxLaunch StaticLift-Off/Airloads 1 +5.1g 0 g +4.1gLift-Off/Airloads 2 0 g +5.1g +4.1gLift-Off/Airloads 3 +3.6 g +3.6 g +4.1 gLift-Off/Airloads 5 +5.1g 0 g -1.4 gLift-Off/Airloads 6 0 g +5.1g -1.4 gLift-Off/Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit ThermalCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Thermal40C bake-out soak
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 34
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003
CAL Tab Loads Static-Equiv Acceleration Pinned Tab Bolted Tab
X Y Z Shear (N)Pull-Out
(N)Pry Mom ent
(N-m )
Env Spec loads 4377 654 1.28
MaxLaunch StaticLif t-Of f /Airloads 1 +5.1g 0 g +4.1gLif t-Of f /Airloads 2 0 g +5.1g +4.1gLif t-Of f /Airloads 3 +3.6 g +3.6 g +4.1 gLif t-Of f /Airloads 5 +5.1g 0 g -1.4 gLif t-Of f /Airloads 6 0 g +5.1g -1.4 gLif t-Of f /Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit Therm alCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Therm al40C bake-out soak
CAL Interface Load RecoveryCAL Interface Load Recovery
• CAL-Grid tab joint
– Pins carry all shear load at joint
– Bolts carry pull-out and prying loads
• Load recovery
– Tab loads separated into 2 types• Shear tabs• Bolted tabs
– All tabs designed to peak limit loads
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 35
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003ACD Interface Load RecoveryACD Interface Load Recovery
• ACD Base Electronics Assembly (BEA) to Grid Joint
– Bolted connection at 4 corners of BEA carry z-direction (thrust) loads only
– Bolted and pinned connections at the center of each of the 4 sides
• Interface load recovery
– Interface loads evaluated by retrieving nodal forces at rigid extension from Grid to BEA
– Loads shown are design loads for each bolt/pin
• Mid-Side Mounts
– Shear: RSS of X, Z shears in plane of Grid wall
– Tens/Compression: normal to Grid wall
• Corner Mounts
– Shear: assumed to carry no shear
– Tens/Compression: parallel to LAT Z-axis
ACD-Grid Mounts Static-Equiv Acceleration Mid-Side Mounts Corner Mounts
X Y ZShear
(N)Tens/Com p
(N)Shear
(N)Tens/Com p
(N)
Env Spec loads 4402 2223 0 1787
MaxLaunch StaticLif t-Of f /Airloads 1 +5.1g 0 g +4.1gLif t-Of f /Airloads 2 0 g +5.1g +4.1gLif t-Of f /Airloads 3 +3.6 g +3.6 g +4.1 gLif t-Of f /Airloads 5 +5.1g 0 g -1.4 gLif t-Of f /Airloads 6 0 g +5.1g -1.4 gLif t-Of f /Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit Therm alCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Therm al40C bake-out soak
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 36
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Electronics Interface Load RecoveryElectronics Interface Load Recovery
• Electronics Box joints
– Rigid stand-offs to the CAL carry z-direction (thrust) loads, and lateral loads and moments
– Flexible connection to the X-LAT Plates allow transverse motion while providing compressive pre-load
• CAL interface load recovery
– Limit loads extracted from model
– Loads shown are at the base (CAL side) of the stand-off
• X-LAT Plate interface load recovery
– Lateral, shearing loads defined to be zero: connection allows lateral motion
– Tension/compression loads arise from deflection of the Grid
Ebox-CAL Stand-Off Static-Equiv Acceleration Interface Load at Base of Stand-Off XLAT-Ebox
X Y ZTension
(N)Com p
(N)Shear
(N)Bending
(N-m )Tens/Com p
(N)
Env Spec loads 3750 2625 1288 19.3
MaxLaunch StaticLif t-Of f /Airloads 1 +5.1g 0 g +4.1gLif t-Of f /Airloads 2 0 g +5.1g +4.1gLif t-Of f /Airloads 3 +3.6 g +3.6 g +4.1 gLif t-Of f /Airloads 5 +5.1g 0 g -1.4 gLif t-Of f /Airloads 6 0 g +5.1g -1.4 gLif t-Of f /Airloads 7 +3.6 g +3.6 g -1.4 gMECO 1 +0.2 g 0 g +6.8gOn-Orbit Therm alCold survival soakHot survival soakInt., TransportIntegration 4 0 g 0 g +1 gIntegration 5 +1 g 0 g 0 gCrane lif t 1 +1 gTest Config'sSurvey 2 +1 g 0 g 0 gI&T Therm al40C bake-out soak
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 37
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Structural Analysis Summary and Further WorkStructural Analysis Summary and Further Work
• Summary
– Subsystem structural models have been updated to reflect CDR designs
– Model quality checks have been completed
• Further Work
UPDATE
LAT-PR-01967 Section 8.3 – Structural Design 38
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Verification Test OutlineVerification Test Outline
• Integration and Test flow
• Qualification and verification flow
– Strength qualification test flow
– Vibro-acoustic test flow
• Dynamic test plans (see LAT-MD-01196, “Dynamics Test Plan”)
– Modal survey
– Sine vibration
– Sine Burst
– Acoustic
• LAT survey plans (see LAT-MD-00895, “LAT Instrument Survey Plan”)
– Optical survey
– Cosmic-ray muon survey
LAT-PR-01967 Section 8.3 – Structural Design 39
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Integration and Test FlowIntegration and Test Flow
LAT Integration and Test FlowLAT Integration and Test Flow
UPDATE
Sine VibeSine Burst
T ow erIntegration
L A TIntegration
L A T T es tObservatoryIntegration
TKR
CAL
TEM/PS
Grid
Radiators
EPU
SIU
GASU
PDU
ACD
IntegrateE-Boxesw / Grid
AlivenessTests
LimitedPerformance
X-LAT Plate
C
CLE A
A
W eight
EM I/EM C
L
Acoustic
L
Cycling
Balance
C L
C
W eight & CG
A
F
F
F
Survey
M
L
O Optical M M uon
IntegrateTKR/CAL &TEM 's w ith
Grid
SurveyO
IntegrateX LAT Plate
M echanical Fit-Checks
Survey (2)
M odalsurvey
E
FunctionalTests
Survey:
L
ElectricalInterfaceTests
ComprehensivePerformance
Environmental Tests
E
v3 C D R 4 /21/03
Htr Sw itch Box
EMI Shield
Integrate ACD
IntegrateEMI Skirt, Htrsw itch boxes
Survey
SurveyO
SurveyMO
O
L
Ship toNRL
M
@ NRL
Th
erm
al
Va
cu
um L
Ship toSLAC
Shipto SA
StoreLAT
LATIntegration
ThermalVac
CL
L
O
C M
Final
CL
@ Spectrum Astro
F
E
M
InstallRad iators
Rem oveRadiators
C
SurveyM
L
C
L
LAT-PR-01967 Section 8.3 – Structural Design 40
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Strength Qualification Test FlowStrength Qualification Test Flow
• Grid Box static loading
– Without Radiators, TKR’s, and ACD
– Includes 16x CAL Plate STE’s
– TKR joints tested one bay at a time
– SC-LAT tested one joint at a time
– Grid Box distorted to strength-qualify CAL joint and Grid Box assembly
• TKR, CAL, TEM/TPS sine burst
– Fixed-base strength qualification of subsystem module and interface design
• ACD Shell and Base Frame Assembly
– Fixed-base strength qualification of internal flexures, subsystem, and interface design
• LAT sine burst
– LAT mounted on vibe test stand
– Completes strength qual of Grid and TKR joint
ACD Sub-Ass’ySine Burst
A
TKR QMSine Burst, Static Load
QACD Shell + BFASine Burst
QCAL QMSine Burst
QTEM/TPS QM’sSine Burst
QE-Box PF QM’sSine Burst
PGrid Box Ass’yStatic Load
PRadiatorStatic Load
P
LAT Ass’ySine Burst
P
GLAST ObsSine Burst
P
Subsystem Qual Tests
Subsystem Acceptance
Tests
LAT-PR-01967 Section 8.3 – Structural Design 41
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Vibro-Acoustic Test FlowVibro-Acoustic Test Flow
• LAT and GLAST vibro-acoustic test plan
– LAT modal survey—without Radiators, while at SLAC
– LAT sine vibration—without Radiators; includes sine sweep signature
– LAT acoustic—without Radiators
– GLAST Observatory sine vibration—with Radiators but without solar arrays (TBR); includes sine sweep signature
– GLAST Observatory acoustic—with Radiators but without solar arrays (TBR)
– GLAST Observatory shock—shock event applied at PAF separation plane
ACD Sub-Ass’ySine Vibe, Random Vibe
A
ACD Sub-Ass’yAcoustic
A
TKR Qual ModuleSine Vibe, Random Vibe
Q
TKR Flt ModulesSine Vibe, Random Vibe
A
ACD Shell + BFASine Vibe, Random Vibe
Q
ACD Shell + BFAAcoustic
Q
CAL QM’sSine Vibe, Random Vibe
Q
CAL FM’sRandom Vibe
A
TEM/TPS QM’sSine Vibe, Random Vibe
Q
TEM/TPS FM’sRandom Vibe
A
E-Box PF QM’sSine Vibe, Random Vibe
P
Grid Box Ass’y
P
RadiatorSine Vibe
P
RadiatorAcoustic
P
LAT Ass’yModal Survey, Sine Vibe
P
LAT Ass’yAcoustic
PGLAST ObsSine Vibe
PGLAST ObsAcoustic
P
Subsystem Qual Tests
Subsystem Acceptance
Tests
GLAST ObsShock
P
LAT-PR-01967 Section 8.3 – Structural Design 42
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Modal SurveyLAT Modal Survey
• Test goals
– Validate the LAT structural finite element analysis (FEA) model by correlating with test results
– Measure all primary modes of the LAT/Grid structure.
– Measure the first mode, and all modes predicted to have high mass participation, for every subsystem
– Measure as many natural frequencies of the LAT up to 150 Hz as practical
– Test results will be used to evaluate the predicted expected modal frequencies and mode shapes, and used to modify the structural FEA, if needed.
– Finalize test environments and notching plans for sine vibration testing
• Configuration
– Fully integrated, except the Radiators are not mounted
– Supported off of its spacecraft (SC) mount brackets,
– +Z-axis point vertically up
– LAT powered off during testing
• Specialized test equipment requirements
– LAT supported by the Vibe Test Plate which provides a rigid support of each mount point
– Vibe Test Plate sits on a massive base-isolated table, to damp high-frequency base noise being transmitted to the structure
– Excited using two stingers, located under the LAT
LAT-PR-01967 Section 8.3 – Structural Design 43
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Modal Survey (cont)LAT Modal Survey (cont)
• Instrumentation
– High-precision accelerometers mounted to the LAT and test stand
• Outstanding technical issues
– Establish excitation levels
– Finalize accelerometers for test, based on predicted test levels
LAT +X
LAT+Y
TKR (z = 640 mm)
CAL (z = -27 mm)
X-TKR
Y-TKR
Grid ( z = 0 mm)
X-TKR
X-TKR X-TKR
XYZ-CAL
XYZ-CAL
XYZ-CAL
XYZ-CAL
Z-TKR
Z-TKR
Z-TKR
Z-TKR
Z-TKR
Z-TKR
0 1 2 3
4
Y-TKR
Y-TKR
Y-TKR
Y-TKR
765
1098
1514
13
12
11
XYZ-Grid
XYZ-Grid
XYZ-Grid
XYZ-Grid
XYZ-Grid
XYZ-GridXYZ-Grid
XYZ-Grid
XYZ-Mnt XYZ-Mnt
XYZ-MntXYZ-Mnt
Y-TKR
X-TKR
X-TKR
X-axis Accel
Y-axis Accel
Tri-axis Accel
Z-axis Accel
Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003
LAT +Y
LAT +Z
ACD: outer surfaceof honeycomb
Tri-axis Accel
Out-of-PlaneAccel
LAT +X
Y-ACD
Z-ACD
X-ACD
Y-ACD
XYZ-ACD
XYZ-ACDXYZ-ACD
XYZ-ACD
X-ACD
LAT +X
LAT+Y
Elec (z = -500 mm)
CAL (z = -251 mm)
0123
47 6 5
10 9 8
15 14 13 12
11
X-axis Accel
Y-axis Accel
Tri-axis Accel
Z-axis Accel
PDU
SIU
SIU
EPU EPU
EPUMTY MTY MTY
MTY MTY
GASU
XYZ-CALXYZ-CAL
XYZ-CAL
XYZ-CAL
XYZ-CAL
XYZ-CAL
XYZ-Elec
XYZ-Elec
XYZ-Elec
XYZ-Elec
XYZ-Elec
ACD Accelerometer ACD Accelerometer PlacementPlacement
CAL Bottom and E-Box Accelerometer PlacementCAL Bottom and E-Box Accelerometer PlacementTKR, CAL, and Grid Accelerometer PlacementTKR, CAL, and Grid Accelerometer Placement
LAT-PR-01967 Section 8.3 – Structural Design 44
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Sine Vibration / Sine Burst TestsLAT Sine Vibration / Sine Burst Tests
• Test goals
– Verify the LAT’s ability to survive the low frequency launch environment
– Test for workmanship on hardware such as wiring harnesses, MLI, and cable support and strain-reliefs which will not have been fully verified at the subsystem level
– Interface verification test for subsystem structural interfaces to the LAT Grid
• Configuration
– Fully integrated, except the Radiators are not installed
– Supported off of its spacecraft (SC) mount brackets, on the Vibration Test Stand
– The LAT is tested in all three axes, X, Y, and Z independently, requiring re-configuration between tests
– The LAT is powered off during sinusoidal vibration testing, and the E-GSE cable harnesses removed
• Specialized test equipment requirements
– The Vibe Test Stand must support the LAT at the SC interface with flight-like connections
– The Stand must allow for reconfiguration to alternate axes, with the LAT attached, to avoid unnecessary handling
LAT-PR-01967 Section 8.3 – Structural Design 45
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003LAT Sine Vibration / Sine Burst Tests (cont)LAT Sine Vibration / Sine Burst Tests (cont)
• Instrumentation
– Accelerometers mounted to the LAT and test stand, to cover the entire dynamic range predicted for the LAT and subsystems
• Outstanding technical issues
– Accelerometer sensitivity—pre-test dynamic analysis will indicate the level of precision and dynamic range needed for this test
– Finalize LAT degrees of freedom at STE connection (simulating a “fixed” connection or a flexure)
– Establish test levels based on Observatory CLA, without exceeding interface limit loads
LAT +X
LAT+Y
TKR (z = 640 mm)
CAL (z = -27 mm)
Grid ( z = 0 mm)
XYZ-CAL
XYZ-CAL
XYZ-CAL
XYZ-CAL
XYZ-TKR
0 1 2 3
4 765
1098
15141312
11
XYZ-Grid
XYZ-Grid
XYZ-Grid
XYZ-Grid
XYZ-Grid
XYZ-GridXYZ-Grid
XYZ-Grid
XYZ-Mnt XYZ-Mnt
XYZ-MntXYZ-Mnt
X-axis Accel
Y-axis Accel
Tri-axis Accel
Z-axis Accel
XYZ-TKRXYZ-TKR XYZ-TKR XYZ-TKR
XYZ-TKR XYZ-TKR XYZ-TKR
XYZ-TKR XYZ-TKR XYZ-TKR
XYZ-TKR XYZ-TKR XYZ-TKRXYZ-TKR
LAT +X
LAT +Z
Radiator Inner Facesheet
Tri-axis Accel
Y-axis Accel
Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003
TKR, CAL, and Grid Accelerometer PlacementTKR, CAL, and Grid Accelerometer Placement
Radiators Accelerometer PlacementRadiators Accelerometer Placement
Qualification Sine Vibration Test LevelsAxis Freq. (Hz) Test levels Sweep Rate
Thrust 5 to 7.4 1.27 cm (0.5 in.) double amplitude 2 octaves/min7.4 to 50 1.4 g (zero to peak)
Lateral 5 to 6.2 1.27 cm (0.5 in.) double amplitude 2 octaves/min6.2 to 50 1.0 g (zero to peak)
LAT Sine Vibration Minimum Test LevelsLAT Sine Vibration Minimum Test Levels
LAT-PR-01967 Section 8.3 – Structural Design 46
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Acoustic TestLAT Acoustic Test
• Test goals
– Verify the LAT’s ability to survive the acoustic launch environment
– Test for workmanship on LAT hardware, especially that hardware which responds to acoustic loading
– Validate the acoustic analysis
• Configuration
– LAT is fully integrated, including the Radiators
– Mounted to STE using the flight-configuration bolted joint
– LAT +Z-axis vertical, and with Radiators integrated to the Grid as well as to the STE at the SC strut mount points
– LAT is powered off during acoustic testing, and the E-GSE cable harnesses removed
• Specialized test equipment requirements
– The Vibe Test Stand must support the LAT in the same degrees of freedom as the SC flexures, to avoid over-constraining the Grid and Radiators
– The STE fills the volume between the Radiators, so must approximate the acoustic behavior of the SC
• Instrumentation
– Accelerometers mounted to the LAT and test stand
– Microphones mounted around the LAT
LAT-PR-01967 Section 8.3 – Structural Design 47
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Acoustic Test (cont)LAT Acoustic Test (cont)
• Outstanding technical issues
– Establish acoustic fill and response requirements of STE to adequately bound response of SC
– Define post-test modal signature test to verify that LAT dynamic response matches baseline
– Finalize accelerometer and microphone placement
– Perform pre-test acoustic analysis
Acoustic Loading
100
105
110
115
120
125
130
135
140
145
150
10 100 1000 10000Frequency (Hz)
So
un
d P
ress
ure
Lev
el (
dB
)
Accept Tes t (dB)
Qual Tes t (dB)
LAT Acoustic Test LevelsLAT Acoustic Test Levels
Source: LAT-SS-0077801, “LAT Environmental Specification,” March 2003
LAT-PR-01967 Section 8.3 – Structural Design 48
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT SurveyingLAT Surveying
• Survey program goals
– Verify as-integrated interface stay-clears
– Verify LAT alignment requirements
– Verify science performance requirements • Validate analytical thermal-mechanical analysis models• Develop correlation functions for thermal-mechanical distortion• Predict the expected on-orbit precision of the instrument
• Survey program description
– Optical surveying• Subsystem inspection measures position of survey retro-reflector balls with respect to physical
features and active elements of subsystem module• After integration, laser tracker measures bearing and distances to balls on the LAT and in the
integration room• Data reduction of measurements produces position location information for all balls relative to
room coordinate system, and prediction of measurement precision• This will establish location of subsystem surfaces and features in their as-integrated positions,
providing a verification check during integration
– Muon surveying• Uses naturally-occurring cosmic-ray muons• Muons generate straight-line tracks through TKR modules• Mis-alignments between modules will show up as a step in the reconstructed track• With muons generating enough cross-tower tracks, the relative locations of tower can be
measured• This will be used to precisely establish the locations and attitudes (and changes) of TKR modules
LAT-PR-01967 Section 8.3 – Structural Design 49
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Surveying (cont 1)LAT Surveying (cont 1)
1A: 1-Toweroptical survey
Integrate Towers Int. ACD Ship/Vibe T-Bal/T-Vac
1B: 4-Toweroptical survey
2A,B,C: LAT baselinemuon survey
1C: 16-Toweroptical/muon survey
3A: Pre-T-Vacmuon survey
4A,B,C: T-Vac muonsurvey at temp
# Goal When/Where Orient. Method Support/Configuration Cooling Temp
1AVerify SS stayclears, TKR alignment accuracy
SLAC, after 1st TKR module is integrated
+Z Up Optical4 corners on GPR; 1 TKR/CAL/ TEM tower integrated. LAT off
None RT
1BVerify SS stayclears, TKR alignment accuracy
SLAC, after 4 TKR modules are integrated
+Z Up Optical4 corners on GPR; 4 TKR/CAL/ TEM towers integrated. LAT off
None RT
1CVerify SS stayclears; establish baseline position of all TKR's
SLAC, before ACD integration
+Z HorizOptical/
Muon3 mid-sides on GPR; ACD not on LAT on. Push on 4th mid-side.
Elec: forced air; Det: conduction
17 C
2A Verify ACD stay-clearsSLAC, after ACD and X-LAT Plate integration
+Z Up Optical4-corners on GPR; ACD integrated. LAT off.
None RT
2BEstablish baseline position of TKR's with ACD on
SLAC, after CPT +Z Horiz Muon 3 mid-sides on GPRElec: forced air; Det: conduction
17 C
2CCharacterize gravity effect on TKR position w/ ACD
SLAC, after CPT +Z Up Muon 3 mid-sides on GPRElec: forced air; Det: conduction
17 C
3ARe-baseline TKR positions after transport, vibe
NRL, after vibe and before T-Vac pump-down
+Z Horiz Muon 3 mid-sides on T-Vac STEElec: forced air; Det: conduction
17 C
4ACharacterize thermal effects on LAT at min temp
NRL T-Vac Chamber +Z Horiz Muon 3 mid-sides on T-Vac STEElec: X-LAT Pl, Det: conduction
-5 C
4BEstablish baseline position of TKR's at nom operating temp
NRL T-Vac Chamber +Z Horiz Muon 3 mid-sides on T-Vac STEElec: X-LAT Pl, Det: conduction
8 C
4CCharacterize thermal effects on LAT at max temp
NRL T-Vac Chamber +Z Horiz Muon 3 mid-sides on T-Vac STEElec: X-LAT Pl, Det: conduction
17 C
LAT Optical and Muon Surveys During Integration and TestLAT Optical and Muon Surveys During Integration and Test
Source: LAT-MD-00895 “LAT Instrument Survey Plan”
LAT-PR-01967 Section 8.3 – Structural Design 50
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 LAT Surveying (cont 2)LAT Surveying (cont 2)
• Instrumentation
– Laser tracker—measurement precision of instrument is less than 10 microns, but actual precision is more a function of room temperature stability, reflector ball location precision
– Tracker—measurement precision and instrument calibration will be verified with Calibration Unit beam tests at SLAC
• Specialized test equipment requirements
– Room temperature controlled to within 5 oC (TBR)
– LAT and GSE/STE temperature stable to within 2 oC (TBR)
– Support stands allow for leveling the LAT to within 0.2 degrees to ensure proper functioning of heat pipes
– Chill plates provide a heat sink for the Grid during in-air testing
• Outstanding technical issues
– Investigating the use of inclinometers during thermal-vacuum testing
– Thermal-mechanical model of LAT in test configuration has not yet been done—this is needed to establish precision and stability requirements for STE
LAT-PR-01967 Section 8.3 – Structural Design 51
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003Summary of Structural Test Issues and Closure PlansSummary of Structural Test Issues and Closure Plans
LAT-PR-01967 Section 8.3 – Structural Design 52
GLAST LAT Project
CDR/CD-3 Review May 12-16 2003 Summary and ConclusionsSummary and Conclusions
• UPDATE
• Structural Analysis Summary
• Verification Test Summary
• Conclusions
• Summary
– LAT Dynamics Test Plan has been written and is ready for initial release
– LAT Thermal Test Plan has been written and is ready for initial release
– LAT Survey Plan has been written, with final pieces coming together for release before CDR
– Test instrumentation and levels are understood
• Further work
– Perform pre-test analysis to finalize instrumentation and STE requirements
– Expand test plans with results of pre-test analysis
– Complete test implementation plans
top related