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31 Dec 1963, DoDD 5200.10; BUORD/Rand Corp. ltr29 Mar 1967

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CONFIDENTiAL

APL/JHU TG 154-16

as

Chapter 16 SOLID FUEL RAMJETS

ROBERT L. WOLF

and

JAMES W. MULLEN II

Experiment Incorporated

•*¥

>-

PatUdudbf

T I A I

T::Z JOHNS HOPKIVS UNIVERSITY APPLIED PHYSICS LABORATORY Silver Spring Maryland

()|xrnlinR under Contract NOnl 7:IKf> wit It

tlie Bureau of OfilroiiH**, l>e|iarlinent t>f llio \;ivy

(K« United S»o'« wtHiin lh« mvon.tig o* M»« ftpieftag* IJ»I Fill* II \ USC. S*ct«n Tf) m*4 794 lit I»-«I*.M.»« »' '•.•(•••on »» •'» <«* t««N i" «nr KMHnar I* ».*• vn«-.-t4t»rn*d po'»on it p>Qfc>b'i»a bf l«w

CONFIDENTIAL

Chapter 16

SOLID FUEL RAMJETS

by

Robert L. Wolf and James W. Mullen II

Experiment Incorporated

(Manuscript submitted for publication December 1951)

CONFIDENTIAL THIS DOCUMENT CONTAINS INFORMATION AFFECTING THE NATIONAL DCFCNSE OF THE UNfTtO STATES WITHIN THE MEANING OF THE ESPIONAtiE LAWS. TITLE it. USC SECTIONS 793 AND 794 '«£ TRANSMISSION OH THE REVELATION OF ITS CONTENTS IN ANY MANNER TO AN UNAl'TH0Rl2ED P£«SO-*' '5 PROHlSlTED 6* LAW

4 v

CONFIDENTIAL

TABLE OF CONTENTS

HISTORICAL BACKGROUND

GENERAL CHARACTERISTICS

Potential Advantages of So

Practical Difficulties

Applications

BURNER PERFORMANCE .

Fuel Charges

Linear Burning Rat

Thrust Control

Burner Efficiency

Combustion Limits

NOMENCLATURE

APPENDIX

REFERENCES .

lid Fuel Systems

1

4

4 Q

15

18

18

24

31

36

41

42

43

49

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!

I

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CONFIDENTIAL

',.

16. SOLID FJJEJ, RAMJETS

by

Robert L. Wolf and James W. Mullen II

16.1 HISTORICAL BACKGROUND

The ramjet powerplant for aircraft propulsion, conceived

nearly 40 years ago [22, 23], has been available in useful form

for less than a decade. Its deve_opers focused their efforts

largely on liquid fuels, particularly hydrocarbons of the gaso-

line or kerosene type. Nevertheless, during the period of re-

surgent interest occasioned by World War II, there was early

recognition that solid fuels might offer certain design and

performance advantages.

Although the Germans were chiefly interested in coal and

even wood, Sanger and Bredt [36] did suggest the use of metal

dispersions to obtain higher flame temperatures and, Hence,

thrust coefficients. Lippisch [20] and Schwabl [37] were first

attracted to solids because of the inherent simplicity of the

fuel system in short-duration missiles and artillery or mortar

shells. They carried out numerous burner tests with briquetted

carbon and natural coal charges, later extending the scope of

their work to designs suitable for piloted aircraft.

At Great Britain's National Gas Turbine Establishment,

Roberson [33] prepared a theoretical performance survey cover-

ing a very large number of solid fuels. Actual experimental

work appears to have been confined to aluminum and was conducted

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CONFIDENTIAL

by Wolfhard and Parker [30], Bowling [9], and Fennell [14] at

the Royal Aircraft Establishment. Some attention was also

given to aluminum hydrocarbon slurries by Mazurkiewicz [25].

In this country, at the Applied Physics Laboratory of

The Johns Hopkins University, Berl [8] developed techniques

for improving the output of a lean propylene oxide burner

through the addition of aluminum and magnesium powders. At the

Jet Propulsion Laboratory of the California Institute of Tech-

nology, Bartel and Kannie [7] used carbon tubes in flow combus-

tion tests and Alperin [1] considered the problem from a theo-

retical viewpoint. Damon and his associates at the Bureau of

Mines [11] initially investigated coal for ramjet use, but

later began to incorporate the light metals in their formula-

tions. Smith [39] extended to ramjet flow conditions the earli-

er fundamental investigations of Hottel and his Massachusetts

Institute of Technology co-workers [44,12,29] into the mechanism

of burning carbon spheres. The experimental phases of the pro-

gram were continued under the direction of Hottel and Williams

[3, 4]. Collins and Squiers of the Continental Aviation and

Engineering Corporation intensively examined the application

of magnesium to booster [24,40] and gun-launched [42] ramjets.

To a lesser extent they also employed aluminum, boron, and

napthaiene in their experimental program. Wolf and others from

Experiment Incorporated [46] assisted in the early magnes-.um

fuel and burner development. Two types of propellant charges

resulted from this joint program. Either of these ^ives satis-

factory performance under the internal flow conditions obtained

in supersonic ramjets and meet to a large extent all other re-

quirements for operational feasibility. Later, the effect of a

solid or liquid dispersed phase, such as magnesium oxide, on the

aerothermodynamic relations employed in ramjet design calcula-

tions was examined [47]. The utilization of aluminum [48] and

- 2 -

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CONFIDENTIAL

boron [49] was also investigated. Finally, a solid fuel pro-

pulsion test vehicle, after extensive development in free-jet

tests [50,53], was successfully flown [38,52] in the velocity

range between Mach 1.8 and 2.1 on January 11, 1952. Gammon

[15,16,17,18] of the National Advisory Committee for Aeronautics

has recomputed the theoretical air and fuel specific impulses

of carbon, magnesium, aluminum and boron. Branstetter, Lord

and Gerstein [10] from the same* organization developed labora-

tory means for feeding aluminum powder and wire to ramjet burn-

ers. At. the N.A.CA. Wallop's Island range Faget and Bartlett

[13,28] have carried out free-jet tests on a system similar to

that developed in the Continental Aviation program to determine

its suitability as a carrier for the flight testing of aero-

dynamic shapes. Olson and Gibbons recently issued a compre-

hensive review of the current status of the solid-fuel ramjet

field [28], It is believed that the North American Aviation

Company had an interest in this subject, but little published

information is available.

Considerable attention has also been given to dispersions

or suspensions of metals in hydrocarbon fuels. Under Project

BUMBLEBEE Berl [8] at the Applied Physics Laboratory and Anderson

[2] at the University of Texas prepared relatively stable sus-

pensions of sodium, magnesium, aluminum, and nickel. In N.A.CA.

investigations, Tower and Branstetter [43] employed a magnesium-

hydrocarbon slurry while Gibbs and Cook [19] made boron the

dispersed phase. Gammon included these same systems in his

theoretical study together with one wherein the metal portion

was aluminum [15,16,17], The Thompson Products Company has also

indicated an interest in boron-oil dispersions [3l],

_ Q

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CONFIDENTIAL

16.2 GENERAL CHARACTERISTICS

Potential Advantages of Solid Fuel Systems

The twofold opportunity oi a simpler, more reliable

engine having a higher performance is the potent underlying

incentive for studying solid fuel ramjet systems. A resume

of the arguments, pro and con, indicating the extent to which

this objective is realized under present day "know-how" is a

principal purpose of this section.

Calculations indicate that sufficient fuel for short

(approximately 20 miles) and perhaps intermediate range (100-

200 miles) missiles can be stored within the combustion cham-

ber proper without occasioning undue internal drag losses. By

this expedient, fuel tanks, pumps, meters, injectors and their

associated plumbing, and even the pilot and flame holders, can

be eliminated. Means for effecting these component savings in

long range missiles (>1000 miles) are not so immediately ap-

parent. The solution, if it exists, must be sought in multiple

or externally packaged charges and in high-energy fuels having

low burning rates.

In considering the performance to be expected of solid

fuels, all pertinent points can be illustrated by limiting the

discussion to carbon, aluminum, magnesium, boron, and decaborane

There are, of course, many other possibilities, but the broad

technical screening available through Roberson [33] places them

in their proper perspective relative to the foregoing selection,

especially when economic considerations are taken into account.

To facilitate comparison, data for kerosene (ANF-32) will be

included.

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In Fig. 16.2-1, theoretical air specific impulse, S ,

is plotted as a function of equivalence ratio, <f>, for the sev-

eral fuels. A more detailed presentation of these calculations

is given in the Appendix. The inflection points in some of the

curves are associated with phase changes in the exhaust products

It is seen that in thrust-producing capabilities the three met-

als and decaborane are superior to kerosene. Carbon is slightly

inferior but still comparable.

A similar graph, Fig. 16.2-2(a), for theoretical fuel

specific impulse, Sf, largely reverses this situation. That is,

the metals on a weight basis appear less economical in fuel con-

sumption. Strictly speaking, however, the comparison should be

made only at a given level of thrust (i.e. of S ). In Table St

16.2-1, this has been done for S = 170, the maximum possible

with kerosene. On this basis the relative position of boron

is not too unfavorable. The boron hydride alone shows to ad-

vantage. Figure 16.2-2(b) extends the comparison to other

thrust levels and shows that the advantage held by decaborane

increases substantially at lower S values. a

Recent information indicates that heat of formation of B„0 is somewhat higher than that used in calculations in this chapter. Calculations using a higher heat of formation show boron to have a higher fuel specific impulse than kerosene over the entire S range l_ 56 1 .

5 -

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On the other hand, in considering over-all missile per

formance, volume is frequently as important a design parameter

as weight. Figure 16.2-3(a) gives the product of the fuel spe-

cific impulse, S-„, and the fuel density, d, as a function of

equivalence ratio. The ratios in the last line of Table 16.2-1

indicate that to maintain a given thrust level (S = 170) for a

fixed time, less storage space is required for the light metals

and for decaborare than for kerosene. With the exception of

magnesium, the saving is considerable. The use of Fig. 16.2-3(b)

permits comparison at any thrust level.

PracUCfll Difficulties

If the advantages cited above are to be realized, a

number of practical difficulties must be overcome. Packaging

the fuel within the combustion chamber to eliminate the fuel sys-

tem components leads to complications as well as simplification.

For example, the problem of obtaining fuel-charge geometries

having sufficient surface exposed to the air stream to provide

the necessary over-all rate of heat release, and yet remain

compatible with the requirement of a low internal drag, plagued

most of the early investigators. In their reports are numerous

drawings of very "unramjetlike" cages and grates for supporting

coal charges. On the other hand, if the fuel is fed to the

burner as a finely divided powder, either in the pure form or

suspended in a liquid carrier, not only is the complexity of

the fuel-supply system enhanced over that originally required

for liquid!* but much of the density advantage responsible for

a high volumetric heat release is also lost. These same con-

siderations partly apply to a wire-type feeder.

- 9 -

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When the advocate of solid fuels proudly discarded the

fuel meter, he still could not escape the fact that some sub-

stitute was required for the function of this useful device.

The attainment of delicate thrust control with solid fuels

still presents certain problems.

The law of natural perversity seems to apply equally

well to solid fuels. The more desirable fuels from the very

important aspect of specific fuel consumption are often the

least reactive and most troublesome to burn. Easy starting

and high combustion efficiencies are more readily obtained

with magnesium than with aluminum. The evidence for boron,

while currently incomplete, appears to bear out this trend.

Even less is known about decaborane, though it should be quite

reactive. In the case of aluminum and boron the hard starting,

Incomplete combustion, and tendency to slag formation, aside

from chemical affinity considerations, may lie in the trans-

port processes so important in heterogeneous reactions. These

systems can only react (a) by diffusion and/or convection of

oxygen to the surface of the solid particle, reacting thereon

with subsequent outward transport of the oxide to leave fresh

material for further oxidation, or (b) by evaporation of the

solid from the surface of the particle to the surrounding air

followed by essentially vapor-phase reaction. Table 16.2-2

lists the melting and boiling points of several fuels and

their oxides together with the approximate peak flame tempera-

ture associated with the combustion process. The transition

points, like much of the other thermal data in these cases,

are subject to some uncertainty. The high boiling point of

boron suggests that the first mechanism, i.e., diffusion of

oxygen to the boron surface, is the more likely. Further dif-

ficulty is indicated by the low melting point and high boiling

point of the oxide; that is, an adherent glassy film of this

11

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material may seal the surface of the metal particle against

subsequent reaction. In contrast, the highly efficient mag-

nesium combustion which has been achieved experimentally ties

in with the low boiling point of that metal. The magnesium

particles probably evaporate at an early stage so that the

main reaction is actually carried out in the vapor phase.

In addition, under most circumstances the high melting point

of the oxide would lead to a brittle, friable coating easily

dispersed by aerodynamic forces. Under this hypothesis alumi-

num should occupy a position intermediate to boron and mag-

nesium in difficulty of combustion, which is largely in keeping

with the observed situation. Carbon offers an example of a

high "boiling" fuel which maintains a clean surface through the

extreme volatility of its oxides.

The problem of ignition in solid fuel charges has its

own peculiar difficulties. Some of the early coal burners took

several seconds, even minutes, to bring up to a point of self-

sustaining combustion. An ignition lag of tenths of seconds or

less is more in line with the starting requirements in many ram-

jet applications.

A number of the more interesting solid fuels have an ex-

haust stream containing a finely dispersed solid or liquid

phase. Other than how to handle their effect in fluid mechani-

cal expressions, they lead to heat transfer problems. No longer

held down by the low radiant component, of the transparent com-

bustion products of conventional hydrocarbon fuels, wall tem-

peratures can become dangerously high, especially if advantage

is taken of the maximum flame temperatures available with cer-

tain metals. Measured losses through the combustion-chamber

wall of a 2-inch magnesium burner have been 12 to 25 per cent

of the total heat release [46], This is roughly two to five

times greater than observed with hydrocarbon fuels. On the

- 13

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ether hand. Tower and Branstetter [43] have reported a lower

transfer to the walls when a given burner was run on hydro-

carbon-magnesium slurries than when run on the pure hydrocar-

bon. Presumably, this was duo to the insulative effect of the

oxide coating built up on the inner surface of the combustion

chamber. On a visit to Wallop's Island, the writers observed

a thin, continuous film of oxide firmly adhering to the walls

of the N.A.C.A. 6-inch magnesium burner [32]. The phenomenon,

however, does not seem to occur to the same extent in their

own 6-inch tests at Experiment Incorporated. Obviously it

would be desirable to induce the build-up of this seif-insula-

ting layer with some degree of reliability. All in all, fur-

ther study of the heat transfer processes in solid fuel ram-

jets is indicated.

The same exhaust condition, high temperatures and smoke,

is the source of another concern: i.e., interference with guid-

ance or telemetering signals. Since no work has been done

along these lines on the systems of immediate interest, an in-

vestigation is again indicated.

Finally, there is the matter of economic considerations.

The better fuels are not only the least reactive, but they are

the most expensive. Finely powdered magnesium can be bought

today for $2,00 a pound, aluminum for $0.27, impure boron for

$12.00 to $15.00, although the pure element is quoted between

$250.00 and $400.00 per pound. There have been informal indi-

cations that this might be reduced in quantity production.

Even so, one manufacturer has pointed out the improbability of

the price of any suitable fuel ever dropping below $1.00 a

pound [45]. In the case of decaborane any meaningful price

would be difficult to establish today. For missile application,

the position taken by Longwell [21] is probably sound. That is,

if one considers how expensive guided missiles are on both a

14

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CONFIDENTIAL

i ! total and a unit weight basis, and the importance of insuring

a successful mission, a fuel that offers operational advan-

tages should not be eliminated on a price basis unless the

fuel cost approaches the cost of the missile.

Applications

To be valuable any consideration of applications should

be based on those characteristics wherein solid fuel ramjets

possess superiority over other forms of propulsion. Thus, in

the earliest German work mortar and artillery shells [20] would

appear to be a more appropriate subject for investigation than

piloted subsonic aircraft [361. Mechanical simplification of

the fuel supply and combustion systems, with the accompanying

increase in reliability, is an obvious asset in all of the sug-

gested applications and, therefore, will not be touched upon

again.

Pursuing this only logical approach that the characteris-

tic should determine the application, the high air specific im-

pulses available with certain solid fuels suggest some form of

booster device or self-accelerating ramjet [34,40,24]. Where

the missile end use can tolerate relatively long acceleration

periods, the initial velocity car; be achieved by release from

conventional aircraft. The boost to final design velocity can

then be achieved by a high thrust, solid fuel charge simply

packaged within the combustion chamber of a conventional hydro-

carbon ramjet. Alternatively, a small rocket can be used to

establish the initial velocity and the second stage boost be

accomplished as before, with the additional possibility of an

externally mounted engine.

- 15 -

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MEW INC Of THE ESPIONAGE LAWS. TITLE 18. USC $£C't.>M$ '93 ANU 794 THf -NSMI, H OH TME "EVELATION Or iT5 CONTENTS l* ANY MANNER TO AN UNAUTHORISED Pf-ON S PW0>-I6IT£D 6* L 4W

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The high volumetric specific fuel impulse of many solid

fuels, particularly in the lower thrust ranges comparable to

hydrocarbon performance, provides an opportunity for the de-

velopment of useful midcourse sustainers [51,35). The feasi-

bility of this application, of course, also depends on the

weight, mechanical complexity, and external aerodynamics of

the mechanism required to incorporate the sustainer drive in

the main missile.

Boron or certain of its solid hydrides more effectively

illustrate the characteristic of high volumetric specific fuel

impulse and oper vhe question of long-range missile applica-

tions. Unfortunately, only cursory investigations have been

made of this possibility. The problem is not simple, gravi-

metric specific fuel impulse and methods of mechanically hand-

ling the i re! charges being only a few of the other influential

factors. High stagnation temperatures with resultant overheating

of the fuel has been one deterrent to flight at speeds much in

excess of Mach No. 3. Metal fuel charges may obviate at least

part of this difficulty in the development of hypervelocity

ramjets [6] .

Experimentally, it has been shown that the combustion

efficiency of magnesium-fueled burners is relatively insensi-

tive to lowered inlet pressures. Extreme altitude ramjets may

be possible through the utilization of this characteristic.

Many solid fuel charges have excellent mechanical prop-

erties, e.g., compressive strength, and. therefore, can with-

stand the stresses of a short boost period. For example [42],

powdered magnesium briquettes have been tested successfully at

accelerations up to 26,500 g. Because of this it appears

feasible to design gun-launched ramjets more reliable than

those originally suggested by Tromsdorf. Preliminary calcula-

tions show that even with diffuser efficiencies as low as

- 16 -

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TM€ REVELATION Of ITS CONSENTS » ANY MANNER TO AM UftAUTHOfttfiS *C*S0N '9 PR0'.i8nTP ft* LA^

CONFIDENTIAL

40 per cent a muzzle velocity of 4000 fps can be sustained and

even increased during the flight of the projectile [6]. Other

studies show that roughly three pounds of a solid fuel would

propel a 20-pound low velocity mortar shell nearly 9000 yards

[6]. Continental Aviation and Engineering Corporation has in-

dicated that artillery shells having ranges on the order of 150

to 200 miles may be within reach. One modification of the sol-

id ramjet charge can be employed to reduce base drag in more

conventional shells, thereby providing worthwhile increases in

range (5 ].

An interesting application to underwater ramjets stems

from the observation that certain light metal charges "burn"

as well under water as in an air stream in accord with the

reaction:

2A1 + 3H20—> A1„03 + 3H£ -*• 1,106,000 BTU/ft3 Al.

The same fuel could also be confined to generate gas for

some form of turbopropeller drive.

In the foregoing discussion only generalized applications

based on the chemical and physical properties of solid fuel

charges were indicated. The weapons designer will see for him-

self numerous combinations of these features provocative of more

detailed consideration in air-to-air [54,55], air-to-ground,

ground-to-air, ground-to-ground, intercontinental, and other

missile fields. Flat-trajectory, high-penetration anti-tank

ordnance is suggested. Simple projectiles for saturation bom-

bardment at greater than rocket ranges are apparent. The em-

ployment of solid ramjets for the routine testing of aerody-

namic forms as attempted by N.A.C.A. has considerable poten-

tiality. These and numerous other opportunities await explora-

tion.

- 17 -

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16.3 BURNER PERFORMANCE

Fvel Charges

Two types of fuel charges [40,46] are available in a

sufficiently advanced developmental state to warrant considera-

tion in current application studies. Both types employ finely

powdered fuel, mixed with small amounts of an inorganic oxi-

dizer and molded under pressure in the desired geometric shape.

A low percentage of some organic binder is incorporated to im-

prove the physical strength of the briquette. This general

formulation was tested by the Germans [20,37] almost at the

outset of their program. They did not, however, carry the

work to its logical conclusion, having been discouraged by the

extensive fracture of the charge during burning, which re-

sulted in over half the fuel being discharged as large unburned

fragments.

The first type, known as the annular charge, is illus-

trated in Fig. 16.3-l(a). A more versatile modification, the

split-flow annular charge [53,54], is shown in Fig, 16.3-l(b).

In either case, a rapid-burning pyrotechnic composition is

integrally molded to the upstream face of the fuel charge.

This charge is touched off with a commercial black-powder squib

imbedded therein to supply instantaneously the ignition energy

for the main charge. The average delay from the moment of

closing the firing sv/itch to development of full thrust is on

the order of 0.2 second. Alternatively, part of the ignition

charge and squib can be mounted in the form of a flare exter-

nal to, but directed at, the rapid-burning upstream face of

the main charge. This technique minimizes the possibility of

fracturing the main charge oy the initial explosion. The flame

from the fast-burning booster layer traverses the passage through

- 18 -

CONFIDENTIAL ThIS DOCUMENT CONTAINS INFORMATION AMECTiNfc THE NATIONAL OSFFNJE OF THE UNITED STATES tf'YMiN TK£

WEANING OF THE CSPHJ-iAQL t.AWj . TtTLE IB. US C 9&C?I9NS ?S* AMU T9* THE TRANSMISSION 0* THE AEVt-ATlON OF ITS CONTENTS IS AN* MANNtft (0 AN UNAUTMOftlZCO *€*50N 'S ^ONlSiTO a? LAW

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CONFIDENTIAL

the center of the annular charge, igniting the inner surface

over its entirety. The principal combustion then ensues radi-

ally and progressively toward the outer wall. Only when a

very thin shell cf fuel remains does the charge break up. The

fuel losses attributable to this cause are minor and in small

burners seldom exceed more than about 5 per cent of the total

charge. It does, however, lead to a moderate roughness in the

last second or so of burning, as can be seen on a typical

thrust chart reproduced in Fig. 16,3-2.

The key to successful performance of these charges is

the small content of inorganic oxidizer. Although the quanti-

ties present are insufficient to sustain combustion in the ab-

sence cf the air stream, they do serve to stabilize the flame

at the surface of tre charge and possibly to sput er hot parti-

cles (and vapor) of unburned fuel toward the center of the duct

for better mixing and contact with the atmospheric oxygen. It

is this latter function of "built-in" fuel injection which forms

the basis of the second or flare-type charge shown in Fig. 16.3-

1(c). Now the oxidizer content has been increased to the point

where the surface combustion, though still very fuel-rich, is

self-sustaining in the absence of air. Upon ignition at the

open end of the container, the surface recedes longitudinally

in the so-called "cigarette-burning" manner. Very hot fuel

particles, or under some circumstances, fuel vapor are ejected

with considerable velocity into the main air stieam. The prob-

lem of controlling the shift in center of gravity of a missile

during burning appears at first sight more serious with the

flare than with the annular charges. The internal burner drag

with all three types of charges seems to be in the range of 4

to 8 inlet dynamic heads.

- 20 -

CONFIDENTIAL THIS (lOCUMCttT OBTAINS INFOaMATION AP*tXT1HC TK£ NATIONAL DEFUSE OF THE uNltl.t) $TAT£S vy;Tl-:r< T^E WEANING OF THE ESPIONAGE LAWS. TITLE 18. US'". SECTIONS 793 AND 79* THE TRAHSMlSS'ON OR THE REVELATION OF ITS CONTENTS IN ANY MANNER TG *U UNAUTHORIZED PERSON 'S eflOH'S'TEO 8" LAW

CONFIDENTIAL

UPPER LINE ~ lb/inz(gouge) IN BELLOWS ON THRUST STAND

[lbs thrust = !. 14 t !b/in2(gouge)]

LOWER LINE ~ FLAME PRESSURE lb/in2(gouge)

TIME SCALE = 2.5 SECONDS PER DIVISION

Fig. 16.3-2 TYPICAL THRUST CHART

21 -

CO^FrDINTiAL IMS OOCUMCWT CONTAINS MEWM1TICN AFrtCT.Wl THE N»TlCNAL OCEENSE Of THE UNITED STATES WITHIN THE UEJWINC 0» 'HE tWXU.it. IU»S. TITLE ID. use SECTIONS T»J MU ?3< THE MaNMISSlON OK THE PEVEUITIOX OE ITS CWTEMTS IN ANY MA«Nt» TO AN UHAUTHO^iZED f^KSO". S PflOHffitTEO BY LAW

CONFIDENTIAL

In the development of these charges the principal effort

has centered on the use of nowdered magnesium as fuel in con-

junction with sodium nitrate as oxidizer. Linseed oil was or-

dinarily employed as the binding agent. Molding pressure was o

1200 lb/in leading to a charge density of 1.35 as compared to

1.74 for the pure metal. Where extremely tough charges are re-

quired, higher pressure molding has produced charge densities

between 1.5 and 1.6 [42]. Efforts to burn pure aluminum powder

[48] have been complicated by poor ignitability, flame "blow-

out" after ignition, low combustion efficiency, and slag for-

mation in burner components or in the nozzle. One explanation

for these difficulties has already been offered. The most

practical remedy uncovered to date appears to lie in admixture

with magnesium and use of higher nitrate concentrations. Cer-

tain additives, such as sulfur, have been found beneficial,

whereas the normal alumina fluxing agents, such as cryolite,

have had little effect. Although these "diluted" aluminum

preparations do not permit full realization of the higher volu-

metric heat content of this fuel, they nevertheless offer an

improvement of at least 35 per cent over the better magnesium

fuels in this respect. Figure 16.3-3 outlines the variation in

volumetric heat content of charges containing different mag-

nesium-aluminum ratios as well as sodium nitrate contents. The

best all-round experimental mixture contains 5 per cent of sul-

fur and is also included on the chart. Charge densities are

roughly 70 per cent of the pure metal. Efforts to burn crude

amorphous boron (86 per cent pure) have met with similar, but

even more severe, difficulties. One apparent drawback is that

in using amorphous boron the charge density seems limited to

the relatively low region of 50 per cent of the bulk density of

the element. This obstacle can probably be overcome with cry-

stalline boron powder if such becomes available.

22 -

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CONFIDENTIAL

The entire study of fuel types has been handicapped by

the lack of a laboratory equipped for the preparation of pow-

dered alloys and intermetallic compounds. Small amounts of

calcium are said to lower the "ignition temperature" of mag-

nesium. Other combinations undoubtedly offer other advantages,

particularly in developing satisfactory fuels based on alumi-

num and boron. The possibilities inherent in alloys can never

be explored as long as formulation is limited to mechanical

mixtures of commercially available powders.

Linear Burning Rate

Of prime interest to the ramjet designer is the thrust

coefficient of the over-all engine. A basic determinant of

this quantity is the burner air specific impulse and this in

turn depends strongly on the air-fuel ratio or more conveni-

ently the air-fuel equivalence ratio. In conventional ramjets

the fuel meter controls and regulates these three important

parameters for various design and flight conditions. In solid

fuel ramjets the fuel-metering function is an inherent property

of the fuel charge which is manifested as its linear burning

rate. Thus, the weight flow of fuel, m_ (lbs/sec), is given

by the product of the linear burning rate, V. (in/rain), the

total area of the burning surface, S (in ), and the density, q

d, of the charge in lbs/ft , or:

V1S d mf = 103,680

- 24

CONFIDENTIAL THIS DOCUMENT CCNTAiNS JW 0* MA 71 ON AffECTlNG TM£ NATIONAL Of'FNSc Of THE UNITED 57ATCS WIT*'* THE MEANING OF 7HF ESPIONAG* LAWS- TITLE iB USC SCCTIOMS ?9S ANL> ?9« THE TRANSMISSION OR *hE ACVEUTION OF ITS CONTENTS iH t-Uf HANNC& TO AN ONAUTHCRlZED PERSON '5 PROHIBITED fir LA*

CONFIDENTIAL

In annular charges S is the surface area of the internal pas-

sage, but in flare charges it is the c^ss-sectional area.

The linear burning rate is also important when taken together

with charge geometry in determining the burning time or dura-

tion of the flight.

In general, the linear burning rate is determined by

formulation variables: e.g.,

1. Fuel type,

2. Size and shape of fuel particles,

3. Type and concentration of oxidizer,

4. Particle size of oxidizer,

5. Type and concentration of binder, and

6. Density of charge.

and by burner-design variables, e.g.,

1. Equivalence ratio,

2. Charge temperature, and

3. Air mass flow per unit cross-sectional area

of central air passage (annular charges).

Considering the first group, few significant comparative

data are available today on the differences in basi<; burning

rates of various pure fuels. In order to get aluminum to burn

at a satisfactory combustion efficiency, it has to be formula-

ted in a 4-to-l or possibly a 6-to-l ratio with magnesium and

"doped" with 10 per cent sodium nitrate and 5 per cent sulfur.

That this charge has roughly the same linear burning rate as a

magnesium one containing only 5 per cent sodium nitrate is but

rather weak evidence for aluminum having a lower basic rate.

In any event, the designer will probably select the fuel on a

thermodynamic basis so that discussion of the other formulation

variables is more to the point.

- 25 -

COMRDiNTSAL THIS DOCUMENT CONTA'NS iN>ORUA7:0M HFFtCTINO T*C NATIONAL DETNSt C* THE UNITEO STATES *ITMK TME MEANING Of THE ESPIONAGE -.A*'.] . 1;Tul 13. •' S C SECT1JNS T93 AhJ ?S4 THE TGANSM^SION on THE REVELATION C :T5 CONTENTS IN ANT KANNEB "0 AN UNAU'.MORIIES 1*»S0* •« !^ONI8'T£0 6' IA*

CONFIDENTIAL

Under present supply conditions the size and shape of

the fuel particle is also a minor factor. Roughly speaking,

the burning rate might be expected to increase with a decrease

in particle size. The observed change, with magnesium at least,

was insignificant between -70 and -200 mesh. As to particle

shape, ground magnesium with its rough irregular particles

(compared to the regular spheres of the atomized material)

burned poorly. The rough particles, however, compact to give

a harder charge, and the decrease in combustibility may have

been due to the density effect described later.

When compared on the basis of available oxygen, differ-

ent oxidizers are probably of greater importance in determining

main fuel dilution and charge stability than burning rate. Thus

substitution of potassium nitrate or potassium perchlorate for

sodium nitrate would have a beneficial effect on moisture up-

take during storage. On the other hand, variation in the con-

tent of a given oxidizer is one of the strongest and most prac-

tical means of influencing burning rate. Table 16.3-1 indicates

the extent of the control available in a 6-inch annular-charge

system in which other flow and burner variables have been held

constant [40j.

Mixtures with slightly higher concentration (15 per cent)

of nitrate are capable of self-sustained combustion in the ab-

sence of air and form the basis of the flare-type charge with

burning rates of 20 in/min, and in certain Bureau of Mines for-

mulations, as high as 180 in/min [11]. A third form of com-

bustion intermediate between the annular and flare type has

been observed with low nitrate concentrations, particularly

with aluminum. Labeled "fizz burning", an annular charge is

ignited at its downstream face and "cigarette burns" in the up-

stream direction. The recirculation zone at the bluff burning

face plays a stabilizing role similar to that in the ordinary

- 26 -

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CONFIDENTIAL

TABLE 16.3-1

Linear Burning Rate in Magnesium Charges

as a Function of NaNO» Content

(2% Linseed oil, 0 1)

Per Cent NaNOg V., in /mln

0 (2.4)*

2.5 2.8

5.0 3.7

7.5 5.1

10.0 7.3

12.5 12.0

* Extrapolated

- 27 -

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CONFIDENTIAL

baffle-type flame holder, Though relatively unexplored, linear

burning rates as low as 1 in/min appear possible under altitude

conditions with this technique. Since large fuel flows are not

required for high-altitude operation, the way may be opened for

achieving the long burning periods (>30 minutes) required for

intercontinental flight.

With some oxidizers, particle size appears to be a rate-

controlling factor. In a 7.5 per cent sodium nitrate annular

charge the burning rate increased linearly by 75 per cent when

the mesh size of the nitrate was decreased from -40 +70 to

-140 +200.

Changing the type and concentration of binder serves a

better purpose when employed to tailor the physical properties

of the charge. Thus, substituting rubber cement for linseed

oil [41] raises the compressive strength of a magnesium charge

by a factor of 6. Ordinarily, the linseed-oil charges crush at 2

roughly 1200 lbs/in . Since one of the principal difficulties

with boron charges is their poor structural properties, this

type of substitution can be very important. Of less practical

use is the 60 per cent decrease in burning rate when the lin-

seed-oil content of a magnesium-ammonitim dichromate charge is

raised from 1 to 5 per cent.

Little leeway is available for controlling the burning

rate of annular charges by changing their density, because of

the overriding need for high structural strength. The tech-

nique may, however, become useful in adjusting the burning rate

of the mechanically supported flare-type charge. For example,

the rate of a SIg-15% sodium nitrate flare can be increased from

20 in/min at a specific gravity of 1.25 to 45 in/min by molding

at a sufficiently lower pressure to obtain a specific gravity

of 0.75.

- 28

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Equivalence ratio and initial charge temperature were

included, perhaps somewhat arbitrarily, in the list of burner-

design variables which could be employed to establish control

over burning rate. Only a brief discussion of their effects is

warranted, since there is little here of utility to the designer,

The burning rate is almost constant with equivalence ratio, de-

creasing no more than 5 per cent as an initial equivalence ratio

of 0.5 is enriched to 1.5 in the lower nitrate charges (approxi-

mately 5 per cent sodium nitrate). The effect is somewhat

greater at higher nitrate concentrations but still amounts to

no more than a 10 per cent decrease over the same range in 10

per cent sodium nitrate compositions. The temperature effect

is similarly small. Lowering the charge to -80°F resulted in a

10 per cent decrease in air specific impulse in the 190-200

range [40], and it is probable that only a part of this loss

can be ascribed to a lowered burning rate.

The third item in this group, i.e., the observation that

the linear burning rate of the annular charges is a strong func-

tion of the air mass flow through the central passage, is one of

great significance. The magnitude of the effect is illustrated

in Fig. 16.3-4. An eightfold decrease in air mass flow per unit

cross-sectional area produces a roughly threefold decrease in

burning rate. In brief, the solid fuel ramjet has a self-

metering characteristic which at least partly compensates for

the otherwise large changes in air-fuel ratio that would be ex-

pected as the ramjet operated across broad ranges of speed and

altitude. Since the data points in Fig. 16.3-4 were obtained

by both varying the mass flow at constant inlet pressure through

the use of nozzles and by lowering both pressure and mass flow

in an altitude test stand, it is believed that the parameter

selected for the abscissa is sufficiently definitive for design

purposes. Intensive study may, however, reveal that a more

- 29 -

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CONFIDENTIAL

general expression in terms of separate pressure and velocity

functions can be written. For example, static tests on flare-

type charges have shown that the burning rate decreases with

lowered pressures [11].

Thrust Control

Since the primary objective of controlling the burning

rate is the subsequent control of the thrust output of the en-

gine, it is desirable to broaden the discussion in the latter

terms. There are two connotations to the phase "thrust con-

trol". The first implies reproducibility, and the problem is

little different from that encountered in solid-propellant

rockets. The data listed in Table 16.3-2 indicate that even

when no extraordinary quality-control procedures were employed

in the formulation stages, reasonable reproducibility was ob-

tained. The second implication is one of variable thrust to

meet varying flight conditions. Several methods for meeting

this requirement in solid fuel ramjets will be outlined in the

following paragraphs.

The simplest and most direct approach is to take advan-

tage of the self-metering characteristic just discussed. Con-

sider a 6-inch diameter missile of the form sketched in Fig.

16.3-1(a). Table 16.3-3(a) summarizes the performance expected

over the flight Mach number range of 1.2 to 2.4 at sea level.

It is apparent that a constant air specific impulse condition

can be established and that the net thrust relationship above

Mach 1.6 is at least compatible with a uniformly accelerating

trajectory. A free-jet test at Mach 1.6 checked these re-

sults insofar as a burning time of 12 seconds and a minimum

air specific impulse of 184 were obtained. Table 16.3-3(b)

- 31 -

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TABLE 16.3-2

Thrust Reproducibility in Magnesium Burners

Run No. Charge Type ma 0 Burn Time S a

Lbs Thrust

X67 2-ln Annular 0.66 0.74 3.5 sec 172 168 ti tt 0.81 3.3 170 170 ti tt 0.64 3.8 175 171 ti tt 0.74 3.5 172

175 it 0.44 0.81 4.8 172 176 *» 11 0.74 5.0 167 177 tt M 0.76 5.0 170

74 2-in Split Flow 22* 0.35 4.0 146 75 tl tt 0.35 4.1 148 82 tt tt 0.34 4.4 148

85 ** » 0.24 5.6 12S 86 tt It 0.24 5.6 126

68 tt 16* 0.37 5.2 139 89 tl " 0.38 5.9 145 67 tt *t 0.39 5.0 144 69 t» tt 0.41 5.4 150

76 tt 10* 0.24 6.6 124 77 tt tt 0.24 S.6 120 78 t« tl 0.23 6.9 114

9 6-in Split Flow** 13.5 330 10 tt 13.0 330 12 tt 13.5 320 20 ft 13.5 310 24 It 13,5 320 25

1 it 14.0 320

* */o total m thru center of charge A

** Free-jet tests (M - 1.57; 2! " 3-°> Ao

- 32

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CONFIDENTIAL

TABLE 16.3-3U)

Constancy of Impulse at Sea Level over Velocity Range

Flight Macn Burning i f — -

S a CT CD

' Net Thrust No. Time, Sec 0 Lbs

1.2 18.8 0.85 189 0.44 1.4 15.0 0.82 188 0.53 1.6 11.1 0,80 187 0.62 0.29 250 1.8 9.8 0.81 188 0.56 0.27 ^75 2.0 s.r- 0.86 190 0.51 0.25 300 2,2 7.4 0.88 191 0.45 0.24 295 2.4 6.4 1.04 193 0.40 0.23 285

Constancy of Impulse at M

TABLE 16.3-3(b)

1.8 over Altitude Range

Altitude. Ft x 10"*

Burning Sa CT D

Net Thrust Time, Sec 0 Lbs

0 9.8 0.81 198 0.56 0.27 275 5 12.5 0.75 186 0.57 0.27 235

15 14.8 0.85 189 0.65 0.27 200 25 22.4 0.87 190 0.73 0.28 160 35 30.4 0.91 192 0.82 0.29 120 45

40.0

• —

1.10 195 0.85 0.30 75

Estimated performance of missile calculated on basis of:

1. 2. 3. 4. 5.

7. 8. 9.

10.

Diffuser ratio - 4:1 Burner drag coefficient • 6 Diffuser efficiency - 60fc No tail constriction Burning rates from experimental results at Continental Aviation and Experiment Incorporated (Fig. 16.3-4) The 3 for various air-fuel ratios was taken from data obtained in 8-inch burner by Continental Aviation Fuel weight - 22 pounds Size of charge • 4 in I.D. x 6 in O.D. x 30 in long Fuel composition - 93% llg , 5% NaNC,, 2% linseed oil Shock on rim at M 1.6, spilling below, swallowed above.

- 33 -

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CONFIDENTIAL

extends the performance calculations to level flight at a

series of altitudes. Again, in spite of the fact that the

air mass flow has suffered an eightfold change between sea

level and 45,000 feet, the air specific impulse is sur-

prisingly constant.

The foregoing basic technique can be given greater

flexibility and made subject to more precise control by going

to the split-flow type of design [Fig. 16.3-1(b)]. The inser-

tion of a flow metering orifice at the downstream end of the

canister eliminates the trend to an Increasing S as the burn-

ing surface becomes larger toward the end of the run. A com-

parison of the two thrust-time curves in Fig. 16.3-5 illus-

trates the effectiveness of this device. Performance predicta-

bility is further enhanced by the maintenance of & constant internal drag. In practice mild steel orifices have heir? uy

quite well in magnesium burners, but graphite or ceramic ori-

fices are required for aluminum. Proper selection of the area

ratio of the internal and external air passages is, of course,

important. The main goal is to have the central flow reduced

or raised automatically, depending upon whether the temperature

produced therein increases or decreases because of altered in-

let conditions in flight. This aerothermodynamic "choking"

control is in the same direction as, and supplements, the in-

herent self-metering characteristic of the charge.

A still further refinement would be the installation of

a valve arrangement (e.g., a butterfly or rotating sleeve in

the extension to the inlet of the central duct). The position

of the valve would be coordinated with the momentary thrust

demand imposed on the engine throughout its flight and maneu-

vering path.

34 -

CONFIDENTIAL TH» DOCUWXT COKTMU WtiMMTON WnCTMG IX M7XMM. DCrc»M C* TrfZ UMTID -,r-T Ei WVxnt THC MCJWM9 0* TMt CWXMMt L*»l. TITLl It. US C. fCCTIM* »•» «~n »• • »*" "

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70O

6 8

TIME (seconds)

Fig. 16.3-5 EFFECT OF METERING ORIFICE AT DOWNSTREAM END OF FUEL CHARGE ON THRUST FROM SIX-INCH SPLIT-FLOW

BURNER

35 -

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No attempt will be made to detail the many other possi-

bilities for thrust control. Their number is limited only by

the ingenuity of the designer. For the purpose of suggestion,

several approaches can be listed.

1. Combinations of flare and annular charges.

2. Multiple charges of one or both types

sequentially fired.

3. Formulation of charges. Entire charge

can be altered, or longitudinal and radial

variations can be introduced in a pro-

grammed manner.

4. Missile can be overpowered and servo-

activated drag spoilers added.

5. Controlled diffuser bleeds.

8. Variable-area intakes and exhausts,

including combustible arrangements

fabricated from the fuel composition.

Burner Efficiency

In Fig. 16.3-8 the experimental air specific impulse ob-

tained under sea-level and altitude conditions with both flare

and annular magnesium charges is plotted as a function of equiva-

lence ratio. A 2-inch diameter burner was employed in most of

the runs, the only exception being a 4-inch unit in the altitude

runs with annular charges. The theoretical air specific im-

pulse-equivalence ratio curve for magnesium is included. Em-

ploying the ratio of observed to theoretical S as a measure of a impulse efficiency, it is seen that all of the points are above

the 80 per cent level and the majority above 85 per cent. These

- 36

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CONFIDENTIAL

percentages may be slightly inaccurate, since absence of ther-

modynamic data for sodium oxide prevented exact determination

of the effect of the sodium nitrate in development of the theo-

retical S curve. Also, the data have not been corrected for a heat losses to the chamber walls. Of particular interest is

the fact that the impulse efficiency seems to suffer but little

from the lowered pressure conditions of the altitude runs.

This is more clearly shown in Pig. 16.3-7 where the impulse ef-

ficiency is plotted as a function of combustion-chamber inlet

pressure. For comparison, a typical performance curve for a

2-inch burner operating on a homogeneous vapor-phase hydrocar-

bon fuel is given [?«*].

Further impulse-efficiency data are given in Table 16.3-4.

The first five runs show that the 2-inch annular magnesium

burner appears to reach maximum efficiency in a 24-incb tail-

pipe. Excessive heat losses to the walls probably account for

the lower efficiencies with the very long chambers. The S

values have not been corrected for these losses which, by di-

rect measurement, amou .ted to 23 per cent and 12 per cent re-

spectively in runs 236 and 225. Under similar conditions with

hydrocarbon burners where the heat loss is about 5 per cent,

an efficiency of 85 per cent is obtained with a 14-inch tail-

pipe [27]. The next eight runs indicate the generally more efficient

operation observed in the split-flow annular type of system.

The heat losses through the wall appear to be small, and the

downstream mixing processes are enhanced by this technique.

Here the initial combustion within the core of the charge is

quite rich (# » 1.5 to 4). The resulting heat release is, how-

ever, Still sufficient to vaporize magnesium. The secondary

and principal combustion thus occurs under the favorable condi-

tion of rapid turbulent admixture of two gaseous streams. The

- 33

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CONFIDENTIAL

split-flow system also allows improved fuel economy. Thus,

the same performance outlined in Table 16.3-3(a) for a 6-inch

missile at an S of 190 can be obtained at 140 by adjusting EL

the inlet area for higher air mass flows. This, of course,

cannot be done with the simple annular charge, since then the

effect of a greater mass air flow is merely to increase the

burning rate and hence the S & a The next three runs reveal that further gains can be

found in the judicious use of mixing devices. The 6-inch

diameter split-flow charge gave an impulse efficiency of 88

per cent under Mach 1.83 conditions in a free-jet test, A

small perforated "can" mixer (see Chapter 3) attached to the

downstream end of the charge increased this figure to between

92 and 93 per cent. No intensive effort was made to optimize

the mixing system. These impulse efficiencies correspond to

combustion efficiencies (based on equivalence ratios) of the

order of SO per cent.

The highly doped aluminum and boron charges described

in an earlier section burned with impulse efficiencies of ap-

proximately 90 and 80 per cent respectively, the theoretical

S in each instance being based on the actual formulation used

Combustion Limits

As ordinarily used, "combustion limits" have little j

meaning in systems where the "diffusion" of atmospheric oxygen

to a solid surface is an important preliminary to subsequent

reaction. That is. the range of stable burning is extraordi- i i

narily broad. The runs in Fig. 16.3-6 lie between equivalence |

ratios of 0,25 and 3.3. These are not true limits, however,

but merely the change extent of the investigations. Thus, in

the split-flow burners the combustion within the charge is of-

ten carried out at equivalence ratios in excess of 4.

-41- • «

1 CONFIDENTIAL TKiX 00COWCN7 CONTAINS tttfOHUATic* ATFECTWC THC 'aTlOWl. DEFENSE Of ?Hf UNI1C0 STATES W'THIM Thf UEINlNG JF THE ESIMGrtAGE LAWS TITLE I*. U S C SECTIONS T91 V L' 7j« TME rftANSMl$S:ON (* THE RCVtUMnOM OF -TS CONTENTS "* Art' MASJHC«* TO SN 'JNAUTMORlZ ED !>£BSON S PWOMBITEC 8r i_A*

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NOMENCLATURE

Symbol Definition Units

(f> equivalence ratio

S air speciiic impulse ib-sec/lb a

Sf fuel specific impulse lb-sec/lb

S f air-fuel specific impulse lb-sec/lb

mf fuel flow rate lbs/sec

m air flow rate lbs/sec

V. linear burning rate in/min

2 S total area of burning surface in

r ratio of specific heats 3

d fuel density lbs/ft

- 42 -

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APPENDIX

THEORETICAL AIR SPECIFIC IMPULSE, FUEL SPECIFIC IMPULSE,

FLAME TEMPERATURE, AND EXHAUST COMPOSITION

FOR SEVERAL SOLID FUEL SYSTEMS

In making the impulse calculations the usual relations

were employed, i.e.,

S . 4/2(7 I af f ygm

I) RI

m. S - S . (1 + -1) , a af m ' a

s m

1 S_, (1 + -*). X a.J. m „

If the exhaust stagnation temperature is in degrees Kelvin, R

becomes 2776 ft~lbs/°K/lb mol. The acceleration due to gravity. o

g, is 32 ft/sec and the air and fuel mass flows, m and m„, are ' ' a i ' in lbs/sec. The presence of the solid (or liquid) phase in the

exhaust was allowed for in the manner suggested by Maxwell,

Dickinson, and Caldin [Aircraft Engineering, XXIII, 212, (IG46)J.

The tarsi, m, which is the average molecular weight for a gaseous

exhaust, is now taken as the weight of exhaust gases plus the j

weight of exahust solids divided by the mols of exhaust gases

only. The specific heat ratio, y, is computed as the C for the exhaust gases plus the C of the exhaust solids divided by j

i the C for the exhaust gases plus the C for the exhaust solids. v p ! Temperature and velocity equilibrium between exhaust gases and

exhaust solids are assumed. That this procedure leads to no

43 f »

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inaccuracies ii excess of 5 per cent in the range of solid-gas

ratios considered was demonstrated by direct experimental in-

vestigation (Reference 47 in text). The thermodynamic data

employed are indicated in footnotes to Tables 16A-1, 16A-2,

16A-3, and 16A-4. Many of these data are questionable so that

the values for the theoretical performances of magnesium,

aluminum, boron, and decaborane should, be employed only in

realization of this fact, It was assumed that no heat was

available from phase changes (condensation and crystallization)

during the passage of the stream from the combustion chamber

tnrough the exit section. The accuracy of this assumption is

difficult to determine, but at least it leads to conservative

theoretical performance figures. In the case of magnesium at

the stoichiometric ratio, if the heats of fusion and evapora-

tion are available, the S is 242, but if unavailable, this is £L

lowered to 220.

- 44

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- 48

CONFIDENTIAL nai DOCUuCMT C0HTAIJI5 WotttnlldN VFtCIDNS TMC «»i»i CCrfNSC OF tx£ UMrtO STtTCS WITHIN THE HCANtMC Of THf tVlCaat iMil TITLf It, U S C. 5CCTI0MS 'PS AND T94 TMC TRANSMISSION 0« TMt »t«LATI0ll ,V* ITS ClVfTeNTS M AK. y*««» W AN UKAUTMOIllZrD INTDSON 'S POOMifliTfO 9T UA»

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REFERENCES

1. Alperin, M., Theoretical Calculations of the Thrust of a Solid Fuel Ramjet, Jet Propulsion Laboratory, California Institute of Technology, Progress Report No. 3-20, 1947.

2. Anderson, R. C., Preliminary Studies on Suspensions of Solids as Fuels for Ramjet Propulsion (Restricted), Defense Research Laboratory, The University of Texas; Applied Physics Laboratory, The Johns Hopkins University, CM-789, 1946.

3. Anon., Interim Progress Report of Meteor Project (Confidential), Massachusetts Institute of Technology, Meteor Report No. 49, 1950.

4. Anon., Interim Progress Report of Meteor Project (Confidential), Massachusetts Institute of Technology, Meteor Report No. 55, 1950.

5. Baker, W. T., Davis, T., and Matthews, S. E., Reduction of Drag of a Projectile in a Supersonic Stream by the Com- bustion of Hydrogen in the Turbulent Wake (Confidential), Applied Physics Laboratory, The Johns Hopkins University, CM-673, 1951.

6. Barr, W. J., Fenn, J. B., and Mullen. J. W.. II, Suggested Applications for Recently Developed Solid Fuel Ramjet Systems (Confidential), Experiment Incorporated, Memo No. 197, 1950.

7. Bartel, H. R. and Rannie, W. D., Solid Fuel Combustion as Applied to Ramjets (Restricted), Jet Propulsion Laboratory, California Institute of Technology, Progress Report No. 3-12, 1946.

8. Berl, W. G., Bumblebee Survey Report No, 40 (Confidential), July 1946 and Bumblebee Survey Report No. 49 (Confidential), December 1946.

9. Bowling, A. G. , Use of Sweat Cooling to Prevent Build-up of Oxide in a Combustion Chamber (Restricted), Royal Aircraft Establishment, England, Tech Note Aero. 1978, S. D. 86, 1948.

10. Branstetter, J. R., Lord, A. U. , and Gerstein, M., Combustion Properties of Aluminum as Ramjet Fuel (Confidential), NACA RM E51B02, 1949,

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CONFIDENTIAL lmS OCCWE/i) C9*'Ai;4S iHrCKS&fiOi* />*FKCT(NG THf. NiTinX'-i DffENSL G-" lHli USfTiU ilATES W'l'WN THf MEANING W THE ESPIONAGE LAWS TlTLS; 19. USC SECTf^b 7»5 *>*>> 754 -:l IrUNiWiJSION OH

THE ."'"VELAriON OF ITS CONTENTS IN ANY MAKNER '0 Ar. JHAUTMOH^EO -^ftSON 'S PROHIBITED 8J LAW

CONFIDENTIAL

i 11. Damon, G. H. and Herickes, J. A., Combustion of Solid

Fuels for Ramjets, Bureau of Mines Progress Report Nos. 3-23 on Navy Department, Bureau of Ordnance Project, (No. 3 Confidential, Nos. 4-17 Restricted, Nos. 18-23 Confidential), October 1946 to December 1951.

12. Davis, H. and Hottel, H. C., Combustion Rate of Carbon, Ind. Eng. Chem., 26, 889, (1934).

13. Faget, M. A. and grout) from NACA, visit to Experiment Incorporated April 6, 1951.

14. Fennell, T.R.F.W., The Approximate Analysis of Aluminum Fuel Combustion Products, Royal Aircraft Establishment, England, Tech. Note Chem. 1087, 1949.

15. Gammon, B. E., Preliminary Evaluation of the Air and Fuel ) Specific-Impulse Characteristics of Several Potential Ram-Jet Fuels, I: Octene-1, Aluminum, and Aluminum- Octene-1 Slurries (Confidential), NACA RM E5_C12, 1951.

16. Gammon, B. E., Preliminary Evaluation of the Air and Fuel Specific-Impulse Characteristics of Several Potential Ram-Jet Fuels, II: Magnesium and Magnesium-Octene-1 Slurries (Confidential), NACA RM E51C23, 1951.

17. Gammon, B. E., Preliminary Evaluation of the Air and Fuel Specific-Impulse Characteristics of Several Potential Ram-Jet Fuels, III: Diborane, Pentaborane, Boron, and Boron-Octene-1 Slurries (Confidential), NACA RM E51D25, 1951.

18. Gammon, B. E., Preliminary Evaluation of the Air and Fuel Specific-Impulse Characteristics of Several Potential Ram-Jet Fuels, IV: Hydrogen, a-Methylnaphthalene, and Carbon (Confidential), NACA RM E51F05, 1951.

19. Gibbs, J. B. and Cook, P. N., Jr., Preparation and * Physical Properties of Metal Slurry Fuels (Confidential), ../ NACA RM E52A23; 1952.

20. Lippisch, A. M., History of the Origin of Project LI-P 13 (Athodyd) , Issued by II. S. Navy Bureau of Aeronautics, Technical Intelligence Liaison Unit, BAGR-DC, Wright Field, Dayton, Ohio.

21. Longwe11, J. P., (private communication).

22. Lorin, R. , L'Aerophile, 22_9_, (1913).

23. Lorin, R. , L'Aerophile, 5.13, (1913).

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CONFIDENTIAL THIS DOCUMENT COWTA.NS INFORMATION AFFECTING THE NATIONAL DEFENSE OF T*C UNfTCC STATES WTWIN THE MEANWG Of TMF. fSPIONAGE L**S. T,*^£ 18 uSC SECTIONS 793 ANU 794 THE TRANSMISSION OR THE REVELATION Of' US CONTENTS -ti *N* MANNER TO AN UNAUTHORIZED ^RSON '$ »*OH>8iTr.O $•/ t_A*

CONFIDENTIAL

24. Mazurkiewicz, E. J., Booster Ramjet Study (Confidential), Continental Aviation and Engineering Corporation, Report No. 375, 1948.

25. Mazurkiewicz, A. G., Some Rheological Properties of Aluminum Suspensions in Kerosene, Royal Aircraft Establishment, England, Tech. Note Chem. 1055, 1948.

26. Mullen, J. W., II and Fenn, J. B., Burners for Supersonic Ramjets. Some Factors Influencing Performance at High Altitudes - A Resume (Confidential), Experiment Incorporated, TM-188; Applied Physics Laboratory, The Johns Hopkins Uni- versity, CF-1383, 1950.

27. Mullen, J. W., II, Fenn, J. B., and Garmon, R. C., Ind. Eng. Chem., 43_, 195, (1951).

28. Olson, W. T. and Gibbons, L. C., Status of Combustion Research on high-Energy Fuels for Ramjets (Confidential), NACA RM E51D23, 1951.

29. Parker, A. S. and Hottel, H. C. , Ind. Eng. Chem. , 23., 1334, (1936).

30. Parker, W. G. and Wolfhard, H. G., Temperature Measurements of Flames Containing Incandescent Particles, Proc. Phys. Soc., £2, Series B, (1949).

31. Pomeroy, A. L., Thompson Products, Inc. private communications, February 1951.

32. Resume of visit to Wallop's Island, Experiment Incorporated Internal Memo, May 1, 1951.

33. Roberson, E. C., Thrust and Fuel Economy Characteristics of Potential Ramjet Fuels (Restricted), National Gas Turbine Establishment, England, Report No. R.17, 1947.

34. Sanford, E. S., Magnesium Fueled Ramjet Booster for Triton, Applied Physics Laboratory Internal Memo to J. H. Walker, October 23, 1951.

35. Sanford, E. S., Solid Fuel Ramjet Midcourse Sustainers for Terrier, Applied Physics Laboratory Internal Memo to J. H. Walker, December 13, 1951.

36. Saenger, E. and Bredt, I., Ueber einen Lorinantrieb fuer Strahljaeger, Berlin-Adlershof, Deutsche Forschungsans- talt fuer Segelflug E. V., October 1943, (Available as A.M.C. translation No. F-TS-901-RE), 1947.

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CONFIDENTIAL TM'S OOCWTBIT CONTAINS INFORMATION AFFECTING THE NATIONAL DEFF.-SF. Of TKE UWTID STATES WITHIN THt MEAN'Nli OF 1HC ESVI0NA3E LA*S . TITLE '5. U S.C SC-T'IJNS 7y» AH0 794. THE TRANSMISSION 0« THE BEVELA1I0N OF ITS CONTENTS IN 4NV MANNER To AN UNAUTHORIZED PEHSCN IS PROHIBITED »Y LAW

CONFIDENTIAL

37. Schwabl, H., Systematische Versuche uber die Verwendung von Festkraftstoffen in Lorin - Triebwerken, Wien. LuftfahrtiorsnnunT ( January 1945. (Available as A.M.C. translation No. F-TS-102I-RE.)

38. Scott, R. C., Bailey, M., Burke, J. A., Mooraaw, C. E., and Wolf, R. L., Polid Fuel Ramjets III. Final Flight Test Report of Six FTV-N-4e (MTV-Mk 1-Mod 3) Magnesium-Fueled Test Vehicles (Confidential), Experiment Incorporated; Applied Physics Laboratory, The Johns Hopkins University, CM-727, 1952.

39. Smith, F. W., Predicted Combustion Characteristics of Brush Carbon Spheres in High-Velocity Air, Massachusetts Institute of Technology, Meteor Report No. 6, 1947.

40. Squiers, J. C. and Collins, W., Solid Fuel Ramjet Development (Confidential), Continental Aviation and Engineering Corp. Summarv Report on Air Force Contract W-33-038-ac-13371, 1950."

41. Squiers, J. C. and Collins, W., Continental Aviation and Engineering Corp. Progress Report on Contract W-33-038-ac- 13371, 1950.

42. Squiers, J. C., Gun-Launched Ramjet Projectile, Continental Aviation Engineering Corp. Progress Report on Army Ordnance Contract DA-20-018-ORD-12270, April 1951 - April 1952.

43. Tower, L. K. and Branstetter, J. R., Combustion Performance Evaluation of Magnesium-Hydrocarbon Slurry Blends in a Simulated Tail-pipe Burner (Confidential), NACA RM E51C26, 1951.

44. Tu, C. M., Davis, H., and Hottel, H C, Combustion Rate of Carbon, Ind. Eng. Chem., 26, 749, (1934).

45. Wascher, W. L., Availability and Cost of High Purity Boron, WADC Memorandum Report, 1952.

46. Wolf, R. L., Solid Fuels for Ramjet Engines, Final Report of Work Done on Purchase Order 40350 for Continental Aviation and Engineering Corp., Experiment Incorporated, TM-229, 1950.

47. Wolf, R. L. and Strode, H. H., Effect of Solid Particles in Ramjet Exhausts, Final Report of Work Done for Air Materiel Command on Contract 12633, Part II, Experiment Incorporated, TM 362, 1951.

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CONFIDENTIAL THIS DOCUMENT GO^TAJNS i•?0RMATl0K AFFECTING THE NATIONAL DEFEND "* THE UNTED STATES W'.THIN THE MEANING OF THE ESPIONAGE LAWS. TITLE IB. U S C. 8*5Tl3W' 95 A 794 THE TRANSMISSION ON THE REVELATION OF ITS CONTENTS IN ANY MANNER TO ... UNAUTHORIZtO PERSON '$ PftONlSlT'O BY LAW

:

CONFIDENTIAL

48. Wvjlf , H. L. , Garmon, R. C. , And Bailey, M. , Use of Aluminum as a Fuel for Ramjet Engines, Final Report of Work Done for the Reynolds Metals Company, Experiment Incorporated, TM-361, 19r>l.

49. Wolf, R. L., Garmor, R. C., and Ancarrow, N. H., Progress reports of work done on Contract 12633 S.A. KS51-2594), Air Research and Development Command, Wright-Patterson Air Force Ba*e, October to July 1952.

50. Wolf, R. L. , Solid Fn?»l Ramjet Studies, Monthly Progress Reports, February through December 1951 on Contract NOrd 9756.

51 Wolf, R. L. and Curdts, W. T., III, Minutes of the Development Subcommittee Meeting, Bumblebee Propulsion Panel (Confidential), Applied Physics Laboratory, The Johns Hopkins University, TG 63-17, 1951.

52. Wolf, R. L., Scott. R. C., Moomaw, C. E., Bailey, M., and Mullen, J. W., II. Preliminary Report on Recent Flight Tests of a Solid Fuel Ramjet [PTV-N-4e (MTV)] (Confidential), Experiment Incorporated; Applied Physics Laboratory, The Johns Hopkins University, CF-1753, 1952.

53. Wolf, R. L., Bailey, M., Burke, J. A., Moomaw, C. E., and Scott, R. C., Solid-Fuel Ramjets II, Development of Split Flow Combustor System (Confidential), Experiment Incor- porated; Applied Physics Laboratory, The Johns Hopkins University, CM-732, 1952.

54. Wolf, R. L., Solid Propellants for Supersonic Ramjets (Confidential), Presented at the Eighth Joint Army, Navy, Air Force Solid Propellant Meeting, Redstone Arsenal, June 6, 1952.

55. Wolf, R. L., Preliminary Calculations on the Use of Solid Fuels in Meteor II, Experiment Incorporated Internal Memos, March 19, 1952 and April 28, 1952.

56. Wolf, R, L. , Garmon,, R. C. , and Longo, A. , Combustion of Boron, Quarterly Progress Report on Contract AF 33(038)- 12633, Air Research and Development Command, Wright- Patterson Air Force Base, 1953.

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CONFIDENTIAL THIS 0OCWMENI CONTAINS INFORMATION AFFECTING THE NATIONAL OFFENSE Of THE UNiTEO STATES WITHIN THE MEAKING OF THE E-^IONAGE LAWS. TITLE IB. USC SECTIONS T93 AND 79* THE TRANSMISSION OR Tl'E REVELATION OF ITS CCW'ENTS IN ANY MANNED TO AN UNAUTHORIZED "EOSON -S PROH BITED 8T LAW

CONFIDENTIAL

ACKNOWLEDGMENT

The authors wish to acknowledge the efforts of

their fellow workers at Experiment Incorporated

who at one time or another have contributed to

the various solid fuel programs. These include

M. Bailey, W. J. Barr. J. A. Burke, Jr., H. F.

Calcote, J. B. Fenn, R. C. Garmon, C. E. Moomaw,

R. C. Scott, and W. T. Wise.

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CONFIDENTIAL 7>«* DOCUUCNT I'ONTAINS IMfORHATION AfF:CTINO TMC MATWttl. PtrTNSC Of THC UWTEO STATES WITHIN THE MCAMINO Of 1-!C IJHOHMt IAWV TITLE IS. USC SCCTIJNS 7SJ ANU 7»4 TMC TRANSMISSION OR THE REVCLATlON Of ITS COrrTEMTS IN ANY MANNER TO AN UNAUTHORIZED PCRSCW '5 PROHIBITED Br LAW