Shock and combustion-wave dynamics in an implosion-driven hypervelocity launcher

SHOCK AND ÇOMB USTION - WAVE DYNAMICS IN AN IMPLOSION-DRIVEN HYPERVELOCITY LAUNCHER

by 1. 1. G!ass

.e

- - - --- --- --

-'

..

ACKNOWLEDGEMENTS

I wish to thank Dr. G. N. Patterson for his encouragement and interest in this project. The driving chamber calculations were per -formed by Dr. H. L. Brode, Rand Comporation, Santa Monica, and this work is sincerely acknowledged. The assistance provided by Mr. G. F. Bremner in the design of the apparatus, by A. Benoit in obtaining the ex-perimental da.ta on combustion, and by Dr. A. Makomaski and J. J. L. Brennan in continuing and extending the experimental research on the

initiation of explosives and launchings respectively, is very much appreciat -ed. The research was supported by the USAF under Contract AF 33(657) -7874 and by the Department of Defence Production and the Defence Research Board of Canada.

SUMMARY

In order to solve many existing problems in planetary entry it is necessary to have facilities that are capable of launching undamaged projectiles at hypervelocities in excess of 50,000 ft/sec. (Ref. 1).

Unfortunately, conventional light-gas guns appear to have reached a

velocity plateau of about 30, 000 ft/ sec or less for launching integral aero-dynamic models. It is shown that by a novel application of combustion-wave and shock-wave dynamics in gases and explosives that it is theore-tically possible to achieve projectile velocities in the desired hypervelocity range. Some details are presented of the analysis, facility, and the re

-search results obtained to date on spherical combustion of stoichiometric mixtures of oxygen and hydrogen diluted with helium or hydrogen, the initiation of propellants and explosives by using deflagration and detonation waves, and some initial launchings.

T ABLE OF CONTENTS

NOTATION v

1. INTRODUCTION 1

2. THEORETICAL AND EXPERIMENT AL CONSIDERA TIONS 1

3. EXPERIMENTAL RESULTS 5

4.

3. 1 Spherical Combustion

3. 2 Surface Initiation of Propellants and Explosi yes by Combustion Waves

3.3 Launching of Aerodynamic Models CONCLUSIONS REFERENCES FIGURES 1 to 28 iv 5 8 9 9 10

A D Q R T a e m p t u u x -_x NOTATION launcher barrel area

specific energy source or loss artificial viscosity pressure radial distance

initial position of a Lagrangian surface temperature

sound speed

specific internal energy

1/3

p

1 R₀3, Lagrangian variable expressing mass per stearadian

pressure time

particle velocity; launcher muzzle velocity

escape speed of driver gas u/f).

distance; launcher barrel length

specific heat ratio density

1. INTRODUCTION

Although cylindrical implosion-wave dynamics in solid ex-plosives have made it possible to achiE;~ve copper jet velooities of 100 km / sec (Ref. 13), it appears that the launching velocity of useful and integral aero

-dynamic models from light-gas guns has reached a current limit of about 30,000 ft/sec. In order to conduct experiments in the hyperbolic entry velocity range it is essential to extend this plateau up to 50, 000 ft/ sec and beyond.

An application of spherical combustion and implosion-wave dynamics indicates that it should be theoretically possible to achieve the desired muzzle velocities for small plastic cylinders in the 100 m gm range. A facility which makes use of this analysis has been built at UTIAS in order to check experimentally some of the predictions. Some prelim-inary results are presented on spherical deflagrating and detonating com-bustion, initiation of propellants and explosives by detonation waves, and initial launchings using driver gases produced by spherical combustion only.

The facility is also very useful for investigating spherical deflagration and detonation waves in the "interior" of the phenomena, rather than at the periphery of a spherical bomb, which has usually been the case.

It mayalso be utilized to produce high-enthalpy, high-density plasrnas for m agnetogasdynam ic studie s.

The success of this facility as a launcher will depend on several factors such as the ability to detonate secondary solid explosives,

by using gaseous detonation waves, instantlyand simultaneously over an entire hemispherical surface; the stability of the resulting implosion wave and the contact surface; losses due to erosion and radiation; ability of the models to withstand the very high peak accelerations.

The preliminary results that have been obtained to date on spherical combustion, initiation of solid explosives, and launchings are encouraging, although many important problems must be solved before superorbita~ velocities can be attained from the present facility.

2. THEORETICAL AND EXPERIMENTAL CONSIDERATIONS

Figure 1 shows a diagramatic view of the UTIAS Implosion-Driven Hypervelocity Launcher. It consists essentially of an 8 in. dia. hemispherical cavity in a steel block which is covered with a heavy steel instrumentation plate !and both are fastened by a steel locking cylinder. The assumed operation of the launcher is as follows. The hemisphere is pressurized with a combustible mixture of oxygen and hydrogen diluted with helium or hydrogen, (i. e. 100 psi). The hemispherical surface is lined with a hemispherical cap of explosive (i. e. O. 1 in. thick). The mix

-ture is ignited by astrong spark or an exploded crimped copper wire at the geometrie centre inducing a detonation wave. (In the analysis it is

assumed that the induction distance is zero. In practice this distance de-pends on th,e method of ignition and type of mixture.) The detonation wave hits the explosive liner and instantly and simultaneously initiates the ex-plosive at the surface thereby gene rating an implosion. (In practice, this is the key to the entire operation and has as yet not been completely solved. )

The physical conditions and waves which are induced by this operation may be determined by solving the set of nonlinear partial differ-ential equations of mass, momentum, energy and state as given bel ow, in Lagrangian form, (Ref. 2 and 3)"

mass: momenturn: energy: 1 1 8R3

-

=

v

=

-om 3

/'

ou

at

oe

at

= -

R2

a

(p

+

Q) am

=

_ (p

+

Q)

~

v

+

D

a

t state: e

=

e(T, v), p

=

p(T, v) (1) (2 ) (3 ) or (4) where p

=

p(e, v), T

=

T(e, v)

'àR

u

=

'at

m

=

i

f\

R03 ,

PI

=

initial gas density, Ro

=

initial position of a Lagrangian surface, u

=

particle ve.1ocity, v = specific volume, R = radial distance,

p = pressure, Q = artificial viscosity pressure, e

=

specific internal energy, T

=

temperature D = specific energy source (or loss) rate m

=

mass per stearadian, t

=

time

(5 )

The set of equations is solved by numerically integrating a set of approxi-mating finite difference equations (using the artificial viscosity technique (Ref. 2» subject to the prescribed initial and boundary con~itions. From Brode's analysis it is theoretically possible to g.enerate very high pressures (250, 000 psi) and ideal temperatures (280, OOOoK) at the centre of the

hemisphere (see Figs. 2,and 3) (Ref. 3).

Figure 2 shows the variation of pressure in the hemispherical chamber as a :function of radius for times ranging from 49.38

r

sec up to

69.00).N sec af ter the detonation wave (F) is instantly induced at the centre of the 8 inch radius hemisphere (the actual radius of the facility shown in Fig. 1 is only 4 inches, and would give pressures and temperatures greater than those shown for the same initial gas mixture and O. 1 in. thick

ex-plosive liner). At 49. 38)h sec the detonation wave hits the explosive (TNT was used as a model since its properties are weU known (Ref. 4), whereas in practice Dupont EL-506 material, DIN A and PETN, which are safe se-condary explosives, will be used for the initial experiments). The im-plosion wave (S) reaches the origin at about 67

fo

sec and reflects. (The detonation wave, implosion wave, and explosion wave have spread transi-tions fronts resulting from the use of the artificial viscosity in the num-erical integrations. These can be made sharp at the point where the vis-cosity is a maximum. )

Figure 3 shows a similar plot of the temperature in the launcher combustion chamber for the same times. The contact surface between the hot, dissociated and ionized gases, consisting mainly of helium, and the relatively cool (about 10000_{K) TNT products, is clearly} indicated in this figure.

These conditions and beyond in space and time are high enough that it appears feasible to launch single calibre plastic cylinders (0.22 in. dia. weighing about 130 mgm) at maximum veloeities in excess of 50, 000

ft/

sec (Fig. 4) from a 6 ft long gun barrel, which is located at the centre of the hemisphere. The results shown in Fig. 4 were comput -ed on the basis of one of the interm-ediate pressure and temperature pro-files shown in Figs. 2 and 3 having the maximum and minimum values indicated on Fig. 4, in order to obtain the corresponding muzzle veloeities. The veloeities were conservatively computed from the ideal baUistics

equation (Ref. 1), Eq. 6,

where, x =

x

= J"-U

=

m

'li

2

~

- 1

-

_u U A U

<><'4=

04

+

1 ~ - 1 (6 )

u

=

muzzle velocity of a projectile of mass m in a launcher barrel of length x and area A

=

escape speed of the driver gas into a vacuum

=

sound speed, pressure, and specific heat ratio of the driver gas

It is seen that minimum values of 20, 000 ft/ sec and maximum values of 60, 000 ft/sec are theoretically possible for a single calibre cylindrical plastic projectile of about 130 mgm. In practice such velocities would be limited by the radiation losses from the hot gas, erosion products off the

base of the projectile and entrance surfaces of the gun barrel, and the

strength of the projectile itself. The actual veloeities that wil! be obtained can only be verified experim entally.

Such a launcher has been built at the Institute for Aerospace Studies in order to investigate experimentally the theoretical predictions

(see Figs .. 5 and 6). Figure 5 shows the assembied combustion chamber prior to a run during the investigation of spherical combustion processes. Figure 6 shows the combustion chamber safety barricade and the aero-ballistics range that wiU be used to measure the projectile velocity and

subsequently utilized to investigate aerophysical problems at hypervelocities. The work is being conducted in three stages A, Band C.

Stage A covers the combustion of stoichiometric mixtures of oxygen and hydrogen diluted with helium or hydrogen. A considerabie number of ex-periments have been run using initial pressures ranging from 75 to 1000 psi at room temperature a.n.d various dilutions ignited by a spark or a

crirnped exploding wire. Detonation limits, pressure histories, thin-film

surface tempera.tur.e and heat-transfer records, ionization probe records and total light output (photodiodes) records have been obtained. It is worth

noting that these records were taken in the "interior" of the spherical

com-bustion processes, at three (or six) radii with angular orientations of 1200 (or 600 ), unlike other previous investigations that were limited to peripheral or central measurernents, (Refs. 5 to 10) by having a well-instrumented

top plate, which forms the major diameter of the hemisphere (see Fig. 7). The top plate also contains the ignition electrodes and the gun barrel. It

is seen that a total of 13 probes can be used. The pressure records can be

compared with computed results for constant-volume combustion including

dissociation reactions whereas the traces from the heat transfer gauges.

ionization probes, light gauges, as weU as from the pressure gauges, can be used to study wave motions.

Stage B covers the very basic problem of surface detonation of secondary or sensitized explosives by deflagration or detonation waves produced in combustible gases. Some initial work has been done on a

pro-pellant (JPN) an insensitive secondary explosive (Dupont EL-506) consisting

of PETN crystals in a rubber-like base, pure PETN crystals, and DINA.

It is anticipated that a very considerabie effort wiU be required in order to

solve this problem since very Iittle theoretical and experimental work appears to have been done in this area to date. Once solved, such implo -sions wiU not only be applicabie to the production of enthalpy high-pressure drivers for hypervelocity Iaunchers but to many basic problems in magnetogasdynamics and plasma physics (Ref. 11 to 13).

Stage C will cover the final launching of aerodynamics

models in the aeroballistics range in order to verify the analytical pre

-dictions, as weU as to study aerophysical problems at hypervelocities. It

is anticipated that this stage will be investigated in about a year or two.

3. EXPERIMENTAL RESULTS

3. 1 Spherical Combustion

A considerabie number of runs of spherical combustion were

made using stoichiometric mixtures of oxygen-hydrogen diluted with helium

or excess hydrogen in the pressure range of 75 to 1000 psi (Ref. 14). The

gases were ignited by using a crimped copper wire (see Fig. 8), strong

spark ignition and a few runs were made using a small explosive detonator

cap. It is estimated that only about 10 percent of the maximum of 400 joules

(8 # f , 10KV, low inductance power supply) was dissipated at the spark or

crimp. The remainder was lost in the mechanical switching arrangement

. (the energy input has been improved by using a thyratron unit). When

sparks were genèrated, 1. 5 mm dia. copper electrodes set with a gap of

1 to 2 mm were used to simulate a point-source ignition.

Kistler type piezo-pressure gauges SLM 605-B in conjunction

with type 652-B calibrators were used to measure pressures at various

radii and orientations (see Fig. 7). Platinum thin-film heat-transfer gauges

having glass, quartz. and a magnesium silicate ceramic as a backing

material were used as wave detectors. These gauges are very useful for

deflagrations but are readi1.y destroyed in detonation runs. Glow discharge

gauges were ernployed to measure the arrival of the ionization front of a wave

and Philips type 0 A P 12 photodiodes were used as light sensors to detect

the arrival of a wave front. Additional details are given in Ref. 14.

In this pressure range and using the methods of ignition and

the energies noted above smooth deflagration took place with helium dilu

-tions of 3 to 15 moles in 3 mol.es (50 to 83 percent by volume) of the

stoi-chiometrie mixture. For dilutions containing 3 moles of helium a transi -tion took place and deflagrating or detonating combustion occurred. How

-ever, below this value detonation was produced. Mixtures leaner than 15

moles of helium could not be ignited by a spar'fi or with a crimped wire.

At 100 psi 7 moles of excess hydrogen ~total of 90 percent by volume) gave

the transition limit and 10 moles (total of 92 percent by volume) gave the

maximum dilution for ignition. Consequently, it appears that excess hy

-drogen dilutions of over double the value noted for helium can still provide

detonating combustion. It should be emphasized that owing to electronic

difficulties*it was not possible in the present runs to measure' the actual

detonation velocities between two gauge stations. However. the following

pressure and heat transfer records leave little doubt that detonation did

occur. It is hoped to redesign the circuitry in sueh a manner that direct

measurement of detonation velocity will be possible for future runs. It

should be noted that Edse and coworkers (Ref. 10) report that they were not

5

able to produce spherical detonations in hydrogen-oxygen mixtures (at room conditions) unless blasting caps were used. They also give a value of 84%

hydrogen as an upper limit for detonation.

Figure 9 shows a deflagrating combustion run for an initial

pressure of 100 psi of stoichiometric oxygen-hydrogen diluted with 70 per

-cent of helium. The piezo-pressure gauge traces at both stations (1 and 0 ,

see Fig. 7) in Fig. 9(a) exhibit a similar accelerating rise in pressure

until the entire mixture has been consumed when the deflagration wave reaches the wall (W) of the hemisphere and the pressure reaches a maxi

-mum value. Thereafter, the pressure decreases (almost linearly for two

or three milliseconds in a number of cases, as in Fig. 9). This decrease

in pressure is not primarily due to cooling but the fact that the piezo gauges

are temperature sensitive, each gauge in a different manner. The theore

-tical pressure ratio after combustion (including dissociation effects) for the run shown in Fig. 9 is 9.28. The inside pressure gauge (1) gives a value of

7.57 and the outside gauge (0) yields a value of 7. 29. It might have been expected that the inverse result would occur since the inside gauge is ex -posed to the hot gas for a longer time than the outside gauge (about 2 to 3

m sec, since the measured average flame speed is around 60 ft/sec).

Many of the runs do show this trend (see Fig. 10, where for a and c the

pressure ratios at C

=

4.86, I = 5. 04 and 0 = 5.00, whereas for band d C

=

4.77, 1

=

5. 12 and 0

=

5.49) and illustrates the complex and

non-reproducible effects of temperature.

It is worth noting on Fig. 9 that the heat transfer gauge

re-cord shows a slight build up in the gauge temperature due to adiabatic com-pres sion before the flame arrives, a nearly discontinuous jump when the flame reaches the gauge, a further increase until the wall is reached, and a smaller increase beyond that point. The position of the flame front is also

marked on the piezo gauge trace. .On trace I a slight pressure decrease

across the deflagration front (F) is readily se en but on trace 0, when the

pressure in the chamber is already high it is difficult to detect. This sub

-stantiates the usual assumption that in spherical combustion as well the pressure across the wave is nearly constant. The thermal effect on the pressure trace is well illustrated in Fig. lOb, where apparently negative pressures occur. This effect can be reduced by applying a coating of sili

-cone grease over the gauge surface. A more permanent solution is to use

"ballistic adaptors", where the gauge becomes thermally insulated but with

a corresponding loss in response time. However, for detonations the adaptors are ruined af ter one or two runs. Figure 11 shows the excellent

repeata-bility that can be obtained in deflagrating combustion. The passage of the

flame front in traces I are well defined and furthermore, all traces show a

consistently higher pressure ratio than for the O-traces, as discussed.

Figure 12 shows combustion in the "critical" region for helium-diluted mixtures where either deflagrations or detonations can be obtained. Figure

13 illustrates fully developed detonation for a 40 percent helium dilution.

The detonation velocity (3100 - 3200 m/sec) is too high to be di'stinguishable

between station land 0 (1-7/8 in. apart, at a sweep time of 1 m sec/cm) of

the piezo-pressure traces . 'The oscillatory trace subsequent to the initial deflagration and the superimposed fine signal structure is very real and not due to mechanical vibrations since the heat transfer record shows the same overall frequency (180 - 200 )1.-sec/cycle). 1t is seen that the flame passes

this gauge at 0.4 m sec and the detonation must have developed af ter this

station and reflected to reach this point again at 1 m sec. Owing to the slow

sweep all three gauge traces show the same time of 1 m sec for this event. The theoretical sound velocity for the given initial conditions is 2007 m / sec. Consequently, if these waves ultimately decayed to sonic disturbance waves, the outside gauge, which is close to the wall, should give a frequency based on the time it takes a sound wave to go 4 in. and back again (100 »>sec/cycle), whereas the inside gauge, which is located nearly half way between the centre

and the periphery, should show twice as many oscillations (50

fo

sec / cycle).

The fact is that both gauges show the same frequency without any distinguish-able phase shift for a disturbance that appears to travel at about half the sonic velocity . This condition has as yet not been satisfactorily explained.

It was expected that detonations in a spherical geometry would develop in a

manner similar to planar detonations (Ref. 15), as illustrated in Fig. 14.

It is seen that the flame front produces a compression wave, which forms

into a shock wave. As in the planar case it is assumed thçlt an explosion occurs at A giving rise to an explosive detonation wave and an implosive shock (retonation) wave. These waves will interact with each other and the existing contact surfaces and will thereby give rise to a superimposed fine structure of the type seen on the pressure trace in Fig. 15. Ultimately, a

single wave will exist that will move back and forth at sonic speeds in the

hemispherical combustion chamber. This model has not been verified ex

-perimentally and t~. do so would require optical techniques, something which

is planned for future experiments. A more detailed view of the structure of the pressure traces for detonation is provided in Fig. 15 for the same initial conditions as shown in Fig. 13.

The symmetry of deflagration waves was also investigated using heat transfer gauges and glow discharge gauges on 3 radii, 120 degrees apart (see Fig. 7), as shown in Figs. 16 and 17, respectively. These

traces show the arrivalof the deflagration wave at the probe station~ and

indicate that very good sym metry can be obtained with care, appropriate

dilution, and reasonably high pressures. If a crimped wire is used attention

must be paid not to dump too much energy, or else . a section of the wire,

rather than the crimped point may be vaporized and this will give ri se to an

elliptical wave surface. (This effect can be seen in run 17c where the time

arrival of the wave for trace I occurs sooner than for the other correspond

-ing traces. ) The results are summarized in Figs. 18 and 19 for various initial pressures and dilutions. There is a tendency for the waves to stabilize as they move outward for higher pressures and dilutions.

Figures 20 to 25 summarize the data obtained from the piezo-pressure gauge records. Figures 20 and 21 show the time required by the

deflagration wave to travel the 4 inches from the centre to the wall (time to

maximum pressure) as a function of initial pressure and dilution. It is seen

. J ..

. . ,

that for deflagration waves the flame speed dect.eases with increasing

pressure and dilution. Fi~uI'es 22 to .~5 show a' ~,omparison of the measured

pressure ratios (final to.;rhitial) as a !ÏJnction'of initial pressure and dilution.

The theoretical curves (includi!lg dissociation) ar'~ shown for comparison.

The data is uncorrected for the thermal effects rioted previously as well as

the drop in pressure due to the cooling of the' gaf? by conduction to the metal

surfaces (which is probably small compared to the thermal gauge effect).

Closer agreement with theory and corrected data (3 to 5 percent) is

report-ed in Ref. 16. It may be concluded that the upper limits given to thè

ex-perimental points on the various graphs can besafely used since they

main-ly represent the highe st pressures fO,und at the outside gauges. which would

be least affected by thermal effects. and would give the most accurate

values of the existing pressures in the chamber.

3.2 Surface Initiationof Propellants and Explosives by Comb~stion Waves

I

It was noted previously that the problem of initiating

second-ary explosives by means of combustion wa,ves may be very difficult. It is

known that primary explosives such as lead azide can be detonated in this

manner. However. from a safety point of view and handling properties it

is undesirable to use primary explosives for this purpose. Consequently.

a one-dimensional combustion chamber (Figs. 26 and 27) has been built for

. this investigation (Ref. 17). The centr~ ignition electrode and the cup that

contains the explosive are readily seen in the preceding figures. This geo

-metry makes it possible to use much smaller quantities of explosive for a

given thickness than in the hemispherical cham.ber (1/60) and to obtain

quan-titative data from pressure. ionization. and photodiode gauges as well as

. wave speed records.

Some prelirninary work has beendone with propellants such

as JPN and secondary explosives EL-506; DINA and PETN. The latter

appears to be successful p~ssibility. The explosive samples used consisted

of discs 0.15 in thick x 1-1/2 in dia weighing 3.69 gm at a 'density of 0.85

gm / cm 3 . The explosive crystals were pressed in the cup and then placed

in the combusiion chamber for initiation by detonation waves in

stoichiome-tric m,.:lxtures of hydrogen-oxygen. It appears th~t the PETN detonated when

the initial mixture was at a pressuve greater than 15 atm. A definite lower

prelsure limit was not established since the chamber length is of the order

of the induction distance for pressures in the range of 10 to 15 atm. The

re-sults appear to agree with those given in Ref.

1' .

.

Further details can be found

in Ref. 17.

The final work wiU be do ne using hemispherical liners of

explosive in the launcher combustion charpber. The liners wiU be mounted

on spun stainless steel (1/10 in. ~hick) protedive hemispheres. It will also

be necessary to investigate implosion wave and contact surface stability

following detonation. .

3.3 Launching of Aerodynamic Models

At each stage (gaseous combustion, propeUants, explosives) models wiU be launched in the range in order to measure the progressive

improvement in rnuzzle velocity with each step. Figure 28 iUustrates the flight of a flared, plastic, two calibre, 0.27 in. dia. cylinder model through

the range shown in Fig. 6. A muzzle velocity of about 5000 ft/sec*was pro-duced by a detonating combustion driver (2H2

+

02

+

2He) at 300 and 600 psi initial pressure. This work now has to be extended systematicaUy to

ascertain in the hemispherical combustion chamber the improvement in

rnuzzle velocity at each step when using combustion alone and then with the

addition of propellants and finaUy with explosives. It is hoped that the new research win form the subject of a future note.

4. CONCL USIONS

Shock and combustion wave-dynamics in gases and explosives

can be applied to produce gases of extreme enthalpies and pressures. Such gases can be used to study problems in magnetogasdynamics and plasma

physics. In particular, it is shown that such gases can be used for hyper -velocity launchers to produce theoretical muzzle velocities of aerodynamic models in the superorbital velocity regime. A facility has been built at UTIAS in order to substantiate these ca1culations. The success of the ex-periments hinges on the following: the ability to detonate at the surface se

-condary explosives by combustion waves (deflagration or detonation) instant -ly and simultaneous-ly over an entire hemispherical surface; the stability of

the resulting implosion wave and the stability of the contact surface between the hot, light, driver gases and the heavy detonation products from the

solid explosive; losses due to erosion and radiation; ability of model to '

with-stand enormous accelerations and remain intaGt. Owing to the velocity plateau that has been reached in present day launchers it is considered weU

worthwhile doing this research despite the considerable technical difficulties. The present facility has been already proved its worth in the investigation of spherical combustion of stoichiometric mixtures of

oxygen-hydrogen diluted with helium or hydrogen in the range of initial pressures of 75 to 1000 psi. It has an advantage over other facilities in that combustion

wave dynamics at high pressures and temperatures can be studied in the "interior" of the processes, rather than at the periphery of a spherical bomb. Therefore, the present method should provide a means of studying

spherical combustion wave phenomena in great detail including waU boundary -layer effects behind the wave in the plane of the major diameter of the hemis

-phere.

The preliminary research on the one-dimensional explosion of pressed PETN by gaseous detonation waves in stoichiometric hydrogen-oxygen mixtures at initial pressures of 15 atm and beyond is encouraging .

. The trial launchings using combustion alone show that if the velocities can now be increased by an order of magnitude by using implosion dynamics,

then a very considerable advance will have been made towards the study of aerophysical and impact problems at superorbital velocities.

9

1. Glass, 1. 1. 2. Brode, H. L. 3. Brode, H. L. 4. Brode, H. L. 5. Manson, N. Ferrie~ F. 6. Zeldovich, Y. B. Kogarko, S. M. Simonov, N. M. 7. Litchfield, E. L. Hay, M. H. Forshey, D. R. 8. Ma~ek, A. 9. Freiwald, H. Koch, W. 10. Plückebaum, J. W. Strauss, W. A. Edse, R. REFERENCES

Hypervelocity Launchers, Part I: Simple Launchers. UTIA Review No. 22, 1963, also USAF ARL Report No. 63-86.

Numerical Solutions of Spherical Blast Waves. Rand Corp. Report RM-1363-AEC, 1954; also J1. App1. Phys. 26,6,p. 766, 1955.

Numerical Ca1culations of Blast Waves. Rand Corp. Report P-1933, 1960. The computations were performed by Dr. H. L. Brode, Rand Corp. - private com munication.

Blast Wave From a Spherical Charge. Phys. Fluids, 2,2, p. 217, 1959.

Contribution to the Study of Spherical Detona-tion Waves. Fourth Symposium (InternaDetona-tional) on Combustion, pp. 486-494, Williams and Wilkins, Baltimore, 1953.

On Experimental Investigation of Spherical Detonation of Gases. Soviet Physics - Tech. Phys. 1, 81, p. 1689, 1956.

Direct Electrical Initiation of Freely Expanding Gaseous Detonation Waves. Ninth Symposium (International) on Combustion, pp. 282-286, Academic Press, New York, 1963.

Effect of Additives on Formation of Spherical Detonation Waves in Hydrogen-Oxygen Mix-tures. AIAA J1. 1, 8, p. 1915, 1963. Spherical Detonations of Acetylene Oxygen Nitrogen Mixtures as a Function of Nature and Strength of Initiation. Ninth Symposium (International) on Combustion, pp. 275-281, Academic Press, New York, 1963.

Propagation of Spherical Combustion Waves. USAF Report ARL 63-101, 1963.

11. Völcker, H. 12. Linhart, J. G. Knoepfel, H. 13. Lunc, M. Nowak, H. Smolenski, D. 14. Benoit, A. 15. Oppenhein, A. K. Manson, N. Wagner, H. G. 16. Lord, M. E. 17. Makomaski, A. H. 18. Andreev, K. K. Maslov, V. P.

Theoretical Investigations of Strong, Spherically

and Symmetrically Converging Shock Waves in

Deuterium Gas. Atornkerenenergie 5, 6,

pp. 209-217 and 7, 8, pp. 262-272, 1960.

Amplification of Magnetic Fields and Heating of a Plasma by a Collapsing Metallic Shell.

Laboratorio Gas Ionizzati (Euratom -GNEN),

Laboratori Nazionali di Frascati, Roma, 1962.

Accelerator for Jets Formed by Shaped Charges.

Bulletin, Polish Academy of Sciences, Vol. 12,

No. 5, p. 295, 1964.

An Experimental Investigation of Spherical Combustion for the UTIAS Implosion Driven

Launcher. UTIAS Technical Note No. 71, 1963.

Recent Progress in Detonation Research.

AIAA Jl, 1, 10, p. 2243, 1963.

Performance of a 40 mm Combustion-Heated

Light Gas Gun Launcher. USAF Report

AEDC-TN-60-176, 1960.

One-Dimensional Study of the Initiation of Solid Explosives by Hydrogen-Oxygen Detonation Waves. UTIAS Technical Note (to be published).

Action of a Gas Explosion on Solid Explosives.

'I'

FIG. 1

~--9·---<

UTIAS IMPLOSION-DHIVEN HYPERVELOCITY LAUNCHEH (view of combustion chamber, gun

106 L

IA

S

-10 5 LV'. V~/ P (psi) ,,~~ '"'~/ TNT LINER

t

I

~rGI/r\lfl

_~

_{\ 1\}

.-

.

/

"

y

I

I

/

10 4

bi;'

7

!?/

)'

1 10 3

l

1 I

r

I I J I

IY '

,~ ' "

,I

I 11 1

_/

102 I ; ; 0

~~~~u

20

CONDITlONS IN A 16 IN. DIA. HEMISPHERICAL HYPERVELOCITY LAUNCHER CHAMBER FOLLOWING THE IGNITION OF A COM-BUSTIBLE GAS MIXTURE (0.2 H 2 + 0.₁₀₂ + 0.7 He) AND A O. 1 IN. THICK HEMISPHERICAL LINER OF TNT. VARIATION OF PRESSURE WITH RADIUS Af A FUNCTION OF TIME. Pi = 100 psi, Ti = 2900K

FIG. 2

.... 106 _u

a::

r-

--r---r----r--" t=67.78ILsec ':..~ -... 105 [

~~M~J

n

T(°K) ~ TNT Liner 10 4

l

I

I

1.1 \ Y __ \ '"1 \

I "

,I

";)OJj

'0".,/ , / ' 103

l

~-W

,.-\1 / ,

I

'R

102 , 11 o 5 10 R(cm) 15

FIG. 3 CONDITIONS IN A 16 IN. DIA. HEMISPHERICAL HYPERVELOCITY LAUNCHER CHAMBER FOLLOWING THE IGNITION OF A COM-BUSTIBLE GAS MIXTURE (0.2 H₂ + O. 1 _{O 2} + O. 7 He) AND A O. 1 IN. THICK HEMISPHERICAL LINER OF TNT . VARIATION OF TEM-PERATURE WITH RADIUS AS A FUNCTION OF TIME. Pi = 100 psi,

Ti = 290oK, Pi = 1. 82 x 10- 3 g/cm 3 , D = Detonation Wave, S = Shock Wave, C = Contact Front.

100 80 60 Ideal Launch Velocity 103 fps 40 20

o

FIG. 4 NO CHAMBRAGE

INFINITELY LONG CHAMBER LAUNCH TUBE. 22"DIA. 6 Ft.

LONG

r

=

1. 66

"

_~

t'-...

P4

=

220, 000 psi

~

T 4 = 240, 000 oK

t----,

P4

=

40, 000 psi

r---.

_T~

20,000 oK 200 400 600 800 1000

Projectile Weight - Milligrams

MUZZLE VELOCITIES BASED ON CONDITIONS IN A 16 IN. DIA. HEMISPHERICAL HYPERVELOCITY LAUNCHER CHAMBER FOLLOWING THE IGNITION OF A 100 PSI COMBUSTIBLE GAS MIXTURE (0.2 H2

+

O. 1 02

+

O. 7 He) AND A 0.1 IN. THICK HEMISPHERICAL LINER OF TNT.

")

G. TOP Pl.ATE uA" AND INSTRUMENTATION. TR.

®

ose.

FIRIN8~ _ _ _ ... --\tl_t--""'" UNIT.

TR. _{() prellure gauge.} • heat transter gauge.

PZC piezocolibrator.

TR.

HTU heat tran.fer unit.

TR triggering pul.e.

e

electrode.

lt. HEAT TRANSFER UNIT. (I) to HTG i (2) to

ose.

,---,

mA

I

I

r-~~~--~

I

I

r

I

I

I

- - - J

L - - _ __ _ _ FIG. 7

0.32 mm dia. x 25 mm long

Cu wire crimped at centre to

O. 10 - O. 15 mm

a,

Initial mixture: 2H2 + 02 + 7 He.

Initial pressure: 100 psi. Time scales: 1 msec. / div.

a) Pressure records: I: 219 psi./div. 0: 236 ps i. /div.

·b

Initial temperature: 297 oK.

b) Heat transfer record (1)

Ro

=

26..n.; i

=

20 mA.; 20 mV/div.

Initial mixture: Initial pressure: Time scales: a c 2 H 2 + 02 + _{8 H 2} 1000 psL a) and c) 5 msec/div. b) 20 msec/div. d) 10 msec/div. Initial temperature: Pressures scales:

FIG. 10 _{DEFLAGRATION PRESSURE HISTORIES}

b d 3030K a) 1310 psi/div. b) 1415 psi/div. c) I: 2140 psi/div. d) I: 1130 psi/div. 0: 1360 psi/div. 0: 1470 psi/div.

/

R.

VN

I.

',,--- 0

---,

---.----!

~~l

____ _

Initial mixture: 2H2 + 02 + 5He

Initial press ure: 75 ps i.

Time scales: 1 msec. / div. Maximum pressure ratio Pf/Pi:

,.

Initial temperature: 297 oK. a) I: 7.18; b) I: 7.07; c) I: 7.07; 0: 7.43 0: 7.47 0: 7.47

FIG. 11 REPEATABILITY OF DEFLAGRATION PRESSURE HISTORIES AT

a _b

c

Initial mixture (nomina!): 2H2

+

02

+

3 He

Initial pressure: 100 p. s. i. Initial temperature: 2960K

Time scales: 1 msec/div.

Pressure scales: 179 psLdiv.

FIG. 12 PRESSURE HISTORIES RECORDED IN THREE TESTS CONDUCTED IN A "CRITICALLY" HELIUM DILUTED MIXTURE.

a.

Initial mixture: 2H2 + 02 + 2 He.

Initial pressure: 100 psi.

Time scales: 1 msec. / div.

a) Pressurehistories: I: 697psi./div.

0: 876 psi. /div.

};).

Initial temperature: 294 oK.

b) Heat transfer histories (1)

Ro = 250.n;" i

=

25 mA.; 1 volt/div.

time (t) 8 C

Ic

I Radius (r) FIG. 14 (1) (3 )

o

W

t <tA t~tB ~ C

=

Contact surface CW

=

Compression Wave D

=

Detonation F

=

Flame R = Rarefaction Wave S

=

Shock Wave (2) t~ tA (4) _t

~tE

Note: All characteristics are shown as straight lines for convenience.

SCHEMATIC DIAGRAM OF FORMATION OF DETONATION WAVE AND SUBSEQUENT WAVE INTERACTIONS.

., ..

"

'

I ,

.

:

I

\ '11" \ \ , \ \ " \

\;~

. ' ,

,.

,,'

\

.

!\,

•

I' iJ'

~

'; \,.

VI

,\,~,

1 , , _________ : I

I

V'

~

'1 .... \.".; //

'

, J,~!,

0

\

_,

·1

_'

':

_·r

_A

_A

';

\!

\

"'V

n \ I}t, . • i

1\

f" , V

V

' .

~

....----

\

\

.'

\ A\fv"vv'i.J\J'J\

a Initial mixture: Initial press ure: Time scales: a) b) 2H2 + 02 + 2He. 100 psi. 500 ,., sec. / div. 200

t'

sec. / div. b

Initial temperature: 297 oK.

Pressure scales: a) I: 775 psi./div. 0: 890 psi./div.

b) I: 680 psi./div. 0: 741 psi./div. FIG. 15 PRESSURE HISTORIES IN DETONATING COMBUSTION

a b RRp/US 3.

I

.---~~

/ /

c Initial mixture: 2H2 + 02 + 6 He.

Initial pressure: 500 psi. Initial temperature: 2980_K. Time scales: 1 msec. /div.

Thin film thermometers (vertical scale~): i = 25 mA.

a) 1.1(Ro =16.4): 50mV/div. b) 1.2(Ro = 520A):lV/div.

0.1 (Ro = 150n): 500 mV/div. _{0.2 (R o =} 8204): lV/div. c) 1.3 (R o = 760 A): lV/div. _{0.3 (Ro = 37.n): 100 mV/div.} FIG. 16 DEFLAGRATION HEAT TRANSFER HISTORIES RECORDED ON THREE

lI

i

I J. I -f

I

I ,

I

Rr.; PJPI

.

s

/.

_I

R ~Z>1. VS

_2..

.~ !!::ij !!!!::~ lil'!!!:

M

lil!: ~ !IIiii:i

0

-

₀

, i I' -"'! , , lI!!!':iiiii

I

, I

_

.

!::iiii

•

I

~ ,

-

--;

f

i

_•

__ l_~~ l J __ ~ lil!!!:: ::::iiiiiiiI ;!::iiiij

!!:iIi

a b

----~--±

I I :_~_--,---~,_~I_~ c Initial mixture: (2 H2

+

02)

+

8 H2

Initial pressure: 400 p. s.i. Initial temperature : 301°K. Time scales: 1 msec/div. Vertical scales: 1 volt/div.

Ignition by crimped copper wire (7 kv).

FIG. 17 GLOW DISCHARGE SIGNALS RECORDED ON THREE RADII 1200 _{APART TO}

60 m/sec 50 40 m/sec 15 10 5

o

n = 5 SC-O

.

-.,..---

----.

SC-I

...

,...--~~ ~~ n = 8 - - - -_{... --- - -IJ;,.- - _ . . .} _ - -_. SC-O

...

_...

_--

-...

----

-

---6---S

_---IJr--.---- ____

C-I ~--

--1

SC-O n = 12

---

_ _

6

-

---.-....--

--. Initial conditions: - room temperature - pressure: 75 psi - mixture: 2H2 + _{O 2} + nHe

- radius 2 parallel to ignition wire

Radius 1 Hadius 2 Radius 3

FIG. 18 AVERAGE WAVE SPEED BETWEEN STATIONS

75

m/sec

50

25

o

Radius 2 is parallel to the ignition wire SC-I

- - - - -

...

-:L-

~2H2

+

_{O 2)}

+

5He, 500 psi - -

~~~

-~---...

--

----.

---... - - - -

_{_----It.--_}

S _{C - O SC-I}

-

---(2H 2

+ 0 )

+

6He, 500 psi ( 2H 2

+ 02)

+

_{8H 2, 100 psi} SC-O S

_---,Ar--_

C-I

-

- - -

_---.

• :A

•

Radius 1 FIG. 19 SC-I Radius 2 Radius 3

AVERAGE WAVE SPEED BETWEEN STATIONS C AND I (SC-I) C AND 0 (SC-O)

10 8 6 4 2

o

100 t (msec) w

•

200

•

300 FIG. 20 2H2 + 02 + 7He 2H2 + 02 + 5He

•

2H 2 + 02 + 2He 400 500 600 700

TIME TO REACH MAXIMUM PRESSURE (t_w)

VERSUS INITIAL PRESSURE (pi)

• _{2H 2 +02 + 6He}

• 2H 2 + 02 + 4He

Pi (psi)

30 tw (msec) 25

----o

-o

-~

•

_ _ - - - - 0

.

_---

---

_o

o

20 15 10

o

• _{2H 2} + 02 + 8He 5

o

2H2 + 02 + _{8H 2} Pi (psi)

o

100 200 300 400 500 600 700 800 900 1000

FIG. 21 TIME FOR THE FLAME FRONT TO REACH THE WALL (t )

w

10J....-

---Pf/Pi

I

1 î

8~ ~

5

~

î

î

~

î

~

5

i

5 7 7 7 7 6 7 7 6 2 H 2

+

02

+

4 He 4 2 - - - - Theory Û I _' 100 200 FIG. 22 300 400 500 600 700 800 900 Pi 1000

FINAL-TO-INITIAL PRESSURE RATIO AFTER COMPLETE

101~--T---~---~---~---~---r---~---r---~---~---' Pi/Pi

---(2 H 2 + 02) + 6 He 9

î

I

f

₄

ï

₄

!

₃

!

~

3

î

8

î

₇ 3 3 3 6 7 7 6 5 4 - - - - Theory 3'~ __ ~ ______ ~ ________ ~ ______ ~ ______ ~~ ______ ~ ______ ~ ________ ~ ______ ~ ________ ~ __ ~ 100 200 FIG. 23 300 400 500 600 700 800 _Pi

FINAL-TO-INITIAL PRESSURE RATIO AFTER COMPLETE COMBUSTION

(Pf/Pi) VERSUS INITIAL PRESSURE (Pi).

Pr

-

Pi

lOri

--r---~----,_---r----_r----~---,----~r---r---~--- --r---~----,_---r----_r----~---,----~r---r---~--- --r---~----,_---r----_r----~---,----~r---r---~--- --r---~----,_---r----_r----~---,----~r---r---~--- --r---~----,_---r----_r----~---,----~r---r---~--- --r---~----,_---r----_r----~---,----~r---r---~---

- - - -

2H2 + O 2 + BHe / _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ ~b.O..!:. __ _ 8 Tbeor.

=:; ;:.:

-6 7 6 4 2

0~1--~---~----~~----~---~---~---~----~---L---~--J

100 200 300 400 500 600 700 800 Pi

FIG. 24 FINAL-TO-INITIAL PRESSURE RATIO AFTER COMPLETE COMBUSTION (Pf/Pi) VERSUS INITIAL PRESSURE (Pi)

10 Pf/Pi

---

...

--

...

...

--

...

I

8

I

4

I

6 9 6 4 2 _{- - - - Theory}

Initial mixture: 2H₂ +02 +nHe.

Initial pressure: 75 psi.

Initial temperature: 294 .. . 298oK.

--

...

--...

I I

_{9 9}

I

10

---..

...

---..

...

I

6 ~ 3 _I 4

---..

...

...

I

₉

_I

6

a.

,

,

,

,

I I "

o

2 4 6 8 10 12 n 14

FIG 25 FINAL-TO-INITIAL PRESSURE RATIO AFTER

COMPLETE COMBUSTION {Pf/Pi> VERSUS DILUTION (n).

I · +

-FIG. 26

2 3

o , 2 I

ONE-DIMENSIONAL COMBUSTION CHAMBER FOR THE INVESTIGATION OF THE SURFACE INITIATION OF EXPLOSIVES BY COMBUSTION WAVES.

r

FIG. 27 a DISASSEMBLED COMBUSTION CHAMBER SHOWING

CONTAINER FOR HOLDING EXPLOSIVE.

FIG. 27 b DISASSEMBLED COMBUSTION CHAMBER SHOWING

(a) (b)

,.

Initial Driver Mixture: 2H 2 + 02 + 2 He at 300 psi.

Muzzle velocity <; 5000 ft/sec, M '" 1. 5

Initial _{Driver Mixture: 2H 2} + 02 + 2 He at 600 psi.

Muzzle velocity ;::. 5000 ft/sec, M'" 2.0 SHADOWGRAMS OF A FLARED SINGLE CALIBRE CYLINDER (0.22 in. dia.) IN SUPERSONIC FLIGHT IN THE UT lAS IMPLOSION DRIVEN HYPERVELOCITY

LAUNCHER RANGE CONTAINING AIR AT 1 atm.