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N A T I O N A L A E R O N A U T I C S A N D S P A C E A D M I N I S T R A T I O N

Technical Report 32-1557

Initiation of Insensitive Explosives

by Laser Energy

Vincent J. Menichelli

Lein C. Yang

J E T P R O P U L S I O N L A B O R A T O R Y

C A L I F O R N I A I N S T I T U T E O F T E C H N O L O G Y

P A S A D E N A , C A L I F O R N I A

June 1, 1972

https://ntrs.nasa.gov/search.jsp?R=19720017842 2018-06-01T16:20:51+00:00Z

N A T I O N A L A E R O N A U T I C S A N D S P A C E A D M I N I S T R A T I O N

Technical Report 32-1557

Initiation of Insensitive Explosives

by Laser Energy

Vincent J. Menichelli

Lein C. Yang

J E T P R O P U L S I O N L A B O R A T O R Y

C A L I F O R N I A I N S T I T U T E O F T E C H N O L O G Y

P A S A D E N A , C A L I F O R N I A

June 1, 1972

Preface

The work described in this report was performed by the Propulsion Divisionof the Jet Propulsion Laboratory.

JPL TECHNICAL REPORT 32-1557

Acknowledgment

The authors wish to acknowledge Mr. H. Jeffries for his careful fabrication ofthe test samples and his assistance throughout the program.

iv JPL TECHNICAL REPORT 32-1557

Contents

I. Introduction 1

II. Laser-Generated Shocks 2

III. Test Apparatus 2

IV. Test Results 8

V. Discussion 9

References 16

Tables

1. Conditions and results for laser testing of HNS and Dipam ... 8

2. Conditions and results for laser testing of PETN 9

3. Conditions and results for laser testing of RDX 10

4. Conditions and results for laser testing of tetryl 12

5. Conditions and results for selected-detonated items 12

Figures

1. Test vehicle for laser initiation study 3

2. Streak camera records of the plasma generated in a vacuum

from a focused Q-switched ruby laser 3

3. Post-irradiation damage to thin aluminum films by a focused

Q-switched ruby laser 4

4. Streak camera records of the plasma generated in a vacuum,

for various thicknesses of aluminum films, from a focused

Q-switched ruby laser 4

5. Block diagram of experimental configuration 5

6. Laboratory arrangement of laser, camera, and firing chamber . . 5

7. Test vehicle with plastic viewing window for laser

initiation study 6

8. Test vehicle with glass tube configuration for viewing

of laser initiation 7

9. Streak camera records of laser-initiated detonation in PETN

(values given refer to Table 5) 13


Contents (contd)

Figures (contd)

10. Streak camera records of laser-initiated detonation in PETN

and RDX (values given refer to Table 5) 14

11. Streak camera records of laser-initiated detonation in RDX

and tetryl (values given refer to Table 5) 15

vi JPL TECHNICAL REPORT 32-1557

Abstract

Instantaneous longitudinal detonations have been observed in confined col-umns of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine(RDX), and tetryl when these materials were pulsed with light energy from afocused Q-switch ruby laser. The laser energy ranged from 0.5 to 4.2 J with apulse width of 25 ns. Enhancement of the ignition mechanism is hypothesizedwhen a 100-nm (1000-A) thick aluminum film is vacuum-deposited on the explo-sive side of the window. Upon irradiation from the laser, a shock is generated atthe aluminum-explosive interface. Steady-state detonations can be reached inless than 0.5 /is with less than 10% variation in detonation velocity for PETNand RDX.

JPL TECHNICAL REPORT 32-1557 vii

Initiation of Insensitive Explosives by Laser Energy

I. Introduction

Immediate detonation of secondary high explosivesrequires a strong shock input, the threshold magnitudeof the shock being dependent upon such parameters asexplosive density, particle size, and confinement. Con-ventional means of achieving detonation in secondaryhigh explosives is by the use of the explosive train. Thesetrains, in general, are initiated mechanically by firingpins (stab or percussion) or electrically (hot bridgewire).The first component in the train is usually a primary highexplosive sensitive to heat, friction, impact, and staticelectricity and also having poor simultaneity character-istics. The train then proceeds with increments of lesssensitive, more energetic explosives. Eventually, in ashort distance, the burning reaction develops into a det-onation. These systems require very little energy to ini-tiate (0.1 J or less) and are quite vulnerable to inadver-tent initiation. To ward- against accidental initiation ofthe main charge, a Safe and Arming mechanism (S andA) is usually employed. Work has been carried out todevelop insensitive explosive trains, using only second-ary high explosives which will initiate from a uniqueenergy source; e.g., Strong light or exploding wire. Theadvantages are many fold: the elimination of primaryhigh explosives, elimination of complicated S and As, andan improvement in simultaniety and functioning time.

Bowden et al. studied the sensitivity of explosives tostrong light sources (Ref. 1), and Leopold was able to

detonate PETN with exploding bridgewires (EBW) (Ref.2). Detonation of PETN by EBW was very dependentupon parameters such as loading density, particle sizeand shape, purity, bridgewire size and material, and dis-charge circuitry.

In order to reach immediate detonation in secondaryhigh explosives such as PETN, RDX, and tetryl, thresh-old external shock strengths ranging from 7 X 105 to15 X 105 N/m2 (7 to 15 kbars) are needed (Ref. 3). In re-cent years, pulsed laser radiation as an energy source toinitiate explosives has been studied. Space OrdnanceSystems, Inc., investigated the sensitivity of pyrotech-nics and propellants to laser energy under a JPL contract(Ref. 4). During this study no unconfined secondary highexplosives could be initiated from a focused ruby or neo-dymium pulsed laser in the free-running mode (up to 15J of energy). Barbarisi et al. at Picatinny Arsenal, NewJersey, studied the reaction of PETN to a pulsed rubylaser (focused) in the free-running and Q-switched modes(Ref. 5). Ignition was obtained in both modes but directdetonations were not confirmed. The Russians have re-ported similar work and successfully detonated PETN(density 1.0 g/cm3) from a pulsed ruby laser (0.5 J) in theQ-switched mode (Ref. 6). Experiments have been car-ried out at JPL to detonate secondary high explosiveswith a focused ruby laser in the Q-Switched mode (Ref.7). Figure 1 shows a cross section of the test vehicle used.Some detonations were achieved with PETN and RDX


as witnessed from a dent obtained on a steel witnessblock and expansion of the steel test vehicle. The time todetonation was not known and it appeared that uncer-tainties such as explosive surface conditions, trappedair, impurities, and crystal imperfections were playingan important role in the initiation mechanism.

II. Laser-Generated Shocks

The interaction of Q-switched laser pulses with a solidtarget was known to result in rapid expanding plasmas(Ref. 8). The process, when observed with a streak cam-era in air at JPL was not clear, possibly due to ionizationof the air by the laser. Figure 2 shows the results of ex-periments conducted with metal targets in a vacuum(1.33 N/m2, or 1 mm Hg).1 The resulting plasma propaga-tion is more clearly defined. An approximation of theshock is measured by the propagation of the luminousplasma boundary. From these results, application of theshock (in the order of several cm/^us) to denote secondaryhigh explosives seemed appropriate. The mechanism issimilar to EBW or exploding foil. However, the lasershock is physically different, in that the shock velocity isan order of magnitude higher and the duration shorter(a few hundred nanoseconds compared to about 2/.i.s).

Selection of target material and thickness for applica-tion to laser initiation of explosives was based on somepreliminary experiments and considerations. In general,the absorption of light in a solid is completed within 20-

;-,;i 100 nm (200-1000A) of light path, which is close to thelight skin depth of the material with the exception of high-ly absorptive materials like carbon black. Carbon blackis difficult to prepare and hard to handle as a thin film.Vacuum deposition of thin metal films is quite easy to ob-tain but is highly reflective at low light energy levels.However, at high light energy levels, a plasma is formedwhich increases the absorptivity by orders of magnitude.Aluminum was selected because it has a low meltingpoint and is easy to vacuum deposit on a glass substrate.Other metals may be more efficient, but a study to opti-mize the target material was not made.

The optimum thickness of the target material wasfound to be about 100 nm (1000A). Films thicker than100 nm caused the average dynamic transmission of theQ-switched laser light to be less than 1.0%, and the amountof post-irradiated film remaining became significant (Fig.

1 Values in customary units are included in parentheses aftervalues in SI (International System) units if the customary unitswere used in the measurements or calculations.

3). There would be no advantage in increasing the thick-ness, because the additional mass would result in a lowertemperature and pressure in the plasma during the laserabsorption period. Films thinner than 100 nm were com-pletely vaporized before absorption of all the laser energy.Aluminum targets of various thickness were irradiatedwith 1.67 J of focused laser energy; the shocks generatedare shown in Fig. 4.

III. Test Apparatus

*A Korad K-1Q laser system with a KDP Pockel cellwas capable of producing 4.5 J of energy in a pulse widthof 25 ns. The laser head utilized a ruby rod 1.43 cm indiameter and 7.6 cm long. The laser beam was focusedwith a double convex lens 30 cm in focal length. An extra 6-plate Brewster stack polarizer was used to completelyeliminate prelasing at high pumping levels.

A schematic of the experimental configuration is shownin Fig. 5. A Beckman-Whitley Model 200 SimultaneousStreak and Framing Camera was used to record the event.The steel mirror was operated at 1000 rev/s, which cor-responds to a writing speed of 2.76 mm/^,s, or at a timeresolution of 50 ns. The laser power supply was triggeredby a synchronous sequence when the rotating mirrorreached a preset position and speed.

The laboratory arrangement for conducting the experi-ments is shown in Fig. 6. The explosive sample is placedin a safety chamber and aligned with the laser. The laserpulse enters the chamber through a portal containingthe focusing lens. The streak camera is aligned perpen-dicular to the axis of the explosive column. Several differ-ent explosive test vehicles were used, which containedviewing optics so that the light from the reaction couldbe recorded.

Figure 7 shows a test vehicle in which a plastic rodserves as the viewing port. The glass window with themetal film facing the explosive column is held in the cav-ity provided with an end plate to contain it. The explo-sive under test is then loaded against the window. A cold-rolled steel witness block completes the test vehicle as-sembly.

A second test vehicle is shown in Fig. 8. The explosiveis loaded into a glass tube and then assembled into abrass fixture in much the same manner as the previous as-sembly. The components are interference-fitted becausegood confinement is critical in the initial phase of ig-nition.

2 JPL TECHNICAL REPORT 32-1557

FOCUSEDLASER

GLASSWINDOW

STEEL BODY

EXPLOSIVECOLUMN

STEEL WITNESSBLOCK

-CLOSURE DISK

Fig. 1. Test vehicle for laser initiation study

-GLASSPLATE

^n /—SLIT

LEGEND

FILM VACUUM-DEPOSITED

DISTANCE

ALUMINUM16.0 nm(160 A)3.25 J

GOLD115.0 nm(1150 A)1.67 J

0

DISTANCE, mm

0 10 20 30 401 1 1

WRITING SPEED:5.52 mm/us

THICKFOIL

BRASS1.67 J

CARBON1.67 J

COPPER1.67 J

LEGEND

Fig. 2. Streak camera records of the plasma generated in a vacuum from a focused Q-switched ruby laser


16.0 nm(160 A)

109.0 nm(1090 A)

218.Onm(2180 A)

ALUMINUM FILMS VACUUM-DEPOSITED ON A GLASS SUBSTRATEMAGNIFICATION X 14.5LASER ENERGY = 2.5 JFOCAL LENGTH OF LENS = 30 cm

Fig. 3. Post-irradiation damage to thin aluminum films by a focused Q-switched ruby laser

5LASS

\

i

k\\\N

7

I

/-SLIT

J LASER

ALUMINUMFILM

LEGEND

218.0 nm(2180 A)

109.0 nm(1090 A)

54.5 nm(545 A)

981.0 nm(9810 A)

436.0 nm(4360 A)

327.0 nm(3270 A)

DISTANCE, mm

0 10 20 30 400

16.0 nm(169 A) 5. 2

tu

f= 4

6

i i i i

WRITING SPEED:5.52 mm/^s

LASER ENERGY = 1.67 J

Fig. 4. Streak camera records of the plasma generated in a vacuum, for various thicknessesof aluminum films, from a focused Q-switched ruby laser


STEEL SAFETY

100% MIRROR

POCKELCELL

-BREWSTER

POLARIZER

RUBYLASER

TIME DELAYEDPULSEGENERATOR

LENS

V FRONT MIRROR

EXPLOSIVE UNITUNDER TEST

Ml

LUCITE WINDOWS

FLASH LAMPPOWER SUPPLY

ABECKMAN &WHITLEY

MODEL 200 CAMERA

Fig. 5. Block diagram of experimental configuration

POCKEL CELL

PHOTODIODE

LASER ANDOPTICALBENCH

Fig. 6. Laboratory arrangement of laser, camera, and firing chamber


2.54-cm dia

3.3 cm

PLEXIGLAS

WINDOW CAVITY

•EXPLOSIVE COLUMN

-PLEXIGLAS

STEEL WITNESSBLOCK

Fig. 7. Test vehicle with plastic viewing window for laser initiation study

JPL TECHNICAL REPORT 32 1557

GLASS TUBE BRASS EXPLOSIVEBODY-? COLUMN-

Wl NDOW CAVITY

SLIT

LASER

STEEL WITNESSBLOCK

Fig. 8. Test vehicle with glass tube configuration for viewing of laser initiation


IV. Test Results

Approximately 90 firings were made involving five dif-ferent explosives: PETN, RDX, tetryl, hexanitro stilbene(HNS), and Dipam. The different parameters studiedwere density, particle size, explosive diameter, laser en-ergy, and the use of plain or aluminized windows. Dipamand HNS did not detonate under any of the conditionstested, although in two cases HNS completely burnedat maximum energy input. Table 1 summarizes the results.

As expected, PETN was the most sensitive to laser en-ergy of the explosives tested. The minimum energy re-quired was below 1.0 J at 34.5 X 106 N/m2 (5 kpsi) load-ing pressure.1 Detonations were observed with 2 J of las-er energy at loading pressures up to 172.5 X 106 N/m2

(25 kpsi). The PETN particle size did not appear to becritical to laser detonation. Table 2 summarizes the PETNdata.

The RDX was tested at loading pressures ranging from6.89 X 106 to 345 X 106 N/m2 (1 to 50 kpsi). Ignitions wereobserved up to 345 X 106 N/m2 but immediate detonationoccurred only up to 34.5 X 106 N/m2. Particle size appar-ently influenced the detonability of RDX, since no detona-tions were observed with coarse material. (This observa-

1 Values in customary units are included in parentheses aftervalues in SI (International System) units if the customary unitswere used in the measurements or calculations.

tion agrees with Stresau's results in Ref. 9). Most detona-tions occurred when an aluminized window was used.The RDX results are summarized in Table 3.

Only seven tests have been completed with tetryl. Twodetonations were observed with milled tetryl at 6.89 X106 N/m2 (1 kpsi) loading pressure and aluminized win-dows. Under the same conditions, but using a plain win-dow, detonation did not occur. The results from thesetests are summarized in Table 4.

The streak camera records of most of the items thatdetonated were analyzed for total reaction time (timefrom laser pulse to the end of the reaction), transient time(time from laser pulse to start of steady-state detonation),and steady-state detonation velocity. Several items thatdetonated are omitted because of the poor quality of thestreak record. Table 5 summarizes the data and comparesthe measured detonation velocities with ideal detonationvelocities. The measured detonation velocities are closeto the ideal detonation velocities. Steel dent values arealso listed, and the depth values are directly ordered withthe detonation velocity.

Figures 9, 10, and 11 show some of the smear recordsobtained of the items in Table 5. In the case of PETN,where coarse powder was used, the transient time is quitelong (microseconds) when compared to the tenths of mi-croseconds for milled PETN. One RDX test had a zero

Table 1. Conditions and results for laser testing of HNS and Dipam

Test Explosive

1 HNS

2

34

567

8

9 HNS

10 Dipam

11 Dipam

12 Dipam

Particlesize

MM

C

cM

MC

Loadingpressure

106 N/m2 kpsi

6.90

6.90

6.9034.569.0

69.0

345

6.906.90

69.0

111

510

10501

1

10

Laserenergy, J

4.0

4.04.2

4.24.2

3.0

3.03.0

4.2

3.83.8

3.0

Chargediameter,

cm

0.3

0.30.24

0.240.24

0.30.3

0.30.24

0.27

0.27

0.3

Chargelength,

cm

2.54

2.54

2.032.032.54

2.032.032.54

Confinement

Glass

Glass

Steel

Steel

Steel

Glass

Glass

Glass

Steel

Steel

Steel

Glass

Window Results

P Failed to ignite

Al Failed to ignite

Failed to ignite

Burned completely

Burned completely

Failed to ignite

AlP

Al

M = Milled for 16 h in chloroform.

C = Coarse (as received).

P = Plain glass window.

Al = 100-nm (1000-A) aluminized glass window in contact with explosive.


transient time. Tetryl had a relatively long transient timeof 1.45 (us . It is noted that the laser energy listed is theenergy measured at the laser head. The lens, lucite en-trance window, and glass window each transmit about92% of light energy.

V. Discussion

In some instances in the tables, a burn to detonation isrecorded rather than a detonation or complete burn. Thestreak camera results for these cases showed burning dur-ing the writing time of the camera. Later the reactionwent to detonation, which was verified by a dent in thesteel witness block. All the streak camera records showedlight streaks at the fixture surface/air interface and alongthe length of the explosive column. This light was emittedwhen the margin of the laser focal spot interacted withthe metal surface. The laser light was also scattered dif-fusively through the glass tubing or lucite rod.

It is apparent that for PETN and RDX, instantaneousdetonations were achieved. In some cases, the transienttimes were less than 0.5 /*s, and variations in detonationvelocity were less than 10%. The PETN did not exhibitan increase in sensitivity when the aluminized window

was substituted for the plain window. The initiationmechanism for PETN may be very complicated, so thatthe effects of the aluminized window are overshadowedby other mechanisms. The RDX appears to be more sen-sitive to detonation when the aluminized window is used.Tetryl definitely demonstrated that the aluminized win-dow is necessary to achieve detonation. In all cases, thefine particle size (less than 40 /us ) and loading pressuresbelow 34.5 X 106 N/m2 (5 kpsi) increased the explosivesensitivity.

Comparison of the laser detonation results with EBWstudies shows that laser-induced detonations are not assensitive to loading density as are detonations with EBW.This may be due to the much higher shock velocity gen-erated by the laser. Probably for this same reason, ex-plosives less sensitive than PETN were directly deto-nated. Small deviations from 1.0 g/cm3 in EBW applica-tions make a considerable difference in sensitivity. Be-cause explosives loaded at densities greater than 1.0g/cm3 can be laser-detonated, a correspondingly higherdetonation velocity can be achieved. The detonation ve-locities obtained by laser initiation are closer to the idealdetonation velocity than those reported by EBW ini-tiation.

Table 2. Conditions and results for laser testing of PETN

LoadingParticle pressure

TP.<*size

106 N/m2 kpsi

1 M 34.5 52 M 34.5 53 M 34.5 54 C 69.0 1056

78

9 C

10 M

11 69.0 1012 ' 172.5 2513

141516

Laserenergy, J

0.80.50.8

4.04.0

3.0

3.0

1.01.0

0.80.82.0

2.03.4

Chargediameter,

cm

0.380.38

0.380.3

0.3

0.38

0.38

0.3

Chargelength,

cm

2.062.06

2.792.03

2.032.03

2.542.54

2.792.06

2.06

2.54

Confinement

SteelSteel

Steel

Glass

Glass

Steel

Steel

Glass

Window

P

AI

AlPP

AlP

AlP

Al

Al

Results

Detonated

Burn to detonationDetonated

BurnedDetonatedDetonated

Failed to igniteDetonated

Detonated

BurnedBurnedDetonated

BurnedFailed to ignite

M = Milled for 16 h in chloroform.C = Coarse (as received).P = Plain glass window.



Table 3. Conditions and results for laser testing of RDX

Test

123456789

1011121314151617181920212223242526272829303132333435363738

M =C =P =

Al =

LoadingParticle pressure

c:-r r

106 N/m2 kpsi

M 6.90 1

MCMC 6.90 1M 34.5 5

MC 34.5 5C 69.0 10MMC

CMCCM

Milled for 16 h in chloroform.Coarse ( as received ) .Plain glass window.100-nm (1000-A) aluminized

Laser:nergy, J

1.01.01.53.53.53.83.83.54.04.21.01.02.853.133.53.53.83.84.04.21.02.12.13.0

3.03.53.53.84.0

glass window

Chargediameter,

cm

0.30.30.10.270.10.270.270.380.10.380.30.30.30.30.10.270.270.270.10.380.380.3

0.30.510.380.380.380.240.240.240.30.380.380.1

in contact

Chargelength,

cm

2.542.542.542.062.542.062.062.791.781.012.54

2.542.062.062.061.781.012.792.542.542.032.542.542.540.762.792.792.792.54

2.542.792.791.78

with explosives.

Confinement

GlassGlassGlassSteelGlass

Steel

SteelGlass

GlassSteel

SteelGlass

GlassSteel

SteelGlassSteel

Window

P

Al

AlPAl

AlPPAl

AlPAlAlAlPAl

AlPAl

AlPAl

Results

DetonatedDetonatedDetonatedBurn to detonationDetonated

DetonatedBurn to detonationComplete burnDetonatedFailed to ignite

Failed to igniteDetonatedDetonatedFailed to igniteDetonatedDetonatedDetonatedComplete burnFailed to igniteFailed to igniteFailed to igniteComplete burnFailed to igniteFailed to igniteFailed to igniteComplete burnComplete burnComplete burnFailed to igniteBurn to detonationComplete burnComplete burnFailed to igniteComplete burnComplete burnFailed to ignite


Table 3. (contd)

Test

39404142

434445

4647

48

4950

5152

ParticleSize

MMC

C

M

MC

Loadingpressure

106N/m2 kpsi

69.0 10

207 30207 30

207 30345 50345 50

Laserenergy, J

4.04.2

4.3

4.34.24.2

4.4

4.64.0

4.04.04.2

4.2

Chargediameter,

cm

0.27

0.3

0.38

0.240.27

0.380.27

0.30.3

0.38

0.380.230.380.38

Chargelength,

cm

2.06

2.54

2.792.54

2.061.01

2.062.54

2.54

2.792.792.79

1.011.01

Confinement

Steel

Glass

Steel

Steel

Glass

Glass

Steel

Window Results

Complete burn

Failed to ignite

Complete burn

Complete burn

Complete burn

Complete burn

Complete burn

Al Failed to ignite

P Failed to ignite

P Complete burn

Al Failed to ignite

Complete burn

Failed to ignite

Complete burn

Table 4. Conditions and results for laser testing of tetryl

Test

1

23

4

5

67

Particlesize

M

M

C

CC

Loadingpressure,

106 N/m2 kpsi

6.90 1

6.90 169.0 10

69.0 10

138 20

Laserenergy, J

3.83.8

4.0

4.0

3.0

3.0

3.0

Chargediameter,

cm

0.27

0.380.3

0.3

0.3

0.380.51

Chargelength,

cm

2.06

2.062.542.54

2.032.54

0.76

Confinement

Steel

Steel

Glass

Glass

Glass

Steel

Steel

Window

AlPP

Al

Results

Burn to detonation

Complete burn

Fail to initiate

Detonated

Fail to initiate

Fail to initiate

Complete burn

M = Milled for 16 h in chloroform.

C = Coarse (as received).



JPL TECHNICAL REPORT 32-1557 11

Table 5. Conditions and results for selected laser-detonated items

Particle Density,Test Explosive sJ2e g/cm3

12

345

67

89

1011

121314

15161718

19

MC

aM.

PETN M 1.58

1.581.64

M

C

C 1.64PETN M 1.72

RDX 1.18

1.181.52

RDX 1.52TETRYL 1.08

Laserenergy,

J

0.80.8

1.01.0

3.03.03.0

4.02.0

1.01.01.5

3.53.8

2.85

3.5

3.83.84.0

= Milled for 16 h in chloroform.

= Coarse ( as received ) .

A. Cook, The Science of High Explosives,

Chargediam-

eter, cm

0.38

0.380.30

0.300.380.30

0.380.30

0.300.100.10

0.27

0.30

0.100.270.270.30

Chargecolumnlength,

cm

2.06

2.792.062.06

2.062.54

2.792.03

2.062.54

2.54

2.062.54

2.542.06

2.062.54

Confine-. Windowment

Steel

Steel

Glass

Glass

Steel

Glass

Steel

Glass

Glass

Steel

Glass

Glass

Steel

Steel

Glass

PAlP

Al

Al

AlP

Al

PPAl

Al

PAl

Time, /js

Total

3.114.82

2.972.90

4.056.95

6.489.42

2.865.433.987.175.00

4.16

4.175.303.62

3.73

5.43


Al = 100-nm (1000-A) aluminized glass

Reinhold Publishing Corp., N.Y., 1958.

tran-sient

0.540.72

0.80

0.431.983.96

2.90

6.680.36

1.660.00

2.530.30

0.60

0.760.400.72

0.54

1.45

window in

Detonation velocity,mm//js

Measured

7.011

7.724

7.620

7.228

7.346

5.6016.836

5.604

7.379

6.4916.374

5.476

5.393

5.750

6.741

5.608

6.741

5.992

5.609

contact with

Ideal"

7.841

7.841

8.078

8.078

8.394

6.728

6.728

7.946

7.946

5.858

Steeldent

depth,mm

0.640.590.76

0.610.530.22

0.810.18

0.760.460.380.20

0.13

0.460.530.28

0.53

0.580.23

explosive.

12 JPL TECHNICAL .REPORT 32-1557

0

2

4

6

8

10

GLASSWINDOW

27.9 mm

GLASSWINDOW

No. 1

No. 5

p = 1.64 g/cmE =3.0 JV = 7.346mm//is

No. 2 No. 4

= 1 .58 g/cm= 0 .8J= 7.01 1 mm/̂ .s

20.3 mm

^̂ •̂ •̂••H•̂ ^^^^ «_

P = 1 .58 g/cmE =0.8 JV = 7.724mm//iS

25.4 mm

— .̂ m^^•̂ ^^^^B

/> = 1 . 64 g/cmE = 1.0 JV =7.228 mm/^ts

27.9 mm^-GLASS

I / WINDOW

No. 6 No. 7

p = 1.64 g/cmE =3.0 JV = 5.601 mm//is

p = 1.64 g/cmE =3.0 JV =6.836 mm//is

Fig. 9. Streak camera records of laser-initiated detonation in PETN (values given refer to Table 5)


a.UJ"

0

2

4 -

6

8

10

No. 8

PETN/> = 1 .64 g/cmE = 4.0JV=5.604

GLASS WINDOW

PETN 3

/> = 1 .72 g/cmE = 2 . 0 JV= 7.379 mm/

25.4mm

No.

RDX 3

p = 1.18 g/cmE = 1.0 JV=6.491 mm/^s

25.4 mm

No. 11

RDX 3

p =1.18 g/cmE = 1.0 JV=6.374 mm/f

No. 12

RDX 3

p = 1.18 g/cmE = 1.5 JV= 5.476 mm/̂ s

No. 13

RDX 3

/> = 1.18 g/cmE =3.5 JV = 5.393 mm//xs

Fig. 10. Streak camera records of laser-initiated detonation in PETN and RDX (values given refer to Table 5)


10

•GLASSWINDOW

25.4 mm

No. 14

RDX -/> = 1.18 g/cmE=3 .8 JV = 5.750mm/Ms

15

RDXp = 1 .52 g/crnE =2.85 JV = 6.741

No. 16

RDXp = 1.52 g/cmE=3 .5 JV=5.608

GLASSWINDOW

GLASSWINDOW

No. 17 No. 18 No. 19

RDXP = } . 5 2 g/cmJ

E=3.8 JV = 6.741 mm/£is

RDXP = 1.52 g/cmJ

E=3.8 JV=5.992 mm//is

TETRYL 3

p = 1.08 g/cmE =4.0 JV=5.602 mm/̂ i

Fig. 11. Streak camera records of laser-initiated detonation in RDX and tetryl ( values given refer to Table 5)


References

1. Bowden, F.P., and Yoffe, A.D., Fast Reactions in Solids, Butterworth's Scien-tific Publications, 1958.

2. Leopold, H.S., Initiation of Explosives by Exploding Wires III, NOLTR 64-2.U.S. Naval Ordnance Laboratory, White Oak, Silver Spring, Maryland, Mar.17,1964.

3. Scott, C.L.,"Effect of Particle Size on Shock Initiation of PETN, RDX, and Tet-ryl," Fifth Symposium on Detonation, U.S. Naval Ordnance Laboratory, WhiteOak, Silver Spring, Maryland, Aug. 1970.

4. Menichelli, V.J., and Yang, L.C., Sensitivity of Explosives to Laser Energy,Technical Report 32-1474. Jet Propulsion Laboratory, Pasadena, California,Apr. 30,1970.

' 5. Barbarisi, M.J., and Kessler, E.G., Initiation of Secondary Explosives by Meansof Laser Radiation, Technical Report 3861. Picatinny Arsenal, Dover, NewJersey, May 1969.

6. Brish, A.A., et al., "Initiation of Detonations in Condensed Explosives with aLaser," Combust. Explosive Phys., No. 3,1966, pp. 132-133.

7. Yang, L.C., and Menichelli, J., "Detonation of Insensitive High Explosives bya Q-Switched Ruby Laser," Appl. Phys. Lett., Vol. 19, No. 11, Dec. 1,1971.

8. Basov, N.G., et al., Letter 6JETP, p.168, Sept. 15,1967.

9. Stresau, R.H.F., et al., "Confinement Effects in Exploding Bridgewire Initiationof Detonation," Fourth Symposium on Detonation, U.S. Naval Ordnance Labo-ratory, White Oak, Silver Spring, Maryland, Oct. 1965


NASA — JPl — Coml., L.A., Calif.

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