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"MEMORANDUM REPORT ARBRL-MR-03107

o SOFT RECOVERY TESTS OF A 155-mm CANNONO LAUNCHED GUIDED PROJECTILE WARHEAD, TYPE T

James W. EvansCarl R. Ruth DT1C

Emerson V. Clarke, Jr...JUL0 6 198'

May 1981

US ARMY ARMAMENT RESEARCH AND DEVELOPMENT COMMANDBALLISTIC RESEARCH LABORATORY

ABERDEEN PROVING GROUND, MARYLAND

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MEMO AND M R POR AR R -M ------ 0... .

'}Soft Recovery Tests of a 15S-mm Cannon Launched' Memorandum epwN_0'-" Guided Projectile Warhead, Type T,_________

S. PERFORMING ORO. REPORT NUMVER

7. AUTHOR(A) 6 . CONTRACT OR GRANT NUMSER(s)(m s W./Evansj Carl R.ARuth/k" SA Emerson V. Clarke, Jre

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It. KEY WORDS (Continue an reverse side it necesaryv and Identify by block number)Large Caliber Soft Recovery System Projectile DisplacementFM/FM Telemeter Base PressureProjectile Instrumentation Body StrainIn-Bore MeasurementsTransducer20.k A?R ACT ('iosd~ sw om r b N areffcamy mdIdentity by block number) *'sThe launch and recovery portion of a launch survival test on a Type T,

155-mm Cannon Launched Guided Projectile (CLGP) warhead was conducted. 'at theSandy Point (Range-18) facility of the Interior Ball:'stics Divi on'allisticResearch Laboratory.%-This test employed the Large Caliber Soft Recovery System(LCSRS). The warhead body was adapted for this test by attaching a forwardwater scoop and a base structure. These components were necessary for launchfrom a 155-mm howitzer a~..'L recovery in the LCSRS. The projectile system was i 'I

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instrumented with a FM/FM telemetry system to measure base pressure, projectile

acceleration, and strains on the inner wall of the warhead.

Three instrumented, CLGP-warhead, test projectiles, were fired from a 155-mm,M185 Howitzer tube using an M4A2, Zone 7, Propelling Charge. Telemetry datawere received from all three and they were successfully recovered in the LCSRS./

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TABLE OF CONTENTSPage

LIST OF ILLUSTRATIONS ...... ....... ................... 5

I. INTRODUCTION ................ ........................ 7

II. DESCRIPTION OF THE LARGE CALIBER SOFT RECOVERY SYSTEM . . 7

III. DESCRIPTION OF THE PROJECTILE .......... ............... 7

A. Water Scoop ...... ..... ...................... ..11B. Base Structure ....... ... .................... .. 11C. Projectile Assembly ........ .................. .. 11

IV. DESCRIPTION OF THE TELEMETRY TRANSMITTING SYSTEM ......... 14

A. Transmitter and Antenna ......... ................ 14B. Voltage Controlled Oscillators .... ............. .. 14C. Piezoelectric Transducers ...... ............... ..16D. Strain Measurements ...... ..... .................. 16P, . Power Supply .......... ...................... ..18F. Packaging ...... ..... ....................... .. 18

V. CALIBRATION OF THE TELEMETRY TRANSMITTING SYSTEM . .. .... 18

A. Pressure Channel ......... ................... ..18B. Acceleration Channel ....... .................. ..20C. Strain Channels ...... ... .................... ..20

VI. DESCRIPTION OF TELEMETRY RECEIVING SYSTEM ............ ..20

A. Radio Frequency Receiving System ................ ..20B. Data Discriminating System ...... .............. .21

VII. ON-TUBE MEASUREMENTS ....... ... ................. .. 21

A. Chamber Pressure ....... ... ................. ...21B. Projectile Displacement ........ ................ 21

3

TABLE OF CONTENTS

Page

VIII. RECORDING AND DATA REDUCTION. .. .............. ........23

IX. RESULTS. .. .. .............................. .......... 23

A. Pressure . ..................... 25B. Projectile Acceleration .. .. ............ ..........25C. CLGP Body Strains .. .. .................... I..I......25

X. CONCLUSIONS. .. .. ................................ ....35

ACKNOWLEDGMENTS .. .. .............. ....................35

REFERENCES. .. .............. .... I.....................37

DISTRIBUTION LIST .. .. ............ ....................39

4

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LIST OF ILLUSTRATIONS

Figure Page

1. Large Caliber Soft Recovery System ....... ........... 8

2. Large Caliber Soft Recovery System, Principle ofOperation ................... ....................... 9

3. Large Caliber Soft Recovery System, DecelerationProfiles .............. ........................... 9

4. CLGP Warhead, Test Projectile ........ .............. 10

5. CLGP Warhead, Test Projectile Components .............. 12

6. CLGP Warhead, Assembled Projectile ..... ............ .12

7. Water Scoop ........... ....................... ... 13

8. Telemetry Transmitting System, Block Diagram .... ...... 15

9. Base Structure Components ...... ................ ... 17

10. Piezoelectric Transducer and Power Supply ........... ... 17

11. Strain Measuring System ........ ................. ... 19

12. Telemetry Receiving System, Block Diagram ........... ... 22

13. Doppler Radar Block Diagram ......... ............... 24

14. Doppler Radar Antenna ........ .................. ... 24

15. Pressure versus Time, CLGP Warhead #1 ............ .... 26

16. Pressure versus Time, CLGP Warhead #2 ............. ... 27

17. Pressure versus Time, CLGP Warhead #3 .............. ... 28

I&. Projectile Acceleration, CLGP Warhead #1 ........... ... 29

19. Projectile Displacement versus Time, CLGPWarhead #3 .............. ....................... ... 30

20. In-Tube Trajectory, CLGP Warhead #3 ...... ........... 31

...

LIST OF ILLUSTRATIONS (Cont'd)Figure Page

21. Strain versus Time, CLGP Warhead #1 ... ............ 32

22. Strain versus Time, CLGP Warhead #2 .. .. .. .. . .. 33

23. Strain versus Time, CLGP Warhead #3 ...... ........... 34

I. INFRODUCTION

With the design and construction of the Ballistic Research Laboratory(BRL) Large Caliber Soft Recovery System1 (LCSRS), a useful test appa-ratus is available to support various research projects. The firsttask that employed the LCSRS was testing the launch survivability of aType T, 155-mm Cannon Launched Guided Projectile 2 (CLGP) warhead. Thewarhead body was fitted with an appropriate nose, base, slip band, andbourrelet to make it compatible both for launch from a 155-mm, M185Howitzer tube and recovery in the LCSRS. The purpose of the test was toexpose the warhead to the in-tube environment of an actual gun launch,soft-recover the projectile, and disassemble the projectile, so postfiring diagnostics and structural tests could be performed on the warhead.

The projectile was also instrumented with a telemetry system for thecontinuous measurement of physical paiameters on-board the projectileduring the propulsion phase of the launch trajectory. These experimentaldata were needed to define the launch environment and to compare with theresults derived from a finite element stress analysis of the warhead.

II. DESCRIPTION OF THE LARGE CALIBER SOFT RECOVERY SYSTEM

A photograph of the LCSRS is shown as Figure 1. A schematicshowing the principle of operation is presented as Figure 2. Soft re-covery of the projectile is achieved by attaching a water scoop to thetest projectile and firing the projectile into a water trough inclinedat a small angle. This presents an ever-increasing depth of water tothe advancing projectile. The impulse of the projectile is convertedinto the momentum of the water ejected forward by the scoop on impact.The 60-meter length of the system is sufficient to stop the projectilewith a maximum deceleration less than 10% of the maximum launch acceler-ation. The theoretical projectile deceleration in the LCSRS is pre-sented as Figure 3 for the CLGP projectile weight (51.9 kg) and a troughinclination angle of 1.20 mils. Predicted launch velocity was 533 metreper second. The drag equation and computer code used to calculate thisdeceleration are given in Reference 1.

III. DESCRIPTION OF THE PROJECTILE

A diagram indicating the location of the various parts of the testprojectile is shown in Figure 4. A photograph of the projectile, broken2 E. J. Halcin and J. A. Pratt, "Design of a Large Caliber Soft RecoverySystem for the Ballistic Research Laboratories," Ballistic ResearchLaboratory Contractor Report No. 308, Honeywell Inc., August 1976.(AD #B013626L)

2 C. R. Hargraves, "Metallurgical Control of Fragmentation, Phase II,"Ballistic Research Laboratory Contractor Report No. 350, Honeuwell, Inc.,September 19?7. (AD #B022333L)

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down into its component parts, is shown in Figure 5 and an end-on viewof the assembled projectile, looking into the scoop with an antennamounted, is shown in Figure 6. The CLGP warhead body was unmodified forthe projectile system shown. All mating parts were made to conform tothe warhead body.

A. Water Scoop

The water scoop was designed, as per LCSRS specification, to havethe necessary interior contour to eject the impacted water forward. Thewater entered onto a conical surface of revolution that blended into aspherical surface of revolution. The antenna and radio frequency trans-mitter, for the telemetry system, were located in the scoop structure(Figure 7). The radiating elements and feed cable of the antenna thatprotruded into the water path were housed in a phenolic fiberglass mem-ber. Upon impact with the water, this structure was designed to breakaway so as not to interfere with the water flow over the scoop surface.

The scoop was attached to the warhead body by a threaded section.The threads were compatible with the existing threads on the forward endof the CLGP warhead body. A surface was provided on the scoop to installa plastic bourrelet. When assembled, the bourrelet was contained betweenthe nose and the warhead (Figures 5 and 6).

B. Base Structure

The base structure (Figure 5) was designed to prevent the propellinggases from entering the warhoad and also to provide a housing for trans-ducers and the telemetry electronics. It was attached to the warheadby an existing threaded section on the warhead. A plastic slip band wasfitted on an existing contour of the warhead and when the projectile wasassembled, the plastic slip band was contained between the warhead andthe base structure.

C. Projectile AssemblyUpon final assembly of the components, the projectile was filled

with an epoxy. The epoxy was used to simulate the high explosivenormally carried in the warhead body and it also provided support forwires that connected the various components of the telemetry system.Filling the projectile was accomplished through a threaded orifice inthe scoop (Figure 6). A vacuum system was used to lower the pressureinside the warhead so the epoxy would flow easily into the cavity andfill all voids. After filling, the orifice was closed with a pipe plug,the protruding material machined off, and an epoxy was used to fill aroundthe plug and match the contour of the scoop surface.

After launch and recovery, the projectile was disassembled by removingthe water scoop assembly and base cap. The projectile was then put into acold chamber at -10C for 24 hours. The difference in the thermal

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Figure 5. CLGP Warhead, Test Projectile Components

Figure 6. CLGP Warhead, Assembled Projectile12

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expansions of the warhead and the epoxy caused them to separate and theepoxy was easily removed from the warhead.

IV. DESCRIPTION OF THE TELEMETRY TRANSMITTING SYSTEM

The telemetry system3 was designed to provide continuous measure-ments of four performance parameters on-board the projectile during thein-bore phase of its launch trajectory: projectile base pressure, linearacceleration, and strain at two locations on the inner wall of the war-head. The strain measurements were made at points under and betweenzones of varying metallic hardness 2 (Figure 4).

Instrumentation for the telemetry system consisted of a dipoleantenna, S-band transmitter, four voltage controlled oscillators (VCOs)and three battery packs. The VCOs were frequency modulated by thevoltage analcg signals produced by the four transducers. The outputsfrom the VCOs were summed and used to frequency modulate the transmitterto form a conventional FM/FM system. A blcck diagram of the transmittingsystem is shown as Figure 8.

A. Transmitter ind Antenna

A Microcom Corp., Model T-4 transmitter (T, Figure 5) with nominalfrequency of 2.22 GHz and output power of 20 milliwatts was mounted inthe water scoop assembly (Figure 7) to the rear of the antenna lead port.The antenna, designed at BRL, consisted of a phenolic member threadedat the base for mounting in the antenna-transmitter adapter. The baseof the antenna-transmitter adapter housed the mating push connector tothe transmitter. A semi-rigid coaxial cable, which passed through thelong axis of the phenolic structure, was connected to fine wires thatformed the dipole radiating elements. These elements were bent to conformto the outside of the phenolic member and ran parallel to its long axis.A small, 100-ohnm resistor, connected across the dipole, was used to broad-band the antenna.

After assembling the transmitter and antenna in the water scoop andconnecting hook-up wires to the transmitter, the warhead cavity, wherethe transmitter was located, was filled with an epoxy.

B. Voltage Controlled Oscillators

The center frequencies (fc) of the Omnitek, Inc. VCOs were 128,192, 256, and 320 kHz with a 16-kHz deviation. The !nput voltagerange for both the pressure transducer and accelerometer modulated

3 J. W. Evans, "In-Bore Measurements of Projectile Acceleration and BasePressure using an S-Band Telemetry System," Ballistic Research Laboratory

i Memorandum Report No. 2562, December 1975. (AD #B008421L)

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VCOs was 0 to S volts. The VCOs modulated by the strain transducershad an input range of 2.5 volts since both tension and compression wereto be measured.

C. Piezoelectric Transducers

The pressure transducer and accelerometer, shown in Figure 9 (P and A),were PCB Piezotronics, lnc., Models 109A4 and 305M5 , respectively. Eachcontained a P-channel, Mosfet, source follower 6 within its housing.These source followers functioned as impedance converters and provideda nominal 100-ohm output impedance. Excitation for these circuits wasprovided by a constant current source and the analog output signal wascapacitive coupled to the VCO. Full scale output for these units was5 volts. The circuit diagrams for the piezoelectric transducers and theexcitation circuit are shown as Figure 10.

The pressure transducer contained a very rigid, acceleration-compen-sated, quartz element coupled to thle source follower. This transducerwas mounted in the base structure (Figure 4) with the gage diaphragmexposed to the propellant gases via a short silicone grease column.

The accelerometer contained a seismic-mass-loaded quartz elementcoupled to the source follower. This transducer was mounted on theprojectile long axis in the base structure of the projectile in tandemwith and forward of the pressure transducer.

D. Strain Measurements

The strain measurements were made with foil-type, resistive, straingages cemented to the inner wall of the warhead body and connected ina bridge network. The strain gages formed two active arms of the bridgeand were located 180 degrees apart on the body surface to compensate forbending moments in the body. The orientation of the gases were such thatthey responded to the axial component of strain in the body. The inactivearms of the bridge consisted of similar strain gages which were isolatedfrom the body strain by implanting them in the base housing. The useof the same type of strain gages throughout the bridge network minimized

4"Model 109A Pressure Transducer Instruction Manual1 " PCB Piezotronice,Inc., Buffalo, NY 14225.

5"Model 305M Accelerometer Instruction Manual," PCB Piezotronice, Inc.,Buffalo, NY 14225.

6 PCB Piezotronice, Inc., General Guide to ICP Instrumentation PamphletG-0001, Buffalo., NY.

16

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Figure 10. Piezoelectric Transducer and Power Supply

17

thermal drift. Bridges for both strain circuits were excited by thesame constant-voltage source. The differential, analog, voltage outputwas amplified by an Omnitek, Inc. amplifier to make it compatible withthe VCO. A circuit diagram for the strain measuring system is shown asFigure 11.

E. Power Supply

The power supply for the transmitting system consisted of three,series-connected battery packs (B, Figure 9) made up of six rechargeable,nickel-cadimum cells each. The current rating of these cells was 250milliampere-hours at a 10-hour rate. This provided about 45 minutesof operation for the transmitting system. Output voltage under load wasa nominal 22-20 volts.

F. Packaging

The electronics for the transmitting system were packaged in a cy-lindrical module (E, Figure 9) and encapsulated in an epoxy compound.The module was mounted in a cavity in the base structure (Figure 4).The battery packs were inserted in three cylindrical cavities located120 degrees apart in the base structure. After all components were as-sembled and connected, all voids within the base structure were filledwith an epoxy compound.

V. CALIBRATION OF THE TELEMETRYTRANSMITTING SYSTEM

The information transmitted by an PM/PM telemetry system is containedin the frequency of the subcarriers 7 . Therefore, it was necessary todefine the magnitude of the physical parameter being measured in termsof the output frequency of the VCO. This was accomplished by convolutionof the transducer calibration factor with the transfer function of theVCO.

A. Pressure Channel

The pressure transducers were calibrated in a dead weight calibrationfacility. They were subjected to seven static pressure levels and theoutput voltages recorded. The set of points resr-lting from this calibra-tion was used to determine the least squares parabola with pressure asthe dependent variable and output voltage as the independent variable(P = a + bV + c V2). The VCO used in the pressure data channel wascalibrated by impressing a series of voltage levels on the input and

7M. H. Nichols and L. L. Rauch, Radio Telemetrid 2nd ed., John Wiley andSons, Inc.,, 1956, pp. 253-26?.

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measuring the resulting output frequency. The measured output frequencywas normalized to a change in frequency (Af) where zero represented theVCO lower band edge (f - 16 kllz). The pressure-voltage relationshipwas used to calculate a corresponding pressure for the various voltagelevel inputs to the VCO. This formed a set of points of pressure andAf that were used to determine the least square parabola with pressureas the dependent variable and Af as the independent variable(P - a + 8Af + pAf 2 ).

Since the output impedance of the pressure transducer was about100 ohms and the input impedance of the VCO was about 150 kilohms, theloading factor was negligible. The VCO did not significantly alter thetransducer output when they were interfaced. Therefore, the techniqueof convoluting the transducer calibration and the VCO calibration wasvalid. The pressure-Af relationship was used in the data reduction pro-cess.

B. Acceleration Channel

The manufacturer's linear calibration factor for the accelerometerwas used since an in-house calibration facility was not available. TheVCO used in the acceleration data channel was calibrated and normalizedsimilar to the pressure channel. The calibration for the accelerometerand the VCO were convoluted and the least square parabolic fit was deter-mined.

C. Strain Channels

The strain channels were calibrated end-to-end by substituting pre-cision decade resistors for the active arms of the bridge. First, thebridge was balanced with all strain gages connected. Then one activearm was disconnected and the decade resistor box substituted. Thebridge was then rebalanced to the previous quiescent point. The otheractive arm was then substituted in the same manner. When both activearms had been replaced, the two decade resistor boxes were varied by thesame increments over the expected range. The VCO frequencies were re-corded for each increment. The resistive increments were convertedto strain increments using the manufacturer-furnished gage factor.The least squares parabolic fit was then made for the strain-Af relation-ship.

VI. DESCRIPTION OF TELEMhTRY RECEIVING SYSTEM

A. Radio Frequency Receiving System

The output signals transmitted from the projectile during the in-tube travel were received via a helical antenna located forward and tothe left of the muzzle. It was found that precise positioning of theantenna was not critical, except that it be placed outside the area

20

of extreme muzzle blast effects to prevent damage. Output signals fromthis antenna were fed into a down converter that translated the nominal2.22-GHz signal to a nominal 235-MHz signal. This was done to avoid thelarge attenuation at the 2.22-GHz frequency caused by the 30.5 metresof coaxial cable between the antenna and the receiver. Signal levelinputs to the receiver was then at -40 dbm.

B. Data Discriminating System

The data discriminators used in the second detection process had aninput bandwidth of 32 kHz and an output low-pass filter bandwidth of8 kHz. The telemetry data channels were interrupted 350 millisecondsprior to the event to insert a voltage staircase calibration. The amp-litude and off-set of the staircase were adjusted to be compatible withthe recording device. The discriminator output voltages were correlatedwith the calibration staircase by adjusting their band-edge voltage out-puts. The lower band-edge (fc - 16 kHz) voltage was adjusted to coin-cide with the staircase baseline and the upper band-edge (fc + 16 kHz)voltage was adjusted to coincide with the staircase top calibration step.These two extremes represented Af equal to zero and Af equal to 32 kHzrespectively in the transducer least square parabolic fit. The recordedstaircase and data from the event represented the VCO frequency excursionwith the staircase steps defining the magnitude of the physical parameterbeing measured. A block diagram of the telemetry receiving system isshown as Figure 12.

VII. ON-TUBE MEASUREMENTS

A. Chamber Pressure

SPropelling gas pressures were measured at two locations in thecannon using Kistler 607C piezoelectric pressure transducers. Thesetransducers were located in the spindle face and in the cannon sidewall near the projectile base when it was seated. These pressures wereused to monitor the charge performance and to correlate with the tele-metered base pressure data.

B. Projectile DisplacementA simple, compact, 10-GHz, doppler radar8,9 was fabricated to obtain

projectile displacement during the in-tube travel. These data were used to8 D. C. Vest, J. E. Anders, B. B. Groliran, and B. L. DeMare, "BallisticStudies with a Microwave Interferometer - Part I, " Ballistic ResearchLaboratory Report No. 968, September 1955. (AD #81617)9 .C. Vest, J. E. Anders, H. C. Smith, B. B. Grc ilman and T'. Kashihara

"Ballistic Studies with a Microwave Interferometer - Part II," BallisticResearch Laboratory Report No. 1006, February 1957. (AD #127631)

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compare with the double integrated, telemetered acceleration data.Since the muzzle of the gun was near the LCSRS, it was not possible toreflect a doppler microwave signal into the gun tube in the conventionalmanner. Therefore, the radar was configured so it could be concealedwithin the LCSRS entrance assembly and have ai expendable antenna. Asimplified block diagram of the doppler radar is presented as Figure 13.The radar was protected from muzzle blast by sand bags and was connectedto the antenna by a one-metre long, semi-rigid, coaxial cable.

The antenna, shown as Figure 14, had a circular ground plane andused the coaxial center conductor as the radiating element. Three smallscrews protruding from the ground plane directed the radiation patterntoward the muzzle. The antenna was mounted about one metre forward ofthe muzzle and just below the line of fire.

VIII. RECORDING AND DATA REDUCTION

The data from the telemetry system and the on-tube pressures wererecorded in real time on an analog-to-digital recorder that was a sub-system of the Ballistic Data Acquisition System (BALDAS). These datawere simultaneously recorded on analog, FM, magnetic tape along with thedoppler signal. These data, including the calibration staircase, weremanipulated, scaled, and converted to engineering units under the con-trol of the BALDAS minicomputer. This system outputted the data in theform of plots on an electrostatic plotter. The data from the dopplerradar were reduced by hand reading a chart recorder playback. The dopplerradar displacement was entered into the BALDAS system via the terminalkeyboard.

IX. RESULTS

Three instrumented, CLGP-warhead, test projectiles were fired froma 155-mm, M185 Howitzer tube using an M4A2, Zone 7, Propelling Charge.All three were successfully recovered in the LCSRS. There was no visibledamage or catastrophic structure failures of the CLGP projectiles. Thethree projectiles were disassembled and the warhead section turned over tothe Terminal Ballistic Division, BRL for structural testing.

The telemetry link, with each of the three projectiles, was estab-lished at system turn-on, prior to loading the projectile. This linkwas maintained throughout the loading and ramming process, during a ten-minute warm-up period, and during the in-tube travel. The signal waslost at or near muzzle exit. All voltage controlled oscillators andexcitation circuitry functioned properly. After recovery, each projec-tile was refitted with a new antenna and the system was turned on andevaluated. All measurable parameters (VCO frequencies, transmitterfrequencies, battery voltage, and transducer quiescent points) on allthree rounds were within the pre-launch specifications.

23

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A. Pressure

The telemetered base pressure data, along with the breech and frontchamber pressure, are presented for the three rounds as Figures 15, 16,and 17. The base pressure for CLGP Warhead #1 was lower than theoreticalcalculations predicted. A finite element analysis of the projectile basestructure indicated that a binding of the transducer sensing shaft inthe mounting hole could occur during pressure loading of the base. Forthe other two rounds, the mounting hole size was slightly increased.This appeared to correct the problem for CLGP Warhead #2 since the basepressure was near the predicted value. Although the base pressure forCLGP Warhead #3 was near the value of Warhead #2, the difference betweenthe base and spindle pressures was larger than the theoretical prediction.Inaccuracies in either or both these pressure measurements could havecaused this discrepancy.

B. Projectile Acceleration

Telemetered, projectile-acceleration data for CLGP Warhead #1 ispresented as Figure 18. The negative excursion of this plot is obviouslynot correct. This was caused by a parasitic transduction-mechanism ofthe accelerometer mounting structure. Since the accelerometer was mountedon an aluminum structure, the distortion could have been caused by basestrain. A steel mounting plate was substituted for the other two rounds,but the same phenomenon occurred on CLGP Warhead #2. To eliminate allsolid material that contacted the accelerometer except for the mountingsurface, the epoxy that filled the voids in the base structure was notused in the accelerometer cavity on CLGP Warhead #3. This change elim-inated the parasitic transduction effect that caused the negative excursion.

The displacement versus time for CLGP Warhead #3, obtained by doubleintegrating the telemetered acceleration, is compared with the displacementobtained from the doppler radar in Figure 19. There is a difference ofabout 4% in the two sets of data. Since there was no dynamic calibrationof the accelerometer for the range it was used, the doppler displace-ment was believed to be more accurate. The accelerometer data was cor-rected by multiplying by the ratio of the doppler displacement to thedouble integrated acceleration. The resulting in-tube trajectory forCLGP Warhead #3 is presented as Figure 20.

C. Body Strain

The strain records for the three CLGP warheads are presented asFigures 21, 22, and 23. From the finite element analysis, all strainsappeared to be reasonable. The accuracy of the various strain channelswas difficult to determine because the strain patches were not exercisedby mechanical loading of the projectile structure after bonding the gages.The nature of the test precluded such a gage calibration.

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340

X. CONCLUSIONS

The LCSRS and the on-board instrumentation proved to be a usefultool for this type.of research project. The successful recovery of theprojectiles accomplished the original task of providing warheads exposedto the launch environment for post-firing diagnostics. The data receivedfrom the projectile-mounted transducers should be useful for correlatingwith the theoretical analysis of the warhead structure. As this typeof program becomes more routine, the real potential of these systems willbe realized.

AC KNOWLEDGMENTS

The authors wish to express their gratitude to Messrs. James E. Bowen,John R. Hewitt and John L. Stabile of the Interior Ballistics Division,Ballistic Research Laboratory for their assistance in conducting the firingprogram.

35

REFERENCES

1. E. J. Halcin and J. A. Pratt, "Design of a Large Caliber SoftRecovery System for the Ballistic Research Laboratories," BallisticResearch Laboratory Contractor Report No. 308, Honeywell, Inc.,August 1976.(AD #B013626L)

2. C. R. Hargraves, "Metallurgical Control of Fragmentation, Phase II,"Ballistic Research Laboratory Contractor Report No. 350, Honeywell,Inc., September 1977. (AD #B022333L)

3. J. W. Evans, "In-Bore Measurements of Projectile Acceleration andBase Pressure Using an S-Band Telemetry System," Ballistic ResearchLaboratory Memorandum Report No. 2562, December 1975. (AD #B008421L)

4. "Model 109A Pressure Transducer Instruction Manual," PCB Piezotronics,Inc., Buffalo, NY 14225.

5. "Model 305M Accelerometer Instruction Manual," PCB Piezotronics, Inc.,Buffalo, NY 14225.

6. PCB Piezotronics, Inc., General Guide to ICP Instrumentation, PamphletG-0001, Buffalo, NY.

7. M. H. Nichols and L. L. Rauch, Radio Telemetry, 2nd ed., John Wileyand Sons, Inc., 1956, pp. 253-267.

8. D. C. Vest, J. E. Anders, B. B. Grollman, and B. L. DeMare, "BallisticStudies with a Microwave Interferometer - Part I," Ballistic ResearchLaboratory Report No. 968, September 1955. (AD #81617)

9. D. C. Vest, J. E. Anders, H, C. Smith, B. B. Grollman and T. Kashihara,"Ballistic Studies with a Microwave Interferometer - Part II," BallisticResearch Laboratory Report No. 1006, February 1957. (AD #127631)

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