t".

GROUND IMPACT SHOCK MITIGATION

HOWITZER 105MM MgA1BY

DAVID 0. WIZDERAN"DIR9URL TR 1030 JULY 3.067

./ /'

AB

SIE'NUNEElNG MECITANICS RESEARCH LABORATORYTIlE ' NIVKIINITY OF TEXAS AUS11N. TEXAN

Reproducf•d by theCLEARINGHOUSE 9

__ - °

THIS D&CUfr HAS VEZ-, APPW-E P.C TR 1020

GROUND IMPACT SHOCK MITIGATION

HOWITZER 105mm M2A1

1'byDavid G. Wiederanders

QUARTERMASTER RESEARCH AND ENGINEERING COMMANDAIRDROP ENGINEERING DIVISION

Project No. 1F121401D195

CONTRACT DA 19-129-AMC-582(N)

ENGINEERING MECHANICS RESE.ARCH LABORATORY

THE UNIVERSITY OF TEXAS

Austin, Texas

t

IIU

PREFACE

This report is the third in a series of four dealing withhigh velocity airdrops of selected military vehicles. Highvelocity in this case means an impact velocity of 50 fps orhigher. The other three reports in the series are entitled

Ground Impact Shock Mitigation M1Si UtilityVehicle (Jeep)

Ground Impact Shock Mitigation Cargo Truck,3/4-Ton M37

Ground Impact Shock Mitigation Cargo TrailerM101, 3/4-Ton

Each of these vehicles were studied previously under

Contract DA 19-129-QM 1383 with the Natick Laboratories. However,in these earlier studies, impact velocities were limited to 30fps and the design acceleration was 16g. These limitations wereimposed by airdrop operational procedures at that time. Resultsof these earlier studies were published in a series of reportsentitled,

Fragility Studies

Fart I Utility Truck 1/4-Ton (Jeep)

Part II Cargo Truck M37 3?4-Ton

Part IV Cargo Trailer M101 3/4-Ton

In the investigation described in this report, the onlylimitation on the impact velocity was the maximum available dropheight at the drop facility. For the howitzer, this height was46 feet. From this maximum height, an impact velocity of 54 fpswas developed. Tne only limitation on the design acceleration was

that it not be so high as to damage the vehicle. The maximumpractical value was 30g. To obtain higher accelerations, astronger cushioning material, or an impractical cushioning areahad to be used. No drive-on, drive-off capability was designedinto the cushioning system since this was intended to be only afeasibility study. However, since the howitzer must be towed,getting it off the cushioning system after a drop presents noserious problem.

E. A. RippergerDirectorEngineering Mechanics Research LaboratoryThe University of TexasAustin, Texas

July 1967

ii

TABLE OF CONTENTS

Page 3Preface . ......... i

List of igures . . . ... . . . . . . . . . . . . . . . .

Abstract . . ........

Introduction.. . . . ... * . . . . . . . . . . . .* 1Pnrodureio *****.........................3iProcedure . . . . . . . . . . . . . . . . . . . . . . . .3

Drop Program................ . ........... 3

Probllfms Encountered .............. .................. 4

Lifting Rig . . . . . . . ................

Platform. . . . . . . . . . . . . . . . . . . . . . ..

Honeycomb ...... ..................... 8

Instrumentation ................. .................... 8

Summary of Drop Parametersand Damage Observed ............ ................... 9

H-105-1 ..................... ........................ 9

H-105-2 . .......................... 9

H-105-3 ....................... ...................... 9

H-105-4 ............. ........................ .i.11

H-105-5 ............. ........................ .l.11

Conclusions ............................ 18

References .............. ........................ ... 19

iii

LIST OF FIGURES

Figure Page

1 Front 1oa preader . .. . .. .. .. .. . .. 5

2 Load Spreaders for the 105mm Howitzer M2AI.. 6-

3 Rigging for Lifting the System ..... ......... 7

4 System during H-105-1 ......... ............. 10

5 Cushioning System before H-105-5. . . . . . . . 12

6 System after H-105-5 ..... ... ...... .. 13

7 Cushioning Stack Placement for H-105-5 ........ 14

iv

ABSTRACT

The 105mm Howitzer supplied to this laboratory by the ArmyTank and Automotive Command through arrangements made withNatick Laboratories has been dropped five times at impactvelocities up to 54.4 fps, and at design accelerations as highas 30g. The initial modifications of the vehicle in preparationfor the drop series and the design criterion for this testseries are presented along with a description of the cushioningsystem used and the damage sustained in each drop.

It is concluded that this vehicle can be dropped at impactvelocities up to 50 fps without any damage, if a properly de-signed cushioning system is used.

V

INTRODUCTION

Twenty-five feet per second has been the nominal designimpact velocity for the air drop of equipment and suppliesfor seviral years. It has been shown, however, by Turnbow andSteyerl that the cost of air drop can be reduced appre-ciably by using a higher impact velocity. This saving resultsfrom the use of relatively inexpensive paper honeycomb to

dissipate the energy, rather than the large expensive parachutesrequircd to achieve the 25 fps impact velocities. In addition,a higher impact velocity reduces the dispersion of the droppedmaterial, increases the accuracy of the drop insofar as hittingthe target area is concerned, and, because of the reduced timethat the equipment is in the air, reduces the danger from possibleenemy action.

In theory, at least, it is possible to cushion a vehicle sothat it will survive an impact of any velocity, but there areother considerations. For example, the space available in air-craft is limited. This obviously places a limit on the impactvelocity that can be sustained because the volume of cushioningmaterial increases with the square of the impact velocity. Inaddition, the stability of the cushioning system becomes a seriousproblem as the height of the cushioning stack increases.

Tn order to study some of the practical problems of cushioi1-ing vehicles against high impact velocities; to discover some ofthe hidden problems which might exist; the program of drops ofthe 105mm Howitzer,, which is reported here, was undertaken.

The primary objectives of this investigation have been

1. to verify that the vehicle could be successfullydropped at impact velocities as high as 50 fps,

2. to determine the maximum design acceleration thatcould be used for such a drop,

3. to work out the essential details of a prototypecushioning system, and

4. to observe the damage susceptibility of the vehicle.

The collection of data regarding the damage susceptibilityof certain specific vehicles is but one phase of the researchprogram which is intended event,,9lly to put the design of cushion-ing systems for the airdrop of equipment on a firm engineering

* Superscript numerals indicate references listed at the endof the report

2

basis. However, a standard cushioning system applicable to all-vehicles is not feasible. Hence, each vehicle must have its Ownsyster., and althoughi these differ somewhat in detail, they shouldall conform to the basic principles of cushioning design a, those'principles are now understood.

I _

U I

PROCEDURE

The approach employed was to make the first drop with a20g design acceleration and a drop height of 10 feet, and thenin successive drops, to gradually increase th(-3e values asseemed warranted by the results of previous drops.

The vehicle used for this test series was a 105mm Howitzer,M2Al and associated carriage assembly M2A2, supplied by theArmy Tank and Automotive Center under arrangements made throughthe U. S. Army Natick Laboratories.

It was dropped in the "as-received" condition except for thefollowing modifications:

1. Lifting wheel plates installed.

2. Extension bar assembly installed.

3. Protective covering installed over sight mountand elevation gear-assemblies.

4. Accelerometers Installed on each trail in the samevertical plane as the C.G. of the vehicle and on theleft -trail just in front of the towing pintle.

These modifications were made to provide lifting points, toreduce the overall length of 'he system as much as possible, byputting the barrel in the recoil position, to protect those areaswhich might be t..amaged by the lifting shackle, and to provideacceleration data during impact, respectively.

irop Program

As previously indicated, the first drop was from a height of1C feet with a design acceleration of 20g. In subsequent drops,both the height and design acceleration were increased as seemedwarranted by the results of the previous tests. This procedurewas followed so an effective cushioning system could be designedand tested at lower impact velocities before relying on thesystem at high impact velocities and accelerations. By followingthis procedure, it was expected that the maximum amount of in-formation would be obtained for the vehicle before it was damagedso much as to make further drops impractical. A drop height of46.3 feet and a design acceleration of 30g were reached in thefinal drop of the series with no significant damage to the vehiclebeing detected during the entire program.

3

4o

Problems Encountered

The main problem encountered during this test series was thelack of sufficient area forward of the C.G. to allow for cushioningsystems in which the moments of the cushioning forces about theC.G. of the vehicle could be balanced. To overcome-this difficulty,a relatively complex loadspreader was used. This spreader, whichwas attached to the bottom of the slide assembly as shown inFig. 1, allowed a cushioning stack to be placed several feetforward of the C.G. thereoy providing the additional moment required ito put the system in rotational equilibrium during crushing.

The area directly under the pivot point of the Howitzerassembly was the source of another difficiity. This area is thepoint of greatest mass concentration in the weapon. To providesufficient area for adequate cushioning at that point, it wasnecessary to design a loadspreader that would contact all thestructural members with sufficient strength to transfer thecushioning force to the weapon assembly. Dimensional sketchesof these loadspreaders are found in Fig. 2.

Lifting Ri~g

The Howitzer weapon system used for this test series wasrigged for drop by attaching lifting plates and shackles to eachof the wheels ýind installing protective wrappings around eachof the trails just behind the carriage locking studs. Tofacilitate the lifting and leveling of the system, chains wereattached to one end of each of four slings, one of the chainswas passed either through the lifting shackles or around theprotected trails and hooked back on itself. This allowed forquick adjustment of the lifting rig to achieve a level attitudeof the system.

Each of these slings was attached to a large lifting shacklewhich was engaged by a helicopter hook. This hook was releasedfor the drop by the Fastax-Camera timing control. The completelifting rig is shown in Fig. 3.

Platform

An Ox16-ft. plywood platform was designed and built,essentially to the specifications for the combat expendable plat-form described in TM 10-500-19-2. This platform was used forthe seven drops of the test series involving the M37 cargo truckand for the five drops of the 105mm Howitzer. The platform per-formed very well and has been damaged only slightly by the twelve

JU

tt W1!

54

-,%N.M-

_ _ 6

131 Front2.v"x l Load Spreader

3Sh~ts 3/4 Plywoo

36"Load Spreader

k3 S9"ts 3/S!t Plywood

T ',i

~..-34" -owlf- 863 Load Spreader er3 Shot 3/6 Plyoo

48'-1ete

"ITI 4 8"

Fig. 2 Load Spreaders for the 105mm Howitzer M2AI

All

8

drops in which it was used.

Honeycomb

The cushioning material used throughout this series was80-0-1/2 paper honeycomb purchased directly from the manufacturer.A honeycomb evaluation test series involving stacks in excessof 12 inches in height provided the values of average crushingstress and energy dissipation characteristics used to design thecushioning system. These values were found to be smaller than tlevalues obtained for single pads because the uniformity of crushingdecreases as the stack height increases. The average crushing Fstrength was determined to be 6430 lb/ft 2 and tho energy dissi-pated was 4500 ft-lbs/ft 3 .

Instrumentation

Accelerometers were mounted on the system in the followingpositions: one on each trail directly on line with the C.G.,and one oi± the left trail directly forward of the towing pintle.

In addition to acceleration records which were recorded byboth an oscillograph and magnetic tape system, high-speed motionpictures were made of all drops. These pictures were studiedto see how the cushioning system performed and for clues as towhat changes should be made to improve the performance of thesystem. Prior to each drop, and at the completion of each drop,documentary photographs were also made. After each drop, theHowitzer was carefully examined for any visible damage and forindications of possible future problem areas.

I.t

SUMMARY OF DROP PARAMETERSAND DAMAGE OBSERVED

H-105-1; Height 10 ft.; Acceleration 20g.

This drop was made using a cushioning system design basedon the measured weight distribution of the weapon in the recoilposition. It is a five-point 2ushioning system with stacksplaced under the C.G., under the trails, under the front end ofthe barrel sleigh, and under each of the wheels. The buildupstacks were designed so that the trails were level at impact andremained so throughout crushing. The given weights of thetipping parts of the cannon were used to locate the C.G. of theseparts independently of the carriage assembly. This was doneso that the reactions at the supporting points could be found.The cushioning system was then designed to subject the sleigh-locking studs to a 4000 lb. force at a design acceleration of20g. The remaining energy at impact, due to the tipping parts,was dissipated by the front crushing stack or transmitted throughthe pivot point to the center cushioning stack.

The drop went as expected with all stacks crushing uniformlyto 65 percent. See Fig. 4. No damage could be detected afterthe drop.

H-105-2; Height 20 ft.; Acceleration 30g.

The second drop of the 105mm Howitzer was made using a designcalculation of 30g but still allowing only a 4000 lb. force to betransmitted through the locking studs of the sleigh assembly.

Loadspreaders were used under the wheels for this drop tomore evenly distribute the cushioning force of the wheel stacksat impact. This system worked well and was used for the re-mainder of the test series.

The system crushed uniformly to 65 percent at impact. Therewas no damage to either the Howitzer or carriage assembly.

H-105-3; Height 30 ft.; Acceleration 30g.

This drop was made to test the cushioning system used inH-105-2 at the higher impact velocities of the 30 ft. drop.

The system crushed evenly to 60 percent on initial impact,but after rebound, the front stack was crushed an additional10 percent. The wheel stacks both crushed slightly to the insideof the stack.

10

* b

IMFn

There was no damage to the weapon or carriage from the dropor the uneven crushing. It was observed that the cannon reboundedslightly to the left side after impact. This was later foundto be due to uneven tire pressure rather than an unbalancedcushioning system and was corrected before the last drop ofthe series.

H-105-4; Height 40 ft.; Acceleration 30g.

This drop was made from a height of 40 ft. in accordance withthe test program to provide an impact velocity of 50.8 fps.

Thb same cushioning system used for H-105-3 was used for thisdrop with the only modification being the additional drop height.The system impacted flat and crushed uniformly to 60 percent.

There was no damage to the vehicle as a result of the dropor rebound. The ruggedness of this Howitzer and its mountingare sufficient, it appears, to justify a higher design acceleration.Further investigation must be made, however, into the problemshigher accelerations may bring before a firm recommendation,either for or against the system, can be made.

H-105-5; Height 46.3 ft.; Acceleration 3;.-

The same cushioning system used for the previous two dropswas used with modifications being made for the additional dropheight.

The system performed well, crushing uniformly to 65 percent.No damage was observed after the drop.

The cushioning system used for this drop is shown beforeand after the drop in Figs. 5 and 6. Although the cushioningsystem performed very well, it cannot be considered the ultimatedesign for the vehicle. The effectiveness of the system dependsheavily on the use of a system of loadspreaders. Although thedesign of these loadspreaders is not overly complex, it may notbe feasible to use such spreaders in an actual airdrop situation.However, since this test series was a feasibility study ratherthan the development of an ultimate system suitable for fielduse, no attempt was made to refine the design of the loadspreadersystem. With the prototype system shown in Fig. 7 and Table 1as a guideline, the development of a system suitaole fo2 fielduse should not present significant difficulties.

No2

II

4-J

*1loo.

_______

i

14 IL0

I

I�S a.E.LI 4

N -4 �Emm I

___ 'K1= Rj L& 0 � s

U -JE

0�mi/ (4.4

4.)

a,Ea)U

...

"-404

0i�1

.4.)CJ2

--4

0--4

C-)

r�.

-'.4

9

15

TABLE 1

Drop 11-105-5

Position Stack Area Dimension Height

Ac. 1.68 ft 2 1.2' - 1.4' 24 in.

Ac 15.56 ft 2 4.0' - 3.9' 24 in.*22

Ac 1.77 ft 2 1.3' x 1.36' 24 in.3

A 1.95 ft 1.62' x 1.2' 24 in.w t

Total height of system including cushioning stacks 86 inches

I.I

II

16

The Howitzer and carriage assembly was examined thoroughlyafter this drop to be certain that no damage was overlooked. Nosign of any dame.- that could be attributed to the five dropswas found.

Average accelerations and peak accelerations for all thedrops of the series are shown in Table ?. In general, themeasured average acceleration is less than the actual designacceleration. This phenomena has been observed in previousstudies and is considered to be due to the flexibility of thevehicle structure which actually provides some shock mitigationfor itself. One might expect that for a rigid vehicle suchas this weapon, the design and the average accelerations shouldbe much more nearly the same than they are for the less rigidvehicles. This did seem to be reflected in the measurementsbut the results are not- conclusive.

In Table 2, Column 8, the integral of the accelerationrecord is shown. For valid acceleration measurements, thisintegral should correspond to the impact velocity shown inColumn 7. The discrepancies between the impact velocity andthe acceleration integration are due mostly to the difficultyin determining Just where to stop the integration. Consequently,the acceleration measurements are considered valid.

U v . . ... C) ~ . . C).a

0 0

> z

eu~~~~~~ c'u co ne ~~ AL AL A

LCL Ln U'% U'% LA tA Lf (r0 0 ý

0 :0

a o0 Do -r4t-c ~ mz 0 O~tl- fico

>* 0 0

000 _-T 0~ OD 0\10 (n~~ cooC~ r-I 0 CM A)

W 00'

H4)

C4-

00

C',

Q-4)

.r. C.)bo 00 0 0 0 0 a0 0 I'D\Z ko

4)4) 4.) 4 o-)

-HO)- 4: 4-) w-4 0) * 0) a 4-)

C)r -HC~f a)CC C ~ C,~

C) 0 d 0 0 d '. 0 '.0 '0 T0C-) C. a) 0 C- a) 0 CIQ 0 U Q

z lUI Ir I0 0 C) 0

ol 'V.

i

CONCLUSIONS

1. The 105mm Howitzer weapon system can be dropped from aheight of 50 feet to land with an impact velocity of 57 fps usingessentially the same techniques used for dropping at 25 fps.

2. A cushioning system designed for 30g average accelerationprovides adequate protection for the vehicle. This design accel-eration could be used even at low-velocity drops to reduce therequired stack heights.

3. There is evidence gathered from the test series that the105mm Howitzer is of rugged enough design to be dropped using acushioning system designed for an impact acceleration of 40g.There is, however, insufficient information available to reach adefinite conclusion at this time.

4. By redesigning certain parts i the carriage assembly,the problem of insufficient area for cushioning without aloadspreader could be largely reduced.

5. Although it appears from the results of this series ofdrops, and of others that have been made, that vehicles can besafely and economically dropped at impact velocities in excessof 50 fps, it is desirable to drop a prototype vehicle of eachtype, under controlled conditions to determine possible sourcesof weakness or other problem areas, and to develop the detailsof the cushioning system for the particular vehicle under con-sideration.

6. In the preparation of a rugged, rigid vehicle such asthe 105mm Howitzer for airdrop, greater attention needs to bepaid to tire pressures than is nec-ssary for the more flexible,sprung vehicles. Equal tire pressures are needed if undesirablerebound characteristics are to be avoided.

18

t

REFERENCES

1. Turnbow, J.W. and C.C. Steyer, Cushioning for Air Drop,Part II, Air Drop Cost Analysis, Structural MechanicsResearch Laboratory, The University of Texas, Austin,1955.

2. Wiederanders, D.G., W.L. Guyton and E.A. Ripperger, GroundImpact Shock Mitigation, Cargo Truck, 3/4-Ton M37,TR LOZZ, Engineering Mechanics Research Laboratory, TheUniversity of Texas, Austin, 1966.

19

194

wI

UnclassiiedSecurity Classification

DOCUMENT CONTROL DATA • R&D(Securtyl classification of Vitle. body of abstacttie ind nexingl anro,'ation musat be enteored in~on the ovratll repol ae €is c losted) 4

I . ORItGINATINO0 ACTIVITV (Carorelf# author) 120. RCPORqT 26rCU~iTY CL-AllSSIFCATION )

The University of Texas Unclassified___Austin, Texas •*o,.,

S. REPORT TI~T~LE

GROUND IMPACT SHOCK MITIGATION HOWITZZR 105MM M2AI

4. DESCRIPTIVE NOTES (TYPe of ,eport and-Incuaive date&)

Third in series of four dealing with high velocity airdrop of nilitary vehicles.S. AUTHOR(S) (Leas name. firsi name. Initial)

Wiederanders, David G.

. REPORT OATE 7a. TOT AL NO. OF PAGES 7b. NO. OF mEaSJuly 1967 19 2

80. C•NTRACT OR GRANT No. DA19-129'-AMC-582(N, 94. ORIG.,-ATOS REPORT NumbERS)6, POJICT 00.68 -- 0-AD

* & PRJECT to. 1121401D195 6

9. 9b. OTHER REPORT NO(S) (Any otharnumbom tat may b., aaaignod/yAhis ,eport)

d. LIRL- TR -102010. A VA IL AUILITY/LIMITATION NOTICES

This document has been approved for public release and sale; its distributionis unlimited.

11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY

Natick, Massachusetts 01760

3I. ABSTRACT

MThe 105mm Howitzer supplied to this laboratory by the Army Tank and AutomotiveCommand through arrangements made .with Natick Laboratories has been droppedfive times at impact velocities up to 54.4 fps, and at design accelerations ashigh as 30g. The initial modifications of the vehicle in preparation for thedrop series and the design criterion for this test series are presented alongwith a description of the cushioning system used and the damage sustained ineach drop.

It is concluded that this vehicle can be dropped at impact velocities up to50 fps without ay damage, if a properly designed cushioning system is used.

DD IoJAN6 1473 UnclassifiedSecurity Classification

Unclassified

14 LINK A LINK " LINK CKiY WORDOS -.-. -

9t0lC WT ROLZ WT 0O1L1 WT

Cushioning 8 6Howitzer 9 7Armed Forces supplies 9 7Honeycomb construction 10Air-drop operations 4 4Impact shock 8 6

INSTRUCTIONS

1. ORIGINATING ACTIVITY: Enter the name and address 10. AVAILABILITY/LIMITATION NOTICES: Enter any lir-of the contractor. subcontractor, grantre, Department of De- itationa oan further dissemination of the report, other than those

0te114 activity at other organizaon (corporate author) issuing imposed by security classification. using standard statementsS the ".port. such tos:2.. REPORT SECUNUTY CLASSIFICATION: Enter the over- (1) "Qualified requesters may obtain copies of thisall security clensificatin of the report. Indicate whether report from DDC.""Restricted Data" is included. Marking is to be in accord-ance with appropriate security regulations. (2) "Foreign announcement and dissemination of this2b. GROUP: Automatic downgrading is specified in DoD Di- report by DDC is not authorized."rective 5200. 10 and Armed Forces Industrial Manual. Enter (3) "U. S. Government agencies may obtain copies ofthe group number. Also, when applicable, show that optional this report directly from DDC. Other qualified DDCmarkings have been used for Group 3 and Group 4 as author- users shall request throughized.

3. REPORT TITLE: Enter the complete report title in all (4) "U. S. military agencies may obtain copies of thiscapiWt& letters. Title* in all cases should be unclassified. report directly from DDC. Other qualified usersIf a meaningful title cannot be selected without classifica- sha.- request throughtion, show title classi•cation in all capitals in parenthesisie"diteiy following the title.,_,,,_,,,_*_4. DUSCRIPTIVV NOTES If appropriate, enter the type of (5) "All distribution of this report is controlled. Qual-teport. e.g&. interim, progress, summary, annual, or final. ified DDC users shall request throughGive the inclusive dates when a specific reporting period is ,,covrs& AIf the report has been furnished to the Office of TechnicalS. AUTHOR(S) Enter the non*(*) of mut*or~s) a shown on Services, Department of Commerce, for sale to the public, indi-or in the report. Enter last name, first name, middle initial. cate this fact and enter the price, if known.If military, show r*le and branch of service. The name oftte principal author is an absolute minimum requirement. 11. SUPPLEMENTARY NOTES: Use for additional explana-6. REPORT DATE: Enter the date of the report sa day, tory notes.month, year. or month. year. If nore than one date appears 12. SPONOR1NG MILITARY ACTIVITY: Enter the name ofon the report, use date of publication, the departmental project office or laboratory sponsorinZ (pay-7.. TOTAL NUMBER OF PAGES. The total page count ing for) the research end development. Include address.

should follow normal pagination procedures, ie.. enter the 13. AI3STRACT: Enter an abstract giving a brief and factus.number of pages containing information. summary of the document indicative of the report, even though

it may also appear elsewhere in the body of the technical re-7b. NUMBER OF REFERENCES& Enter the total number of port. If additional space is required, a continuation sheetreferences cited in the report. shall be attached.

as. CONTRACT OR GRANT NUMBER. If appropriate, enter It is highly desirable that the abstract of c!assified re-the applicable number of the contract or grant under which ports be unclassified. Each paragraph of the abstract shallthe report was written. end with an indication of the military security classification

k, sie h 4d. PROJECT NUMBER. Enter the appropriate of the information in the paragraph, represented as (TS), (S),military department identification, such as project number. (C). or (U).subproject number, system numbers, task number, etc. There Is no limitation on the length of the abstract. How-

9a. ORIGINATOR'S REPORT NUMBER(S); Enter the'offi- ever. the suggested length is from 150 to 225 words.cial report number by which the document will be identified 14. KEY WORDS: Key words are technically meaningful termsand controlled by the originating activity. This number must or short phrases that characterixe a report and may be used asbe unique to this rMortu index entries for catalcging the report. Key words must be96. OTHER REPORT NUMBER(S): If the report has been selected so that no Recurity classification is required. Iden-assigned any other report numbers (either by the originator tiers, such as equipment model designation, trade name, "ili-er by the sponeor), else enter this number(s). tary project code name. geographic location, may be used as

key words but will be followed by an indication of technicalcontext. The assignment of links, rules, and weights is

I optional.

UnclassifiedSecurity ClassifiCation