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LFC

MEMORANDUM REPORT No. 1020

JULY 1956

Aerodiynamic Propert~iesOf 60-MM Mortar Shell, T24

EUGENE D. BOYER

OtPAPTMIENT OF THE ARMY PROJr=CT No. SSO3..O3-001*ORDNANCE RESEARCH AND DEVELOPMENT PROJECT No. TB3-0108(

BALLISTI1C RESEARCH LABORATORIES

ABERDEEN PROVING GROUINDt MARYLAND

BALLESTIC RESEARCH LABORATORIES

MEMORANDU4M REPORT NO. 1020

JITLY 1956

AERODYNAMIC PROPERTIES OF 60-MM MORTAR SNELL, T24

Eugene D. Boyer

Department of the Army Project No. 5B93-03-001Ordnance Research and Development Project Kc. TB-_=Olr8

ABERDEEN PROVING GR0UN D, MARYLAND

TABLE OF CONTENTS

Page

A B S TRRACT ............. ................ 3

TABLE O1, SYMBOLS AND COEFFICIENTS ................. 4

INTRODUCTION ... ... ...................... 5

EXPERIMETAL PROCEDURE ...................... 5

EXPERIgnTAL RESULTS ........................ 6

A. Drag . . . . . . . . . . . . . . . . . . . . . . . . 6

B. Yawing Motion .............. .................... 6

C. Roll ..................................... .7..

APPENDICES ..................... ............................. 9

APPENDIX A: Tables of Data .......... ............... 9

Table 1 - Aerodynamic Data .......... 9

Table 2 - Roll Data ....... ............. 10

APPENDIX B: Graphs and Photographs ...... ........... 11

APPENDIX C: References ..... ................. 21

DISTRIBUTION ..................... ........................... 25

BALLISTIC RESEARCH LABORATORIES

MEMORA1NDUM REPORT NO. 1020

EBoyer/rfAberdeen Proving Ground, Md.July 1956

AERODYNAMIC PROPERTIES OF 60-MM MORTAR SHELL, T24

ABSTRACT

The spin histories, drag, and yaw properties of the 60-mm T24 mor-

tar shell are presented. These data were obtained from Transonic Range

firings.

Ii

['I

TABLE OF SYMBOLS AND COEFFICIENTS

A axial moment of inertia

B transverse moment of inertia

cm center of mass

d- diameter

M Mach number

K D drag coefficient

KM moment coefficient

KM moment coefficient due to cross acceleration (Reference 5)

Ký lift coefficient

damping coefficient

roll rate (deg./ft.)

x 1,2 yaw damping rates

b eine of the angle of yaw

2- mean squasred yaw

2 2 01 1K1 0 2 +

S2 K102 + K 20O2 + _+ _______ effective squared yaw for KMe 10l + 20 '2

CL ro3.l moment derivative due to canted surface

C L roll moment derivative due to rolling velocity

p

P density of air

total velocity

h|

U

INTRODUCTION

In connection with a mortar project of the research division of the

Bucid Company, Picatinny Arsenal requested that the Ballistic Research

Laboratories study the aerodynamic properties, particularly roll, of the

60-mm T24 mortar shell. The shell was tested with three different fin

assemblies: non-canted fins, fins with two degrees of cant on the after

section, and fins with four degrees of cant on the after section

(Figure 7a). The firings were conducted in the Transonic Range. This

report is a brief account of the firings and the results obtained.

EXPERIMENTAL PROCEDURE

The shell were launched from a trigger-fi red 60-mm mortar tube

mounted in a 105-nm howitzer field mount (Figure 7b). At normal veloci-

ties and the elevation angles necessary to fire through the Transonic

Range instrumentation the morter shell would hit within the range build-

ing. Hence it was necessary to fire the program from within the range

building and forego some of the instrumentation. For the shell to enter

the instrumentation, it was necessary to start its flight approximately

nine feet above the range floor. To obtain this height, the field

carriage was loaded in the rear of a 2-1/2 ton shop truck (Figure 8)

and the program fired from a point between the first two groups of6

range stations . As a result only twenty of the twenty-five spark

photographic stations could be utilized. Timing cables were rear-

ranged to permit thirteen time-of-flight measurements to be taken.

To determine the roll histories of the shell, sets of three yaw

cards were placed at the beginning and end of the shadowgraphic instru-

mentation. The shell were equipped with two "pop-out" pins which re-

mained -within the shell's contour during launching and emerged when the

projectile entered free flight. The pins extended beyond the maJor di-

ameter and cut the yaw, cards. From these cuts the roll history of the

projectile was determined. To extend the roll measurements to longer

ranges (1.800 feet) it was necessary to fire a few rounds outdoors. The

higher angle I-raj~etoeies requtirpd for the .Jonver rareerA y 'el-ld r]ot b.

firnc from. inside the range building.

Nineteen rounds were fired through the range and eleven outdoors.

A-l of the rounds were fired at a nominal velocity of 500 fps. Twelve

of the nineteen shell fired through the range had trajectories suitable

for determining aerodynamic data. Roll data at 1800 feet were obtainable

from only four of the eleven shell fired outside the range. A sketch of

the shell and its physical measurements are given in Figure 6.

EXPERIMENTAL RESULTS

A. Drag

The drag coefficient does not appear to be-noticeably affected by

the presence of different fin cents. Any differences that may exist3 are

well within the scatter of drag data expected from round to round vari-

ation with production shell. However, a definite variation of drag with

yaw level is evient (Figure 1) and, fitting a least squares to

KD-K + K 28 yields:D D. D6

K ý0= o.0761 + 0.0008

K 2 = 2.1 _+

where 8 is in radians. All errors are standard errors.

B. Yawing Motion

The values of the yaw properties for each round are given in Table

1. As seen in Figures 2 and 3 the moment coefficient, K, and the lift

cbefficient, K, are influenced by the magnitude of the yaw. These coef-

Ificients have been reduced to zero-yaw4 values by the ralationships:

where righting moment pd3 5L + b2 5

U -U

6 2

K 2and e is a function of the amplitude of the two yaw components and the

rates as defined in the Table of Symbols and Coefficients. In Reference4it is aho-w•, Chat if non-linearities in aerodynamic forces ar(I moments

2 K20are representable by cubics in yaw, then KM Vs. 5 e and KL vs. K10) + 2

form linear combinations.

Fitting by least squares gives: *

=I- 0.84 + 0.02

'P- = -10 +2

K1 = 0.91 + 0.04

KL2 18 + 5B2

when yaw is expressed in radians.

The yaw damping coefficient, I - A was poorly determined due to

the presence of emall asymmetries in the shell and no correlation with

yaw was apparent. A value of.f - KlA = 8.0 seems representative of this

shell. The amplitude of yaw damps fifty ]er cent in approximately two

cycles of yaw, a distance of 300 feet.

C. R6ll

The roll data, as determined from yaw card measurements, are given

in Table 2 and Figures 4 and 5. Slight inconsistencies in performance

from round to round, as shown in Table 2, are probably due to minor fin

misalignments and manufacturing variations in the cents of the trailing

edges of the fins. Yaw card measurements for the shell with the un-

canred fins indicated that the shcll were not spinning significantly.

Tric e rounds were not inulided in fitting 1•.

The differential equation of motion of a rolling finned missile for

a range trajectory is of the form':

+ C• 2 02

The constants wore determined from fitting the yaw card measurements and

are:

20 cant C = 0.014 (l/ft)

S2= 0.007 (1/ft2 )

f4o cant C1 = 0.0017 (i/ft)

0 2 = 0.017 (1/ft2

Nominally C1 should be the same for missiles differing only in fin cant

and C2 should be proportional to the cant. The given C 's are essentially

equal, within the signiTicance of the determination, and in the same sense

(on a per degree of cant basis) so are the C2_s. Average values would be:

Cz1 = 0.00155 (1/ft)

C2 = 0.004 (1/ft 2) per degree of cant.

If one assumes the canted area of the fins to be one-tenth of the total

fin area, where the fin area is approximately 2.07 square inches, the

aerodyrnamic coefficientsI for the 4 degree canted fin are: *

CL =3.0

PC L .21.

EUGENE D. BOYER

I

(\J n 0 00 'N.4 Co n 0 A 140lk C4 N. K

i Ni 'Il C 'Il Ni Nq 1q N'4 N N

0 OH 70cC 00 CX 00 H H~ N N )' 7 0C 0 .0 '0)0 0ON N C 01 UN N N 0

A( ýa'~

N 70 H 00

0- 0o 0) 0 0, 0 0o 0, 0 d

"0IC, IQ, 4. 0)-o

ONd t-0 f O -70- - 70

0'- 01 0 - 40 'o cc

-11

0 t

H 4 8

o N

H~ 4Q 4

co HO)a t

"o oHN N t"0

440

0)4 '0 0417' -4 co1

a) Co H ý 017) .0 700 t-.

co) COO 00.) )

'o -1 0, co r- 0' t- -t0 N P 0

o7 C)) o7 C) o0

__ __ _ __ _ __ _ __ __ _ __ _ __ _ __ __ _ __ _ __ __)_0- v0 wr w1 N

9 u(I

TABIE 2

Roll Data(deg/ft)

DistanceDowr

Roll Rate For Various RoundsRange (ft) Fin Cant 2

3594 3595 3596 3597 3598 Field Firings35 0 .1 .4 - .150 .4 .1 o 1335 1.3 1.5 i.o 1,3 1.6615 2.6 2.4 2.0 2.5 2.3630 2.6 2.8 1.9 2.6 2.5680 2.6 2.9 1.9 2.7 2.5725 2.9 3.4 2.4 2.8740 3.0 3.1 2.3 3.01775

-:1790 5.2 6.6795.6

7.2

Fin Cant 403588 3589 3590 3591 3593 Field Firings

35 .1 .6 .3 .2 050 .2 .3 .3 .5 .3335 2.3 2.4 2.0 2.8 3.4615 4.0 4.5 3.7 4.1 6.0630 4.3 4.6 3.7 5.0 6.1680 4.9 4.9 3.8 4.9 •6.6725 5.0 5.0 4.0 5.1 6.8740 5.2 5.3 4.5 445 6.917751790 12.814.3

14.3

1O

APPENDIX B

Graphs and Photographs

Figure 1 - Drag Coefficient vs. Mean Squared Yaw

2Figure 2 - Moment Coefficient vs. 5 2e

Kl2 2Figure 5 - Lift Coefficient vs. K + K2

Figure 4 Roll Rate vs. Distance Down-Range, Fin-Cant 20

SFigure 5 - Roll Rate vs. Distance Down-Range, Fin-Cant 40

Figure 6 Sketch of Shell, 6 0-mm Mortar Shell 124

Figure 7a - Shell with Non-Canted Fins, 20 Canted Fins, 40 Canted Fins

Figure 7b -6 0-mm Mortar Tube Mounted in a 105-mm Howitzer Recoil

System

Figure 8 - Gun Mount Loaded on a 2-1/2 Ton Shop Truck

iii

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z 9"0

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PIGUE7:Se hNnCneFICT~j'pEo 2a SelWtIomCantedFisF qs 2Cnted Fine ,

Mou qnted Fin sP

Howitzer Recoil Sv~tem

Ij - ,

64ItoII _ _ _ _

PI

APPENDIX C

REFERENCES

1- Boz,R.ER Nicolaides, J.D., A Method of Determining Some AerodynamicCoefficients from Supersonic FreeBRL Report 711, November 1949.

2. MacAllister, L.C., Comments On the Preliminary RedUction of Symmetricand Asymmetric Yaw Motions of Free Flight Range Models, BRLM Report781, May 1954.

3. MacAllister, L.C., Roschke, E.J., The Drag Properties of Several Wingedand Finned Cone-Cylinder Models, BRLM Report 849, October 1954.

4. Murphy, C.H.-•, The Measurement of Non-Linear Forces and Moments by Meansof Free Flight Tests, BRL Report 974, 1956.

5. Murphy, C..1., Nicolaides, J.D., A Generalized Ballistic Force System.BRL Report 933, May 1955.

6. Rogers, W.K., The Transonic Free Flight Range, BRL Report 8419 , Febru-ary 1953.

II

21

DISRTIBUZ[ON LIST

No. of No. ofC22iee Organization Coies n

Chief of Ordnance 3 CommanderDepartmc-t of the ;c W Naval Ordnance Test Station

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Attn:sh RDUg - D.c China LJohe, California

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Officer DirectorArmed Se-rvices Technical4 Canadian Army Staff Information Agency

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Nashington 8, D.GC. Knott BuddirporDayton d, Ohio3 Chief, Bureau of Ordnance Attn: DSC-SD

Department of the Na-vy

Ashnttn: 2e , D.Ný"-aional Advisory Committee

A0for AeronauticsLewis Flight PropulsionS2 Commander Laboratory.•. "Naval Proving Ground Cleveland Airp~ortSDah~lgren, Virginia Cleveland, Ohio

2 CmnaderAhtn: F. K. Moore2 Commander

Naval Ordnance Laboratory I Commanding General""White Oak Redstone Arsenal

Silver Spring 19, Maryland Huntsville, Alab-aAttn- Mr. Nestinger Attn: TecicaluaDr. may ldbrary1 S rCommanding General

1 Superintendent Picatinny ArsenalNaval Postgraduate School D ,'0,. New JerseyMonterey, California Attn: Saniel Felt:an

Aoqnmunition LahT .Naval Air Missile Test Center Vf;wv.. JgGeeaPoint Magu., California Frankford Arsenal

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