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MEMORANDUM REPORT NO. II80 DECEMBER 1958
DRAG AND STABILITY PROPERTIES OF
THE IOSMM SHELL, HE, T388 (U)
EUGENE D. BOYER
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By authority of ftl/JLjftQ 3aS~/n~7 Date IzL&teL
DEPARTMENT OF THE ARMY PROJECT NO. SB03-03-00I
ORDNANCE RESEARCH AND DEVELOPMENT PROJECT NO. TB3"OI08
BALLISTIC RESEARCH LABORATORIES , Jni^M'r :i'n.iiiLnVifii|T li^lrjM^^iiT./jfl i'J: Hjfi* ii. L ':" n'.f^ •.>•>:•'• JM""^'' '^''^•Vyftauwns.'V.'Ji jj"1«ii.' J"> I.JM'M'.JI' 'infih""! iijt> i,i""."i ••!>(• 1111^ . 1 -jr •••> 1 ijijt
ABERDEEN PROVING GROUND, MARYLAND
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MEMORANDUM REPORT NO. Il80
DECEMBER I958
DRAG AND STABILITY PROPERTIES OF THE 105MM SHELL, HE, T588 (u)
Eugene D. Boyer
Reguests for additional copies of this report will be made direct to ASTIA.
Reproduction of this document in whole or in part is prohibited except with permission of the issuing office; however, ASTIA is authorized to reproduce this document for U. S. Government purposes.
Department of the Army Project No. 5BO3-O3-OOI Ordnance Research and Development Project No. TB3-OIO8
ABERDEEN PROVING GROUND, MARYLAND
BALLISTIC RESEARCH LABORATORIES
MEMORANDUM REPORT NO. Il80
EDBoyer/sec Aberdeen Proving Ground, Md. December 1958
DRAG AND STABILITY PROPERTIES OF THE 105-MM SHELL, HE, T588 (U)
(UNCLASSIFIED) ABSTRACT
The drag and stability properties of the 105-mm, HE, T388 shell are
presented. These data were obtained from Transonic Range firings.
f
(UNCLASSIFIED) TABLE OF SYMBOLS
A Axial moment of inertia (lb - in )
2 B Transverse moment of inertia (lb - in )
d Diameter (in)
m Mass (lb)
IC Drag coefficient
K^ Overturning moment coefficient
K_ Lift force coefficient
K-j - K^ Damping moment coefficient
K„ Magnus moment coefficient
2 2 6 Mean squared yaw (deg )
_2 K^ 2 Yaw drag coefficient (rad )
6 3-1 A,, „ Yaw damping rates (ft x 10 )
s Gyroscopic stability factor
s Dynamic stability factor
N Number of yaw stations
N-, Number of timing stations
e Error in yaw fit (rad)
e Error in swerve fit (ft) s v '
K, 9 Sizes of yaw arms at mid range •*->'-
0' 0 Turning rates of yaw arms (deg/ft)
(CM—BBBft) INTRODUCTION
At the request of the Canadian Armament Research and Development
Establishment (CARDE), BRL fired, through the Transonic Range , four
versions of the 105-mm, HE, T388 shell, designed at CARDE (Figure l).
The four types varied only in body length and were designed to bracket
a stability factor of 1.8 at M = 1.1. These firings were suggested by the
Bi-partite Standardization Committee as a part of the development of improved
105-mm howitzer ammunition. The firings were to determine the drag properties
of these shell from M =0.6 to M =1.5 and the gyroscopic stability factors
at M = 1.1.
Early tests indicated that the drag of these shell was approximately 2 5
20$ lower than that of the standard Ml shell ' . The T388 shell has a long
hollow boattail and it was thought that the drag could be further reduced by
bleeding air into the base from the body of the shell. Three shell of each
type were available for stability firings at M = 1.1, and an additional ten
shell of Type 1 for base-bleed experiments.
The shell were launched from a 105-mm howitzer (l - 20 twist). A yaw
inducer was employed on the six rounds at M = 1.1. This was done in order
to obtain adequate yaw levels for a yaw reduction. The physical properties
of the shell are given in Figure 1.
PWnillirT ^ STABILITY
The stability factors and other aerodynamic properties of the shell are
given in Table I. The reduction parameters are given in Table II. The
stability factors, as determined at ^65 feet from the muzzle, at about M = 1.1,
vary from 1.66 for Type 1 to 1.95 for Type 2. All types are dynamically
stable at the velocity tested, M = 1.1. No yaw analysis was made at other
velocities fired. The yaw damping rates appear to be sensitive to yaw level
but the evidence, on this small sample, is rather weak.
(t DRAG COEFFICIENT
The drag force coefficient, IC, was obtained by fitting a cubic equation
to the time-distance data for each round. These data were then reduced to 2
zero-yaw by the relationship IC = IC + Krj p 5 • \\ 2' the yaw ^T&^ o 5 5
coefficient, was determined to be 2.0 (per square radian) at M = 1.1. This
value was used to reduce all drag values to zero yaw (Figure 2). A shadow-
graph of Type h at M = 1.086 is given in Figure 3- Three shell of Type 3
and one shell each of the other three types were fired at M = 1.1. When no
difference was noted in the drag for the different types, the six remaining
shell were fired over a range of Mach numbers to establish the drag curve.
In comparing drag values of the Ml with that of the T388 (Figure 2) it is
seen that in the subsonic region drags are the same for both shell while in
the supersonic region the T388 drag is 20$ less than that of the Ml.
To test base-bleed designs Picatinny Arsenal modified ten Type 1 T388
shell by drilling bleed-holes with a 0.25 inch diameter at 29 to the axis
of the shell. Five variations of vented areas varying from 6 to 48 holes,
located before and/or after the rotating band, were tested (Figures k and 5)«
Details and physical properties for each type are listed in Table III. These
designs showed no improvement in drag (Figure 2). In fact, for the two
rounds fired in the subsonic region there appears to be an increase in drag.
The 20$ drag increase at M>1.2, for modification 1, however, is due to the
removal of the boattail and not to the presence of the vent holes.
8
(4V0BRfflB9"»' CONCLUSION
The ballistic characteristics of these four types of shell differ
very little. At M = 1.1 the gyroscopic and dynamic stabilities are similar
and adequate. Therefore, because of the measured similarities of the
ballistic characteristics of all four types the selection of the final type
can not be made on the basis of these characteristics.
The hoped for further reduction in drag by bleeding air into the base
was not achieved. The intakes were located upstream of the boattail where
the surface pressures are higher. These locations, however, severely limit
the total intake area which can be achieved without jeopardizing the strength
of the projectile. Hence, only about one half of the optimum intake area
could be achieved even with kQ holes. This partially accounts for the
negative results, and perhaps inefficient ducting with l/l4-inch diameter
holes further reduces the amount of air bled into the base cavity. It is
rather doubtful that further experimentation with base-bleed with this design
would be fruitful.
EUGENE D. BOYER
(UNCLASSIFIED) REFERENCES
Rogers, W. K. The Transonic Free Flight Range. Ground: BRL R-1CM, June 1958.
Aberdeen Proving
Boyer, E. D. Some Aerodynamic Properties of Three 105-MM Shell, Ml, T57T, and T107. Aberdeen Proving Ground: BRL M-13M, April 1958.
Roecker, E. T. The Aerodynamic Properties of the 105-MM HE Shell, Ml, in Subsonic and Transonic Flight, Aberdeen Proving Ground: BRL M-929, September 1955.
10
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