ei vices lecnmca Ripriduced ly DOCUMENT SERVICE ßEHTE KHOTT BUIimilt. BUTT»!. 2.

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1 ttummmmmmmt: ^htf^ay-y'^"^' v --'''^--t-.ir^vii»^--mvai--a r ei vices lecnmca Ripriduced ly DOCUENT SERVICE ßEHTE KHOTT BUIimilt. BUTT»!. 2. FOR f ICRO-CARD COfNlTROL ONLY NOTICE: WHEN GOVERNENT OR OTHER DRAWINGS, SPECIFICATIQS OR OTHER DATA ARE Ü5ED FOR ANY PURPOSE OTHER THAN IN COKKECTIOK WITH A DEFINITELY RELATED GOVERNENT PROCUREENT OPERATION, THE U. S. GOVERNENT THEREBY INCURS NO RESPONSIBILITY, NOR ANY OBLIGATION WHATSOEVER; AND THE FACT THAT THE GOVERNENT AY HAVE FORULATED, FURNISHED, OH IN ANY WAY SUPPLIED THE BAIT/ DRAWINGS, SPECIFICATIONS, OR OTHER DATA IS NOT TO BE REGARDED BY IPLICATION OR OTHERWISE AS IN ANY ANNER LICENSING THE HOLDER OR ANY OTHER PERSON OR CORPORATION, OR CONVEYING ANY RIGHTS OR PERISSION TO ANUFACTURE, USE OR SELL ANY PATENTED INVENTION THAT AY IN ANY WAY 3E RELATED THERETO. ßisaöi*':

2 ««.«- ^».». s CJ? C^CO HI 11«iiil f. a III ll EORANDU REPORT No APRIL 19S7 m i A Revised Drag Coefficienlv Kp, Based On The 8-Inch Howitxer Shell, HE, I06 m CHARLES T. ODO OEPAHTENT OF THE ARY PROJECT o RESEARCH AND DEVELOPOfiT PROJECT N«. t BALLISTIC RESEARCH LABORATORIES ^ ^^^^^^^^^^^^^^^^^^^^^^^ ABERDEEN PROVING GROUND. ARYLAND

3 BALLISTIC RESEARCH LABORATORIES EORANDU REPORT NO APRIL 1957 A Revised Drag Coefficient, K, Based on the 8-Inch Howitzer Shell, HE, l06 Charles T. Odom Department of the Army Project No. 5B Ordnance Research and Development Project No. TB ABERDEEN PROVING GROUND, ARYLAND

4 BALLISTIC RESEARCH LABORATORIES EORANDU REPORT NO CTOdom/wc Aberdeen Proving Groand, d. AprU 1957 A Revised Drag Coefficient, K-., Based on the 8-Inch Hovritzer Shell, HE, l06 ABSTRACT A drag coefficient, K n, based on radio doppler measurements of the 8-inch, HE, 106 Shell, was presented in BRL Technical Note 1041, October The application of this drag coefficient to full scale range firings indicated that it should be revised before being used in the computations of a firing table for the 8-inch, HE, l 06 Shell. The revised drag coefficient, and the ballistic coefficients of the shell with respect to the revised drag are presented in this report, which supersedes Technical Note 1041.

5 INTRODUCTION BRL Technical Note Number 1041, October 1955, presented a drag coefficient, K Q, of the 8-inch howitzer Shell, HE. l06. "Tiis drag coefficient, based on radio doppler measurements of the i06 Shell, was tabulated as a function of the ach Number,. Also given were five analytical expressions, piecemeal fits of the radio doppler drag data used to generate the values of K n appearing in the Technical Note. These expressions, when applied to full scale range firings conducted prior to the radio doppler drag tests, produced however, considerable variation about the average form factor so further range firings were planned to supplement the original range data. The supplemental range firing was completed in December 1955 and application of the five part draj- fit of Technical Note 1041 to this firing showed that the sonic and supersonic portions of the fit were adequate in that the higher muzzle velocities produced forrn factors near unity. The fit in the subsonic portion of the drag curve, however, did not appear to be adequate in that subsonic muzzle velocity range data produced form factors ten to fifteen percent in excess of unity. The subsonic portion of ehe drag curve was, therefore, adjusted upward to decrease the form factors of shell fired at low muzzle velocities. Follow, ing arc the adjusted fittmg expressions: In the Interval 0< < < Ü I6< K n is given by << K) ,2 -{0. C C ) 1/2 Range data from the additional range firing, reduced using the above expressions, produced the iollowing ballistic coefficients, C, and form factors, i which are being used in the preparation of the revised 8-inch howitzer Firing Table 8-J-2: Charges 1-4, 6 and 7 0< 800 mils ^> 800 mils C = , i =.9601 C = j ^ ^

6 Charge 5 ^< 800 mils C = , i =, > 800 mils C = ^ ^2 The ballistic coefficients above are computed for a standard Shell weight of 200 pounds. Charles T. Odom

7 t-^t-h NOTE: all dimensions In colibeis I ealfbitr «8.000 Ineiiss FIG.!. SHELL,8-INCH, HE, I06 WITH FUZE,PD,5IA4

8 o u> o s UJ X -1 -r ft t f tftthf Hrthr in oi -J UJ s 3: o O 2 C -~ oe 00 Ui m Ü. 2 o «n 3 - z H- Z x UJ o o < s u. Ü. p o CO < QC Q S C O «J. o XL

9 TABLE of DRAG COEFFICIENTS

10 Drag Coefficients :* i , ,

11 Drag Coefficients S i ^ ] ^ S li

12 Drag Coefficients «0 1.06( ) Ö i 1.05S LOW 1, % , i , Ö ^ i , ' ; f i () C i «; I 2. 08im l a Z4 ] J ! ^