CO 1, FIDE% 11 U.S. NAVY BOMB DISPOSAL Intelligence BULLETIN»JUNE 1945*°1. 2, No. 2 CONTENTS Jap Rocket Ordnance.......... I Trends in Japanese Ordnance 12 Earth quake Bombs............... 14 Acknowledgements............... 24 Bomb Dump Accidents......... 25 T82 VT Bomb Fuze............. 29 Ordnance Nomenclature...... 30 Attack on Jap B-8(a) ........... 32 Japanese Warning Signs .. 32 This document is issued to graduates o f a course in Bomb Disposal, by the Officer in Charge, Navy Bomb Disposal School, under authority o f Bureau o f Ordnance letter F41-6 (L) o f 22 April 1944. It is for information and guidance only and is not a Bureau o f Ordnance Publication. It should be destroyed OeketORDNANCE Japanese rocket ordnance can I .. best organized by grouping die ous pieces according to intended as follows: 1. Propulsion units. A. Take off assist for aicraft (docu­ mentary) . B. Baka bomb (Models 10 and 20) Motors. 2. Bomb conversion for land bom bard­ ment. A. Pusher Type separate from bond) (60 kg.). B. Integral, with motor bolted min) bomb (250 kg.). 3. Airborne series, Bomb and It Q(»kTi A. Mk 4 (Type 3 No. 25, Mk . 1 1 l,milp, Documentary). B. Mk. 19 (7.5 kg., documentary I. C. Mk. 27 (Expt. 18 No. 6 . Mk. 27 Bomb, documentary). D. Mk. 28 (Type 3 No. 1, Mk. 2M, documentary). 4. Bombardment types for ground use. A. 20 cm. Navy spin stabilized. B. 45 cm. Navy spin stabilized. C. 20 cm. Army spin stabilized. D. 12 cm. Navy spin stabilized. The chart on the following page gives die known and recovered pieces All known rocket propelled ord­ o f Japanese rocket ordnance. The nance developed by the Japanese and Japanese designation o f each it’ *111 is recovered by Allied forces, either in given, along with data on propellant die form o f actual rounds or documen­ charge and the use for which the tary evidence, is summarized here. rocket was developed. Only the short Information gained from documents code designation is given for die pro­ is included to give a more complete pellant. BDIB Vol. 2, No. 1, contains picture o f rocket ordnance, and to fill a discussion on code designation o f in gaps o f development. W hen data propellants and should be referenced from this source is used it will be so in connection widi diis article. indicated and evaluated where pos­ A discussion o f each individual piece sible. o f rocket ordnance follows. CONFIDENTIAL 1 TYPES OF JAPANFst: ROCKET ORDNANCE o Japanese desi CO In 1 -4 a® W -4 a® 1 S In W e n 6. 6. 6. a. 6. 4, £ ___________ A m c n Take-off Assist Rocket Mod ----------- C a r r i e r A i r c r a f t _____ Thrust 700 kg. 3 sec. 3 — 04 Rocket Device Type 4 Mk. 1 Mod. S Thrust 400 kp. 8 'seen 10. CD Rocket Device Type 4 Mk. 1 Mod. S o-fcs Thrust 800 kg. 8 (sec-)- 20. CO CO M 01 e g IQ OQ 0T> W □ fo o o i i i 1 | i 1 Bombi i 1 | 1 Launching Rocket Device o = Range 1.000 m. < ! o M o d e l 10. N. ' ' Bomb Launching Rocket Device i M b (?)- P T y p e 3. GO GO o' Special M k. 1 Rocket Device M odel 250 kg. bom b ................ Range *.000 m. P OO 21. P 0 _______________ ' Special Mk. I Rocket Device Model 250 kg. bom b. ___ _ R u«r M M «*. 2 2 . U TNTN1 .41 T y p e 3 No. 2? M k. 4 bom b. ................ 250 k|. R < i f h o c; a . « e m ta m m m . — OO — T yp e 3 N-.-. I M k. 28 b ~.t> 10 kg Rocket * i M m., «M K « 0 H « r o o - Expt. 18 N Mk. 2“ B. n - M > . i 6 0 k g k e i f ML 19 7-5 U - .W p A . O g ? 1 20 cm. Rocket W - «• «- 0 45 cm. Rocket * -r i any Ji'P 0 o-> M m m 2JB D yds CONFIDENTIAL j 0 .O _ _ _ _ l » c r * l 12 c m . V r r y to that used in the pusher unit tie* TAKE-OFF ASSIST veloped to launch 60 kg. and 2S0 kg, bombs. Although it is not possible at present to positively predict the FOR AIRCRAFT type of explosive used in an 444411.- covered item, available information I h alimentary evidence indicates suggests a correlation between the that there is in existence a rocket unit short code name and actual chemical for carrier aircraft designated "Take­ analysis. off Assist Rocket Model 1." Accord­ ing to the document the unit gives a Three grains of 343 Special DT, thrust of 700 kg. (1,540 lbs.) for a propellant are used. Each grain is period of 3 seconds during take-off. 78.6 mm. (approximately 3 inches) in The propellant charge, according to diameter and 512 mm. (approximate­ the code designation, is comparable ly 20 inches) in length. BAKA BOMB In appearance, the Baka bomb re­ 6.1, potassium sulfate 2.9, volatiles 1.3, sembles a single-seat midwing mono­ ash 2.8). According to a captured plane having twin fins and rudders. document an alternate propellant may The wings and tail surfaces are molded also be found containing N. C. 60-64 plywood, fabric covered. The fuse­ percent, N. G. 30 percent, potassium lage is of metal construction. It is sulfate 2 percent, plasticizer 4-8 per­ approximately 18 feet in length, the cent. Two forms of the Model 20 arc wingspan is about 15 feet, and the used, one as the main motor located pilot's canopy is of panelled plexiglas. in the after portion of the fuselage, The recovered Baka bombs have no and one as .a wing unit. provision for landing gear or skid, in­ It is thought that the Baka may dicating that the bombs may all be have been designed to be launched launched from a parent plane. from a ship or land base. This would The rocket units for the Baka are make the extra propulsion units at­ designated Type 4 Mk. 1 Model 10 tached to each wing necessary. and Model 20. According to docu­ Both the Model 10 and Model 20 ments the Model 10, which has not are the same diameter, the variation been recovered, has three grains of in size is in the length. propellant of the same dimensions as those used in the Model 20. The Documentary evidence indicates that Model 20, which has been recovered, the Model 10 is designed to be used contains 6 grains of 500 special FDT6 as a wing unit. One motor being at­ (nitroglycerin 26.9, nitrocellulose 59.9, tached to each wing. ' It is shorter centralite 2.9, mononitronapthalene than the Model 20 and contains only CONFIDENTIAL 3 Motor Unit Model 20. Propulsion unit for Baka Bomb. three grains as compared to the six The warhead located in the fore­ grains used in the Model 20. most part of the bomb contains the Three Model 20 motors are used as explosive charge. By analysis the main propulsion units in the after end charge was found to be cast trinitro- of the fuselage. They are arranged anisol. Total weight of the war­ in the form of a triangle with two on head is 2,215 pounds and weight of bottom and one on top. The ven­ filling alone 69(1 pounds. The after turi tube of the upper motor extends end of the warhead is threaded to take aft beyond the ends of the venturi the base plate, which is locked in place tubes of the two lower motors. The overall length of a single rocket by a grub screw, 1,.; inches long. A motor is 78 inches with a total weight second grub screw in the nose secures of 266 pounds. the nose fuze in place. The nose fuze The motors are ignited by an elec­ is of the same basic construction and trically fired squib which threads into design as the A-3(d). Probable des­ the forward end of each rocket motor. ignation will be A-3 (g). Operation The igniter is connected to the elec­ is identical to the A-3 (d). tric firing circuit of the plane by a The base plate is of one piece steel four-socket female plug, and a 26-inch construction and has four tail fuze two-strand insulated cable. A se­ pockets grouped around a central lector in the pilot's cockpit permits threaded hole in a slightly raised firing of any one of the three fuselage portion of the base plate. motors or the wing motors. The There are two each of two types of cable leads to two high resistance tail fuzes. One type utilizes the all­ wire igniter bridges around each of which are wrapped a small quantity ways action principle and is des­ of guncotton. A flash from the gun­ ignated the B-9 (a). The other type cotton ignites a small black powder utilizes the inertia-striker principle charge, which in turn ignites the block and is designated B-10 (a). For a powder contained in the perforated complete report on these fuzes see igniter body. BDIB Vo. I No. 85. BOMBCONVERSIO^oi^^^^^^^^H BOMBARDMENT A. Pusher type separate from bomb.— and the short model is designated in This device has been recovered in documents as "Bomb Launching two sizes.