Page 81 - Marutas of Unit 731

“Ha Bomb—e 40 kg Ha bomb was a fragmentation bomb designed for

destructive effect by projection of bomb fragments and shrapnel

contaminated with anthrax spores. e bomb was double walled, having a

central burster tube surrounded by an iron fragmentation wall 10

millimeters in thickness, and a payload chamber bet ween the wall and the

steel bomb case. e payload chamber was of 700 cubic centimeters capacity
and contained about 1,500 steel pellets to augment the destructive e ects of

the bomb fragments. e payload chamber and the steel pellets were coated

with a bakelite varnish to prevent corrosion. Armed with nose and tail

impact fuses and containing 3 kilograms of TNT in the nose and tail

compartments and central burster tube, the bomb exploded upon impact
scattering bomb fragments, shrapnel and anthrax spores at high velocity in a

horizontal direction.

Field trials of the Ha bomb were made during 1938 and 1939. Dye

solutions and organisms were used as ll for the static tests. Size,

distribution and penetrating power of the bomb fragments and shrapnel
were determined by using a grid consisting of upright board targets

arranged in concentric circles from the point of bomb burst. Test animals

were distributed in like pattern. In winter, fragmentation distribution was

determined by recover y of particles from the frozen, icy ground. Fragments

and shrapnel were projected for distances of 400 to 500 meters with a
density of about one fragment or shrapnel per square meter within a radius

of 50 meters. Bomb fragments and shrapnel were recovered and examined

for viability of attached organisms. Drop trials were made from aircra for

the purpose of deterring bomb function and percentage of duds.

Additional fragmentation studies were made by bur ying the bomb in
sand to a depth of 5 meters. e bomb was then exploded electrically and