Fig. P.1 Cross-sectional drawing of Y-1852 Little Boy showing major components. Not shown
are radar units, clock box with pullout wires, barometric switches and tubing, batteries, and
electrical wiring. Numbers in parentheses indicate quantity of identical components. Drawing is to
scale. Copyright by and used with kind permission of John Coster-Mullen. A Front nose elastic
locknut attached to 1-inch diameter Cd-plated draw bolt. B 15.125-inch diameter forged steel nose
nut. C 28-inch diameter forged steel target case. D Impact-absorbing anvil with shim. E 13-inch
diameter 3-piece WC tamper liner assembly with 6.5-inch bore. F 6.5-inch diameter WC tamper
insert base. G 14-inch diameter K-46 steel WC tamper liner sleeve. H 4-inch diameter U-235
target insert discs (6). I Yagi antenna assemblies (4). J Target-case to gun-tube adapter with 4 vent
slots and 6.5-inch hole. K Lift lug. L Safing/arming plugs (3). M 6.5-inch bore gun. N 0.75-inch
diameter armored tubes containing priming wiring (3). O 27.25-inch diameter bulkhead plate.
P Electrical plugs (3). Q Barometric ports (8). R 1-inch diameter rear alignment rods (3).
S 6.25-inch diameter U-235 projectile rings (9). T Polonium-beryllium initiators (4). U Tail tube
forward plate. V Projectile WC filler plug. W Projectile steel back. X 2-pound Cordite powder
bags (4). Y Gun breech with removable inner breech plug and stationary outer bushing. Z Tail tube
aft plate. AA 2.25-inch long 5/8-18 socket-head tail tube bolts (4). BB Mark-15 Mod 1 electric gun
primers with AN-3102-20AN receptacles (3). CC 15-inch diameter armored inner tail tube. DD
Inner armor plate bolted to 15-inch diameter armored tube. EE Rear plate with smoke puff tubes
bolted to 17-inch diameter tail tube
Fig. P.2 Schematic illustration of projectile/target assembly process
xiv
Preamble
are radar units, clock box with pullout wires, barometric switches and tubing, batteries, and
electrical wiring. Numbers in parentheses indicate quantity of identical components. Drawing is to
scale. Copyright by and used with kind permission of John Coster-Mullen. A Front nose elastic
locknut attached to 1-inch diameter Cd-plated draw bolt. B 15.125-inch diameter forged steel nose
nut. C 28-inch diameter forged steel target case. D Impact-absorbing anvil with shim. E 13-inch
diameter 3-piece WC tamper liner assembly with 6.5-inch bore. F 6.5-inch diameter WC tamper
insert base. G 14-inch diameter K-46 steel WC tamper liner sleeve. H 4-inch diameter U-235
target insert discs (6). I Yagi antenna assemblies (4). J Target-case to gun-tube adapter with 4 vent
slots and 6.5-inch hole. K Lift lug. L Safing/arming plugs (3). M 6.5-inch bore gun. N 0.75-inch
diameter armored tubes containing priming wiring (3). O 27.25-inch diameter bulkhead plate.
P Electrical plugs (3). Q Barometric ports (8). R 1-inch diameter rear alignment rods (3).
S 6.25-inch diameter U-235 projectile rings (9). T Polonium-beryllium initiators (4). U Tail tube
forward plate. V Projectile WC filler plug. W Projectile steel back. X 2-pound Cordite powder
bags (4). Y Gun breech with removable inner breech plug and stationary outer bushing. Z Tail tube
aft plate. AA 2.25-inch long 5/8-18 socket-head tail tube bolts (4). BB Mark-15 Mod 1 electric gun
primers with AN-3102-20AN receptacles (3). CC 15-inch diameter armored inner tail tube. DD
Inner armor plate bolted to 15-inch diameter armored tube. EE Rear plate with smoke puff tubes
bolted to 17-inch diameter tail tube
Fig. P.2 Schematic illustration of projectile/target assembly process
xiv
Preamble