Preamble
Fundamental Data on Little Boy and Fat Man
Throughout this book, reference will frequently be made to the
235 U-fueled
Hiroshima “gun-type” Little Boy bomb and the
239 Pu-fueled Nagasaki
“implosion-type” Fat Man bomb. For easy reference, fundamental data on these
devices is summarized in this Preamble. Technical terms used here are developed in
more detail in later chapters.
The diagrams of the bombs appearing in Figs. P.1 and P.5 were prepared by and
are used with the kind permission of John Coster-Mullen. John’s fantastic book on
the designs of the bombs and the bombing missions should be on the shelf of any
serious student of the Manhattan Project [Coster-Mullen (2016)].
P.1 Little Boy
The core of this bomb comprised two pieces of
235 U that were assembled into a
supercritical whole by propelling a hollow cylindrical “projectile” piece of
235
U
initially located in the tail of the bomb forward to seat with a solid cylindrical
“target” piece of
235 U located in the nose. The target and projectile pieces were
contained within what was essentially the barrel of an artillery cannon, and upon
assembly were surrounded by a tungsten-carbide (steel; WC) tamper. Little Boy is
drawn to scale in Fig. P.1, and the projectile seating arrangement is sketched in
Fig. P.2. In World War II, the highest velocity that could be achieved for an artillery
shell was about 1000 m s
−1 . The target and projectile pieces were on the order of 20
cm in length (more precise dimensions are given below), which means that the time
required for the projectile to become fully mated with the target piece from the time
that the leading edge of the projectile met the target piece was *200 ms. This will
prove to be an important number.
xiii
Fundamental Data on Little Boy and Fat Man
Throughout this book, reference will frequently be made to the
235 U-fueled
Hiroshima “gun-type” Little Boy bomb and the
239 Pu-fueled Nagasaki
“implosion-type” Fat Man bomb. For easy reference, fundamental data on these
devices is summarized in this Preamble. Technical terms used here are developed in
more detail in later chapters.
The diagrams of the bombs appearing in Figs. P.1 and P.5 were prepared by and
are used with the kind permission of John Coster-Mullen. John’s fantastic book on
the designs of the bombs and the bombing missions should be on the shelf of any
serious student of the Manhattan Project [Coster-Mullen (2016)].
P.1 Little Boy
The core of this bomb comprised two pieces of
235 U that were assembled into a
supercritical whole by propelling a hollow cylindrical “projectile” piece of
235
U
initially located in the tail of the bomb forward to seat with a solid cylindrical
“target” piece of
235 U located in the nose. The target and projectile pieces were
contained within what was essentially the barrel of an artillery cannon, and upon
assembly were surrounded by a tungsten-carbide (steel; WC) tamper. Little Boy is
drawn to scale in Fig. P.1, and the projectile seating arrangement is sketched in
Fig. P.2. In World War II, the highest velocity that could be achieved for an artillery
shell was about 1000 m s
−1 . The target and projectile pieces were on the order of 20
cm in length (more precise dimensions are given below), which means that the time
required for the projectile to become fully mated with the target piece from the time
that the leading edge of the projectile met the target piece was *200 ms. This will
prove to be an important number.
xiii