[Texas Fossil]

Like “Little Boy”.

Sounds simple but speed of combining is critical.

Simpler, but not simple.

Critical mass device.

Implosion requires even more precision.

[njslim]

Check out Nuclear Weapon Archive for precise details on
weapon design (unclassified)

Cary Sublette, the author, also is regular on USENET
group alt.war.nuclear, always willing to answer questions

http://nuclearweaponarchive.org/