the 15 lb. plutonium core of the bomb, in case the 5,300 lbs. of
conventional high explosives surrounding the core exploded without
setting off a nuclear blast, and in the process scattering the costly
plutonium (about 250 million dollars worth) across the dessert. After
extensive research and testing of other potential containment ideas,
the concept of Jumbo was decided on in the late summer of 1944.

However, by the spring of 1945, after Jumbo had already been built and
transported (with great difficulty) to the Trinity Site by the
Eichleay Corporation of Pittsburgh, it was decided not to explode the
Trinity device inside of Jumbo after all. There were several reasons
for this new decision: first, plutonium had become more readily
(relatively) available; second, the Project scientists decided that
the Trinity device would probably work as planned; and last, the
scientists realized that if Jumbo were used it would adversely affect
the test results, and add 214 tons of highly radioactive material to
the atmosphere.

Not knowing what else to do with the massive 12 million dollar Jumbo,
it was decided to suspend it from a steel tower 800 yards from Ground
Zero to see how it would withstand the Trinity test. Jumbo survived
the approximately 20 kiloton Trinity blast undamaged, but its
supporting 70-foot tall steel tower was flattened.

Two years later, in an attempt to destroy the unused Jumbo before it
and its 12 million dollar cost came to the attention of a
congressional investigating committee, Manhattan Project Director
General Groves ordered two junior officers from the Special Weapons
Division at Sandia Army Base in Albuquerque to test Jumbo. The Army
officers placed eight 500-pound conventional bombs in the bottom of