At its test it yielded only 190 tons; it failed to achieve fusion and only the initial fission explosion worked correctly.

Very high temperatures and pressures, which could be produced only by a fission explosion, would be required to ignite the fusion reaction between hydrogen isotopes.

Hydrogen bombs use the energy from an initial fission explosion to create an even more powerful fusion explosion.

Second, the radiation from the fissioning of the primary would be used to compress and ignite the secondary fusion stage, resulting in a fusion explosion many times more powerful than the fission explosion alone.

The second test Orange Herald was the modified fission bomb and produced 720 kilotons-making it the largest fission explosion ever.

They were virtually indestructible except to heavy weapons, direct fission explosions, or similar catastrophic applications of force.

And much of the intense radioactivity from the fission explosion would be spread over the immediate neighborhood - about one kilometer or so.

This led to a large fission explosion which released radioactive materials into the atmosphere.

"How about any sign of those fission explosions?"

You power them with a fission explosion.