Re:Basic Science! (Score 1)

Correct. The exact nature of the pile determines the amount of heat that can be generated which in turn determines the maximum specific impulse. Hydrogen ends up being a good reaction mass because of its low molecular weight.

As to the safety of the rocket, chemical rockets today are little more than well controlled bombs. That's the primary reason why launches occur in equatorial coastal regions, i.e. if it goes boom, it goes boom over fishies instead of us. I think you could make safe and reliable piles that would survive the destruction of the rocket. The problem would be continuing to dissipate the heat they would generate. Seawater seems like a pretty good coolant to me. The key would be to have the containment vessel maintain its integrity even in corrosive environments.

Having said all that, my favorite propulsion technology remains plasma based, either Kauffman ion sources or variable Isp plasma rockets.