rickshaw said:
I've often wondered how these nuclear aircraft were meant to work (or rather their engines). How does a nuclear jet engine work?
Simplest version: nuclear ramjet. In short, air is fed into a reactor, a reactor which is real close to meltdown. The air serves as coolant for the reactor, in the process getting very hot. The heated air is expelled directly, producing thrust. In essense, the heat from the reactor replaces the heat from normal ramjet combustion.
Turbojet version, simple: similar as above, but instead of providing direct thrust, the heated air is blown past a turbine, with the reactor takign the place of regular burner cans in a turbojet. The turbine then provides mechanical power to run a conpressor and/or an extenal propellor (nuclear turboprop).
Turbojet version, complex: A heat exchanger is placed between the air and the reactor. The reactor is now cooled with some fluid - compressed helium, lithium, various salts, etc. - and the now-heated fluid in turn heats the air. The fluid and the air do not come into direct contact; fluid is contained within metal tubes (like the coolant in a regular car engine, just vastly hotter).
Surely it would spew radiation all over the countryside?
In direct cycle engines, like the first two described above, yes. In indirect cycle engines, no. The reactor is still hot and emits gamma rays and neutrons, but does not emit radioactive exhaust.