Nuclear photonic rocket

In a nuclear photonic rocket, a nuclear reactor would generate such high temperatures that the light from the reactor would provide thrust. Think of a nuclear light-bulb, with a reflector. The big advantage is that no material leaves the spacecraft, so only nuclear fuel is depleted. The disadvantage is that it takes a lot of power to generate a small amount of thrust this way, so acceleration is very low. The reactor would be constructed of graphite and tungsten.

A variation is the photon rocket proposed by the German rocket scientist Eugen Sänger, using antimatter annihilation as a light source and an electron-mirror as a reflecting medium. None of his mirror designs seem to work in reality, however.

The specific impulse would be 300,000,000 m/s or, expressed as a time, one year. $P=mca$, i.e. the power needed to accelerate 1 kg 1 $m/s^{2}$ is 300 MW.

See also: spacecraft propulsion