Space/Science — HabitableZone

Space/Science » in reply to Could these thrusters be used for lunar landing/ascent?

A few issues
Adam — (archived)

Hi Lee

Ion drives and plasma drives, as a rule, have high exhaust velocities - the ion-drive you linked to gets 190 km/s - but very low thrust. The reason is pretty straight forward - not enough power available. A simple equation governs the power of a rocket's jet...

P = T.V/2

...where T is the thrust, V the exhaust velocity. With a high exhaust velocity many kilowatts are needed per newton of thrust - a 20 ton lunar lander using a 100,000 m/s ion-drive needs at least 1.62*20,000*50,000 = 1.62 gigawatts of jet power. That's rather hard to supply. The main issue is power-density of the energy source - even nuclear reactors struggle putting out 250 W of electrical power for every kilogram of mass.

So, for now, we're stuck with old fashioned chemical rockets for even lunar landing missions. Unless you're an elevator car on a lunar space-elevator, but that's another story...

Adam

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