Q&A: ion drive and vasimr rockets?

Question by Random Questions: ion drive and vasimr rockets?
I fully understand how each of these systems operates and I don’t want to get into detail about it, but I wish to know some other information about them. The first is i know that they could travel longer than a conventional rocket but are they faster then the shuttle and by how much? The second is suppose I use a mass driver or a rail gun type launch to get the craft going and then turn on the ion drive will it continue at that speed(don’t take newtons 1 law into affect) or will it add on to the speed of the craft soon after the launch? Finally would a vasimr rocket work inside the earths atmosphere under gravity and air or does it not have enough thrust( same applies to the ion drive)?

Best answer:

Answer by eelfins
The thing about the vasimr is that it’s variable: if you open the choke it gets a lot of thrust with little efficiency. If you narrow it you get a lot of efficiency with little thrust. Lots of thrust is needed in low orbits in order to capitalize on gravitational energy, but in open space high-efficiency is required because there is no gravitational sling-shot. I don’t think a vasimr could be launched from earth’s surface, it would most likely have to be built in orbit.

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