Why Plasma Engine Couldn't Using On Earth?

[Future JPL Space Engineer]

I don't understand why plasma engine could not using on the Earth, Ground.

Because of gravity?

[Strange]

My understanding is that plasma, and ion engines generally, can only produce low levels of thrust but do so very efficiently. So they do not produce enough thrust to overcome gravity, but are suited to long duration missions where a small acceleration for a long time is useful.

[Fuzzwood]

Because ion engines in contrast to things like turbojets/fans don't use the atmosphere they move in for propulsion and thus gain nothing from the velocity difference of the outside air with regards to the engine. Ion engines, but also liquid fuel/oxidizer rockets thus solely depend on the exhaust velocity of their propellant to reach their Isp, which in atmosphere is a whole lot lower than in the vacuum of space.

 

http://en.wikipedia.org/wiki/Specific_impulse

 

Also: kerbal space program (I hate to commercialize this game in this fashion, but it has the potential to teach a lot about orbital mechanics, but also things like thrust and specific impulse, which due to the nature of this question can provide quite a lot of insight).

Edited October 15, 2014 by Fuzzwood

[Enthalpy]

Besides the already mentioned faint thrust, the natural choice to move near the ground is to use air in an engine, instead of ejecting a propellant carried by the vehicle. As long a this is possible, that is, Mach 3 for a long time, Mach 6 in the near future.

[Future JPL Space Engineer]

My understanding is that plasma, and ion engines generally, can only produce low levels of thrust but do so very efficiently. So they do not produce enough thrust to overcome gravity, but are suited to long duration missions where a small acceleration for a long time is useful.

Thank for your reply!