Talk:Magnetoplasmadynamic thruster

From Wikipedia, the free encyclopedia

I really strongly feel that this technology will advance the future of deep space exploration.

[edit] Advantages

What does this mean: In theory, MPD thrusters could produce extremely high specific impulses (I_sp) of up to and beyond 11,000 s (110 km/s exhaust velocity)...? 11,000 seconds? Should it be m/s? But that's 11 km/s. Ehn 19:37, 16 October 2005 (UTC)

See specific impulse - for some reasons the specific impulse is traditionally given as (real specific impulse, i. e. the exhaust velocity)/(gravitational acceleration at earth's surface). So you've to multiply by a factor of about 9.8 to get the exhaust velocity in m/s from I_sp in s. 193.171.121.30 10:42, 17 October 2005 (UTC)

MPD thrusters should make a good second stage engine when launching satellites into Low Earth Orbit (LEO) from a Space Elevator. The electric motors that lift 20 metric ton climbers will need about 1.8 MW of electrical power, this is similar to a MPD thruster. For a 400 km LEO orbit climb the Space Elevator to 23 804 km release the satellite and circularise the orbit with a delta-v of -2.132 km/s. A MPD thruster supplying 200 Newtons will take about 7.5 days to circularise the orbit.

Using Newton's Laws of Motion Force F is mass m time acceleration a, F = m a and final velocity v equals initial velocity u plus constant acceleration a times time t, v = u + a t then t = delta-v * m / F = -2.132 km/s * 20 000 kg / 200 N = 213 200 seconds (about 2.5 days)

In a highly eccentric Hohmann transfer orbit the space craft can only use its engine to slow down at the bottom near the periapsis, say a third of the time. (Change of inclination burns are performed near the apoapsis.) If the climber climbs at 200 km/h the journey time becomes T = (23 804 km / 200 km/h) / 24 h + 2.5 days * 3 = 12.5 days

Andrew Swallow 19:49, 13 November 2006 (UTC)