Electric Propulsion for ISS

[jongoff]

Some figures.
F = m a
v = u + a t so a = delta-v / t

setting t = half a year
ISS station keeping delta-n to 100 m/s (from Wikipedia)
ISS mass to 419,455 kg

F = m * delta-v / t = 419,455 * 100 / (0.5 * 365.25 * 24 * 60 * 60) = 2.658 N

The off the shelf NEXT ion thruster, which produces 0.236 N at 6.9 kW and Isp 4190 s

so 2.658 / 0.236 = 11.26 thrusters are needed

Power = 11 * 6.9 kW = 75.9 kW

By increasing the burn time fewer thrusters and small solar panels can be used but the same quantity of propellant will be needed.

For stationkeeping in LEO and other high thrust maneuvers you don't want to run in high-Isp mode, because P=1/2*F*Ve/eta, where Ve = Isp*g. For these applications you probably want something like an electrospray thruster, or a plasma thruster that uses neutral injection/charge exchange collisions to maintain highish efficiency at lower Isp values.

Ignoring all of the other problems that have already been raised re plasma thrusters on ISS...

~Jon

[A_M_Swallow]

AIUI, most of those things are CGM desat and DAM. Those simply can't be made with SEP. I remember that we had calculated the drag and it was around 0.25N/s

A pair of thrusters and a single solar array should be able to handle that. Stick a Common Berthing Module (CBM) on the front end and you may have a sell-able product.