VASIMR plasma drive in GURPS...

[Anthony]

Originally Posted by Ulzgoroth

Er, I think your arithmetic is badly off.

My own estimate, which is about 40 W/kg ship mass (derived from the power output of high-TL chemical power plants), is good for about 0.005 mps*g.

Hm. Okay, 0.005 mps/tank is an exhaust velocity of 0.1 mps or 161 m/s. 1G is 9.8 N/kg. Power would thus be 9.8N/kg * 161m/s * 0.5 = 789W/kg.

If you want, we can break down further. For a 1 kg ship, 9.8N at 161m/s is a mass flow rate of 0.0609 kg/s, with a ke of 0.0609 * 161^2 * 0.5 = 789W.

I suspect your math error was by using exhaust velocity = mps/tank, not exhaust velocity = 20*mps/tank. Dividing by 20 does yield your numbers.