Reply To: extracting energy out off the plasma soup

[vlad]

Formula that links rocket engine power, thrust and its specific impulse is more than simple 🙂
P = I / 2
where P is specific power of rocket engine (in the sense of 1 Watt per 1 N of thrust), without loss of course
and I is a specific impulse of rocket engine, in m/s

specific impulse of the rocket engine in m/s is equal to the speed of exaust velocity
hence for specific impulse of 0.03c (9E6 m/s) and power of 5MWt the thrust would be… about 1 Newton
not too much I believe 🙂

To travel to Mars you definetely should “exchange specific impulse to thrust”
You can (very) roughly estimate optimal specific impulse for some space route as… say equal or – much better – twice to the deltaV of this route.
So if your estimate deltaV for the route from Earth low orbit to Mars low orbit and back to… say 40 km/s (for fast piloted mission with flight time measured by weeks not months) then the optimal specific impulse would start from 4000s, and 8000s would quite nice.