Jumping the Gun.

Combs, Mike wrote:

>>Is it more efficint than a chemical
>>propulsion system?
>>
>>
>
>Seems like I remember O'Neill commenting that a mass-driver engine could
>have twice the specific impulse of the Space Shuttle's chemical main
>engines.
>
Mike, if I remember right, you voiced some doubt about mass-driver
achieving delta-vs of more than 2 km/s
due to some inherent delay in switching on/off the magnetic coils?
In that case mass drivers would have only half the specific impulse of
chemical rockets.

Even if this limit could be overcome by adding more and more stronger coils,
the ratio between ship mass and fuel mass ejected per time unit will
result in a low thrust engine.

> But as Rick commented, the big advantage is that they could
>use just about anything lying around for reaction mass: oxygen from an
>ore-refining operation, regolith from an asteroid, etc..
>
Agreed.

Regards,
Axel