Third way

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Robert

> the problem is not the energy sourse, its the fuel.
> if hes heating air in a kind of jet, he could get
> considerable altitude and speed from it, but he'd
> still have to carry propellant to get out of the atmosphere.

Yes, it's certainly acknowledged that one needs on-board propellant for
the final push into orbit. Still, it's a significant savings in
propellant, plus the propellant can be chosen for its utility as
reaction mass rather than its energy content. For example, I've seen
proposals for using ice as reaction mass (perhaps mixed with a bit of
black plastic to aid in the absorption of laser energy).

I think Myrabo recommends hydrogen as propellant, but then we're still
saving the weight of the oxidizer we'd normally have to carry for a
rocket. We're relying on an external power source rather than on the
chemical energy in the fuel combination we're carrying.

Regards,

Mike Combs