[ExI] rocke fuel was Re: SpaceX launch

[Adrian Tymes]

On Thu, Dec 9, 2010 at 7:39 PM, Keith Henson <hkeithhenson at gmail.com> wrote:
> Spike is correct here.  The best you can do with hydrogen and oxygen
> is about 4.5 km/sec exhaust velocity.  You need about twice that to
> get a mass ratio 3 rocket into LEO.
>
> Heating hydrogen to 3000 deg K will get you 9.8 km/sec exhaust
> velocity.  It's entirely possible to do this with a big laser beam,
> several GW, for a reasonable sized vehicle.  3000 deg K is 600 deg
> under the melting point of tungsten.

Could you use tungsten as a heat exchanger?

Have an onboard energy source, optimized for heat generation instead
of thrust.  (Maybe even fission/radioactives, so long as they don't get
into the exhaust.)  Use tungsten to transfer the heat into hydrogen,
which is gently forced past.  The heat greatly increases how fast it
goes when it leaves.