Ways to sidestep gravity?

Lucio de Souza Coelho wrote:

> I have already converted myself to the Space Elevator Cult. It will come and
> free us all! ;-)

It might. It might not though. Until we have the material AND
the manufacturing process AND the money we ain't gonna get
there.

Still, I went to a talk yesterday about laser powered launch
systems. The guy described a system of using a 100 Mw laser
(cost: around $1 billion, dropping at 30% per year in price
currently) used to point at hydrogen monopropellent vehicle
the vehicle uses a heat exchanger to boil the LH upto a
relatively low temperature 1000C and then chucks it out through
a conventional or aerospike nozzle.

The ISP turns out to be 600, c.f. the space shuttle SSME ISP
of ~450 (the reason is that the space shuttle uses LOX/LH but
this system would use just LH, so the average exhaust velocity
goes up- Ox is heavy and reduces the ISP.)

This makes the vehicle much simpler, cheaper and more powerful.
He was talking a few tens of k per vehicle, either expendable
or reusable I guess. Noteably, turbopumps are not required.

He was talking of a 500kg vehicle delivering 140kg to LEO,
although it wasn't SSTO. He thinks the price ends up south
of $100/kg... It's not clear whether 140kg is enough to launch
a person, but even if it doesn't the system is very scalable.

The system seems about 5 years off right now; including R&D.

Oh yeah, this guy Jordin Kare who did the talk isn't an
amateur- he's worked on many different projects for the
government; including some classified projects.

The cost of the laser isn't as big a problem as you might
think. If it enabled space tourism (and it easily could in
my opinion), the cost would be amortised over upto 35000
launches in the first year alone.

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding
technological civilization?"
- Gerard O'Neill