In article ,
Charles Talleyrand wrote:
I'm trying to imgaine cheap space flight. I'd also like to see it
sooner rather than later. Given this I believe we are limited to
chemical rockets.

There are actually a number of alternatives that would be realistic on
a timescale of a few decades, e.g. laser launchers. However, taking the
question as read...

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years?

That depends enormously on just how things evolve -- it is not primarily a
technological question. To the extent that it is technological, the
technical issues are things like heatshield maintenance requirements,
which are very difficult to predict.

Will we see $100/pound to orbit? How about $10/pound?

The former is very likely. The latter is conceivable but rather a
stretch: a cheap propellant combination like LOX/propane can in theory
put stuff in orbit for $1-2/lb of dry mass, but *payload* will be only a
modest fraction of the dry mass, and getting maintenance and overhead down
to the point where fuel cost is a large fraction of total operating cost
would be challenging.

And what underlying technology will this rocket use?

The best bets, in my opinion, are (a) carbon-fiber or *possibly* nanotube-
composite structures, (b) innovative engine designs with rather better
performance than conventional approaches, and (c) reentry concepts that
unfurl or inflate a large heatshield, much larger than the vehicle proper,
so as to reduce the demands on the heatshield materials. But there are
alternative approaches aplenty; again, much will turn on non-technical
issues.

don't say "carbon nanotubes will solve everything" unless you also
believe that we will build 50,000 lbs structures in carbon nanotubes
sometime in the next 50 years.

I think that's credible, but by no means certain. Making a good composite
structural material using nanotubes as the fiber is much harder than just
making nanotubes. Lots of people are working on it, but it's a difficult
problem and it might not *have* near-term solutions. (People have been
trying for nearly 20 years to make high-power wire using liquid-nitrogen
superconductors, with only the most limited results so far.)
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |