"Charles Talleyrand" writes:

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.

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?


$10/pound is close to the ultimate limit, barring miracle tech,
of three times the fuel/energy cost. That's where the airline
industry has stabilized after a hundred years of manned airline
flight, and the same economic logic seems to apply.

But it took a hundred years for the airline industry to get where
it is today, and anyone suggesting we've already had fifty years
of actual progress in space launch will be laughed at. Fifty
years from now, we'll probably still be at the $100/pound level
and still trying to figure out the ultimate best way to run the
show.

The underlying technology will be, well, rocketry. Pump liquid
oxygen and probably something hydrocarbonish into a metal chamber,
burn same, and exhaust through a converging/diverging nozzle.
Use some fraction of the propellant that hasn't been burnt yet
to A: regeneratively cool the whole assembly and B: run the fuel
pumps. This works as well as anything that can be expected to;
it converts 95+% of the energy content of the propellant into
kinetic energy at a prodigious rate in an extremely compact
system.

There may be some use of airbreathing engines and wings to augment
rocketry during the early part of the mission, especially if the
best system turns out to be two-staged. I strongly doubt that this
will ultimately be the best, but it makes for an easier introduction
to the field and may still be state-of-the-art in 2053 even if I
expect it to be quaintly archaic by 2103.

The only advanced technology at less than the miracle level that
will really change things is materials science; better structural
materials and better thermal protection systems will be seriously
helpful. What is actually necessary, is better systems engineering,
and that's mostly not a technology issue.


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