[AR] Re: Alternative propulsion was: Flying to Orbit with Hydrogen?
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 25 Dec 2019 23:42:07 -0500 (EST)
On Wed, 25 Dec 2019, John Dom wrote:
Skylon, Space X, NASA, India, China, Japan: what am I missing is why
non-chemical propulsion gets no priority (in order to make it real).
Like fission or fusion propulsion or space elevators.
The reasonably-proven fission technology doesn't have enough advantage
over chemical to justify the massive hassles of developing it. (You could
launch many kilotons of LOX and kerosene to LEO for the cost of the first
operational nuclear engine.) More advanced fission is a considerable
technical challenge, fusion is worse, and space elevators are still worse.
And the big snag, always, is what Jeff Greason said at Space Access 2016:
"The existing markets have poor elasticity and the elastic markets have
poor existence." For investing billions in radical new launch technology,
private money wants to see near-certainty of massive return on investment,
and government money wants to see firm requirements for it from funded
missions, plus near-certain technical success. No such certainties are
available.
As for an energy source on the surface, I'd but my bets on lava streams
below heat exchangers like Iceland does. Not windmills, nor powersats.
There are just too few places where there is lots of reasonably accessible
geothermal heat. Hundreds of megawatts, yes, in good places like Iceland.
Gigawatts, maybe in a few places with a concerted effort. But getting the
world off its fossil-fuel addiction, despite the transition of Asia and
Africa to industrial societies, needs tens of terawatts.
Very few power sources scale up that far (in fact, it's not clear that
fossil fuels can, for any realistic length of time). We badly need to
waste fewer resources and less enthusiasm on concepts that inherently
cannot do even a useful fraction of the job.
Henry
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