[AR] Re: Nothing to do with rockets.
- From: Peter Fairbrother <peter@xxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 5 Oct 2021 00:05:22 +0100
On 04/10/2021 22:55, John Stoffel wrote:
It might also be a vehicle for large things that people can't launch
even now without major contortions, here's looking at you JWST! Just
imagine how good a telescope you could send up if you didn't have to
pack it into an A5 fairing. Or what about those SAR satellites with
big radar dishes?
As I see it the best solution isn't developing a big launcher, it's
developing on-orbit assembly facilities.
Not an expert here, but given the choice between one 200-ton launch and
seventeen 10-ton cargo launches with three crewed launches for humans to
do the assembly and troubleshooting, I'd go for the latter every time.
Those big dishes and mirrors are mostly made in segments these days,
even for ground use, then aligned. It's straightforward if you have
people (or robots) onsite, but if not - look at the JWST, the troubles
they had with the self-erecting multilayer insulation. Or the repairs to
Hubble.
A few humans with tools and spare parts would be easier and more reliable.
Structures need to be engineered to withstand the stresses of launch,
and the bigger the payload the bigger the stresses - this usually
results in a structure which is stronger and heavier than its space
duties require. Or you can separate the payload and pack it in
styrofoam, then assemble for a truly low-space-mass structure.
There is also the launch ratio, as Henry mentioned - developing a a big
rocket to launch five or ten times is much more expensive than
developing a smaller rocket system to launch 100 or 1,000 times.
Note I'm not talking about reuseability here, so far anyway, but I could
start..
I could go on, but the thing is we don't have a permanently-manned
assembly station in equatorial orbit - when we do, the landscape changes.
Personally I think the sweet spot is about 10 tons in LEO. Big enough
for a useful cargo or crew (reentry) module, needs a minimum of
development cost, GSE cost etc.
And if you can fly from an airfield - well, we have lots of those already.
Peter Fairbrother
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