XPost: rec.arts.sf.written, sci.space.policy, sci.physics
From: fjmccall@gmail.com
Thomas Koenig wrote on Wed, 6 Jun 2018
06:21:34 -0000 (UTC):
>Jeff Findley schrieb:
>
>> We've had this debate a long, long time ago in the sci.space newsgroups.
>> The fact is that there are many stages which are theoretically capable
>> of performing SSTO with minimal payload. No one has ever done it
>> because the cost to get that payload into orbit is typically higher than
>> it would be if you just used a smaller TSTO (or higher number of
>> stages). In other words, it just makes no sense to fly a disposable
>> SSTO.
>
>There are also other considerations to take into account.
>
>One of them is mechanical. A first stage flying with a much smaller
>payload than the current second stage + actual payload would
>have much lower mass towards the end of the burn, resulting in
>higher acceleration and higher mechanical stress. Buckling could
>be something that needed to to be guarded against, as could be
>outright failure due to compression stress.
>
If you're going for orbit you're well out of the atmosphere at the
'end of the burn'. Neither of those are an issue.
>Possible solutions if it turns out to be a problem:
>
>Turn down the engine thrust (How far is that possible? Can the
>engines even do that? What will it do to the specific impulse?)
>or switch off individual engines (what happens if you swith off
>one half a second later than the others?).
>
Of course it's possible. What do you think they do approaching max Q
now? It doesn't do anything to specific impulse (do you know what
that means)? It just means the engine burns longer.
>
>Strenghten the strucutre. This would add mass, and it would not
>be the same first stage anymore.
>
Stress on the first stage is probably higher with all that mass
mounted on it than it would be otherwise.
--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
--- SoupGate-Win32 v1.05
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