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#1420
by
Tnarg
on 08 Nov, 2010 14:47
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If you used a single Space Shuttle main engine for the first stage of a normal rocket how much would it's payload to LEO be? and how do you work it out?
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#1421
by
Danny Dot
on 08 Nov, 2010 15:17
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If you used a single Space Shuttle main engine for the first stage of a normal rocket how much would it's payload to LEO be? and how do you work it out?
Divide the sea level thrust by 1.2 and then take 5% of that as a first cut. I come up with about 20,000 pounds.
Danny Deger
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#1422
by
nickyp
on 08 Nov, 2010 20:30
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Is the SSME in any way related to the J-2 family of engines?
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#1423
by
kraisee
on 08 Nov, 2010 20:45
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No. Some of the general depth of knowledge & understanding that was developed during Apollo, certainly fed into the engineering process that ultimately produced SSME, but beyond that there is little, or even no, heritage back to J-2. SSME was a thoroughly clean-sheet design intended to push the envelope in nearly every area -- and it did.
Ross.
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#1424
by
lucspace
on 10 Nov, 2010 13:00
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Some basic questions about rocket fuel tanks, I think, but connected with Discovery's current hold-up:
The leak occurred in a pipe carrying excess hydrogen away from the tank. How can it occur that there is EXCESS hydrogen when the tank is not completely full? I would think all fuel is required to end up in the tank?
How does boil-off work? When the fuel is in the tank, a sealed vessel, how does liquid H2 disappear?
Thanks,
Luc
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#1425
by
Lee Jay
on 10 Nov, 2010 13:11
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Some basic questions about rocket fuel tanks, I think, but connected with Discovery's current hold-up:
The leak occurred in a pipe carrying excess hydrogen away from the tank. How can it occur that there is EXCESS hydrogen when the tank is not completely full? I would think all fuel is required to end up in the tank?
How does boil-off work? When the fuel is in the tank, a sealed vessel, how does liquid H2 disappear?
Thanks,
Luc
The answer to both is the same - boiloff. The liquid H2 is at roughly 4 degress above absolute zero so it's always boiling (turning to a gas) because it's absorbing heat from the Florida environment (which is distinctly above 4K) and the gas needs to be removed or the tank will over pressurize and explode.
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#1426
by
lucspace
on 10 Nov, 2010 15:57
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Thanks Lee!
I guess the trouble of cooling a rocket to keep the fuel liquid just would be too cumbersome to make it practical or worthwhile?
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#1427
by
sbt
on 10 Nov, 2010 18:07
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Thanks Lee!
I guess the trouble of cooling a rocket to keep the fuel liquid just would be too cumbersome to make it practical or worthwhile?
Cooling is generally done by passing a cold fluid to the object to be
cooled, allowing it to absorb heat from that object, and then removing
it from the object. In most systems the fluid is then recycled by
allowing it to shed its heat energy in some way - but not in all cases.
Think about cooling a burn by running water from a tap over it or
blowing air past the CPU in your PC (although mine is water cooled -
but you get the idea).
What is happening in the LH tank is that a cold fluid, LH2, is passing
into the tank at a slow rate ('Topping') to replace the boiloff. The
LH2 is absorbing the heat and boiling, producing GH2 which is removed.
The 'Topping' of the tank with LH to replace the H2 lost as GH is doing
the cooling - the working fluid is just not being recycled, but then
Hydrogen is relatively cheap. Any additional cooling system would have
to be more cost effective overall than the current method.
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#1428
by
lucspace
on 10 Nov, 2010 19:18
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Thanks guys, I learnt useful and interesting stuff today!
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#1429
by
sdsds
on 10 Nov, 2010 22:15
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When a Shuttle stack is at the pad, are the forward SRB attach points accessible for examination? Speculatively, if as the STS-133 tank were being filled there had been relative motion at one of those points, could it have led to both observed failures, i.e. pulled the GUCP out of alignment and placed the intertank stringer under out-of-specification transient loads?
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#1430
by
Jim
on 10 Nov, 2010 23:02
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When a Shuttle stack is at the pad, are the forward SRB attach points accessible for examination? Speculatively, if as the STS-133 tank were being filled there had been relative motion at one of those points, could it have led to both observed failures, i.e. pulled the GUCP out of alignment and placed the intertank stringer under out-of-specification transient loads?
There is always relative motive. The ET contracts several inches and the stack leans several inches when propellants are loaded.
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#1431
by
DaveS
on 11 Nov, 2010 14:09
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Does anyone know how many stringers there are on the ET intertank? Also how much are they separated by (in degrees)?
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#1432
by
AnalogMan
on 11 Nov, 2010 14:33
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Does anyone know how many stringers there are on the ET intertank? Also how much are they separated by (in degrees)?
Eighteen external stringers per normal skin panel with 6 panels per intertank. The two machined thrust panels do not have stringers, but instead have external stiffening ribs (26 longitudinal & 7 circumferential) formed by milling the solid metal.
Each panel occupies 45 degrees, so the stringers are separated by 2.5 degrees on those panels that have them.
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#1433
by
DaveS
on 11 Nov, 2010 17:01
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Does anyone know how many stringers there are on the ET intertank? Also how much are they separated by (in degrees)?
Eighteen external stringers per normal skin panel with 6 panels per intertank. The two machined thrust panels do not have stringers, but instead have external stiffening ribs (26 longitudinal & 7 circumferential) formed by milling the solid metal.
Each panel occupies 45 degrees, so the stringers are separated by 2.5 degrees on those panels that have them.
Thank you very much.
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#1434
by
Chris Bergin
on 12 Nov, 2010 11:24
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REALLY dumb question, but my mind has gone completely blank.
Why can't they roll out the stack to the pad with the payload already installed?
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#1435
by
psloss
on 12 Nov, 2010 11:31
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REALLY dumb question, but my mind has gone completely blank.
Why can't they roll out the stack to the pad with the payload already installed?
Can't install payloads in the VAB. No clean environment (environmental control is opening doors), no access to the payload bay for installing payloads.
Some payloads did roll out to the pad in the orbiter, but were installed in the OPF before the orbiter was mated. Or were installed at the pad and then rolled back to the VAB in the orbiter. Some payloads that were more environmentally sensitive (like HST and components) probably couldn't spend any time in the VAB.
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#1436
by
Chris Bergin
on 12 Nov, 2010 11:35
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Boom, there we go. Thanks Philip
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#1437
by
Fequalsma
on 12 Nov, 2010 14:22
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Does anyone have photos or diagrams of the Orbiter hoist point fittings that they can share? I assume that they are covered with TPS after the Orbiter is mated to the ET. Or are they left uncovered for launch?
F=ma
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#1438
by
Jim
on 12 Nov, 2010 17:24
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uncovered.
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#1439
by
DaveS
on 12 Nov, 2010 17:47
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uncovered.
Sorry Jim but here you are wrong. Both the forward and aft hoist points on the orbiter is covered with TPS while in the VAB prior to rollout.
