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#1960
by
Lee Jay
on 19 May, 2009 13:13
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Two scenarios - you use a highly-modified tank to launch nothing but itself, and then modify the heck out of it in space to make it usable for something. Or, you leave the tank as light as possible and launch something in an already-usable form that has twice the mass of the empty tank. Why would you ever do the first one?
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#1961
by
mmeijeri
on 19 May, 2009 13:16
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Two scenarios - you use a highly-modified tank to launch nothing but itself, and then modify the heck out of it in space to make it usable for something. Or, you leave the tank as light as possible and launch something in an already-usable form that has twice the mass of the empty tank. Why would you ever do the first one?
I don't know, I'm just trying to get a feeling for how difficult it would be. Why did von Braun seriously consider the wet workshop idea? Did he underestimate the problems?
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#1962
by
William Barton
on 19 May, 2009 13:31
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Two scenarios - you use a highly-modified tank to launch nothing but itself, and then modify the heck out of it in space to make it usable for something. Or, you leave the tank as light as possible and launch something in an already-usable form that has twice the mass of the empty tank. Why would you ever do the first one?
I don't know, I'm just trying to get a feeling for how difficult it would be. Why did von Braun seriously consider the wet workshop idea? Did he underestimate the problems?
I think it was the only way to get that kind of volume on orbit, without using a Saturn V. Once a Saturn V became available, Skylab as we know it became feasible. Same thing with the original question. You can launch the tank and modify it on orbit, or you can launch something usable with twice the weight of the tank and a fraction of the volume. To modify the tank, you have to ship up its contents. To get that volume the other way, you have to ship up multiple bits. It's the difference between wet workshop (launched on multiple Saturn IBs) and Salyut/Mir (launched on multiple Protons and Soyuzes).
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#1963
by
C5C6
on 21 May, 2009 13:30
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I'd like to ask you people, if HST deploy was on tuesday, why does landing takes place three days later??
I see in the NASA TV Wednesday schedule activities such as PAO events, ISS/STS-125 communication and free duty time...
...couldn't they just focus on wednesday on late TPS inspections and deorbit preparations for landing on Thursday??
I know that free duty time is compulsory -and obviously they deserve it- and there are loads of things to do before deorbit but isn't safer to bring them back home as soon as possible???
I'm not against PAO activities or free duty I'm just asking if the risks of LOC arent's significantly decreased by landing a day earlier....or if crew fatigue is such they really need some time to rest and be prepared for landing...
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#1964
by
rdale
on 21 May, 2009 15:20
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Someone just asked this yesterday and it was answered - crew needs to rest before getting things configured and landing safely. You don't want them missing steps or not at 100% when flying home.
Also if there's a contingency or bailout, do you want them doing that with a lack of sleep and exhausted bodies?
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#1965
by
C5C6
on 21 May, 2009 16:43
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in fact it was me who asked, but as I received only one answer I thought it would be enriching for this topic to be asked again so more people can answer and read it...
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#1966
by
mdo
on 21 May, 2009 23:38
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Anybody who worked overtime for two weeks in a row knows that taking a day off is important for many reasons. Why this day was scheduled the way it was, namely so late in the mission timeline of STS-125 - rather than halfway through the EVAs when it would have had a potential positive impact on crew performance - is a very good question.
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#1967
by
butters
on 22 May, 2009 01:12
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OK, here's that old chestnut again: reusing the ET on orbit.
The SLWT is 26.5 mT dry. J-130 would lift 70 mT to LEO. That seems like enough margin to fashion it into a habitat. Just launch a dry tank on top of the wet tank. This doesn't reuse the launch tankage, but it does reuse the tooling and production assets.
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#1968
by
rdale
on 22 May, 2009 01:45
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why this day was scheduled the way it was, namely so late in the mission timeline of STS-125 - rather than halfway through the EVAs when it would have had a potential positive impact on crew performance - is a very good question.
As mentioned above, the goal is to have the crew ready to land the shuttle and do any emergency work needed in case. Better to have a tired crew take an extra 20 minutes on an EVA, than a tired crew flipping the wrong switch in an emergency situation on reentry.
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#1969
by
zeke01
on 22 May, 2009 01:53
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#1970
by
mdo
on 22 May, 2009 04:03
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As mentioned above, the goal is to have the crew ready to land the shuttle and do any emergency work needed in case. Better to have a tired crew take an extra 20 minutes on an EVA, than a tired crew flipping the wrong switch in an emergency situation on reentry.
So, the criterion is the proximity of off duty period and landing. What I missed was that
emergency work is expected - probability wise - to happen towards the nominal end of mission. The loss of another ASA channel, for instance, could have prompted an early return at a random point in time.
Thanks for the clarification.
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#1971
by
ginahoy
on 24 May, 2009 20:25
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My first post. I was curious about why a 4-person crew was assigned to STS-400. Since it would obviously be a tight fit with 11 crew and special seating, why not just fly STS-400 with 2 crew, as was the done during initial test flights?
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#1972
by
Jim
on 24 May, 2009 21:17
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4 crew is required for SAS. Also rendezvous and EVA require 4.
Edited.
Danny, you should know what SAS is.
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#1973
by
Danny Dot
on 24 May, 2009 21:42
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4 crew is required for SAS. Also rendezvous and e a require 4
What is SAS and "e a"?
Danny Deger
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#1974
by
Jorge
on 24 May, 2009 21:48
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4 crew is required for SAS. Also rendezvous and e a require 4
What is SAS and "e a"?
Danny Deger
SAS=Space Adaptation Syndrome
e a=I suspect misspelling of EVA
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#1975
by
ginahoy
on 24 May, 2009 23:03
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4 crew is required for SAS. Also rendezvous and EVA require 4.
Thanks Jim. Here's another question for speculation:
I read that the capability to auto land the shuttle was never fully developed. During early testing, shuttle commanders had trouble inserting themselves into the loop at the most critical time, thus the risk of further testing wasn't justified.
www.spaceref.com/news/viewsr.html?pid=10518Had the STS-400 mission become necessary and the damage was not obviously catastrophic, do any of you think NASA would have tried to save Atlantis via automatic landing, presumably at Northrop or Edwards?
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#1976
by
Jim
on 25 May, 2009 00:47
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Had the STS-400 mission become necessary and the damage was not obviously catastrophic, do any of you think NASA would have tried to save Atlantis via automatic landing, presumably at Northrop or Edwards?
Edwards would put too many at risk
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#1977
by
ginahoy
on 25 May, 2009 01:35
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Edwards would put too many at risk
Sorry, I didn't mean to drill down on which landing facility. I'm curious if NASA would have even tried. Based on the testing done, once the shuttle survives reentry (which would be over the ocean for any viable landing location), the automatic landing system has been demonstrated as reliable to 125 feet AGL,
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#1978
by
Danny Dot
on 25 May, 2009 02:47
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Edwards would put too many at risk
Sorry, I didn't mean to drill down on which landing facility. I'm curious if NASA would have even tried. Based on the testing done, once the shuttle survives reentry (which would be over the ocean for any viable landing location), the automatic landing system has been demonstrated as reliable to 125 feet AGL,
I don't think STS-125 had the kit onboard to allow such things as the gear to be lowered. IIRC flights to ISS have an autoland planned if the damage isn't too great. I don't know what site the landing will go to.
Danny Deger
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#1979
by
ChrisGebhardt
on 25 May, 2009 02:52
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Edwards would put too many at risk
Sorry, I didn't mean to drill down on which landing facility. I'm curious if NASA would have even tried. Based on the testing done, once the shuttle survives reentry (which would be over the ocean for any viable landing location), the automatic landing system has been demonstrated as reliable to 125 feet AGL,
I don't think STS-125 had the kit onboard to allow such things as the gear to be lowered. IIRC flights to ISS have an autoland planned if the damage isn't too great. I don't know what site the landing will go to.
Danny Deger
Atlantis did not carry the RCO cable necessary for deploying the landing gear. The plan always was that if Atlantis were damaged and the STS-400 rescue flight launched, Atlantis would have been destructively reentered. Basically, to answer your first question ginahoy, NASA would not have tried to save orbiter Atlantis
if the STS-400 rescue flight was required.
To answer the question about which landing field would be used during an unmanned/damaged orbiter reentry and landing would be a function of orbital inclination, orbital phasing, level of damage to the orbiter, and land overflight restrictions. Obviously, to reach any landing site in the US the orbiter would have to fly over land. However, there are ways to adjust orbital phasing to ensure a reentry over the Pacific, Caribbean, and Atlantic that would land the Orbiter at KSC without violating the land overflight rules. Remember, the orbiter's have a large cross-range capability.