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#460
by
billshap
on 27 Aug, 2009 14:40
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With all the references to the MMT, there is never any discussion of who is on it. We only hear from Mike Moses at the Cape and Leroy Cain in Houston. Who exactly is on the MMT? Is there a different MMT pre-launch at KSC than during a mission at JSC?
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#461
by
iprefermuffins
on 27 Aug, 2009 19:37
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I've read that the aft skirts of the SRBs support the entire weight of the shuttle on the pad. However, it seems like they would be offset by quite a bit from the CG of the entire stack, considering that there's an orbiter hanging off one side and not the other. Is there any other structure providing a lateral force to keep the stack from tipping over? Or are the hold-down posts on the skirts enough to keep the stack securely upright?
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#462
by
Jim
on 27 Aug, 2009 19:46
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I've read that the aft skirts of the SRBs support the entire weight of the shuttle on the pad. However, it seems like they would be offset by quite a bit from the CG of the entire stack, considering that there's an orbiter hanging off one side and not the other. Is there any other structure providing a lateral force to keep the stack from tipping over? Or are the hold-down posts on the skirts enough to keep the stack securely upright?
The 8 hold-down posts do every thing
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#463
by
ChrisGebhardt
on 27 Aug, 2009 19:50
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When the GOX vent arm is extended for ET loading, the beanie cap is lowered into position for final fit checks. Then, the beanie cap is raised but the arm is left extended. Why is the beanie cap raised up like this?
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#464
by
Lee Jay
on 27 Aug, 2009 19:53
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I've read that the aft skirts of the SRBs support the entire weight of the shuttle on the pad. However, it seems like they would be offset by quite a bit from the CG of the entire stack, considering that there's an orbiter hanging off one side and not the other. Is there any other structure providing a lateral force to keep the stack from tipping over? Or are the hold-down posts on the skirts enough to keep the stack securely upright?
You need to realize that the orbiter only weighs on the order of 1/10th as much as two fueled SRBs, so the CG isn't offset all that much. The moment it applies is the same regardless of the SRB mass of course, but even that moment isn't all that much - around 100 metric tons times something in range of high single-digit meters. That's nothing for a large steel tube to take in bending (much less two of them) and the 8 bolts Jim mentioned are large and widely spaced from each other.
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#465
by
iprefermuffins
on 27 Aug, 2009 20:15
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You need to realize that the orbiter only weighs on the order of 1/10th as much as two fueled SRBs, so the CG isn't offset all that much. The moment it applies is the same regardless of the SRB mass of course, but even that moment isn't all that much - around 100 metric tons times something in range of high single-digit meters. That's nothing for a large steel tube to take in bending (much less two of them) and the 8 bolts Jim mentioned are large and widely spaced from each other.
Thanks (& to Jim too). The weight difference had occurred to me but I didn't know it was quite that much.
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#466
by
Jim
on 27 Aug, 2009 20:26
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You need to realize that the orbiter only weighs on the order of 1/10th as much as two fueled SRBs, so the CG isn't offset all that much. The moment it applies is the same regardless of the SRB mass of course, but even that moment isn't all that much - around 100 metric tons times something in range of high single-digit meters. That's nothing for a large steel tube to take in bending (much less two of them) and the 8 bolts Jim mentioned are large and widely spaced from each other.
Thanks (& to Jim too). The weight difference had occurred to me but I didn't know it was quite that much.
The force of the main engines during start up push the stack the opposite direction with more force than the weight of the orbiter
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#467
by
Danny Dot
on 28 Aug, 2009 00:08
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Does anyone know the difference in q between a high q and low q profile? I also need to know how much performance gain there is.
Danny Deger
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#468
by
simcosmos
on 28 Aug, 2009 21:03
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#469
by
Hungry4info3
on 28 Aug, 2009 22:55
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Hypothetically,
If a foam strike occurs while climbing to orbit, and severe damage is very obvious (i.e. can be seen to anyone looking at the camera mounted on the ET that is usually shown on the public channel), could they do an RTLS abort based on that?
(not that I hope this ever occurs)
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#470
by
ChrisGebhardt
on 28 Aug, 2009 22:57
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Hypothetically,
If a foam strike occurs while climbing to orbit, and severe damage is very obvious (i.e. can be seen to anyone looking at the camera mounted on the ET that is usually shown on the public channel), could they do an RTLS abort based on that?
(not that I hope this ever occurs)
No. Ascent would continue as planned. The FD2 OBSS inspections performed, docking undertaken, and CSCS implemented if a patch of the area cannot be safely accomplished.
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#471
by
Hungry4info3
on 28 Aug, 2009 22:58
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Thanks
On that note, what
does qualify for an RTLS abort? Engine or two going down I would assume, but is there anything else?
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#472
by
psloss
on 28 Aug, 2009 22:59
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Hypothetically,
If a foam strike occurs while climbing to orbit, and severe damage is very obvious (i.e. can be seen to anyone looking at the camera mounted on the ET that is usually shown on the public channel), could they do an RTLS abort based on that?
(not that I hope this ever occurs)
Also asked and answered here before...start with this and read down:
http://forum.nasaspaceflight.com/index.php?topic=14583.msg323022#msg323022
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#473
by
ChrisGebhardt
on 28 Aug, 2009 23:13
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Thanks
On that note, what does qualify for an RTLS abort? Engine or two going down I would assume, but is there anything else?
RTLS is any system error (single engine or dual engine failure or severe cabin leak, etc....) that prevents you from either safely reaching orbit or safely executing a TAL before the moment of Negative Return (approximately T+4 mins) -- at which point the Shuttle vehicle has passed too far downrange and gained too much forward moment to safely return to KSC.
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#474
by
psloss
on 28 Aug, 2009 23:52
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Thanks
On that note, what does qualify for an RTLS abort? Engine or two going down I would assume, but is there anything else?
RTLS is any system error (single engine or dual engine failure or severe cabin leak, etc....) that prevents you from either safely reaching orbit or safely executing a TAL before the moment of Negative Return (approximately T+4 mins) -- at which point the Shuttle vehicle has passed too far downrange and gained too much forward moment to safely return to KSC.
A dual engine failure early in ascent is probably more a contingency abort case than RTLS -- if Mark's nearby, you can ask him.
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#475
by
ChrisGebhardt
on 29 Aug, 2009 00:04
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Just asked Mark (he's sitting right behind me). Duel engine failure is most likely a contingency abort. Could be RTLS but depends on the MET failure times of the two engines (would have to be fairly let in RTLS capability zone to make it an RTLS v. contingency).
Page 2-46 of ascent cue card has the engine out abort scenarios.
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#476
by
glen4cindy
on 29 Aug, 2009 01:15
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Noticed this when we were at Kennedy for STS-127, searched the Q&A but didn't find any mention of it.
At various times during the countdown, I noticed a helicopter circling the KSC complex.
Is this a security measure to make sure that there are no unauthorized persons anywhere they are not supposed to be during a launch?
It seems that it would be a rather difficult thing for anyone to actually gain access to any critical area because of things being so locked down.
Remember the movie Jumper? I would love to have his ability during a launch where I would teleport myself to the roof of the VAB for a prime view. But, then, I would have to avoid being seen too.
Thanks for this site. I can't afford L2, but, there is so much great information I have learned here.
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#477
by
Danny Dot
on 29 Aug, 2009 02:33
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Vast majority of reason for RTLS is single engine out during something like the first 2 minutes of flight. After that TAL. For cabin leak and I think 2 APUs down and one failing an RTLS can be done. Lets just put it this way, we hated RTLS so bad that as a person that use to make a living putting failures in the simulator to force an abort, making us go RTLS after TAL was available was available was very hard to do.
Oh and I forgot the one single stuck in the throttle bucket and one failed to force a TAL. It was a pain in the rear to time the second failure to not go contingency, or not go TAL. I used to have so much fun trying to force a given abort. The problem was, we would have a whole script of failures based on a given abort. If I failed in my job to produce an RTLS and we went TAL instead, I got lots of dirty looks from my fellow instructors.
Danny Deger
Edit: I forgot this one. The cracked thermal window pane due to a bird strike. The idea was to never get to high Mach numbers and avoid heating. It was next to impossible to get this case without prebriefing the commander on this. The abort call is made on what the command was observing.
On getting the right abort, my worst day in the world in this matter was a rare long duration integrated simulation to exercise all of NASA on a major, Columbia like, problem on orbit. We decided to do an abort to orbit on ascent for some reason. I was new and screwed it up and sent us back to KSC with an RTLS. It took us 20 minutes or so to turn the sim around and get everyone synced up and going again. I think god him self was monitoring the flight loops. I know the administrator at the time was. Have you ever seen the Southwest Airlines commercial "Do you want to get away?"
Danny Deger
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#478
by
Jim
on 29 Aug, 2009 12:45
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1. Is this a security measure to make sure that there are no unauthorized persons anywhere they are not supposed to be during a launch?
2. It seems that it would be a rather difficult thing for anyone to actually gain access to any critical area because of things being so locked down.
1. Yes
2. Not really. There isn't a fence around the whole center.
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#479
by
Antares
on 29 Aug, 2009 19:45
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