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#1840
by
JayP
on 25 Mar, 2011 14:39
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I take it the unmanned shuttle would have landed at Edwards?
Correct, that's what the plan has in it. But there also is plenty of talk that it'd be safer just to let it burn up over the Pacific this late in the game.
My understanding was that Vandenberg was the preferred landing site (if there was to be one), having the lowest risk to the public or ground resources.
I don't think Vandenberg has a MSBLS anymore, so they couldn't use the autoland there. Plus, they wouldn't have braking or nose wheel steering so keeping it on the runway durring rollout might be interesting.
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#1841
by
MarsMethanogen
on 25 Mar, 2011 19:45
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Chris Bergin, in today's article on the STS-134 process flow you state:
"The operation to transport the payload down the crawlerway to the pad and into the PCR all proceeded normally, allowing the RSS to extend back into the mate position on Thursday for the installation operation."
However, is looking in the image embedded in the article adjacent to this text, it sure appears as if the payload caravan is NOT using the crawlerway, but rather a paved road, perhaps adjacent to the crushed stone crawlerway. I can see where this might be the case, as the payload will certainly weigh no where near the CT/MLP and shuttle stack. So my question (to anyone); is the crawlerway being used here or an adjecent, paved road? Thanks.
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#1842
by
padrat
on 25 Mar, 2011 23:21
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It's a paved road that runs along the crawlerway. Most wheeled vehicles would get stuck trying to drive on the crawlerway, as someone usually finds out here at the pad when the orbiter rolls out. They plow rock across the road for the crawler to run on and someone usually tries to drive over it and sinks right in, especially since they replaced all of the rock recently. Those fresh stones are quite slippery!
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#1843
by
psloss
on 26 Mar, 2011 11:18
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I take it the unmanned shuttle would have landed at Edwards?
Correct, that's what the plan has in it. But there also is plenty of talk that it'd be safer just to let it burn up over the Pacific this late in the game.
My understanding was that Vandenberg was the preferred landing site (if there was to be one), having the lowest risk to the public or ground resources.
I don't think Vandenberg has a MSBLS anymore, so they couldn't use the autoland there. Plus, they wouldn't have braking or nose wheel steering so keeping it on the runway durring rollout might be interesting.
For the folks who asked, the RCO capability has been discussed here frequently:
http://forum.nasaspaceflight.com/index.php?topic=6156.msg165683#msg165683http://forum.nasaspaceflight.com/index.php?topic=10600.msg411433#msg411433The feasibility of fully automating an OFT in 1980-1982 is another question.
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#1844
by
parham55
on 30 Mar, 2011 18:32
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1. With regard to the MMU retirement was it deemed too risky after Challenger because of known problems or was its retirement due to more of a general change in NASA culture becoming more risk averse?
2.Have there been any serious thoughts of bringing the MMU out of retirement during the Shuttle program?
3.Any opinion and elaboration is appreciated.
Please move if this is too off topic for Shuttle Q&A.
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#1845
by
Jim
on 30 Mar, 2011 18:58
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1. With regard to the MMU retirement was it deemed too risky after Challenger because of known problems or was its retirement due to more of a general change in NASA culture becoming more risk averse?
2.Have there been any serious thoughts of bringing the MMU out of retirement during the Shuttle program?
3.Any opinion and elaboration is appreciated.
.
It was retired because there is no known use for it, not for any safety or risk reasons.
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#1846
by
Jorge
on 30 Mar, 2011 19:53
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1. With regard to the MMU retirement was it deemed too risky after Challenger because of known problems or was its retirement due to more of a general change in NASA culture becoming more risk averse?
2.Have there been any serious thoughts of bringing the MMU out of retirement during the Shuttle program?
3.Any opinion and elaboration is appreciated.
.
It was retired because there is no known use for it, not for any safety or risk reasons.
To elaborate, the MMU was originally deemed necessary because the orbiter was thought to be too cumbersome to maneuver in close proximity to spacecraft not specifically designed for it. The orbiter turns out to be more nimble than that, and all missions for the MMU *that were actually funded* could be done by a combination of maneuvering the orbiter and EVA astronauts in foot restraints (either on the tip of the RMS or, as we saw on STS-49 and 87, on the payload bay sill).
If there was ever a chance the MMU could have been revived, it would have been at the start of the ISS era when the issue of rescue during ISS stage EVAs was addressed. But the MMU was deemed too expensive for that role and the cheaper SAFER was developed instead.
Other than that, revival of the MMU has not been seriously considered.
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#1847
by
Robotbeat
on 30 Mar, 2011 20:00
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1. With regard to the MMU retirement was it deemed too risky after Challenger because of known problems or was its retirement due to more of a general change in NASA culture becoming more risk averse?
2.Have there been any serious thoughts of bringing the MMU out of retirement during the Shuttle program?
3.Any opinion and elaboration is appreciated.
.
It was retired because there is no known use for it, not for any safety or risk reasons.
To elaborate, the MMU was originally deemed necessary because the orbiter was thought to be too cumbersome to maneuver in close proximity to spacecraft not specifically designed for it. The orbiter turns out to be more nimble than that, and all missions for the MMU *that were actually funded* could be done by a combination of maneuvering the orbiter and EVA astronauts in foot restraints (either on the tip of the RMS or, as we saw on STS-49 and 87, on the payload bay sill).
If there was ever a chance the MMU could have been revived, it would have been at the start of the ISS era when the issue of rescue during ISS stage EVAs was addressed. But the MMU was deemed too expensive for that role and the cheaper SAFER was developed instead.
Other than that, revival of the MMU has not been seriously considered.
I realize this is off-topic, but has there been any thought given about using the MMU for a mission to an asteroid? Walking wouldn't be terribly practical.
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#1848
by
Jim
on 30 Mar, 2011 20:08
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If there was ever a chance the MMU could have been revived, it would have been at the start of the ISS era when the issue of rescue during ISS stage EVAs was addressed. But the MMU was deemed too expensive for that role
And too cumbersome also, I believe.
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#1849
by
Robotbeat
on 30 Mar, 2011 20:27
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I realize this is off-topic, but has there been any thought given about using the MMU for a mission to an asteroid? Walking wouldn't be terribly practical.
Huh? Are you talking about a single person strapped in an MMU and blasting off to an asteroid or an MMU being used to explore an asteroid?
If it's the former the MMU doesn't have the Delta-V - If it's the latter this scenario was depicted in a Constellation mission video.
Certainly the latter. Was this Constellation mission video
merely an artist's rendering, or was the MMU seriously analyzed for this purpose?
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#1850
by
HIPAR
on 31 Mar, 2011 16:23
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What percentage of NASA occupied floor space at KSC is shuttle specific? After the last shuttle flight, fixtures for shuttle processing will obviously become superfluous. Will they be scraped? Will the scaffolding in the vertical assembly building be dismantled and scraped?
--- CHAS
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#1851
by
Lee Jay
on 15 Apr, 2011 03:01
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If the O-ring leak on 51L had occurred in a different location such that it didn't burn through the strut, it was still going to cause an underspeed due to the loss of pressure. My question is, what would have been the result of that underspeed? ATO? AOA? TAL? I'm asking because I have a vague memory of reading about this but endless searching hasn't turned up anything and I want to know if I'm just imagining it.
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#1852
by
TFGQ
on 15 Apr, 2011 10:26
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what they should have done was goto the bolted joints by aerojet alot safer than the current design
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#1853
by
Lee Jay
on 15 Apr, 2011 13:08
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what they should have done was goto the bolted joints by aerojet alot safer than the current design
I fail to see how that answer has any relation at all to the question I posed.
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#1854
by
JayP
on 15 Apr, 2011 14:06
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If the O-ring leak on 51L had occurred in a different location such that it didn't burn through the strut, it was still going to cause an underspeed due to the loss of pressure. My question is, what would have been the result of that underspeed? ATO? AOA? TAL? I'm asking because I have a vague memory of reading about this but endless searching hasn't turned up anything and I want to know if I'm just imagining it.
As I recall, the delta P between the motors was still very small at LOS. That would imply that the motor was still generatating most of the thrust it was supposed to. Your question is one of magnitude and has a lot of unknown variables (would the leak keep getting worse and the presure in the case drop more or not? where would the vehicle be at staging in reguards to where it was supposed to be?) Without knowing those things, I don't think there is a way to determine what the final outcome would have been.
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#1855
by
Lee Jay
on 15 Apr, 2011 14:36
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If the O-ring leak on 51L had occurred in a different location such that it didn't burn through the strut, it was still going to cause an underspeed due to the loss of pressure. My question is, what would have been the result of that underspeed? ATO? AOA? TAL? I'm asking because I have a vague memory of reading about this but endless searching hasn't turned up anything and I want to know if I'm just imagining it.
As I recall, the delta P between the motors was still very small at LOS. That would imply that the motor was still generatating most of the thrust it was supposed to. Your question is one of magnitude and has a lot of unknown variables (would the leak keep getting worse and the presure in the case drop more or not? where would the vehicle be at staging in reguards to where it was supposed to be?) Without knowing those things, I don't think there is a way to determine what the final outcome would have been.
I finally found the post that might have been vague in my memory and it was from Jorge saying it might have resulted in ATO, indicating as you said that it wasn't a massive thrust difference. Of course, you are correct that we'll never know what would have happened for sure.
http://www.spacekb.com/Uwe/Forum.aspx/space-history/2411/STS51L-Accident-QuestionsIt would not be far off course. The side force was not that great compared
to the thrust of the SRBs; the issues were that 1) the torque from the side
force could have exceeded control authority, and 2) there could have been
enough underspeed at SRB sep that the SSMEs alone couldn't make it up
during second stage, resulting in an ATO.
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#1856
by
Lee Jay
on 18 Apr, 2011 03:24
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Next, realize that the ascending and descending nodes are around 12 hours apart. So, in one case you might have to sleep-shift a bit forward (earlier) during the mission to meet that timeline, in the other case you might have to sleep-shift later (by a total of up to a maximum of 12 hours), thus "earning" some extra time in the mission because you are living 25 hour days or so during the mission.
The principle is correct, but ascending and descending nodes are ~6 hours apart.
Okay, I've thought about this all day, and I don't understand why these are 6 hours apart and not 12. Can someone help me please?
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#1857
by
Jorge
on 18 Apr, 2011 03:35
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Next, realize that the ascending and descending nodes are around 12 hours apart. So, in one case you might have to sleep-shift a bit forward (earlier) during the mission to meet that timeline, in the other case you might have to sleep-shift later (by a total of up to a maximum of 12 hours), thus "earning" some extra time in the mission because you are living 25 hour days or so during the mission.
The principle is correct, but ascending and descending nodes are ~6 hours apart.
Okay, I've thought about this all day, and I don't understand why these are 6 hours apart and not 12. Can someone help me please?
They would be 12 hours apart if the landing site was on the equator. But because the landing site is around 30 degrees north latitude, it doesn't take as long for the Earth to rotate from the ascending to the descending opportunity. So about 6 hours from ascending opportunity to descending opportunity, then about 18 hours until the next ascending opportunity (and actually not even that simple, since the shuttle's crossrange capability usually allows multiple opportunities both ascending and descending).
It's a lot easier to show this with a globe and a hula hoop than to describe it verbally.
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#1858
by
wally
on 18 Apr, 2011 10:32
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Recently, while praising the shuttle, I keep hearing that she has two million moving parts. I wonder if this is true. Of course, the whole orbiter plus boosters and main tank are moving during lift-off, but I'm curios if the orbiter itself holds (around) two million moving parts relative to its center of mass (valves, relays, pistons, etc) - I won't call the windows or the wings moving parts although they clearly move during liftoff, orbital maneuvers and re-entry in respect to Earth. So, does the orbiter itself hold two million moving parts or it's just to far fetched statement?
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#1859
by
Lee Jay
on 18 Apr, 2011 12:51
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Next, realize that the ascending and descending nodes are around 12 hours apart. So, in one case you might have to sleep-shift a bit forward (earlier) during the mission to meet that timeline, in the other case you might have to sleep-shift later (by a total of up to a maximum of 12 hours), thus "earning" some extra time in the mission because you are living 25 hour days or so during the mission.
The principle is correct, but ascending and descending nodes are ~6 hours apart.
Okay, I've thought about this all day, and I don't understand why these are 6 hours apart and not 12. Can someone help me please?
They would be 12 hours apart if the landing site was on the equator.
While I was lying in bed late last night, I was wondering if that might be the case.
Let me try to paraphrase to see if I've got this. The ascending node is going to move largely from South-West to North-East while the descending node is going to move largely from West to East. This means the descending node is going to travel a lot farther East from initiation than the ascending node is, and this is because of the latitude of the landing site and because of the inclination of the orbit. So, to extremely simplify, the ascending node is going from the bottom of the sine wave to the top (looking on a flat map instead of a globe), while the descending node is going from a little left of the top peak of the sine wave to a little right of the top peak.
As always, thanks for the help, Jorge.