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#1180
by
Robotbeat
on 17 May, 2010 22:19
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#1181
by
JayP
on 18 May, 2010 02:44
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Early 1990s, went from the AP-101B to the AP-101S, binary-compatible with the old GPC, has the I/O Processor (IOP) integrated into the GPC case, twice as much memory (enables the entry software to be stored in an upper-memory archive for quick recall in case of emergency deorbit), solid state memory instead of core.
I remember reading someware once that after the Challenger accident, they were able to reconstruct some of the data from the GPCs memory. The ferrite core cells maintained its magnetized state after the power failed. That wouldn't happen with modern, solid state memory.
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#1182
by
Chandonn
on 18 May, 2010 02:56
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Early 1990s, went from the AP-101B to the AP-101S, binary-compatible with the old GPC, has the I/O Processor (IOP) integrated into the GPC case, twice as much memory (enables the entry software to be stored in an upper-memory archive for quick recall in case of emergency deorbit), solid state memory instead of core.
I remember reading someware once that after the Challenger accident, they were able to reconstruct some of the data from the GPCs memory. The ferrite core cells maintained its magnetized state after the power failed. That wouldn't happen with modern, solid state memory.
I hadn't heard that about Challenger, but I believe they were able to reconstruct some of the last moments of Columbia in that manner.
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#1183
by
Jorge
on 18 May, 2010 03:35
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Early 1990s, went from the AP-101B to the AP-101S, binary-compatible with the old GPC, has the I/O Processor (IOP) integrated into the GPC case, twice as much memory (enables the entry software to be stored in an upper-memory archive for quick recall in case of emergency deorbit), solid state memory instead of core.
I remember reading someware once that after the Challenger accident, they were able to reconstruct some of the data from the GPCs memory. The ferrite core cells maintained its magnetized state after the power failed. That wouldn't happen with modern, solid state memory.
I hadn't heard that about Challenger, but I believe they were able to reconstruct some of the last moments of Columbia in that manner.
No, he's right, Challenger's GPC memory could be partially reconstructed, but Columbia's could not. The Columbia reconstructions were done using the MADS recorder and a couple of bursts of downlist data that were recorded at White Sands but rejected at Houston in realtime because they failed the quality tests.
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#1184
by
MP99
on 19 May, 2010 19:45
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Question from Chris's article at
http://www.nasaspaceflight.com/2010/05/sts-132-atlantis-sunday-docking-extremely-clean-et-136/.
“No problems or issues were noted during the ascent phase,” listed the official MER report. “The Reusable Solid Rocket Booster (RSRB) shutdown occurred at 134/18:22:09 GMT [00/00:02:06 Mission Elapsed Time (MET)] and the separation was visible.
“A nominal Orbital Maneuvering System (OMS) assist maneuver was performed following SRB separation. Ignition occurred at 134/18:22:24.3 GMT (00/00:02:16 MET, and the maneuver was 90.2 sec in duration. MECO occurred at 134/18:28:34 GMT (00/00:08:32 MET).
What is this OMS assist maneuver, and under what circumstances would it be required?
Many thanks, Martin
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#1185
by
alexw
on 19 May, 2010 20:05
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What is this OMS assist maneuver, and under what circumstances would it be required?
Many thanks, Martin
The OMS engines fire during second-stage flight as additional thrust. In effect, the shuttle is both a hydrolox and hypergolic rocket at that point. The effect is quite small, naturally, but apparently it adds a little extra mass delivered to ISS, part of seeking to maximize every bit of performance out of STS.
A while back, someone mentioned (IIRC) that this was controversial when first proposed, operating both MPS and OMS simultaneously adding risk?
-Alex
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#1186
by
aurora899
on 19 May, 2010 20:46
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What is this OMS assist maneuver, and under what circumstances would it be required?
Many thanks, Martin
The OMS engines fire during second-stage flight as additional thrust. In effect, the shuttle is both a hydrolox and hypergolic rocket at that point. The effect is quite small, naturally, but apparently it adds a little extra mass delivered to ISS, part of seeking to maximize every bit of performance out of STS.
A while back, someone mentioned (IIRC) that this was controversial when first proposed, operating both MPS and OMS simultaneously adding risk?
-Alex
Yes, wasn't Mike Mullane tasked to work on it and he found himself being bitterly opposed by John Young? Mullane refers to it in "Riding Rockets" I think.
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#1187
by
brahmanknight
on 20 May, 2010 01:09
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What is this OMS assist maneuver, and under what circumstances would it be required?
Many thanks, Martin
The OMS engines fire during second-stage flight as additional thrust. In effect, the shuttle is both a hydrolox and hypergolic rocket at that point. The effect is quite small, naturally, but apparently it adds a little extra mass delivered to ISS, part of seeking to maximize every bit of performance out of STS.
A while back, someone mentioned (IIRC) that this was controversial when first proposed, operating both MPS and OMS simultaneously adding risk?
-Alex
Yes, wasn't Mike Mullane tasked to work on it and he found himself being bitterly opposed by John Young? Mullane refers to it in "Riding Rockets" I think.
Affirmative, it was described in Mike Mullane's book.
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#1188
by
MP99
on 20 May, 2010 06:43
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Many thanks for all the answers.
cheers, Martin
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#1189
by
elmarko
on 20 May, 2010 09:21
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I always wondered why they didn't just not load that OMS propellant, I wasn't sure whether the extra thrust produced outweighed the amount of OMS that was burnt.
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#1190
by
KelvinZero
on 20 May, 2010 11:35
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I just had a throw away question not important enough for its own thread.
I was thinking of an Ares 1-like rocket, but where the second stage is positioned so that it can also contribute to the thrust during lift off, throttling back to keep acceleration constant as total mass drops, and then is restarted or throttled up when the first stage drops away.
However this would put the exhaust of the second stage, being on top, rather close to the solid first stage. I was wondering if that was acceptable for solid rockets or rules this idea out. Also I was wondering what seriously considered plans most resembled this.
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#1191
by
Jim
on 20 May, 2010 11:59
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I just had a throw away question not important enough for its own thread.
I was thinking of an Ares 1-like rocket, but where the second stage is positioned so that it can also contribute to the thrust during lift off, throttling back to keep acceleration constant as total mass drops, and then is restarted or throttled up when the first stage drops away.
However this would put the exhaust of the second stage, being on top, rather close to the solid first stage. I was wondering if that was acceptable for solid rockets or rules this idea out. Also I was wondering what seriously considered plans most resembled this.
Side mount SDLV
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#1192
by
iskyfly
on 20 May, 2010 13:41
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I always wondered why they didn't just not load that OMS propellant, I wasn't sure whether the extra thrust produced outweighed the amount of OMS that was burnt.
i seem to remember that very questioned was asked, answered and discussed somewhere on here....
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#1193
by
iskyfly
on 20 May, 2010 13:47
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There was a "Fail to sync" of GPC @ on the first free flight of Enterprise, it occured right at separation from the SCA (747).
If you look on this site (NSF) you should be able to find the ALT Program Flight Test results document (I don't know the exact title) and it should go into a lot of detail on what happend. If it is not here you might try the NASA Tech Reports server.
Mark Kirkman
Many thanks to everyone who responded to this. According to this;
http://klabs.org/DEI/Processor/shuttle/alt_gpc2/index.htmIt was a solder problem;
However, the problem was reproduced at the vendor's facility when the flight unit (input-output processor, serial number 7) was subjected to low-level vibration testing at 0.01 g2/Hz. Subsequent inspection revealed a solder crack at a prom lead on the queue page (fig. 7-3). The solder had failed to wick in a plated-through hole. The unit had been acceptance tested at 0.04 g2/Hz after 1848 hours of field run time.
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#1194
by
tminus9
on 20 May, 2010 14:59
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When is the inclination correction made, and how does the real shuttle does that?
The shuttle launches in-plane with ISS, so no "inclination correction" maneuver is necessary. There is a placeholder for a planar correction burn (NPC) on flight day 2, but it is normally only needed to take out dispersions.
I have a few related questions about rendezvous and ascent G&C, specifically about the target orbital plane.
I read in the Ascent Guidance and Flight Control Workbook (in L2, I believe) that the I-loaded target orbital plane (IY) is defined by the longitude of the ascending node and the inclination. Are these specified relative to M50?
I assume the IY values are based on the longitude of the ascending node and inclination of the ISS orbit. If so, are they based on those values at T-0 or is it more complicated than that?
The layman's explanation of selecting T-0 is that it is the moment when the ISS plane passes directly above the launch site, but I have a feeling that's the simplified version. Nodal regression rates differ by altitude and inclination, and the shuttle generally orbits at a lower altitude until rendezvous. Therefore, I would guess that in order to match the ISS plane at rendezvous, the orbiter's initial plane would have to be slightly different. How is this difference accounted for (i.e., how is IY calculated, given the ISS orbital elements)? Are there any other factors that affect the calculation of IY? In practice, how different is IY from the ISS plane at T-0?
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#1195
by
sivodave
on 20 May, 2010 15:17
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Does anybody know if it has ever been a mission in which they had problems in opening/closing the payload bay doors? Furthermore do you know if there is any document explaining how the payload bay can be closed by means of EVA? I remember reading in Skywalking that Tom Jones briefly describe the procedure but I don't have the book with me and anyway I'd like to read some document explaining this contingency EVA in more details.
Thanks
Davide
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#1196
by
Jim
on 20 May, 2010 15:26
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Does anybody know if it has ever been a mission in which they had problems in opening/closing the payload bay doors? Furthermore do you know if there is any document explaining how the payload bay can be closed by means of EVA? I remember reading in Skywalking that Tom Jones briefly describe the procedure but I don't have the book with me and anyway I'd like to read some document explaining this contingency EVA in more details.
STS-3
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#1197
by
Jorge
on 20 May, 2010 16:05
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When is the inclination correction made, and how does the real shuttle does that?
The shuttle launches in-plane with ISS, so no "inclination correction" maneuver is necessary. There is a placeholder for a planar correction burn (NPC) on flight day 2, but it is normally only needed to take out dispersions.
I have a few related questions about rendezvous and ascent G&C, specifically about the target orbital plane.
I read in the Ascent Guidance and Flight Control Workbook (in L2, I believe) that the I-loaded target orbital plane (IY) is defined by the longitude of the ascending node and the inclination. Are these specified relative to M50?
Yes, M50 is the standard inertial frame used by the shuttle. IY is defined by the ascending node and inclination, but internally it is represented by a unit vector normal to the plane, in the opposite direction of orbital angular momentum.
I assume the IY values are based on the longitude of the ascending node and inclination of the ISS orbit. If so, are they based on those values at T-0 or is it more complicated than that?
The layman's explanation of selecting T-0 is that it is the moment when the ISS plane passes directly above the launch site, but I have a feeling that's the simplified version. Nodal regression rates differ by altitude and inclination, and the shuttle generally orbits at a lower altitude until rendezvous. Therefore, I would guess that in order to match the ISS plane at rendezvous, the orbiter's initial plane would have to be slightly different. How is this difference accounted for (i.e., how is IY calculated, given the ISS orbital elements)? Are there any other factors that affect the calculation of IY? In practice, how different is IY from the ISS plane at T-0?
IY targets a "phantom plane" that will regress into the ISS orbital plane by the time of the planned rendezvous. It will vary based on the phase angle between the shuttle and ISS because large phase angles require lower altitudes to catch up by a given time, while small phase angles require higher altitudes.
IY is uplinked by FDO on launch day and represents the phantom plane at the opening of the launch window. As the launch slips, the phase angle changes and the target orbit plane regresses, and so a new IY is computed onboard at SRB ignition using the node slope equation.
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#1198
by
sdsds
on 20 May, 2010 16:50
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an Ares 1-like rocket, but where the second stage is positioned so that it can also contribute to the thrust during lift off, [putting] the exhaust of the second stage, being on top, rather close to the solid first stage. [...] what seriously considered plans most resembled this.
Side mount SDLV
KelvinZero seems to be suggesting an in-line arrangement, where the second stage (ground-started) SSMEs are turned outward (presumably on gimbals) such that their exhaust plumes pass by the first stage. Could the SRB continue to function safely in the periphery of the SSME exhaust plumes? What about in the extreme case where the gimbals point the throttled back SSMEs out at 90 degrees during the first stage of flight?
Tractor-style abort motors do something like this, don't they?
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#1199
by
Jorge
on 20 May, 2010 17:22
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an Ares 1-like rocket, but where the second stage is positioned so that it can also contribute to the thrust during lift off, [putting] the exhaust of the second stage, being on top, rather close to the solid first stage. [...] what seriously considered plans most resembled this.
Side mount SDLV
KelvinZero seems to be suggesting an in-line arrangement, where the second stage (ground-started) SSMEs are turned outward (presumably on gimbals) such that their exhaust plumes pass by the first stage.
Incredibly wasteful due to cosine losses on the thrust, would require additional weight for TPS to protect from plume impingement.
What about in the extreme case where the gimbals point the throttled back SSMEs out at 90 degrees during the first stage of flight?
One SSME failure = instant LOC due to pitch rate and excessive side loads on vehicle. You wouldn't be able to shut the opposing engine down prior to loss of control/breakup.
Tractor-style abort motors do something like this, don't they?
Yes. They don't need to be efficient, just high thrust, and they don't impinge on the launch vehicle throughout the entire first stage like this design does.
