Author
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Topic: Did canceling Apollo 18 prevent an abort?
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Maia12 Member Posts: 11 From: Portugal Registered: Nov 2015
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posted 10-07-2018 06:40 PM
As we know, the Skylab Saturn V was originally assigned to Apollo 18. That being said, the extreme vibrations during the launch phase wouldn't trigger an abort? I believe reading somewhere that if the Saturn V was manned, there were no way the mission control would let the crew fly on such conditions. |
SkyMan1958 Member Posts: 880 From: CA. Registered: Jan 2011
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posted 10-07-2018 08:08 PM
The Skylab Saturn V performed just fine. It was the highly modified S-IVB third stage that had the issue. |
Maia12 Member Posts: 11 From: Portugal Registered: Nov 2015
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posted 10-08-2018 08:38 AM
Joe Kerwin, in the documentary "When We Left Earth: Part 4," said that at launch there was a sudden acceleration. This couldn't cause the vibrations? And if the launch was manned, trigger an abort? I know that most of the problems were caused by the loss of the micrometeroid shield that ripped off a solar array and prevented the jettisoning of S-IC/S-II interstage. |
Space Cadet Carl Member Posts: 225 From: Lake Orion, Michigan Registered: Feb 2006
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posted 10-08-2018 11:38 AM
You probably won't believe it, but before Skylab's launch I honestly wondered how they were possibly going to be able to keep that shield intact during launch phase. |
holcombeyates Member Posts: 253 From: UK Registered: Dec 2010
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posted 10-08-2018 11:46 AM
Or do you mean had the interstage skirt remained attached AND it was a lunar bound mission would an abort have been commanded?
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Maia12 Member Posts: 11 From: Portugal Registered: Nov 2015
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posted 10-08-2018 03:59 PM
No, I was referring the sudden acceleration that Joe Kerwin mentioned which caused the vibrations. If it was a lunar mission and the interstage remained attached, I believe they would abort. |
oly Member Posts: 971 From: Perth, Western Australia Registered: Apr 2015
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posted 10-08-2018 09:27 PM
At the 39 minute time stamp of this video, Kerwin states that there had been a G-Shock, a sudden acceleration. The accelerations referred to were recorded by the X and Y axis accelerometers, caused by the aerodynamic disturbances that as the OWS meteoroid shield became detached torn from the structure at T+63 seconds. Here is the post mission report for anyone wanting a long read. The acceleration was not a "POGO" type acceleration, it was a non commanded roll of 2.2 degrees/second that lasted 0.09 seconds. Not a significant event, and non actionable by the Saturn LVDC, which only samples such accelerations each second. There were no high amplitudes. Another vibration was recorded at T+593 seconds caused by the partially deployed SAS Wing No. 2 being rotated past its fully deployed position and torn from its hinges by impingement from the S-II retro motor plume. Here is an abbreviated review of the events. As stated by the report, "The origin of these anomalies was in a unique payload and external to the launch vehicle; therefore, no launch vehicle corrective action is necessary." There were no "extreme" vibrations, and nothing that would have caused an Apollo 18 abort, because the issue was with the Skylab structure, not the Saturn V. |
Maia12 Member Posts: 11 From: Portugal Registered: Nov 2015
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posted 10-09-2018 07:34 AM
It seems that this issue is settled then. Thank you all.It would be interesting if the hypothetical launch of Skylab B would also go through the same. |
Fra Mauro Member Posts: 1624 From: Bethpage, N.Y. Registered: Jul 2002
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posted 10-09-2018 08:13 AM
Very interesting topic. I'm sure that if there was a Skylab B, corrections would have been made to the wings and station to prevent another mishap. Sounds like a design flaw.It's ironic how the report states that no changes to the vehicle are necessary since it was the last Saturn V. |
Maia12 Member Posts: 11 From: Portugal Registered: Nov 2015
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posted 10-09-2018 09:06 AM
It is incredible that despite all these shortcomings, they have managed to make the station operational and complete three successful missions. I mean, looking at the report, Skylab was on the verge of being a complete failure.Since Skylab B was identical to Skylab A, I believe the redesign was impossible. They would probably have to find some better way to hold the meteoroid shield in it's place As for the part of the report that says there is no need to make changes to the launch vehicle, when the report was written (July 1973), there was still some hope of flying Skylab B. The cancellation of Skylab's backup capacity was given in August 1973. |
Jim Behling Member Posts: 1488 From: Cape Canaveral, FL Registered: Mar 2010
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posted 10-09-2018 09:29 AM
quote: Originally posted by Maia12: They would probably have to find some better way to hold the meteoroid shield in it's place
That would be the "redesign."
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Maia12 Member Posts: 11 From: Portugal Registered: Nov 2015
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posted 10-09-2018 02:12 PM
You're right. But I took the word "redesign" in the sense of major modification to the station. |
oly Member Posts: 971 From: Perth, Western Australia Registered: Apr 2015
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posted 10-09-2018 09:57 PM
Any potential modification may not be a major item necessarily. If the shield detachment was a failure of the strength of a retaining device or local structure, it may just require a material change or some reinforcement.It may simply have been a case of positive locking or latching, or the shield design may not have been structurally up to the task. As indicated by others, hindsight shows the design was lacking. I doubt NASA would have attempted another launch without putting in place some tested design improvements, they may not have been significant changes. But it was never to be. |
Space Cadet Carl Member Posts: 225 From: Lake Orion, Michigan Registered: Feb 2006
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posted 10-11-2018 05:16 AM
quote: Originally posted by oly: It may simply have been a case of positive locking or latching, or the shield design may not have been structurally up to the task.
I competed in the Skylab Student Project contest in high school and was sent a very detailed wall poster of Skylab before launch for my submitting to NASA. The wall poster clearly showed the micrometeoroid shield was spaced outward a few inches away from the main body of Skylab. When I looked at that poster, I honestly wondered how that shield was staying intact during launch. |
oly Member Posts: 971 From: Perth, Western Australia Registered: Apr 2015
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posted 10-11-2018 05:42 AM
It would be great to see a copy of the poster you received way back when. It has been documented that the shield sat proud of the structure, many people have passed comment over the years stating it looked unusual. Somewhere along the way the design passed the checks and balances required to make it to the launch pad.Previous posts regarding the shield here cover the basic design, why it failed and what could be done to prevent it is mute these days, we will never know for sure. It would have been great to see something like this. |
Blackarrow Member Posts: 3160 From: Belfast, United Kingdom Registered: Feb 2002
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posted 10-11-2018 09:49 AM
quote: Originally posted by oly: As indicated by others, hindsight shows the design was lacking...
On 20th May, 1973, the London "Sunday Times" reported at length on the Skylab launch problems, quoting Chris Kraft, then director of JSC, as stating that the micrometeoroid shield had proved troublesome during testing at KSC and that there had been a "great battle" about whether it should be fitted at all. The same report quoted NASA's own estimate that the MMS "increased the chance of a successful mission by seven-tenths of one per cent."Between school and university, and after the successful salvaging of Skylab, I wrote to NASA to ask why such a flimsy and controversial component had been added to Skylab for such a (relatively) small increase in the chance of mission success. I received a long, two-page typed reply, signed by John Disher, Deputy Director of the Skylab Program, which addressed all of the points I had made. Some extracts: The principal reason for the OWS meteoroid shield was to decrease the probability of meteoroids penetrating the OWS... The probability of such a penetration during the planned overall Skylab Program was only 0.995 (five out of 1000 programs) with the shield but it is up to about 0.95 without the shield... It would have been ten times as safe with the shield."The meteoroid shield was designed basically as an 0.025 inch thick aluminum band fitted tightly around the outside of the OWS for launch, and then deployed to a 5-inch stand-off position in orbit. As such a tight band, the shield was not a flimsy device and actually added strength to the stage tank-wall. There were flanges fore and aft to provide support and keep out the slipstream. It was an oversight of design detail that allowed airflow to occur in the auxiliary tunnel that induced a pressure differential that raised the shield into the airstream where it was torn off. We do not consider that our micrometeoroid shield failure was due to "wrong decisions" but rather to lapse in communication between the structural designers and the aerodynamicists. Unfortunately, Chris Kraft makes no comment in his book, "Flight", about that "great battle" over the MMS. |
oly Member Posts: 971 From: Perth, Western Australia Registered: Apr 2015
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posted 10-11-2018 10:41 AM
Wow, great information to have. As you have stated, the shield deployed because airflow forced the edge into the slipstream. This may not have occurred if the shield structure were of a different design or the latching mechanism design prevented the shield distortion. As I mentioned, it has been commented on by many that the design was lacking (see results) but the engineers considered the items to be important enough to design, construct and install. |
Blackarrow Member Posts: 3160 From: Belfast, United Kingdom Registered: Feb 2002
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posted 10-12-2018 10:59 AM
I felt flattered to receive such a long and careful reply. After all, I wasn't an American taxpayer! I was never quite sure whether the reply indicated some sensitivity in the Skylab office about press criticisms, or just a very diligent manager giving a thoughtful answer to someone who was obviously keen on space research. Probably a bit of both. I suspect that today the inquirer would get a standard email reply along the lines of: "Thank you for your enquiry. Your correspondence is very important to us. We appreciate your interest in NASA." |