Thrust
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Why Skylab Failed On Its Launch

Tue Sep 06, 2011 7:13 pm

I'm basically trying to figure out whether the Skylab 1 disaster was caused by the design of Skylab itself, or if the Saturn V was just an extremely bad choice for launching it. Someone I was discussing with claimed the G forces of a Saturn V launch were too extreme for it to handle.
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nomadd22
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RE: Why Skylab Failed On Its Launch

Tue Sep 06, 2011 7:38 pm

The meteoroid shield deployed while the launcher was still thrusting and ripped one of the solar arrays loose and blocked the other from deploying. I never was clear if it was a failed latch or a command that caused the deployment.
I'd call it a malfunction. If it was a disaster there wouldn't have been three successful Manned missions. NASA tends to be at it's best when it has potential disaster to fix.
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rwessel
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RE: Why Skylab Failed On Its Launch

Tue Sep 06, 2011 11:21 pm

Quoting Thrust (Thread starter):
I'm basically trying to figure out whether the Skylab 1 disaster was caused by the design of Skylab itself, or if the Saturn V was just an extremely bad choice for launching it.

And just what, pray tell, would NASA have used to launch a 170,000lb space station if not the S-V? (Given that the "wet" S-IVB/lab concept had been abandoned at that point).

And honestly, just how stupid do you think the guys at NASA are? Sure they can screw up like everyone else, but how can even imagine that they didn't consider the launch stresses? That's utterly fundamental. Do you think they built it, and said, "hmmm... lets put it on an S-V and see what happens!" Seriously?

That being said, it's never been clear why the micrometeoroid shield deployed a minute into the flight. Best guesses are a faulty latch allowing the cover to come off in flight, or a spurious signal from the control system causing the latches to release.
 
mffoda
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RE: Why Skylab Failed On Its Launch

Wed Sep 07, 2011 12:44 am

Quoting rwessel (Reply 2):
And just what, pray tell, would NASA have used to launch a 170,000lb space station if not the S-V?

I agree rwessel... But don't you think you're being a little hard on the beaver?
 
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Thrust
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RE: Why Skylab Failed On Its Launch

Wed Sep 07, 2011 8:16 pm

Quoting rwessel (Reply 2):

Forgive me if I miscommunicated that I actually believed the Saturn V was a bad choice. I think the Saturn V was a perfect choice. Somebody on youtube was trying to convince me otherwise, so I came on here hoping that the "voice of reason" would explain that away, because while I was fairly certain I could explain it away, I needed a second opinion. No, I don't think NASA was that incompetent, and no, I don't think NASA just bet tons of money on a gamble.
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rwessel
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RE: Why Skylab Failed On Its Launch

Wed Sep 07, 2011 10:51 pm

Quoting Thrust (Reply 4):
Forgive me if I miscommunicated that I actually believed the Saturn V was a bad choice. I think the Saturn V was a perfect choice. Somebody on youtube was trying to convince me otherwise, so I came on here hoping that the "voice of reason" would explain that away, because while I was fairly certain I could explain it away, I needed a second opinion. No, I don't think NASA was that incompetent, and no, I don't think NASA just bet tons of money on a gamble.

My apologies, I appear to have read more into your post than was intended.

Skylab was a modified S-IVB, which had obviously flown a number of times as part of the S-V stack. The original plan was to launch it on an S-IC, and actually have it an active stage – hence the metal mesh floors to avoid blocking the flow of fuel inside the “fuel tanks”. In the end it lost its J-2 and associated gear, and was flown dry instead.

To be sure, much of the stuff they bolted to the outside was new, and obviously some of that (specifically the shroud) failed. But the notion that "forces of a Saturn V launch were too extreme for it to handle" are a bit silly. The S-V didn't have particularly high G forces (as evidenced by humans flying on it), nor particularly high aerodynamic stresses or vibration levels. It was just particularly large.

As a general rule, nobody builds spacecraft boosters* with excessive values of any of those, for the simple fact that the payload needs to survive the trip to orbit. Sure, you could build a launch vehicle that hit 20G on the way up (and all other things being equal, that might well reduce the required size of the booster), but think of the enormous structural penalties that would bring.


*Not necessarily true for ICBMs
 
connies4ever
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RE: Why Skylab Failed On Its Launch

Sat Sep 10, 2011 12:04 am

Quoting rwessel (Reply 5):
To be sure, much of the stuff they bolted to the outside was new, and obviously some of that (specifically the shroud) failed. But the notion that "forces of a Saturn V launch were too extreme for it to handle" are a bit silly. The S-V didn't have particularly high G forces (as evidenced by humans flying on it), nor particularly high aerodynamic stresses or vibration levels. It was just particularly large.

I tend to think the Apollo 2 and 13 launches were near failures due to vibration - the 'pogo effect'. In fact on 13 the S-II centreline engine cut out during ascent and they had to burn the outer units a little longer.
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zanl188
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RE: Why Skylab Failed On Its Launch

Sat Sep 10, 2011 10:45 am

Quoting connies4ever (Reply 6):
I tend to think the Apollo 2 and 13 launches were near failures due to vibration - the 'pogo effect'. In fact on 13 the S-II centreline engine cut out during ascent and they had to burn the outer units a little longer.

That would be Apollo 6 that had two engines out on the S-II not Apollo 2
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connies4ever
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RE: Why Skylab Failed On Its Launch

Sat Sep 10, 2011 1:18 pm

Quoting ZANL188 (Reply 7):
That would be Apollo 6 that had two engines out on the S-II not Apollo 2

My bad, you're correct.   
Nostalgia isn't what it used to be.
 
Thrust
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RE: Why Skylab Failed On Its Launch

Mon Sep 12, 2011 2:44 am

Quoting rwessel (Reply 5):

Apology accepted. Thanks for your input. Learned something about g forces.
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Thrust
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RE: Why Skylab Failed On Its Launch

Mon Sep 12, 2011 3:01 am

Quoting connies4ever (Reply 6):

As I recall, Apollo 6 also had engine failures due not only to pogo the way some of the systems were hooked up..I'm not certain of exactly what it was, but I remember somebody on here mentioning it...something like fuel lines or something like it. I thought that some of the SII's systems were reworked or redesigned slightly after Apollo 6 and that the way they were hooked up contributed partially to engine failure in addition to pogo effect. This could be wrong, so if it is, feel free to correct me. Other than that, I'm not sure what else was done to fix the pogo problem. Whatever was done, if anything, it appears it obviously didn't work since it reoccured on Apollo 13. But after Apollo 13, I thought the pogo problem was fixed for good. It was never an issue on the next 4 launches to my knowledge.
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Areopagus
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RE: Why Skylab Failed On Its Launch

Tue Sep 13, 2011 11:01 pm

I recall reading long ago that due to budget cuts, the Skylab design was not wind-tunnel tested as much as it should have been, and it was air loads that caused the failures.

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