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#520
by
STS-500Cmdr
on 12 Dec, 2006 23:13
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Sort of an answer to your question, and for a similiar common Q about why they are commander and pilot--This started when we started flying spacecraft with 2 or more people--starting with Project Gemini--after we had the 1-man Mercury--we had Gemini and we had to have titles for the people---as you can imagine astronauts back then and still do--have huge egos--we need big spacecraft just for their egos--anyway the natural titles would be pilot and co-pilot--no one in the astronaut corp wanted to be called co-pilot--hurts the the guy's ego--especially back in the glory days when these guys were driving around in the Corvettes and buzzing low over the space center in their T-38s, walkin around with the sunglasses, etc I wonder if astronauts still drive around in Corvettes these days
BTW--that sound is the APUs usually hear it a few seconds after the PLT starts them--sometimes you dont hear it for some reason. But i love that sound--it sounds like shes alive--give the shuttle that much more personality to it.
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#521
by
psloss
on 12 Dec, 2006 23:49
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psloss - 12/12/2006 6:41 PM
The noise I'm referring to occurs "once" more or less -- right at T-4 minutes, which is why I always associated with the GLS milestone and call from the console operator that followed it...I'll see if I can pull together a few audio clips.
It doesn't sound to me like the APUs, but that's why I'm curious, because it doesn't sound to me like the APUs.
Commentary or just not having the sound at the pad mixed that high often makes it hard to hear this sound or inaudible to me.
Actually not that difficult to find a few examples of what I'm hearing, but even as audio clips they're too big to attach here, so I'll see about posting the video excerpts on L2 in a little bit and seeing if you folks can identify what the sound is...
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#522
by
Austin
on 13 Dec, 2006 02:58
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psloss - 12/12/2006 4:32 PM
psloss - 12/12/2006 6:41 PM
The noise I'm referring to occurs "once" more or less -- right at T-4 minutes, which is why I always associated with the GLS milestone and call from the console operator that followed it...I'll see if I can pull together a few audio clips.
It doesn't sound to me like the APUs, but that's why I'm curious, because it doesn't sound to me like the APUs.
Commentary or just not having the sound at the pad mixed that high often makes it hard to hear this sound or inaudible to me.
Actually not that difficult to find a few examples of what I'm hearing, but even as audio clips they're too big to attach here, so I'll see about posting the video excerpts on L2 in a little bit and seeing if you folks can identify what the sound is...
I assume you're referring to the continous "shuck-shuck, shuck-shuck" heard around the T-4 minute mark. It is definitely the APUs. I always wondered, though, why it takes a full minute for them to be audible, when the PLT starts them at T-5. I have always assumed that it took several seconds for them to power up, hence the delay in the sound being audible.
Mr. Copella, if you're around, can you confirm, sir?
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#523
by
psloss
on 13 Dec, 2006 03:06
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Austin - 12/12/2006 10:41 PM
I assume you're referring to the continous "shuck-shuck, shuck-shuck" heard around the T-4 minute mark.
No, the chugging of the APUs can be heard before, during, and after the noise I'm referring to...
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#524
by
Austin
on 13 Dec, 2006 03:10
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psloss - 12/12/2006 7:49 PM
Austin - 12/12/2006 10:41 PM
I assume you're referring to the continous "shuck-shuck, shuck-shuck" heard around the T-4 minute mark.
No, the chugging of the APUs can be heard before, during, and after the noise I'm referring to...
Hmm....you've got me stumped then.
If you find a launch video where the sound is particularly noticeable, post it if you would. I'm curious now.
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#525
by
psloss
on 13 Dec, 2006 03:14
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Austin - 12/12/2006 10:53 PM
Hmm....you've got me stumped then.
If you find a launch video where the sound is particularly noticeable, post it if you would.
We're working on it...bad timing on my part, though, since the staff and some of the regulars here are busy covering STS-116.
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#526
by
Austin
on 13 Dec, 2006 03:20
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Copy...Thanks!
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#527
by
mkirk
on 13 Dec, 2006 14:01
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Austin - 12/12/2006 9:41 PM
I always wondered, though, why it takes a full minute for them to be audible, when the PLT starts them at T-5. I have always assumed that it took several seconds for them to power up, hence the delay in the sound being audible.
Yes, it does take a few seconds to throw all of the switches and to get the APUs up to speed…initially for STS-1 & 2 the Pilot would start each APU 1 at a time (in serial) but that procedure was changed because it took too long. Beginning with STS-3 the APU start procedure was changed to a parallel operation where all three APUs are started together.
The APUs are started as late in the count as possible to conserve fuel but early enough to have the hydraulics up and checked before some of the other countdown events such as the aero surface and engine gimbal movement checks are performed.
The GLS (ground launch sequencer) will verify the APU Prestart is complete at T-5 minutes 25 seconds and that the actual APU start is complete at T-4 minutes 5 seconds, if they are not then a hold in the countdown will occur.
A certain PLT (pilot) found this out the hard way and in a very public manner a few years back. I don’t want to mention “ANDY ALLEN” by name or anything, but during the countdown for STS-46 he didn’t get all of the switches configured quickly enough during the APU Prestart and the countdown stopped at T-5 minutes for an unplanned hold of about 48 seconds…OOPS!!
The APU Prestart used to begin at T-6 minutes but now the procedure begins at T-6 minutes 15 seconds which provides a few extra seconds to check all of those switches.
Mark Kirkman
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#528
by
Austin
on 13 Dec, 2006 14:52
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Mark, much obliged for your always knowledgeable posts!
Figured that was the case with the APUs. I just didn't know if the "delay" (in hearing them) was due to the amount of time required for them to power-up or for the PLT to complete switch configurations. Now I know its the latter.
I had never heard that about Andy Allen...but he did go on to command STS-62 so luckily for him, it wasn't a career-stopper. Also lucky for him...the PAO didn't not say something to the effect, "We will be holding the count at T-5 minutes to allow PLT ANDY ALLEN (echoing across the Cape -- allen, allen, allen) time to complete APU prestart switch configuration.
But seriously, I remember that during the ascent on STS-62, several seconds after the roll program, he radioed, "we're showing, uh, 45 percent on the left." (yes, sad that I actually remember these things). I don't remember the reason for the anomally (false SRB chamber pressure reading, perhaps?) but he seemed to handle it well. So if you happen upon this post, Andy we're just funnin' ya!
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#529
by
psloss
on 13 Dec, 2006 15:08
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Austin - 13/12/2006 10:35 AM
But seriously, I remember that during the ascent on STS-62, several seconds after the roll program, he radioed, "we're showing, uh, 45 percent on the left."
That was STS-75 -- he was CDR. It was a main engine Pc tape meter...
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#530
by
mkirk
on 13 Dec, 2006 15:09
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Austin - 13/12/2006 9:35 AM
But seriously, I remember that during the ascent on STS-62, several seconds after the roll program, he radioed, "we're showing, uh, 45 percent on the left." (yes, sad that I actually remember these things). I don't remember the reason for the anomally (false SRB chamber pressure reading, perhaps?) but he seemed to handle it well. So if you happen upon this post, Andy we're just funnin' ya!
I believe you are thinking about STS-75 with Andy as Commander and Doc Horowitz as Pilot.
The SSME PC (chamber pressure gauge) was showing around 45 percent at liftoff. Actual thrust was okay, the indicator was just scaled (calibrated) incorrectly.
I forget how it came up but Doc mentioned it at the SRB test last month and said from his persepective he was expecting a pad abort...then suddenly they were flying.
I was at that launch and when I heard the call I thought that such a low percentage shouldn't even be possible (not stable...hell idle is 67%) and then I thought I was about to see an abort until I heard MCC acknowledge the call from the crew by saying that they showed the engine running fine.
Mark Kirkman
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#531
by
psloss
on 13 Dec, 2006 15:17
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mkirk - 13/12/2006 10:52 AM
I believe you are thinking about STS-75 with Andy as Commander and Doc Horowitz as Pilot.
The SSME PC (chamber pressure gauge) was showing around 45 percent at liftoff. Actual thrust was okay, the indicator was just scaled (calibrated) incorrectly.
I forget how it came up but Doc mentioned it at the SRB test last month and said from his persepective he was expecting a pad abort...then suddenly they were flying.
I'm getting deja vu on this...if I recall correctly, they also got a temporary amber light on the engine shortly after liftoff (command path issue). There's also an old Florida Today interview floating in "webspace" with Andy Allen about this.
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#532
by
psloss
on 13 Dec, 2006 15:29
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#533
by
Fred Clausen
on 13 Dec, 2006 15:41
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I hope I am not posting a duplicate question.
I am curious how the shuttle missions get numbered? Why is this mission currently flying STS 116 when it is the 117th shuttle mission (I think I caught that bit of trivia from NTV, I could be wrong), and why has STS 121 flown before 116? They don't seem to be going in order, and it is not based on how many shuttle missions have flown before.
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#534
by
Jim
on 13 Dec, 2006 15:46
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The numbering is based on when the mission complement was baselined, not the flight order
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#535
by
Austin
on 13 Dec, 2006 22:19
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mkirk - 13/12/2006 7:52 AM
I believe you are thinking about STS-75 with Andy as Commander and Doc Horowitz as Pilot.
The SSME PC (chamber pressure gauge) was showing around 45 percent at liftoff. Actual thrust was okay, the indicator was just scaled (calibrated) incorrectly.
I forget how it came up but Doc mentioned it at the SRB test last month and said from his persepective he was expecting a pad abort...then suddenly they were flying.
I was at that launch and when I heard the call I thought that such a low percentage shouldn't even be possible (not stable...hell idle is 67%) and then I thought I was about to see an abort until I heard MCC acknowledge the call from the crew by saying that they showed the engine running fine.
Mark Kirkman
You're right...it was STS-75 aboard Columbia.
Can't imagine Horowitz's suprise when the solids lit following such a low engine PC reading. I was thinking in terms of SRB chamber pressure as a result of Allen's "45 percent on the left" comment (thinking left/right was a reference to left or right SRB).
Thanks much for the clarification.
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#536
by
spaceshuttle
on 13 Dec, 2006 22:58
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1. Why are the main engines knocked out of line before main engine gimbal check?
2. Why do the rear main engines gimbal closer together after ignition?
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#537
by
Jim
on 13 Dec, 2006 23:04
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They are spaced apart to allow for motion during the start transient. They might bang together if they were in the flight position.
Don't understand first question. They are just in a ground position before the gimbal test
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#538
by
psloss
on 13 Dec, 2006 23:23
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Austin - 13/12/2006 6:02 PM
Can't imagine Horowitz's suprise when the solids lit following such a low engine PC reading. I was thinking in terms of SRB chamber pressure as a result of Allen's "45 percent on the left" comment (thinking left/right was a reference to left or right SRB).
SSME 1 = center
SSME 2 = left
SSME 3 = right
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#539
by
shuttlefan
on 13 Dec, 2006 23:30
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psloss - 13/12/2006 10:00 AM
mkirk - 13/12/2006 10:52 AM
I believe you are thinking about STS-75 with Andy as Commander and Doc Horowitz as Pilot.
The SSME PC (chamber pressure gauge) was showing around 45 percent at liftoff. Actual thrust was okay, the indicator was just scaled (calibrated) incorrectly.
I forget how it came up but Doc mentioned it at the SRB test last month and said from his persepective he was expecting a pad abort...then suddenly they were flying.
I'm getting deja vu on this...if I recall correctly, they also got a temporary amber light on the engine shortly after liftoff (command path issue). There's also an old Florida Today interview floating in "webspace" with Andy Allen about this.
So, am I correct in assuming the engine gauge already read only 45% thrust before SRB ignition?