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#1820
by
rdale
on 24 Apr, 2009 01:26
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#1821
by
Captain Michael
on 27 Apr, 2009 10:58
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What altitude are the SRBs Jettosined and how fast is the shuttle traveling?
Andrew
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#1822
by
tva
on 27 Apr, 2009 11:41
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What altitude are the SRBs Jettosined and how fast is the shuttle traveling?
Andrew
At aprox 29,5 statue miles and at a speed of 3650 miles per hour.
See attached file for datails. It came from the web-site of Bill Harwood, CBS News Space Analyst
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#1823
by
Lawntonlookirs
on 27 Apr, 2009 14:37
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I was just reading some information on the SSME that kind of surprised me. The Shuttle was originally set up to be a reusable orbitor. However I recently read that the SSME are more expensive than an expendable rocket motor would have been. Can anyone shed some light on why the reuasble engine would be more expensive?
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#1824
by
maicod
on 27 Apr, 2009 17:39
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See attached file for datails. It came from the web-site of Bill Harwood, CBS News Space Analyst
wow what an intresting document. thanks very much !
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#1825
by
Jim
on 27 Apr, 2009 18:09
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I was just reading some information on the SSME that kind of surprised me. The Shuttle was originally set up to be a reusable orbitor. However I recently read that the SSME are more expensive than an expendable rocket motor would have been. Can anyone shed some light on why the reuasble engine would be more expensive?
It has to be reusable vs expendable. reusable would have higher margins, more material, higher labor costs, etc.
A useable soda bottle is more expensive than a disposable aluminum can
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#1826
by
Jorge
on 27 Apr, 2009 19:12
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I was just reading some information on the SSME that kind of surprised me. The Shuttle was originally set up to be a reusable orbitor. However I recently read that the SSME are more expensive than an expendable rocket motor would have been. Can anyone shed some light on why the reuasble engine would be more expensive?
It has to be reusable vs expendable. reusable would have higher margins, more material, higher labor costs, etc.
A useable soda bottle is more expensive than a disposable aluminum can
Right. Reusables only "pay back" their higher costs by flying multiple times. At high flight rates their lifecycle costs become less than expendables. SSME never flew enough to get the costs down that far.
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#1827
by
Lawntonlookirs
on 27 Apr, 2009 19:49
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Thanks for the answers. I do remember that expected to get a lot mor flights out of the SSME than they are getting.
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#1828
by
butters
on 28 Apr, 2009 06:40
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Right. Reusables only "pay back" their higher costs by flying multiple times. At high flight rates their lifecycle costs become less than expendables. SSME never flew enough to get the costs down that far.
But did the SSMEs not fly enough for lack of enough shuttle launches over the life of the program or because the engines reached the end of their serviceable lifetimes after an insufficient number of reuses?
I seem to recall something about SSMEs being retired after something in the neighborhood of 10-15 flights, which isn't enough to justify the operational cost of reusing them even once.
Look at the direction that SpaceX is taking. They've designed for the possibility of reuse, but they clearly decided to make their engine cheap enough to be expendable in case it doesn't work out.
An engine that's too expensive to be expandable may also be too expensive to be reusable.
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#1829
by
Mach25
on 28 Apr, 2009 14:21
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I seem to recall something about SSMEs being retired after something in the neighborhood of 10-15 flights, which isn't enough to justify the operational cost of reusing them even once.
Look at the direction that SpaceX is taking. They've designed for the possibility of reuse, but they clearly decided to make their engine cheap enough to be expendable in case it doesn't work out.
The low flight number per engine was not known when the SSMEs were designed. If it had been, you can bet the designers probably would have gone down a different path.
SpaceX has the benefit of that knowledge AND 35+ years of technoligical advancement in rocket engine design and materials over Shuttle. Of course they would decide to do something different.
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#1830
by
MarsMethanogen
on 28 Apr, 2009 15:12
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Well said, Mach 25. The concept and development of the Orbiter SSME's started back in the early 70's. The development of a reusable cryogenic propellant rocket engine was a quantum leap at that point in time. It should be no surprise that some of the expectations were not met, as successful as they were in overcoming some incredible technical obstacles of all sorts. Indeed, the literature indicates that this (and the TPS) was THE pacing item in the development of the shuttle. Remember, that if you're out on the bleeding edge and on the frontier, you should expect to find a few arrows in your back. And that SpaceX is using these "lessons learned" is what any bleeding edge technological development is all about.
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#1831
by
Antares
on 29 Apr, 2009 05:03
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I submit this to the assembled masses:
Every liquid rocket engine is a reusable rocket engine.
Every acceptance test of a liquid rocket engine ends in a hot fire abort.
Every liquid rocket engine is designed for some number of starts in excess of one and some factor of a complete flight duration also in excess of one.
Every liquid rocket engine I've seen has been designed for and tested to at least 2.5x the number of starts and seconds its users would accept at the end of its flight mission. Some engines have demonstrated 4x this number. Some components have demonstrated 5x this number. I can't speak to the engines that had already flown out by the time I drew a paycheck.
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#1832
by
brahmanknight
on 29 Apr, 2009 22:33
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Will the crew of the sts 400 be at KSC when sts 125 lifts off? Or, once needed, would they fly out to KSC from Houston?
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#1833
by
Captain Michael
on 30 Apr, 2009 16:19
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What Altitude are the SRBs jettosined and how fast is the shuttle traveling at that altitude??
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#1834
by
waf102
on 30 Apr, 2009 16:37
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SRB sep @ 150,000 feet (24 nautical miles/28 statute miles).
Velocity is about Mach 4.
(Get a couple of sources before you rely on those numbers...better safe than sorry!)
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#1835
by
MarsMethanogen
on 30 Apr, 2009 16:45
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Here are some numbers (Mission Elapsed Time and Altitude) for the last mission, STS-119:
T+02:04...BOOSTER SEPARATION.........................3,641
It will vary from mission to mission, but Harwood's site (the Ascent Event Timeline) is a good source just prior to launch. I took these numbers from the STS-119 site (now arcchived).
http://www.cbsnews.com/network/news/space/119/STS-119_Archive.htmlScroll way down to find the above numbers.
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#1836
by
Sesquipedalian
on 03 May, 2009 04:20
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I have a question.
STS-125 will be, AFAIK, the 126th flight of a space shuttle. Yet it will be using ET-130. Why isn't it using ET-126; what happened to the extra four tanks?
I believe I heard that one tank was built for Enterprise's fit checks at Vandenberg but was not designed for flight. I think I also heard there was one spare LWT in storage that is not being used due to unsuitability for ISS flights. And of course ET-122 was damaged by Katrina and was taken out of the tank rotation. That still leaves one more tank though.
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#1837
by
Jorge
on 03 May, 2009 04:29
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I have a question.
STS-125 will be, AFAIK, the 126th flight of a space shuttle. Yet it will be using ET-130. Why isn't it using ET-126; what happened to the extra four tanks?
I believe I heard that one tank was built for Enterprise's fit checks at Vandenberg but was not designed for flight. I think I also heard there was one spare LWT in storage that is not being used due to unsuitability for ISS flights. And of course ET-122 was damaged by Katrina and was taken out of the tank rotation. That still leaves one more tank though.
ET-93 was used by the CAIB for testing.
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#1838
by
Thorny
on 03 May, 2009 04:41
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STS-125 will be, AFAIK, the 126th flight of a space shuttle. Yet it will be using ET-130. Why isn't it using ET-126; what happened to the extra four tanks?
According to Jenkins, STS-1 flew ET-2/SWT-1.
The first SLWT was ET-96, STS-107 flew ET-93 and ET-94 was used in the investigation, so that leaves ET-95 missing, presumably a canceled LWT.
So...
ET-1 (the one at the KSC visitors center?)
ET-94 (CAIB Guinea Pig)
ET-95 (?)
ET-122 (Katrina damage)
Addition...
Jenkins says one thing, Lockheed says another.
http://www.lockheedmartin.com/data/assets/ssc/michoud/FactSheets/ETFactSheet.pdfThis table starts at ET-1 and seems to have lost ET-7. Jenkins starts at ET-2.
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#1839
by
Jorge
on 03 May, 2009 04:42
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STS-125 will be, AFAIK, the 126th flight of a space shuttle. Yet it will be using ET-130. Why isn't it using ET-126; what happened to the extra four tanks?
According to Jenkins, STS-1 flew ET-2/SWT-1.
The first SLWT was ET-96, STS-107 flew ET-93 and ET-94 was used in the investigation, so that leaves ET-95 missing, presumably a canceled LWT.
So...
ET-1 (the one at the KSC visitors center?)
ET-94 (CAIB Guinea Pig)
ET-95 (?)
ET-122 (Katrina damage)
Ah, I confused 93 and 94.