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#840
by
Bret
on 15 Aug, 2007 16:03
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John Shannon mentioned at the 118 briefing yesterday that the added hour in the countdown hold time for the ice team inspections might be contributing to the formation of extra ice. This got me wondering about a simple physics question: is ice formation on the ET more problematic during a summer launch (when temp differential and humidity are high) or during a winter launch (when it is simply colder all over)?
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#841
by
brahmanknight
on 15 Aug, 2007 18:19
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Did the pilots get RMS training before ISS flights?
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#842
by
Jorge
on 15 Aug, 2007 18:42
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brahmanknight - 15/8/2007 1:19 PM
Did the pilots get RMS training before ISS flights?
Only if the flight had enough RMS work to require it. It happened but it wasn't common before the ISS era.
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#843
by
BigKiai
on 15 Aug, 2007 20:51
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Are the astronauts given "suicide pills" ?
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#844
by
gordo
on 15 Aug, 2007 20:54
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BigKiai - 15/8/2007 9:51 PM
Are the astronauts given "suicide pills" ?
no
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#845
by
AstroRJY
on 16 Aug, 2007 02:45
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Question on thrust/ power equivalents of the Space Shuttle launch vehicle:
I have read that the 3 SSMEs have the energy equivalent generated by 18 or 23 Hoover Damns... Can anyone confirm the accuracy?
Also- what is the horsepower of the engines and SRBs. both separately and together. I am figuring it is in the 100-120 million range for the whole vehicle lifting off. I beleive someone said the Saturn V had 120 million horsepwoer and the shuttle has similar thurst.
In the STS-1 film from 1981, "Space Shuttle: A Remarkable Flying Machine" the narration said the 3 SSMEs on second stage generated "more than 42 million horsepower."
I read somewhere that the SRBs (this was also in a book from the early 1980s when the SRBs each had 2.9 or 2.95 million lbs. thrust, not 3.3 millions per today's vehicles) that the SRBs generated 44 million horsepower, but it didn't clarify if that was both or each SRB.
If anyone can provide accurate facts about the energy equivalency and thrust, I'd appreciate it.
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#846
by
AstroRJY
on 16 Aug, 2007 03:01
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Trekkie07 - 15/8/2007 12:46 AM
Quick question... how long does it take to turn a shuttle launch pad around from launch to rollout of the next shuttle?
Well, the record for the same pad was 17 days between 2 shuttle launches on pad 39A from April 12th to April 29th, 1985 between STS-51D and STS-51B.
I do know they have stated they go through 8 full days of cleaning the launch pad and tower after a liftoff to scrub down and remove all the debris and dirt caused by the SRB smoke and heat from the engines.
After a rollout, Launch Director Mike Leinbach has said it takes anohter 8 days of validation/ verification checks to make sure the MLP is parked at precisely the correct points and that all the connections are secure and the vehicle is locked down properly. He stated this at a press conference in late August 2006 when they were deciding to rollback Atlantis / STS-115 stack because of a tropical storm threat close enough to the Cape Canaveral area. They did start the rollback but after only an hour or two the forecast completely changed, they changed their decision and returned the stack to the pad, and still had to go through the 8 days of checks and validations.
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#847
by
Lee Jay
on 16 Aug, 2007 03:03
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Turning rocket thrust into power-equivalent is a touchy process. Rockets produce thrust relative to themselves, not something they push against. You need a velocity to turn a thrust into a power and a velocity is relative to something else. What do you use in a rocket? That's why rockets aren't usually measured that way. All three SSMEs firing at 104% on the pad impart zero power to the vehicle. At MECO, if you assume a velocity relative to the launch pad, they're imparting something in the 40GW range to the vehicle. Yet, they only (only!) consume about 18GW of chemical energy. Are they over 200% efficient? Obviously not. Every time I hear a rocket described in horsepower, or watts, or "Hoover Dams", I cringe.
Useful round numbers to me are that each SSME *consumes* around 6GW of chemical energy (18GW for all three) and each engine nozzle is providing around 300MW of heat to the fuel (which is used to cool the nozzle). To put that in context, all the thermal power plants running to supply my entire state (Colorado) with electrical power at the peak hour of the summer consume around that same amount (18GW), providing around 7GW of electricity. And that's the relatively-small (but supremely efficient) SSMEs. At launch the SRBs provide around 80% of the total combined thrust of the entire STS. They're big and powerful, but heavy and inefficient.
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#848
by
AstroRJY
on 16 Aug, 2007 03:05
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Assuming Giggawatts and Megawatts from the GW and MW in your answer?
I still need an answer on the totla thurst from someone else please.
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#849
by
Lee Jay
on 16 Aug, 2007 03:07
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#850
by
AstroRJY
on 16 Aug, 2007 05:08
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#851
by
LSainsbury
on 16 Aug, 2007 08:03
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gordo - 14/8/2007 9:54 PM
BigKiai - 15/8/2007 9:51 PM
Are the astronauts given "suicide pills" ?
no
Why would they? In what circumstances would they consider taking them?
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#852
by
SpaceNutz SA
on 16 Aug, 2007 10:15
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LSainsbury - 16/8/2007 10:03 AM gordo - 14/8/2007 9:54 PM BigKiai - 15/8/2007 9:51 PM Are the astronauts given "suicide pills" ?
no
Why would they? In what circumstances would they consider taking them?
I think this question was asked during the Apollo era. Buzz Aldrin (I think?) answered that it wasn't neccessary - if you want to die in space simply open the hatch (or depress the cabin).
I can think of a number of situations where they COULD be considered where there was no hope of a successful re-entry (loss of main engines for TEI, failure to rendezvoux with the CSM or failure to lift off of the lunar surface) but the nature of the 'test pilot right stuff' people who flew the missions would be to keep trying till the bitter end.
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#853
by
padrat
on 16 Aug, 2007 10:39
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Trekkie07 - 14/8/2007 11:46 PM
Quick question... how long does it take to turn a shuttle launch pad around from launch to rollout of the next shuttle?
Lately it's been a matter of 3 or four weeks. All really depends on how much launch damage there is. With minimal damage I'd say it could be done in two weeks with round-the-clock work. It actually would HAVE to be able to be done within a week or two for the LON option to even be viable.
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#854
by
brahmanknight
on 17 Aug, 2007 11:44
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Do the FRCS thrusters on the side ingest any plasma during re-entry?
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#855
by
Jim
on 17 Aug, 2007 13:17
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brahmanknight - 17/8/2007 7:44 AM
Do the FRCS thrusters on the side ingest any plasma during re-entry?
Doesn't matter, since they expell "plasma"
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#856
by
brahmanknight
on 18 Aug, 2007 13:41
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Can you spacewalk 3 astros from Quest, a la STS 49?
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#857
by
brahmanknight
on 18 Aug, 2007 13:52
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Sorry, posted in the wrong forum.
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#858
by
GLS
on 18 Aug, 2007 13:57
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If you could fit 3 EMUs in the crew lock... but it looks too tight.... Why do that if you have PIRS...
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#859
by
brahmanknight
on 18 Aug, 2007 14:13
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I never thought you would have a reason for 3 astro EVA until STS 49. I'm still not sure how that worked.