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Author
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Topic: Shuttle main engines at 104 percent?
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jasonelam
Member Posts: 691
From: Monticello, KY USA
Registered: Mar 2007
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posted 03-12-2008 09:59 PM
   
I have an interesting question that has boggled my mind for quite some time as a space enthusiast, and I haven't received a good answer about this, so here goes:During a launch, I have always heard the call for "Go at Throttle Up", and also noticed that the engines are at 104% of rated thrust during launch and for most of the way uphill. Why wouldn't the engines be at 100%? Does this cause more wear and tear to the engines? I have also been told that in the event of an abort the engines would throttle up to 109% of thrust. How is it possible for an engine to have more throttle than it should? I know this may be a simple question, but is one that has boggled me for years. Thanks! |
Robert Pearlman
Editor Posts: 42988
From: Houston, TX
Registered: Nov 1999
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posted 03-12-2008 10:27 PM
The percentage level does not indicate actual power (as would be reasonable to assume) but rather rated output.The SSMEs are rated to provide 375,000 pounds of thrust at sea level. However, through the combination of upgrades and certification, the SSMEs are capable of providing more thrust than the baseline. When a higher percentage is cited, it refers to levels that are above the 375,000-lb. mark. Or, to quote NASA: quote:
The main engines can be throttled over a range of 65 to 109 percent of their rated power level in 1-percent increments. A value of 100 percent corresponds to a thrust level of 375,000 pounds at sea level and 470,000 pounds in a vacuum. A value of 104 percent corresponds to 393,800 pounds at sea level and 488,800 pounds in a vacuum; 109 percent corresponds to 417,300 pounds at sea level and 513,250 pounds in a vacuum.
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Tom
Member Posts: 1597
From: New York
Registered: Nov 2000
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posted 03-13-2008 03:07 PM
And just to add one more bit of information, since STS-95, the main engines actually are throttled up to 104.5% thrust. |
Aztecdoug
Member Posts: 1405
From: Huntington Beach
Registered: Feb 2000
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posted 03-13-2008 04:27 PM
quote:
Originally posted by Robert Pearlman:
However, through the combination of upgrades and certification, the SSMEs are capable of providing more thrust than the baseline.
The members of Spinal Tap would be proud to learn that NASA has developed the proverbial 11.  ------------------
Kind Regards Douglas Henry Enjoy yourself and have fun.... it is only a hobby!
http://home.earthlink.net/~aztecdoug/ |
Mr Meek
Member Posts: 353
From: Chattanooga, TN
Registered: Dec 2007
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posted 03-13-2008 06:35 PM
quote:
Originally posted by Aztecdoug:
The members of Spinal Tap would be proud to learn that NASA has developed the proverbial 11.
They'll be disappointed, though, by the failure of their letter campaign to get the first Orion test article christened "Big Bottom". |
WSTFphoto
Member Posts: 70
From: Las Cruces, NM, USA
Registered: May 2005
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posted 03-19-2008 08:46 PM
I think they got it right in the movie "Space Balls" with ludicrous speed. | |
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