bruce@idsssd.UUCP (Bruce T. Harvey) (10/08/88)
In article <8837@watdragon.waterloo.edu>, hjespersen@trillium.waterloo.edu (Hans Jespersen) writes: > When the shuttle goes to 104% trottle what does the 104% represent. > 104% of what?? You would think 100% was full trottle and it would > not be possible to go any higher. What is full trottle?? Previously, discussion seemed to accept that the 100% figure represents the ORIGINAL shuttle design specifications and that the design has been improved. The values never changed, so the increased power shows up as 104% rather than 100% (i.e., "104% of original spec. rated power"). I see this as completely believable that the design would change without a corresponding change in specs, but could it also (or instead) be that the specifications call for "reserve" power, and that the 100% refers to a kind of "cruise" rating and 104% refers to "all-out-hell-bent-for-leather?" It's just that I keep reading about planes rated for "300 knots at maximum cruise" and "325 emergency." Could it be the same with the shuttle? Please don't "knee-jerk" in response. Think about it for a while. -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Bruce T. Harvey (B-}> | ... cp1!sarin!wb3ffv!idsssd!idssup!bruce (Title depends on day) | ... ctnews!idsssd!idssup!bruce (301) 584-1960 | Convergent Route Distribution Sys. - Hunt Valley, MD
mcd@iconsys.UUCP (Mark Dakins) (10/22/88)
In article <497@idsssd.UUCP> bruce@idsssd.UUCP (Bruce T. Harvey) writes: |In article <8837@watdragon.waterloo.edu>, hjespersen@trillium.waterloo.edu (Hans Jespersen) writes: || When the shuttle goes to 104% trottle what does the 104% represent. || 104% of what?? You would think 100% was full trottle and it would || not be possible to go any higher. What is full trottle?? | |Previously, discussion seemed to accept that the 100% figure represents |the ORIGINAL shuttle design specifications and that the design has been |improved. | | ...but could it also (or instead) be that the |specifications call for "reserve" power, and that the 100% refers to a |kind of "cruise" rating and 104% refers to "all-out-hell-bent-for-leather?" | I tried posting this earlier but, it never got out so, I'll try again. Mr. Harvey's speculation is close to being correct. When the RFP's for the SSME's were issued they described an engine with certain thrust, specific impulse, run time, and reliability parameters. A particular thrust was defined as 100% and the run time and reliability parameters were based on this thrust level. However, the spec also called for the ability to run the engine at up to 110% of "rated" thrust. Note: this was in the original spec, not a later, discovered improvement. If run beyond 100% rated thrust the "run time before overhaul" goes down, actually I think it goes way down. Yes I know that they overhaul them after every flight but, this was a spec, remember? It doesn't have to relate to reality. I think that they try to keep the peak thrust down as far as possible but I don't know if any launches have stayed at or below 100%. I think they usually stay at or below 105% but, I seem to have a vague memory of a launch that went to 109%. The above info was gleaned from old AW&STs, various NASA and contractor publications, and my memories of discussions and news briefings at STS-1. -- Mark Dakins, Icon International uplherc!nrc-ut!iconsys!mcd@utah.cs.edu 774 South 400 East, Orem, UT.
henry@utzoo.uucp (Henry Spencer) (10/26/88)
In article <280@iconsys.UUCP> mcd@iconsys.UUCP (Mark Dakins) writes: >I think that they try to keep the peak thrust down as far as possible >but I don't know if any launches have stayed at or below 100%. I >think they usually stay at or below 105% but, I seem to have a >vague memory of a launch that went to 109%. Historically, the levels that have been in use are 100% (and lesser values), 104%, and 109%. I'm not sure whether 109% was ever actually used. NASA is now very reluctant to use 109%, for safety reasons. -- The dream *IS* alive... | Henry Spencer at U of Toronto Zoology but not at NASA. |uunet!attcan!utzoo!henry henry@zoo.toronto.edu
holroyd@dinl.uucp (kevin w. holroyd) (10/26/88)
In article <280@iconsys.UUCP> mcd@iconsys.UUCP (Mark Dakins) writes: stuff deleted > >A particular thrust was defined as 100% and the run time and reliability >parameters were based on this thrust level. However, the spec also >called for the ability to run the engine at up to 110% of "rated" >thrust. Note: this was in the original spec, not a later, discovered >improvement. If run beyond 100% rated thrust the "run time before >overhaul" goes down, actually I think it goes way down. Yes I know >that they overhaul them after every flight but, this was a spec, >remember? It doesn't have to relate to reality. > stuff deleted Remember the 737 crash onto the 14th street bridge in Washington D.C.? The pilots went to only 100% thrust at the very end, NOT maximum thrust. There was some speculation about wether full thrust would have made a difference or not. It seems they were reluctant to damage the engines by overthrust, and so damaged them by impact with the ground. Kevin W. Holroyd