behr8762@fredonia.UUCP (Mike Behr) (04/17/89)
The Challenger mishap has brought about added safety features to the
space transportation system (ie. revamped Solid Rocket Boosters, crew
escape system using an escape pole, etc.). This, no doubt, has cut the
shuttle's maximum payload capacity from 65,000 pounds to around 55,000
depending on the orbiter (Columbia being the oldest and heaviest of the
fleet probably is even more limited in regards to its payload).
The shuttle main engines during flight are used at 104% rated thrust.
I understand the maximum rated thrust is 109% (correct me if I'm wrong)
but have not to my knowledge been throttled to 109% since the shuttle has
been operational. Does anybody know why - is it because the engine
hardware will be pushed to their limits increasing the chances of
catastrophe??? Anyway, say that sometime in the future the space shuttle
main engines (SSME's) will be flight certified to run at 109%, will this
increase the payload capacity, if so by how much - maybe back to past
levels?? I wonder if NASA should devote the resources to more powerful
and efficient main engines rather to a new more expensive and possibly
risky generation of solid or even liquid boosters to replace the ones
presently used.
--
*NIXON'S THEOREM:********************** Mike Behr *****************************
* The man who can smile when things decvax!sunybcs!fredonia!behr8762 *
* go wrong has thought of someone behr8762@snyfreba.bitnet *
* that he can blame it on. fredonia!behr8762@joey.cs.buffalo.edu *phil@titan.rice.edu (William LeFebvre) (04/18/89)
In article <1521@fredonia.UUCP> behr8762@fredonia.UUCP (Mike Behr) writes: > The shuttle main engines during flight are used at 104% rated thrust. >I understand the maximum rated thrust is 109% (correct me if I'm wrong) That's correct. >but have not to my knowledge been throttled to 109% since the shuttle has >been operational. Does anybody know why - is it because the engine >hardware will be pushed to their limits increasing the chances of >catastrophe??? Certain scenarios that involve loss of an SSME are considered catastrophic. If one of those was to fly apart at full throttle, there's no way to predict what damage it could do. They have noticed problems in the past with main engines and are probably a little nervous about them. Why push it when you don't have to? William LeFebvre Department of Computer Science Rice University <phil@Rice.edu>
phil@titan.rice.edu (William LeFebvre) (04/18/89)
In article <3108@kalliope.rice.edu> I wrote: >Certain scenarios that involve loss of an SSME are considered catastrophic. >If one of those was to fly apart at full throttle, there's no way to predict >what damage it could do. Someone has pointed out to me that the difference in throttling between 104% and 109% isn't going to make that much difference if the engine flies apart. However (as he also pointed out), running at 104% produces less wear on the engine and thus reduces the chances of failure. I concur. Besides, I don't think that the difference in thrust would be all that significant, especially where payload capacity is concerned. During the first two minutes of flight, the large majority of the thrust is coming from the SRB's, not the SSME's. Wouldn't that be more of a limiting factor? William LeFebvre Department of Computer Science Rice University <phil@Rice.edu>