Xref: utzoo sci.space:25436 sci.space.shuttle:6593 Newsgroups: sci.space,sci.space.shuttle Path: utzoo!henry From: henry@zoo.toronto.edu (Henry Spencer) Subject: Re: New Shuttle Engines Message-ID: <1990Nov13.190528.5893@zoo.toronto.edu> Organization: U of Toronto Zoology References: <10948@milton.u.washington.edu> Date: Tue, 13 Nov 90 19:05:28 GMT In article <10948@milton.u.washington.edu> brettvs@blake.u.washington.edu (Brett Vansteenwyk) writes: >Not long ago it was noted that the first of Endeavour's engines had arrived >at KSC. Some mention was made that these engines were "new and improved". Don't read too much into this. There has been no major design change, just a bunch of small incremental improvements. >[1].Are these new engines useable in the older shuttles? ... Yes. >[2].Are these engines part of a more "mature" system? In other words, has >there been a batch of changes made to the manufacture/design of these "new" >engines that will improve their servicability and ease of refurbishment? That's the hope. Considering the magnitude of the failure to meet the original targets in these areas, there is room for a lot of improvement. >This engine has been in use for almost 10 years, and it would seem >that it could be classified as a "mature" system by now--a learning curve >with subsequent reduction in refurbishment costs as well as a more reliable >engine. Is there evidence to indicate that this has happened? ... Well, maybe some. The thing you learn from the learning curve in this case is really "these things will never be wonderful without major redesign". >[4].Whenever I see any discussion about new launcher development, I never, >or almost never see any suggestion to using the SSME's, nor do I see any >indication of an engine derived from SSME technology. The tendency is >to discuss systems originating 25 or even 30 years back. I am assuming >that the SSME was the most recent major engine development. Has all the >time and talent spent to make the SSME work been wasted on what is now >considered an evolutionary dead-end? ... Very nearly. The Japanese decided to adopt a similar approach (although a from-scratch design) for their H-2 booster, and are now regretting it. Most everyone else proposing new launchers wants to use less ambitious and more dependable engines, either old ones or new developments. The SSME concept wasn't bad in principle, and maybe it is the wave of the future if you're patient enough, but making it work well seems to be exceedingly difficult today. Certainly the SSME itself shows no signs of ever becoming particularly cheap. >[5].If not the evolutionary dead-end as postulated in [4], could there be >an SSME derivative for an expendable launcher... The definitive Shuttle C proposal wanted to use life-expired shuttle engines in an expendable launcher. The Hughes/Boeing Jarvis proposal also used expendable SSMEs, after they tried very hard to come up with a viable scheme for reviving the F-1 and J-2 and couldn't make it work. The SSME is just too expensive to be a good expendable engine, though. -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry