gandalf@pro-canaveral.cts.com (Ken Hollis) (11/21/90)
Greetings and Salutations: >From: henry@zoo.toronto.edu (Henry Spencer) >Subject: Re: SSME's >In article <5667@crash.cts.com> gandalf@pro-canaveral.cts.com (Ken Hollis) write s: >>The SSME is made for a MAN RATED rocket. Redundancy, double checks, etc... >>... When the unmanned rocket motors are designed, >>they don't need all of the safeguards... >Uh, let us not forget that most of the major "unmanned" rocket motors designed >in the US are, or have been at one time, man-rated. Atlas and Titan have both >launched manned spacecraft, Delta uses Atlas-derived engines, and the Saturns >were man-rated from the start. None of them had anywhere near the hideous >engine cost and complexity problems of the SSMEs. This is an excuse, not a >reason. Please be reminded that these are the first engines rated from sea-level all the way to the vacuum of space. They are not staged engines designed to work in only 1 region (ie sea level to XX Thousand feet, and another engine to take over from there). This is a completely re-designed engine, although admittedly Rocketdyne had the experience to build them. They are also more complex because they COULD be made complex. Computer systems & control systems that couldn't be made in Saturn days are now used on the SSME's. Ken Hollis ProLine: gandalf@pro-canaveral Internet: gandalf@pro-canaveral.cts.com UUCP: crash!pro-canaveral!gandalf
henry@zoo.toronto.edu (Henry Spencer) (11/21/90)
In article <5759@crash.cts.com> gandalf@pro-canaveral.cts.com (Ken Hollis) writes: >Please be reminded that these are the first engines rated from sea-level all >the way to the vacuum of space... Nonsense. The center engine on the Atlas, dating to the mid-1950s, burns all the way from launch to orbit on a mission without an upper stage (e.g., the Mercury orbital flights). Actually, I'm afraid Ken hasn't thought this one through at all. Even first-stage booster engines are in near-total vacuum at burnout. For example, shuttle SRB burnout is at an altitude of over 40km, which is in vacuum for all practical purposes (including rocket engine design). There is enough air there to be detectable, but not enough to have major effects on engine performance, since pressure and density are well under 1% of sea-level numbers. >... They are also more >complex because they COULD be made complex. Computer systems & control >systems that couldn't be made in Saturn days are now used on the SSME's. And they have gained us virtually nothing to pay for all that extra complexity. Complexity for complexity's sake is a bug, not a feature. Its only function is to keep lots of engineers and technicians employed, which drives costs up and up and up. -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry
dsmith@hplabsb.HP.COM (David Smith) (11/22/90)
In article <5759@crash.cts.com> gandalf@pro-canaveral.cts.com (Ken Hollis) writes: >>>The SSME is made for a MAN RATED rocket. Redundancy, double checks, etc... >>Uh, let us not forget that most of the major "unmanned" rocket motors >>designed in the US are, or have been at one time, man-rated. >Please be reminded that these are the first engines rated from sea-level all >the way to the vacuum of space. Not so. The Atlas sustainer (center) engine fired from the pad all the way to orbit carrying manned Mercury capsules. -- "Some fear that Newtonian physics | David R. Smith, HP Labs governs superpower relations: | dsmith@hplabs.hp.com What goes up must come down." | (415) 857-7898 Time Magazine, interviewing Gorbachev, June 4, 1990
pstinson@pbs.org (11/22/90)
In article <5759@crash.cts.com>, gandalf@pro-canaveral.cts.com (Ken Hollis) writes: > Greetings and Salutations: > >>From: henry@zoo.toronto.edu (Henry Spencer) >>Subject: Re: SSME's >>Uh, let us not forget that most of the major "unmanned" rocket motors > >>launched manned spacecraft, Delta uses Atlas-derived engines, and the Saturns >>were man-rated from the start. None of them had anywhere near the hideous >>engine cost and complexity problems of the SSMEs. Actually the engines used by Delta are Thor-derived, not Atlas.
henry@zoo.toronto.edu (Henry Spencer) (11/22/90)
In article <1990Nov21.120559.10809@pbs.org> pstinson@pbs.org writes: >>>... Delta uses Atlas-derived engines... >Actually the engines used by Delta are Thor-derived, not Atlas. Go back farther and you will find that the Thor first stage engine is basically an Atlas booster engine (Atlas has two booster and one sustainer). Even after considerable divergent evolution, the two are still similar enough that the 1986 Delta failure put Atlas launches on hold until the problem was understood. -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry