Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: SSME's
Message-ID: <1990Nov15.164306.5927@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <5667@crash.cts.com>
Date: Thu, 15 Nov 90 16:43:06 GMT

In article <5667@crash.cts.com> gandalf@pro-canaveral.cts.com (Ken Hollis) writes:
>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.

Lest anyone claim that reusability makes the difference, note that all
regeneratively-cooled liquid engines are reusable in principle, and some
of them are cleared for far longer use without maintenance than the SSMEs.
The RL-10 in the Centaur is cleared for something like seven firings with
a total burn time of over an hour... on a single mission, no maintenance.
-- 
"I don't *want* to be normal!"         | Henry Spencer at U of Toronto Zoology
"Not to worry."                        |  henry@zoo.toronto.edu   utzoo!henry