Re: Future of Orion??

On Mar 7, 8:42 am, "Jorge R. Frank" <jrfr...@xxxxxxxxxxx> wrote:
"ed kyle" <edkyl...@xxxxxxxxxxx> wrote innews:1173244154.705840.40180@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

On Mar 6, 10:24 pm, "Jorge R. Frank" <jrfr...@xxxxxxxxxxx> wrote:
"ed kyle" <edkyl...@xxxxxxxxxxx> wrote
innews:1173240759.534853.186140@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

But it will fly. When it does, I think that it has a very good
chance
of proving to be the safest human launch system ever fielded.

I think Orion's chances of flying over fifty flights in its entire
operational lifetime are low, but assuming it does, its chances of
getting through its first 58 flights without a fatal accident (which
is what it will need just to match the shuttle's safety record,
currently the best of any manned spacecraft) are even lower.

What makes you think that?

Several reasons. I've been thinking about it overnight to try to rank
them and right now this is the best I have:

1) Human error is the cause of 80% of aviation accidents and this pattern
is continuing in spaceflight. Out of five fatal accidents (Apollo 1,
Soyuz 1 and 11, STS-51L and 107), human error was a primary cause of all
but Soyuz 11. .... There is no reason to believe that Orion will be
immune to this.

2) All spacecraft have design flaws; ... And Orion already has one
obvious flaw, common to all current and historical capsules: the
necessity of jettisoning critical parts of the spacecraft during the
window between deorbit and entry interface. ....

3) Orion's projected flight rate is so low that I believe reusability
will prove to be non-viable. That means a big hit to component
reliability since Orion's systems will never get out of the "infant
mortality" part of the "bathtub curve."

I attribute at least some of the failures you mentioned
(the U.S. failures especially) to design flaws.

It is true that Orion won't be immune to any type of
failure, but I believe that it has a good chance of
being measurably safer than Shuttle and Soyuz and
Shenzhou, for the following reasons.

Orion should be quite a bit safer for crews than shuttle
simply because it will have the launch escape system
that shuttle lacks. It will be at least as safe as shuttle
in the reentry phase, and probably safer because
it will have a smaller, more rugged heat shield less
exposed to damage and will spend less time exposed
to the reentry heating phase. Yes, Orion will have to
jettison its service module, but shuttle has to retract
antennas, close its payload bay doors, start its APUs,
etc. before reentry. Yes Orion will have to deploy
parachutes, but shuttle has to fly to a precision
landing, deploy landing gear, etc.

Orion has a chance to prove safer than Soyuz and
Shenzhou for the following reasons. It will ride what
should be a more reliable launch vehicle than either
Soyuz or Shenzhou. Ares I will have one big solid
motor and one liquid upper stage engine with two
separation events. Both the Soyuz and the CZ-2F
launchers have six propulsion units with six engines
and six separation events. In reentry, Orion will
have fewer modules to jettison than either Soyuz or
Shenzhou.

This is all on paper, of course. Orion should, and
could, prove safer, but the development has a long
way to go. The CEV design was born with safety
as the primary design driver in the immediate wake
of the Columbia disaster. It remains to be seen if
safety will remain paramount during the execution
of the spacecraft's development phase.

- Ed Kyle

.

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