2) All spacecraft have design flaws; unlike aviation, we have not gone
through enough design generations to weed them out. The staleness of the
current US experience base due to the long gap between design generations
increases the likelihood of a flaw in Orion.

Is Orion to the moon a good "practice" mission for a trip to Mars?

"ed kyle" <edkyl...@hotmail.com> wrote innews:1173244154.705840.40180@j27g2000cwj.googlegroups.com:

On Mar 6, 10:24 pm, "Jorge R. Frank" <jrfr...@ibm-pc.borg> wrote:
"ed kyle" <edkyl...@hotmail.com> wrote
innews:1173240759.534853.186140@c51g2000cwc.googlegroups.com:

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."

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.

- Ed Kyle

I have another question. Is Orion to the moon a good "practice" mission for
a trip to Mars?

2) All spacecraft have design flaws; unlike aviation, we have not gone
through enough design generations to weed them out

I would argue strongly that design flaws still exist in just about every
aircraft ever built and flown. They just haven't all bitten anyone on the
ass yet.

Soyuz has two fatal accidents in 95 flights (1 in 47.5) and four fatalities
in 228[*] person-trips (1 in 57). Soyuz has had 85 safe landings since the
last fatal accident.

[*] - this is the only number I'm not certain of - it may be 225 but I
don't have my spreadsheet handy.

Because one major difference between Soyuz and STS is the fact that a
launch failure with STS almost surely means loss of the crew, while this
is not neccessarily the case with Soyuz.

I have another question. Is Orion to the moon a good "practice" mission for
a trip to Mars?

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.

To a certain degree, yes. It will get mission designers back into the
practice of deep space operations sooner than a straight-to-Mars
project would, so we should (re-)learn many lessons before we start
the much higher risk Mars expeditions.

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.

On 7 Mar 2007 08:12:53 -0800, "ed kyle" <edkyle99@hotmail.com> wrote:
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.

Before re-entry but not before the entry burn. Soyuz is committed
after the burn and *must* seperate cleanly. Shuttle can make sure
everything is good before committing to the burn.

Brian

"ed kyle" <edkyle99@hotmail.com> wrote in message
news:1173283973.145899.139360@64g2000cwx.googlegroups.com...

snip

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.

And don't forget that a capsule has a good chance of bringing a crew home
alive its entry flight control system fails. This was THE requirement
that took NASA from winged vehicles back to capsules during the Orbital
Space Plane program. The entry without flight control requirement has
been watered down now, but a capsule will give the crew a good shot of
surviving a passive entry.

Danny Deger