Re: Man-Rating Atlas V


lou@xxxxxxxxxxx wrote:
Will McLean wrote:

This argument would be more compelling if the Atlas V was a vehicle
with a well established track record. Not that it's a bad record, it
just isn't enough flights to confidently much more than its probably at
least 90% reliable.

And it really is significantly different from Atlas II, with different
tank structure and different main engines.

Agreed - the Atlas II experience proves little. This is exactly the
problem with "shuttle derived", as well.

Nor are the changes for the CEV version *that* minor. Besides the
changes you mention, NASA believes it needs a higher thrust upper
stage, probably with more RL-10 engines. And the three core
configuration, which Atlas has never built.

No, the Atlas that is proposed to be man-rated is the 401 varient, with
just one core engine, a single centaur, and no solids. See
http://www.lockheedmartin.com/data/assets/13344.pdf
where this is very explicit. This is because this is the simplest
configuration, with the least to go wrong, and has the most experience
(which it can share with un-manned launches, which should help by
creating a larger experience base). This is also the one that is
launched in a higher stress configuration when launched with solids, so
we know the structural margins are there. There is a hit (estimated at
about 10%) for using the single Centaur, since then trajectory changes
are needed to enable aborts throughout the flight. There is a two
engine centaur varient, but Atlas is not proposing to use it since it
is not proven yet - a sensible approach.

This does seem a trifle more convincing than the Ares 1 Man rating
case.

This configuration launches a 9 ton capsule which is fine for ISS and
Bigelow, but not for lunar access. The logical thing to do would be to
implement this for ISS ASAP and then see about upgrading it to carry a
CEV.

.

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