"M" wrote in message
...

What piqued my interest in that document was the reliability ratings
for manned spaceflight. I have no idea how they figured tehat the Ares
designs were safer than the Delta or Atlas.



Oh that's easy. It's called wishful thinking.

Seriously, they do a lot of stuff like fault-tree analysis. The problem is
that's only as good as your fault-tree.

For example, ice puncturing the RCC on the shuttle wasn't considered
possible, so wasn't in any fault-tree (as far as I know).

The reality is while you can do a lot of good analysis, until you've flown
any craft a few hundred times, it's still a lot of guess work.

So, we're going to take the shuttle, with a database of 100+ flights (and
200+ successful SRB flights) and replace it with a "safer" vehicle with an
all new SRB design. Somehow a brand new vehicle will be safer on day one.