Re: Losses not acceptable
A further thought, in war there are a lot of people dedicated to making enemy planes fall from the sky. Unless you go along with some of the nutty terrorist theories, everyone involved was dedicated to bringing the shuttle down safely.
I do agree that there must be some level of risk that is acceptable, and that it has to be relatively high for such a dangerous venture as space travel, but 1 in 50 seems too high for a space taxi, especially if due to "low tech" failures that should have been preventable with proper engineering and quality checks.
If 1 in 50 manned Mars missions failed, that would be more acceptable. 1 in 50 shuttle flights isn't good enough.