Rand Simberg wrote:
On 22 Feb 2005 08:27:22 -0800, in a place far, far away, "Ed Kyle"
made the phosphor on my monitor glow in such a
way as to indicate that:

No-solids would shut
out Lockheed Martin's existing Atlas V
models after all.


That's one reason why. It would also preclude the desire of some in
the astronaut office for a "single-stick" SRB-based design.

The failure mode they seem most worried about is the sort of
catastrophic case/nozzle failure that have already killed at least one
Delta (@ KSC) and one Titan IV (?, @ VAFB). No warning -- just *blam*
followed by insta-chaff. I imagine it's a pretty difficult abort
problem to solve -- you begin your abort already having given a good
head-start to the blast wave & fragments, rather than just getting away
from a booster that has begun to act up.

I don't think that the SRB-based boosters would have *that* problem,
necessarily. For one thing, an argument could be made that they're
already man-rated in some sense. For another, I would like to think
that the sort of case failure that would represent the same (or similar)
failure mode has been either designed out (over-strength case, different
materials) or quality-assured (x-ray or other testing of the case &
filling) out of them.

It might be possible to give the Atlas & Delta strap-ons the same level
of confidence with some cost & weight penalty -- but you'd have to take
into account that you would probably be using several of the motors and
would have to be (individually) more rigorous in your testing to get the
same level of confidence in the result (a 99%/motor success rate for one
motor is only 94% when you have to use 6 of them).


--
Reed Snellenberger
GPG KeyID: 5A978843
rsnellenberger-at-houston.rr.com