On 7/30/2010 3:29 PM, David Spain wrote:


What is missing from the discussion 'until now :-)' is the operational
cost of all these alternative plans. Do these capsules land on land or
water? Are they reusable?

If you wanted to save a lot of money and weight, you would jettison a
ablative heatshield after reentry - since it can't be reused, and any
sort of reusable one is probably going be too fragile to survive impact
with the sea or ground.
That's what the Russians do with Soyuz to greatly cut down the overall
weight of the descent module and parachute size needed for landing...
and something we were heading for back in Project Mercury, although in
our case the heatshield stayed attached to the base of the capsule by a
fabric cylinder with holes in it to act as a air compression shock
absorber on sea impact to cut down overall G-loads on the astronaut.
In the case of Orion, the original heatshield was a odd hybrid of
expendable and reusable; three or four blow-off ablative panels would
detach from it after reentry, letting landing legs or airbags extend for
a hard surface touchdown, yet the majority of the heatshield would be
reusable.
This, like the Shuttle, was a case where technological "sweetness" was
being allowed to overpower the bottom line in operating costs.

Pat