Colonization of Space

Ed M.
>> Contrast this with Shenzou. That heat shield is expendable,
>>radially symmetric (many identical parts), and ablates while forming
>>a ceramic on its leading edge during reentry. The exotic, space-age
>>material used? Wood.

>Andy Goddard wrote:
> Oak /has/ been used as an ablative shield on some earlier re-entry
>vehicles built in China, but I can't find any references to its use on
>Shenzhou.
> And - before people scoff at the application of natural materials in
>spacecraft - I believe resin-impregnated wood formed part of the
>Apollo hatch.

And cork was used in the heatshield on the two recent MER craft. An
improvement on the original formula used on the Viking landers.

>> The second big problem area would be the engines. Although they
>>are "reusable", the amount of testing and maintenance required
>>between flights is enormous... In the long run, it would be
>>cheaper to simply make new engines for every launch.
>
> An SSME is, what, 40 million US$? A /production line/ of SSME's, built in
>bulk, and used en masse to reduce individual failure risks on a disposable
>rocket makes so much more sense.

Or not use SSMEs due to the higher production costs -all to throw them
away. Is the loss in performance made up by the cheaper engines?
This topic has application in the hypothetical Shuttle-C vehicle, too. Most
depictions show SSMEs in a recoverable aft prop & avionics pod, but it may
have worked out that it's cheaper overall to use other engines and toss the
entire thing in the drink after use.

> Ground the shuttle.

Hear, hear. Tons of funding for buying Soyuz, developing the OSP/CEV,
maybe use the infrastructure to fly Shuttle-C to build the ISS (would it be
cheaper to do this, than to keep the Shuttle flying?), fly something manned
with an arm and some payload and an interior workspace to do the HST refits
they already have the parts for.

> Pour all the money into a ballistic replacement.

Like the Sea Dragon. Old fashioned, maybe not even recoverable (except for
the first stage maybe), not as sexy as the Shuttle's image was touted to be,
but effective, sure, and cheap, and it gets us to the Moon and Mars. Does
anybody think orbital assembly of the parts of an interplanetary vehicle -the
parts sent up on EELVs is going to be cheap & easy compared to
development of a BDB that does the entire mission in one shot?
>In the meantime keep the knowledge base in Russia intact by buying
>in Soyuzes.

Above all, keep manned spaceflight going strong, without the somewhat
ridiculous posture of insisting on keeping a second Shuttle ready for 40-90
day launch to rescue astronauts from the ISS "safe haven".