Re: Reinforced Carbon/Carbon Replacement?


"John Schutkeker" <jschutkeker@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:Xns98017A97367C7lkajehoriuasldfjknak@xxxxxxxxxxxxxxxxx
henry@xxxxxxxxxxxxx (Henry Spencer) wrote in
news:J2DsE5.KJJ@xxxxxxxxxxxxx:

In article <Xns97FEF354AAA53alsfaskldfjaklsdfj@xxxxxxxxxxxxxx>,
John Schutkeker <jschutkeker@xxxxxxxxxxxxxxxxxxxx> wrote:
According to Wikipedia, 2300 F is the temperature above which RCC must
be used instead of the silica tiles. Do you know how far the wing
temperature goes above th threshold, and what is the melting point of
the RCC?

Remember also that there are severe weight constraints.

I assume that these constraints would be based on vehicle balance during
re-entry, re-entry speed, which of course translates to temperature, the
ability to achieve orbital altitude, and fuel consupmtion at launch. Is
there anything I've forgotten, and are any of the above four issues
substantially less important that any of the others?

You missed the big one, payload. The only use for the shuttle at this point
is to finish ISS. A possible Hubble repair mission is the only exception to
this rule. Ignoring center of gravity issues, which you mention, every
pound of mass added to the orbiter reduces its payload by that same pound.
If the added mass causes CG issues which causes you to add ballast, then the
payload hit can be more than the mass of the change itself.

The other things you mention don't make much sense to me, especially the
last two since you can't really change the amount of fuel in the SRB's (at
least not without a fairly big redesign, like 5-segment SRB's). Beyond
that, you can't change the fuel load in the ET without a redesign. There
really isn't any spare capacity in the system when it comes to payload.

How much would, say, alumina relacements for the RCC panels weigh?

Even if it were a viable option from a mass perspective, I doubt that the
change could be done in a timely fashion. Just look at how long NASA has
been fretting over the shedding foam issue. I'd guess changing the RCC for
another material would take years and billions of dollars.

The high fixed costs of grounding the shuttle kill you, even if the
development costs are "free". Either it's safe enough to fly now (perhaps
with minor changes here and there that can be slipped into the schedule), or
it's not and the program should end now. The 2010 end of the program is
coming up fast.

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)


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