As I said in my original post, C/SiC is as difficult to fabricate as RCC.
The really tough problem is developing the tooling that will take the 3,200F
processing temperature. A lot of the time and expense is spent in getting
this tooling to work properly, i.e. to hold 0.010" tolerances from room
temperature to 3200F and then back to room temperature. The product yield
from these high temperature composite manufacturing processes can be
distressingly low (~50%).

The rib-reinforced C/SiC panels that we developed and tested for X-33
applications were relatively easy to fabricate because of the simple shape.
The shuttle RCC parts have pretty complex shapes with fairly tight
tolerances (~0.010") and probably would be a bear to fabricate compared to
our X-33 panels.

Later
Ray Schmitt



"Mike Dennis" wrote in message
.. .
Do you have any sense of how difficult it is to fabricate "seasick"?
Also,
did anyone ever bring up the idea of using it on the shuttle?

Thanks.


"rschmitt23" wrote in message
news:2m5Na.87288$Pc5.67581@fed1read01...
Nomex and kevlar would fry at 3000F RCC temperatures.

If I'm not mistaken, the latest and greatest RCC-like material is called
*carbon/silcon carbide*, abbreviated *C/SiC* and pronounced *seasick*. I
worked on 14" x 14" inch C/SiC panels in 1995-96 as part of the
technology
development effort in support of the ill-fated X-33 program. C/SiC is
supposed to have superior strength and oxidation resistance compared to
RCC.
I nearly wore out my arm one afternoon trying to cut through a 3mm thick
piece of this material with hammer and cold chisel (I was too lazy to
walk
to the next building at the McDonnell Douglas Huntington Beach facility
where the diamond saw was located).

We tested a 4x4 array of these panels in the 60MW arcjet facility at
NASA-Ames in early 1996. The material worked OK, but we could only get
about
35MW out of the arcjet before it would begin to self-destruct (It's an
old
facility dating from the early 1970s and has had little maintenance on
the
large elliptical nozzles since the early 1980s). As a result, the skin
temperature only got to about 2600F. However, the seals between the
panels
worked OK, a major part of the test. We ran out of time and money so the
testing was terminated.

I suppose NASA could develop a *second generation* shuttle leading edge
design using C/SiC. But that stuff is at least as difficult to
manufacture
as the old RCC material. So I would expect a 4-5 year effort would be
required to produce three sets of leading edge panels and some number of
spares. I don't see NASA jumping at this prospect.

Later
Ray Schmitt



"Jon Berndt" wrote in message
...
Just out of curiousity, is anyone aware what new technology exists to
perhaps fabricate new leading edge panels that would be more robust
than
the
current RCC ones? Perhaps something involvinga a composite of some of
the
materials nomex, kevlar, whatever (I'm not a composite materials
guys).
I
don't see replacement leading edge panels viewed as a priority; is
that
the
concensus - that the current ones are OK?

Jon