Another possibility might be the inflatable, flexible thermal protection
material NASA is investigating for lightweight thermal protection for
manned Mars missions. It can withstand temperatures up to 1,260 C. I was
investigating this for the lightweight nozzles I wanted. While it is
lightweight, it is not at the ultralightweight level I was envisioning for
upper stage nozzles that might be at an expansion ratios of hundreds to 1.
Still it might be usable for making nozzles gimble.
Video: NASA engineers test inflatable reentry heat shield prior to flight
test
Published on July 10th, 2012 | By: Eileen De Guire
http://ceramics.org/ceramic-tech-today/video-nasa-engineers-test-inflatable-reentry-heat-shield-prior-to-flight-test
Bob Clark
On Sat, Mar 3, 2018 at 8:04 PM, Norman Yarvin <yarvin@xxxxxxxxxxxx> wrote:
On Sat, Mar 03, 2018 at 02:29:28PM -0500, Henry Spencer wrote:
The hot-gas seals used in the nozzle gimbals for
the big solids were a considerable technological achievement, and took
quite a while to develop, which is why a bunch of other vectoring methods
were used in the early days of big solids.
Indeed, one might wonder how it's possible _at all_ to seal a moving
joint against gas that is at high pressure and also is at a
temperature high enough to destroy pretty much any material that is
flexible. I think the answer is that the sealing can be done in two
stages: high temperature refractories on the inside to channel the
main flow of the hot gases, and an outer seal that holds the pressure.
To a first approximation, the gas that gets past the first seal just
sits there rather than being a constant flow, and as it first flows
in, it's cooled by exchanging heat with the nozzle structure. So the
outer seal still has to tolerate high temperatures, but not crazy
temperatures; it could be something like a stainless steel bellows.
(Then once you try such a thing, you get to tear your hair out over
all the little things that can break down that "first approximation".)
