[AR] Re: Regarding Univerity solid rockets for cube-sat launch to orbit
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 3 Mar 2018 20:04:20 -0500
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".)
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