I'm working on a design for a gun system, using recoverable shells.
Assuming the use of SO2 (as H2S) is toxic, I'm trying to work out the
temperature of the payload. This is far harder than I was expecting,
and I'd appreciate some help from the group.
The issues to consider are as follows
1. The payload temperature mustn't melt or soften the shell material.
2. The shell should splashdown as near to empty as possible
3. The payload should end up as a gas, at our near the ejection altitude
4. The payload should be at max density when loaded - ie a solid or liquid
5. Ejection will be at about 25kms. This is roughly -60C and
0.025-0.05 atm pressure
There appears to be two strategies:
A) Pre-heat the loaded shell to around 850C. This should ensure that
there's enough thermal energy to instantaneously vaporize all the
payload, and deliver it as a gas at ambient temperature and pressure.
It does, however, rule out the use of aluminium or epoxy composite
shells, and the use of brass or nylon driving bands.
B) Use a much lower temperature - sufficient only to vaporize a small
proportion of the liquid, before the expansion cooling causes
vaporization to stall. This will then force aerosols, or a liquid
jet, out of the shell apertures (rather like a deodorant can). It's
been suggested to me that the liquid will quickly mix with the ambient
air, warm and evaporate. My concern with design B is twofold:
i) is that significant rain out of payload liquid will occur
before this happens, as the air is thin and cold, thus limiting heat
transfer to the liquid spray.
ii) cooling due to expansion will mean a significant volume of
liquid will remain in the shell, and will return to the Earth's
surface.
I'd appreciate the group's thoughts on the above.
A
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