In the "sugar" world where dry mixing and melting is common, they did
some basic sensitivity tests of putting the propellant on the skillet
or whatever and seeing how much excess heating it takes to set it off.
It turns out that it's usually quite a lot, though it's a proof test
that should be redone when things like catalysts are added.
I don't know how AP mixes compare for autoginition or decomposition
temperatures. But you can run the process with an inert oxidizer
stand-in, to look for hot spots and see how the viscosity works out at
a given dry proportion to melted.
Supposedly the big "hybrid" of doom has (or had) some oxidizer mixed
into the fuel grain to increase performance, so there's probably
someone out there who would really like to talk about casting a ton of
thermoplastic nylon with oxidizer.
On Wed, Jul 8, 2020 at 8:13 AM William Claybaugh <wclaybaugh2@xxxxxxxxx> wrote:
There are today plenty of “rubbery” thermoplastics available. If we accept
somewhat lower performance then a professional propellant, it seems—in
principle—that making and casting solid propellant using a thermoplastic
binder should be relatively simple, as previous RRI experience w/ asphalt
suggests.
The problem for me has been figuring out a relatively safe process:
Dry mixing the ingredients and then melting seems—again, to me—too sporty.
Dry mixing the Al and binder seems safe enough; melting that and breaking
into pellets for later processing also seems safe up to the point that AP is
added.
Any thoughts as to how to cast a thermoplastic grain w/o having to mix dry
fuel and oxidizer before melting?
Bill