[AR] Re: RP-1 versus ethanol for a student rocket?
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 14 Oct 2020 18:48:00 -0400 (EDT)
On Wed, 14 Oct 2020, David Gregory wrote:
For students, I’d recommend what’s easy to procure, which means IPA,
JetA, or even ultra low diesel or kerosene. I don’t understand the
fascination with solvents.
Students might (optimistically) plan to build only one chamber, in which
case they don't want to run experiments that risk gunking up its cooling
passages, i.e. they want advance assurance of the thermal stability of
their fuel. Things that are sold as *fuels* generally don't come with
promises of that -- until you get into exotica like RP-1 -- because jet
engines (for example) don't bake their fuel before burning it. (Things
like JetA tend to have pretty broad specs to make them cheap to produce,
so even a successful test with one batch doesn't necessarily read over to
the next batch.)
Well-chosen solvents *do* make promises about this, one way or another.
Sometimes it's explicit in the spec sheet, sometimes it's just inherent
because (e.g.) pure IPA is known to be thermally stable.
As an aside I don’t think Rp1 really exists anymore, you’re really
talking RP2 if anything.
DLA's current price list, interestingly enough, just says "rocket grade
kerosene". The only RP it knows about is "RP-2S, special blend", whatever
on Earth that is (more than twice the price of "rocket grade kerosene", so
it better be pretty special...).
But that would be a poor choice for an amateur group unless someone
happened to hand you the barrel for free.
Maybe even then, because if you're successful you'll probably want another
barrel eventually. :-)
(Isn't that what drug dealers allegedly say, "the first one's free"? :-) )
Henry
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