They dont do regen
-------- Original message --------
From: Paul Mueller <paul.mueller.iii@xxxxxxxxx>
Date: 4/1/17 4:51 PM (GMT-08:00)
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: [LPL] IPA Effects on Copper
I see that the new Vector-R launch vehicle is LOX/propylene (first stage,
https://vectorspacesystems.com/vector-r/). I wonder how they handle the
polymerization issues.
On Sat, Apr 1, 2017 at 5:07 PM, Henry Spencer
<hspencer@xxxxxxxxxxxxx<mailto:hspencer@xxxxxxxxxxxxx>> wrote:
On Sat, 1 Apr 2017, Brian Feeney wrote:
Anthony Ceasaroni wrote:Sulphur is not the dominating issue.
What is / are the dominating issue(s)?
Depends on the fuel and the chamber materials.
For kerosene and suchlike -- that is, complex mixtures of higher hydrocarbons
-- you get classical coking, which is essentially reactive components of the
fuel polymerizing into solid organic gunk, and then gradually baking down to
mostly carbon, under heat and pressure. Sulfur might perhaps help this along a
bit, but isn't at all necessary. What distinguishes RP-1 (and such) from (say)
Jet A, is that RP-1 has essentially none of the troublemaking components, and
so it doesn't polymerize easily.
(There has been speculation in the past that things like ULS -- Ultra Low
Sulfur -- diesel fuel might be similarly heat-resistant, not because of the
lack of sulfur but because the treatments used to get rid of sulfur impurities
also tend to get rid of the reactive hydrocarbons in the mix. And if you want
CO2 brownie points, peanut oil is quite heat-resistant and might be suiable...)
Simple hydrocarbons like methane and propane, when reasonably pure, simply
don't polymerize on their own. For them, the big issue is sulfur corrosion,
especially in copper chambers. It doesn't take much -- the Aerojet guys found
heavy deposits of copper sulfides with 10ppm of CH3SH in methane. (CH3SH,
methyl mercaptan, is a common "stenchant" in methane, natural gas, etc., added
to make them smellable.)
(RP-1 is officially limited to 50ppm of sulfur, but normally has very little.
They tried adding 50ppm of a mercaptan to it, and it showed major sulfur
corrosion too, at rather lower temperatures than needed to make it show
classical coking.)
One problem with commercial fuel "propane", and to a lesser extent with LNG as
well, is that they're not pure propane and methane respectively. "Propane"
usually has some propylene (which most definitely does polymerize), and
especially in hot climates it may also have a fair bit of butane and pentane to
reduce its vapor pressure. LNG is mostly methane but has small amounts of
other hydrocarbons too, and if it has ethylene or propylene, you may again be
in trouble. Possibly the biggest headache with heating-fuel grades is simply
that their compositions aren't well controlled -- even the choice of stenchant
can change -- so good results with one batch don't guarantee anything about the
next batch.
(I'm told that propane sold as vehicle fuel has *much* tighter specs, but I
haven't verified this.)
Henry
