[AR] Re: SSTO fuels (was Re: SSTO)
- From: Evan Daniel <evanbd@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 14 Feb 2018 14:59:25 -0500
On Wed, Feb 14, 2018 at 1:55 PM, William Claybaugh
<wclaybaugh2@xxxxxxxxx> wrote:
If we are considering tripropellants, then the Hydrogen would presumably be
used as the coolant (optimizing Isp by altitude is achieved by varying the
percentage of Hydrogen and Hydrocarbon being burnt). But that still leaves a
potential coking problem at the hydrocarbon injectors and upstream after
shutdown; a hydrocarbon that evaporates w/o residuals seems likely to be a
better choice than one that does not (like kerosene) if one is looking to
avoid a post firing purge.
Part of XCOR's approach was to use a kerosene that evaporated without residuals.
Doug's post on 3/29/17 to this list includes a photo and AIAA paper:
https://www.freelists.org/post/arocket/LPL-IPA-Effects-on-Copper,5
And a selected quote that the archives don't seem to display:
"...dry-residue-free fuels are strongly advisable, so that greasy
films cannot be created by fuel spills. We have had good results in
using 99% isopropyl alcohol as fuel; we even use the same supply for
the cleaning solvent to prepare the oxidizer plumbing. In the
transition to kerosene based fuels, we have settled on a grade of
kerosene equal or even superior to RP-1, a multiply-distilled product
with no non-volatile components. Conventional Jet-A or JP-4 has too
many high molecular weight species, aromatic compounds, and [too much]
sulfur content to be used in a long-life regeneratively cooled rocket
engine where low coking is mandatory. The jet fuels leave long lasting
residues, incompatible with oxygen, if spilled."
Evan Daniel
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