Alcohol is easier to source and to work with, yes. Generally easier to
get to ignite reliably and combust stably/efficiently than kerosene,
also considerably easier to purge completely from small engine passages
between firings too. If you do go with alcohol, you might consider
isopropyl rather than ethanol - it also can be watered down for extra
cooling at need, it's generally cheaper, and there are no concerns over
what they may have "denatured" it with since it's not drinkable in the
first place.
One factor to keep in mind in deciding, by the way, is how close to the
limits of your team's available time, talent, and resources will your
project push? (Keep in mind the first rule of projects: EVERYTHING
takes longer and costs more than planned.) One way to improve the odds
your team won't hit a wall short of useful results is to simplify
wherever possible at the start.
If you do prefer to work with kerosene for the better post-graduation
industry applicability, one possible lower-cost easier-availability
substitute for RP-1 is a refined-kerosene industrial solvent called
Exxsol D40. It does not have RP-1's density, thus is somewhat lower
performance, but it is non-coking, fully evaporable with no residue, is
reliably consistent chemically, and you can buy it by the drum for a few
bucks a gallon. And it's more or less as difficult to get to ignite,
combust, and purge cleanly as any other kerosene, so you will get plenty
of relevant experience.
FWIW XCOR used LOX/isopropyl for the EZ-Rocket (before my time there)
and LOX/Exxsol D40 kerosene for the X-Racer. Never saw a trace of
coking with it in many, many firings of the copper-chamber regen-cooled
X-Racer engine, and I was the guy who photo-documented the state of the
engine components every time Mike Laughlin disassembled it to inspect
condition and service the seals.
good luck!
Henry
On 10/13/2020 9:42 PM, Yucca Works wrote:
Hello all, my team is considering RP-1 and ethanol right now (to be paired with LOX) for our main propellant and I was wondering if anyone has any input on which fuel to use given some constraints and thoughts to follow. For one, we don't have an infinite budget at our disposal so Ethanol becomes immediately appealing because it is easy to source, this is on top of the fact that Ethanol is not ITAR protected and can be mixed with water for "inherent" cooling. What made RP-1 appealing was the fact that it is used in the industry so gaining experience with it seems extremely appealing and, I think, would make our work more "useful/notable" but sourcing RP-1 is difficult and it is expensive. A slightly tangential consideration is using lower grade kerosene which I have seen other college students do but I am concerned with using low-grade kerosene in regen cooling channels and it obviously has poor performance.