Interesting. I've done some tests with kerosene in an ablative chamber
where we used K1 lamp grade, which was perfectly satisfactory for our
application and easy to source from a local hardware store.
I've never heard of Exxsol D40 before. Do you order it directly from the
manufacturer? What sort of price does it go for and what are the minimum
order quantities?
On Wed, Oct 14, 2020 at 10:29 AM Doug Jones <rocketplumber@xxxxxxxxx> wrote:
I also agree that IPA is an excellent fuel for all the reasons listed
above. We used it in four engine designs, and since I used it to clean the
kerosene combustion sludge from the Rotary Rocket high pressure LOX-cooled
kerosene engines I suggested it in 2000 because I was damn tired of
cleaning up sludge. (The LOX cooling condensed partial pyrolysis products
out of the 2.6:1 O:F main combustion remarkably well, resulting in several
millimeters of undoubtedly carcinogenic black slimy crud. In later
kerosene-cooled engines the crud didn't occur, but IPA is simply MUCH
easier to work with.)
If you must use kerosene, use Exxsol.
On Wed, Oct 14, 2020 at 5:49 AM Ben Brockert <wikkit@xxxxxxxxx> wrote:
Thirding the arguments to use Shellsol/Exssol D40 or isopropyl alcohol.
I’ve used both and had good results. I’ve also used liquid methane,
denatured ethanol, and RP-1 and don’t think they are as suitable.
If you add a small percentage (~1%) of PDMS to isopropyl you get a
similar/better thermal effect to the char layer of kerosenes; about 50%
reduction in heat flux across the wall. Sold as 50cst silicone oil. It’s
not soluble in ethanol though.
In general alcohol rockets are easier (fuel spills are forgiving, it
purges easier, there’s more volume of fuel for coolant, you need it on hand
for LOX cleaning anyway) but kerosenes are more relevant to future industry
work.
Both work fine in spark torch igniters running off tank pressure, which
is the most effective way to make a reusable rocket engine. And even if the
rocket is expendable it’s best practice to build the engine to be reusable
because you want to test it easily. Pyro igniters are a pain in the ass and
TEA-TEB is a big hurdle for a student or amateur group.
Both competitors that won prizes in the NASA-funded Lunar Lander
Challenge a decade ago were running spark torch ignited lox/alcohol
rockets.
Ben
On Wednesday, October 14, 2020, Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
wrote:
One thing I will mention is that for a regen engine using kerosene-type
fuels (kerosene, Jet A, RP-1), you get a benefit from the carbon deposits
in the combustion chamber. There are some plots in NASA SP-125 as it acts
as an insulator and reduces the heat transfer to the walls. Obviously
people have made LOX/alcohol work but just thought I'd point it out as it
could potentially help your cooling problem converge, especially at smaller
thrust levels. It does make it harder to clean up afterwards as you have
to use an abrasive (scotchbrite) to clean it off. Other than the potential
for coking in the cooling passages on long runs, Jet A, RP-1, and kerosene
should be equivalent. I've never seen any coking in the cooling passages
for runs < 30 seconds. However, if I was doing a new engine, I would try
to make LOX/alcohol work before I went with kerosene, just from the cleanup
factor. I will say one thing though, you know when you've cleaned all the
kerosene out as it has a strong smell so maybe it's less likely that you'll
leave some fuel in a place where it shouldn't be.
-Bob
On 10/14/20 3:03 AM, roxanna Mason wrote:
Everything combustible ignites easily in a pure oxygen atmosphere and
Jet A evaporates surprisingly fast compared to standard kerosene or RP-1.
Ethanol also has a volumetric O/F of unity and easily adjusted by
biasing the mass O/F and/or water concentration, also the least toxic of
the common alcohols,
there are denaturing formulas that are lower toxicity than others just
shop around. You can get a federal permit to make your own ethanol too w/o
the $28/gallon excise tax. Also has a somewhat pleasant sweetish odor
especially compared to the doctor's office smell of rubbing isopropyl
alcohol, but that is subjective. And there's tons of data on LOx/Ethanol
systems being by far the most used alcohol in history as rocket fuel
including the V-2 and Redstone ballistic rockets, the X-1 LR-11 manned
rocket planes etc. See pic of a single chamber LR-11 captive test of one
metric ton thrust, LOx/75% ethanol.
Again it all depends on your requirements and cooling method.
Performance wise you can't beat hydrocarbon fuels compared to the alcohols.
K
On Tue, Oct 13, 2020 at 11:41 PM Wyatt Rehder <wyatt.rehder@xxxxxxxxx>
wrote:
I've long maintained that Isopropyl Alcohol is the ideal propellant for
the amateur liquid rocketeer.
- Has a close to 1:1 volumetric O:F ratio with LOX which simplifies
your feed system some (can use similar tank design for both)
- Is easy to obtain at 99% without additives for a low cost (~$500 for
55 gal last I checked) and no regulation issues
- Has a high vapor pressure and does not leave a film. So spills take
care of themselves, doesn't leave residues in your chamber after you purge
it
- You can perform your LOX service cleaning with it
- Has a short bio-persistance, as it readily biodegrades in soil and
water. So regular spills at your test stand, or a splattered rocket isn't
going to contaminate the ground soil unlike how kerosene can. Granted this
isn't a huge issue at amateur scales.
- Wyatt
On Tue, Oct 13, 2020 at 10:01 PM Henry Vanderbilt <
hvanderbilt@xxxxxxxxxxxxxx> wrote:
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.