Nice write up and thank you for a little bit of history. We looked
into the Shell 205 for our peroxide project.
S205 is an Iridium based catalyst on an alumina support was in the
past been considered a good N2O
catalyst during it's run and shell and now at Aerojet as S205. I'm
know expert on the use of it by any means
and only had a small quantity to use in a peroxide motor which we
never did. However, in drop tests, once it
got going it decomposed 30% peroxide very well, O2 production was 10
to 15% above silver. Newer catalysts
for N2O are TiO2 doped Ir/Al3O2 which we have also tried and the
latest thing to hit the research papers is
Mn based spinels.
Robert
At 08:47 AM 8/31/2016, you wrote:
Pioneer did work in several types of applications of N2O.
An early idea was to use 2 N2O to make... 2 N2 and O2 !
(seemed obvious to me at the time, like scuba Nitrox)
There was a patent filed, then people shuffled, then
Mark Berggren took over the project and built an SCBA system.
It was kind of scary, when you looked at all the filters
trying to get the NOXs out before you put the regulator in
your mouth. (I never did). Another big challenge was to
get the heat transfer and cooling right. The project was
never finished as far as that went. Seems like microchannel
heat exchangers were the next thing to try when the
money ran out. There was a licensing deal with a mine
escape breathing system, but that went bad for personality
reasons (Zubrin). It also cheated the patent inventors out
of their percentages. As far as I know, in 20 years, this
is the only non Sbir money Pioneer has ever really earned.
The idea of taking it to the ISS was proposed but never
really considered. An employee or two went on to start
Firestar with friends and almost got some N2O to the
station, until reality was considered.
If I remember correctly, the catalyst was Ruthenium on
an Alumina pellets. Tony Muscatello (now at NASA) started
that way back when. Turns out if you are a loud mouth
mars nut, all those nasty EPA regulations about disposing
toxic waste, like reagents and heavy metals, doesn't apply.
Just flush it into the Denver Sewage treatment system for
resale to California. :) Lead acid batteries and monitors
can similarly go to the landfill.
The Ruthenium on Alumina was a pretty low temp catalyst as
I recall. Seems like about 400 C. at the lower flows, the
'combustion' wasn't as complete as it could be, so some
brown nasties came out.
Pioneer also used the N2O in biprops, monoprops, hybrids, and
premixed (bombs) propellants.
In the monoprops we were looking at basic RCS thrusters, especially
for MMUs. The idea that it was much better than N2 cold gas
and didn't pollute space suits like MMH. The most common
catalyst we used was simple zirconium pellets. seems like
it dropped it down into the 500 C range. Powders were used a
little, especially in the premixed trials (Firestar got it's
start right there).
Playing with trying to get lower Catalyst use temperatures was
done with a bench top test stand that consisted of stainless
cans filled with the stuff of interest, torches and thermocouples.
The Ruthenium (on the Alumina) would leave pretty fast after a
full temperature run with the nitrous, but we tried titrating
it down with very small flows initially, to ramp up the temperature.
We thought we were getting very low starting temps (200-300?
it has been a decade !) but part of the success was the effects
of leftover cutting fluid on the stainless.
At the time, for one or two tests, the only thing that kept the
Premixed monoprop (alcohol and N2O) from back propagating and
blowing the main tank, was the powdered Zirconium. but that was
suspect since those tests were done on the last day and not
repeated. The tests on the first day with a conventional injector
also looked promising, but turned out to be a lack of premixing.
The biprops never used anything but a simple spark igniter and a
small 'pilot flow'. the main valves had some needle valve and solenoid
bypass. 5 second preheat always had good starts.
The hybrids were running centrifuge tests on paraffin and carbon foams
and used an APCP slug for ignition.
The zirconium based monopropellant thrusters were either a simple
counterflow system of overlapping tubes inside (bench tests) or a
regeneratively cooled / preheated thruster. With the simple system
it was pretty easy to overheat and fail the can. With the regen
style, we had to be careful that the actual flame temperature was
considerably higher than the nominal decomposition temperature of the
N2O. I mean that the decomposition added heat, but added it to the
already almost 700 C gas, which then got cooled to the exhaust
temperature, which would be the expected decomposition temp.
A materials gotcha from lack of deep thought on what was happening
inside the engine.
At one point we were supposed to try the Shell 405 catalysts, but we
never got around to cutting up the leftover Centaur RCS thrusters.
(They were just to pretty :)
N2O is an interesting propellant, I don't know if I would recommend
it or not.
-Gar.
>
> From: Paul Mueller <paul.mueller.iii@xxxxxxxxx>
> Date: Tue, 30 Aug 2016 22:20:26 -0600
> Subject: [AR] Re: interesting conclusions
>
> Oops, sorry Bill!
> I do remember Bob Zubrin's company touting the transport of N2O to the
> space station and then decomposing it into nitrogen and oxygen to create
> something similar to breathing air (
> http://www.pioneerastro.com/Projects/Nitrous_Oxide_Based_Oxygen_Supply_System.html).
> I looked at the patent and it looks like they cited every possible type of
> catalyst possible!
>
> On Tue, Aug 30, 2016 at 5:44 PM, <qbert@xxxxxxxxxxxxxxx> wrote:
>
