Troy, the test I conducted with a colleague was for Space Launch Corp
George Withinghill's brain child back in 2003.
The test was a compatibility experiment between liquid nitrous oxide and
FMC 98% H2O2. This was a development program for an air launched self
pressurized 35KLbF hybrid under a phase 2 DARPA contract conducted at the
Mojave Airport. We were befuddled by anomalous reading in our data that we
finally linked to the extremely slow thermal equilibrium of the fluids
under test. So we airconditioned our test cell so everything inside the
cell was at the same temp. before the test. This was summer in the
Mojave Desert with measured daytime temps in the 120F range. We also
conducted out test at night to minimize the delta-T between in/outdoors.
A sobering epiphany once we figured out the anomaly.
K
On Wed, Jul 22, 2020 at 10:01 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Ken,
I wasn’t aware of that. Looking at some numbers, it’s about ½ that of
PVC, acrylic and polycarbonate ?
I’m curious to know what that experimentation was about?
Cheers,
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *roxanna Mason
*Sent:* Thursday, 23 July 2020 2:41 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Continuation of small hybrid motor design
You probably already know it but nitrous is an excellent insulator so much
so we had to wait upto a half hour to get a column of nitrous to
reach thermal equilibrium throughout the column and this was a 1" plastic
tube half full with ~ 1/2" of H2O2 floating on top.
On Wed, Jul 22, 2020 at 5:38 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
The biggest issues I would have with running a hybrid upside down with
what effectively is a siphon tube (I imagine?) is the trueness of the
representation of operation. Like, what kind of pressure drop will you be
seeing along the siphon tube and what influence the thermal feedback is
across the injector plate ie. does it boil the liquid N2O on the tank side
in the upright orientation, does the injector plate rely on that heat
transfer for cooling or flow characteristics and will the phase flow
through the injector(s) be similar in both orientations?
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *David Summers
*Sent:* Thursday, 23 July 2020 10:24 AM
*To:* arocket <arocket@xxxxxxxxxxxxx>
*Subject:* [AR] Re: Continuation of small hybrid motor design
Pointing the nozzle upwards increases chamber pressure!
(Unless using hydrogen, another drawback of hydrogen)
(**Hides**)
On Wed, Jul 22, 2020 at 2:20 PM Joe Bowen <joe.b.bowen@xxxxxxxxx> wrote:
So this link might explain the "how" (
https://drive.google.com/file/d/1tuXXeG6bGfcnJgQdyrtOA7IeK5vk2cz0/view?usp=sharing)
there's a n2o rated hose that runs from the back of the combustion chamber
(left hand side of picture) to the n2o tank (right side). This hose snakes
down the large green tube and out to connect with the hanging n2o tank.
This picture might help too (
https://drive.google.com/file/d/1uOGwF4YcV3SGkWQ-KRiqHd_id25OARZy/view?usp=sharing)
and if this is still confusing, I can take more pictures to clarify.
The "why" probably isn't going to be a really satisfactory answer. In the
video, that's not my test stand but I believe the "nozzle pointed up" was
done as a safety feature. Although I suspect the "nozzle pointed up" as a
safety feature is probably as divisive as the "Tabs vs Spaces" are in
computer programming, so I'm not entirely sure that I would make the strong
claim that it's the right/best option, but the idea seems reasonable. I
ended up designing my motor to handle that because the forward n2o vent
needs to be higher than the n2o tank rear bulkhead for these style
hybrids. And then I ended up building my own test stand using the same
ideas (load cell under a swing arm and nozzle pointed up). At some point I
also envision some future development that will require tank separation;
motor gimbaling, throttling valve, full body tank with a std motor (think
V2). Granted, I'm probably a few years away from any of those ideas but
this motor is turning into a decent development/testing platform (although
if I were doing it over, I would've gone with a 75mm motor, not 54mm to
have more space for sensors). I also eventually want to put a load cell on
the n2o tank hanger so I can chart things like fill and drain rates.
Joe
PS. Quick note about the other thread (which I don't want to join, but had
a quick thought on)... As someone who's trying to learn all this stuff as a
hobby, I enjoy learning from all the people on this list that are/were pros
and actually know what they're talking about. I'm all for some good faith
moderation for people who aren't making good faith efforts to have good
conversations, if that's what it'll take to not drive away the people who
make this email group worth it. Also, Terry, seeing your post reminded me
that I've been meaning to buy your book on composite propellent
manufacture, so I did. Hope you stay. :-)
On Wed, Jul 22, 2020 at 5:45 PM <mark.spiegl@xxxxxxxxx> wrote:
Joe Bowen wrote:
Here's the most recent test: https://youtu.be/tqLjWhM3kv8
How and why are firing the motor nozzle up??
--MCS