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
<mailto: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
<mailto:mark.spiegl@xxxxxxxxx> > wrote:
Joe Bowen wrote:
Here's the most recent test: https://youtu.be/tqLjWhM3kv8