Nice motor Aidan!
-G
- Regards
Gene Engelgau
Web: http://fruitychutes.com - Professional Aerospace Recovery Systems
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On Sun, Jul 19, 2015 at 9:27 PM, Aidan Sojourner <aidan@xxxxxxxxxxxx> wrote:
Ok, here are some details about the static test that.
The formula itself is not very interesting, pretty typical low solids
pourable stuff. The interesting part is the grain design. As you guys know,
most motors have a small number of grains which usually have the same
diameter core.
This motor is based on a design by Geoff Huber, in turn based on the Super
Loki motor. The design was one giant (25.375") grain that continuously
tapered from the top to a small diameter about 40% of the length of the
motor and then out again to larger diameter for the remaining length (see
attached drawings). This is extremely advantageous because the propellant
essentially serves as a thermal insulator for itself - burning only from
the inside out, and not at the faces of the grains like in typical BATES
motors. This makes the design useful for odd case sizes where liners might
not be easily acquired.
In addition to slowing down the gas flow as it exits the motor- resulting
in less erosion and less pressure, the tapered core also raises the
port/throat ratio to a comfortable level. The port/throat ratio is
proportional to gas flow velocities out of the core and throat; If the
port/throat ratio is too low, the motor can experience severe erosive
burning and potentially spike the pressure to unsafe (CATO) levels.
This motor simulated out to a 20% L710. I do not have any data acquisition
equipment as of now, this static test was a "proof of concept" scaled down
version of a 3.5" N motor I am designing for next year. It burned a bit
faster than was expecting, and I think it had a lot less total impulse than
the simulation says. The simulation thinks that the propellant mass is 1450
grams when in reality it was around 1320. I am not really sure where I lost
100 grams of propellant but I think it has to do with simulating the motor
in 0.25" chunks rather than the reality, a smooth taper. I was originally
going to fly this motor in a 54mm minimum diameter at Aeronaut in two weeks
but I think I'm gonna stick to a typical BATES motor for that flight.
Aidan
On 19/7/15 18:26, James Dougherty wrote:
Awesome! What was the formulation Aidan?
On Sun, Jul 19, 2015 at 5:50 PM, Cliff Sojourner <cls@xxxxxxxxxxxxx>
wrote:
On 2015-07-19 10:01, Eric Melville wrote:
I am editing now and will post shortly. Of course, I am totally self
centered when
it comes to flights and I do not have a single rocket shot other than my
own. I did
get one of the Aiden L static test, though!
OK, finally got to a place with wifi to upload. here's the 210 frames
per second slow-motion of the L static test
https://www.youtube.com/watch?v=q_hFb65pObI
enjoy! maybe Aidan will fill in details of the motor, it's an
interesting design.
sorry didn't trim the first realtime second of nothing which means 7
seconds on the video. the focus isn't perfect, the video looks fine in
640x480. there is a way to get the camera to precision focus but it is too
hard in the heat and sun.
