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 <mailto: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.
Attachment:
burnsim.PNG
Description: PNG image
Attachment:
25.375 Grain.JPG
Description: JPEG image
