|Static tests of
Loki Research 54mm motor
burning 3 KN/Sucrose propellant grains
|Launched on 12/13/03!
Click Here for details
Received 12/4/03: one 3-grain 54mm motor casing with extra
nozzle and a bunch of case liner and casting tubes.
Previously received: A pile of O-rings and the recommended snap-ring pliers from McMaster-Carr
Also recently received: 50 pound bag of fertilizer-grade KNO3
Isn't it pretty? This is made by Jeff Taylor, of Loki
Research, who with Darren Wright made the P-motor for this year's JAMSTAR
project. As I understand, Jeff made the motor and Darren made the
propellant. (Am I right? Please correct me if you know better.)
Here I compare the motor with my PML Sudden Rush airframe. No, I did not consult Martha Stewart on this issue - the color match was pure coincidence. Yes, the shirt is from K-Mart. So are the pants. But I built and painted the airframe long before deciding to order this motor and/or knew that it would be anodized blue. Is this an omen?
Grains are molded in the casting tubes provided Jeff/Loki. The casting tubes fit precisely in the phenolic-impregnated case liner, also provided. I like this idea. In the 38mm project, I made my own inhibitors and case liners for the Dr. Rocket casings. They worked OK, but there was always some irregularity in my products which took up case space, limiting propellant capacity to a degree.
These grains are 3.15 inches long, have a 5/8 inch core, and each contains about 185 grams of propellant, total 555g. Since I am getting about 1.13 N-secs from each gram of recrystallized KN/sucrose, the motor should provide about 630 N-seconds of thrust, making it a high-end I motor. The grains are a bit loose, and could stand to be a bit longer. So I might be able to pack in a little more propellant and push it into the baby-J range, as if that matters.
Hey! It just occurs to me that I could use the nozzle as a casting base for the lower grain to make a nice cone to fit the convergence and squeeze in a few more grams.
But for now, I will squeeze the motor into the ground. My last pvc-motor CATO broke the funky test stand. That's when I decided to order this motor casing.
The blue plastic bag is not just for aesthetics, it is to keep dirt out of the motor. I left it there when the motor was fired. You will see it waft up real fast in the video.
So here are the specs:
Propellant: Recrystallized KN/Sucrose, made with "food
grade" KNO3 from Skylighter.
Grain configuration: Three Bates grains, each 3.2 inches long, 1.764 diameter (inside diameter of casting tube) with a "5/8" inch core, actually averaging 0.63 inches.
Nozzle: 29/64ths inch throat = 0.435 inch
Initial Kn ratio: 214 - Initial pressure: 700 psi
Maximum Kn ratio: 254 - Maximum pressure: 900 psi
Final Kn ratio: 232 - Final pressure: 750 psi
Ignitor: E-match with 0.3g black powder and a pinch of magnesium turnings.
Videos of static tests:
Test 1: 12-07-03a
(1 meg download, about 4 seconds of video)
Using standard recrystallized KN/sucrose propellant as described above. Excellent ignition. Strong burn for 1.3 seconds.
Test 2: 12-7-03b
(3.5 meg download, about 13 seconds of video)
Similar to Test 1, but this time using recrystallized propellant made with fertilizer-grade KNO3, which I just recently acquired for less than $1.00 per pound, shipping included! This cooks a little differently, and I severely overcooked this batch. Understanding that there might be anomalies, I made it into grains and fired it anyway. Good burn for a second or so, but with several funny chuffs at the end. Entertaining though it may be, I will NOT be using this propellant at the upcoming launch. It needs further development.
So far I have made enough propellant for 3 launches with this motor,
and may make more before then. I also have a number of grains for
the 38mm Dr. Rocket casings, and hope to use them all at the amateur launch
on Saturday. Seems like I am more likely to run out of time than
out of propellant. With lotsa luck, the airframe will survive to
the end. One crash, and my show is over.