|Rocket Electronics & Recovery|
|Launch & Static Tests|
|Motor Class Table|
|Iowa Amateur Rocketry Group|
|Don't Click Here!|
|Grain||Propellant Weight||Tube Length||Propellant Length|
Casing Internal Length: 19.62"
Throat Diameter: .86"
Propellant Diameter: 3.0"
Core Diameter: 1.27"
Core to Throat Ratio: 2.18 to 1
Kn: 199, 211, 181
Expected Total Impulse: 834 pound seconds
Expected Burn Time: ~1.57 seconds
Timer: 14 seconds on drogue 2 @ 2 grams, and drogue 1 @ 2 grams as back up ejection to nose cone pull
P6K: Apogee @ 9 grams, mach delay set to 5 seconds, main @ 3.6 grams set to 400'
ARB3D: Apogee @ 9 grams, main @ 3.6 grams set to 800', stage @ 2 grams on drogue 2 set to 14 seconds from launch detect, LED output.
Loaded Motor Weight: 12.8 pounds
Propellant Weight: 6.6 pounds
Upper Body Loaded Weight: 18.8 pounds
Rocket Lift Off Weight: 59.6 pounds
Here is a detail shot of the motor mount. There are two plywood centering rings, one at each each end. The motor is retained by 2) 3/16" bolts running through the fin can holes into a tapped/threaded hole in the motor casing. You can see one of the retaining bolts at the 12 o'clock position. The aft rail guide is a 1/4" bolt also through one of the fin can mount holes, just to be safe I used a longer bolt and added a nut inside the body tube.
Everything is set for a morning launch. This being a test of a new deployment system makes the outcome questionable. I started thinking when I was casting grains for this motor, this will be the largest KNSU motor I've fired. I really should have done a static test of this motor first. I guess the worst that can happen if it cato's is I loose a $200 fin can, a $120 aluminum body tube, the motor I'm using on the test... Oh well, that's the way the game is played I guess.
I checked the center of gravity after installing the motor, the rocket is very overstable. It shouldn't be a problem if the winds stay light, as I do have almost 9:1 thrust to weight ratio. That's if the motor stays dry and burns at the speed I expect. I went to extremes to keep the propellant dry after loading the motor. There are two layers of foil tape over the nozzle, then I wrapped the exit cone in a plastic bag and sealed it to the throat with electrical tape. I really need this motor to burn fast, thus the reason and concern for keeping the propellant dry. I had almost forgot what a pain KNSU propellant is compared to KNER. I had considered using a long 2.25" motor with a load of KNER, and I'm having second thoughts if that's not the route I should have taken.
It's too late now to make any changes. It's the night before jitters I'm sure, that's when the rocket is prepped and ready to fly, there's nothing else to do except sit around and worry about what could go wrong! I'm sure it'll all go well, then there's that new launch rail that hasn't been tested yet...
Bill and I headed out just after sunrise, the ground was exceedingly wet from dew, making it miserable as water was sloshing in my shoes in no time. But we went about setting up regardless. This was a new location to launch from as well. In case anything went wrong and this 60 pound rocket went unstable, or into a horizontal flight path I didn't even want the chance it would hit a farm acreage, so I launched from dead square in the middle of the section (1 square mile).
Set up went very well. We had the rocket loaded on the rail and the rail set up in no time.
Bill and I raise the tower into position. I do have a cable winch I'm going to install to raise the tower, but didn't have all the hardware I needed to finish it.
A couple of steps up the tower to arm the electronics. The tower was nice and stable, even with a 60 pound rocket and my 220 pounds on it.
The problem came when we checked continuity on the igniter. For some reason I had a bad batch of igniters, and two in row checked bad. Finally the third igniter tested good and was installed. Bill was on the launch controller, I was on the big Panasonic camera, Bill had the small Sony camera.
5,4,3,2,1 and ignition!
Click Here for both videos in one file, 2 minutes 1 second, 9.67 MB
Click Here for a video of the stationary camera from set up to launch with commentary about what we were doing added later. 9:42 43.5 MB
The "L" class KNO3/sugar motor lit quickly, and sent Defiance up the rail for the first time.
Two seconds into the flight. The rocket was just a little slow off the rail, and started a slight gravity turn down range. Once the rocket built up some speed the slight turning ended and the rocket proceeded in a straight flight. The motor burned a little longer than expected, likely due to the humidity. The lower initial thrust and overstable rocket contributed to the slight gravity turn.
Shortly after apogee and both drogue chutes are deployed.
The drogues were causing a lot of spin, but remained inflated and separate.
Here you can see the moment of main chute deployment, the dark gray next to the red chute is the deployment charge smoke, the gray main chute is just coming out of the upper body tube.
Here the main is trying to inflate, but is caught on the drogue chute shock cord.
The main chute hopelessly tangled, but both drogue chutes stay open.
The main does manage to at least partly inflate.
Another gray smoke cloud from the second altimeter firing the main charge at 400'.
A couple seconds later, not much changes.
You can see the slack in the main shock cord to the right.
Into the corn she goes!
Using my radio direction locating receiver, we quickly found the rocket only about 20 yards into the corn field. Other than the nozzle packed with dirt, the rocket was in perfect condition.
The one major fear I had using this deployment configuration came to fruition, that is, the main chute being shot right into the drogue chutes. While the flight and recovery were successful, it clearly points out some changes are needed. Of course, that was the whole point of this test.
I like the idea of dual drogues at apogee, and that seemed to work fine. But the main chute just added to much laundry and shock cords out there. What I may try is to have both drogues attached to a central PIRM2, that way if one or both of the drogues deploy, they will pull the main chute out. Keeping the chutes separate.
The flight itself went pretty much as expected, apogee was reported at 2,400 on the P6K and about 2,100' on ARB3D. All charges fired properly and all chutes deployed. Only the tangle problem remains to be solved. That just means another test flight in the near future, oh darn!
The evening of the launch I was cleaning up the rocket, and noticed something interesting. The nose cone was through two of the shroud lines on the main chute. Interesting, to say the least. So I went back and watched the video, and rewatched the video, in both slow motion and regular speed. Now I've come to a new conclusion as to what actually caused the tangle of the chutes.
When both drogues deployed, they separated from each other forming about a 70 degree angle between the shock cords. Despite the fact that things were swinging around pretty well, the drogue chutes stayed away from each other by a good distance. So when the main chute deployed, it should have deployed right between the drogues and been fine. What looks to have happened is the nose cone swung right through the shroud lines on the main.
I usually position the drogue chute at the top the shock cord, with the nose cone below it, then the rocket body at the end. But with the nose cone pulling the drogue out the way I did it, the best option looked to be to have the nose cone at the top of the shock cord, followed by the drogue. But this allowed the nose cone 4 or 5 feet of free line to swing about, the result was it swung into the main as it deployed. I can remedy this, but it will require that I double the shock cord back into the drogue mortar tube.
Armed with this new information, I now believe the recovery can work as it is, with the only change being rearranging the order of the drogue and nose cone. We've already seen the rocket can recover safely with just the drogues, so I think I'll try another flight only changing the nose cone and drogue order.