July 25, 2014 in Uncategorized
I attended LDRS 33, one of the annual Tripoli Rocketry Association launches, hosted by Tripoli Wisconsin and Quad Cities Rocketry Society at the Bong State Recreation Area near Kenosha, Wisconsin. I had two main goals for this launch. The first was to complete my level 2 certification with a flight of my new rocket “Home Alone” on a J motor, and the second was to make my first flight of more than a mile in altitude. Everything went very smoothly for me and I achieved both of these goals.
Day 1 – Friday, July 18
The event began on Thursday, but to save a vacation day and a hotel night, I drove up to Kenosha on Thursday afternoon and didn’t go to the range until Friday. The predicted weather was very similar throughout the event: mid- to upper 70s, clear and calm. A breeze might have made it a little more comfortable, but all things considered, we couldn’t have asked for better conditions to fly rockets.
I prepped Home Alone according the detailed checklist I had been obsessing over for the past several weeks and loaded up my certification motor, a Cesaroni J430. This was the smallest motor I was comfortable flying; being a fast-burning 2-grain motor, it would only lift the 9-pound rocket to around 3000 feet. At that altitude I expected that my certification observer and I would both be able to see the rocket’s entire trajectory and make sure everything worked properly.
I admit my hands were shaking as I hooked the rocket up on the launch pad. My jitters soon subsided, though, as the fast-moving launch crew started my countdown almost before I could get back to the spectator area and start my camera. Home Alone flew perfectly straight up to its predicted altitude of 3000 feet, remaining just under the scattered clouds, and arced over towards the spectator area as its apogee event fired and it deployed its streamer. Descending under streamer, the rocket continued to drift over the spectators and towards the parking area, causing the LCO (launch control officer) to call for a “heads up.” When I could no longer see the rocket, I packed up my camera and radio tracker and headed back towards the parking area as the LCO (also my certification observer) congratulated me on a successful certification flight.
I went back to my car and dropped off my camera and tripod, and debated whether I should take the tracker with me. I had just decided that I probably wouldn’t need it, and stowed it in the back of my car, when I turned around and saw my rocket lying on the ground next to another rocketeer’s EZ-up tent across the aisle. My first thought was that he must have found my rocket and brought it back to his tent already, but when I approached it became apparent that it had landed right where it was, with the shock cords and parachute strewn around three sides of the tent. My neighbor didn’t seem to be too put out by the near miss, and I had a very short walk back to my car.
Wildman Dual Deploy “Home Alone” flight #1:
Motor: Cesaroni Pro54 821J430-18A White Thunder
Altitude: 3034 feet AGL
Max velocity: 318 MPH (Mach 0.42)
Motor burn time: 1.84 sec
Peak acceleration: 10.3 G
Descent rate: 59.47 ft/s (40 mph) under drogue streamer, 18.39 ft/s (13 mph) under main chute
Flight duration: 91.5 sec
Result: Landed in parking area; apogee and main recovery deployment nominal; successful recovery, no damage; certification attempt successful
Day 2 – Saturday, July 19
My goal for my second flight was to exceed a mile in altitude. From my first flight I found that my actual altitude differed from my simulation by about 5%, which was about what I expected due to the extra drag of the camera shroud (which my simulator can’t simulate easily). I had originally planned to fly either a 4 grain sparky or a 4 grain smoky motor, either of which should have put me at around 6000 feet and met my goal with a little bit of a cushion. However, since the first flight had gone so well, I decided to push my luck a little more and reach for another (completely arbitrary) milestone – exceeding 500 mph. This would require a slightly higher-impulse motor, and after running some more simulations I settled on a 4 grain motor with Cesaroni’s red propellant, “Red Lightning.”
I purchased the motor at the Wildman Rocketry trailer and returned to my workspace to get things ready to go. While I was working, another SLRA member, Craig, stopped by. He and his wife had decided to come up for the weekend to spectate and take photos, and he helped me get the rocket hooked up at the pad.
Again, I barely had time to get back and start my camera before the LCO called for my countdown. Home Alone shot off the pad on the red motor and quickly disappeared from view completely. I was starting to worry about finding it, and was still scanning the sky overhead, when people to my left started shouting for a heads-up and I saw my rocket drifting down under parachute only about 150 feet up. It came down in the grass just across the road from the spectator area, about fifty feet from where I was standing with my camera and tripod. I wish I had caught sight of it earlier and been able to watch the deployment, because from the altimeter data and the on-board video, it appeared that the main parachute didn’t fully inflate until the rocket was at around 300 feet altitude (after the ejection which should have occurred at 800 feet), which meant it must have come out somewhat tangled.
Without actually seeing it, I think the way in which I folded the main chute may have led to the tangling. For future reference, I’ll note here that it was folded according to the Top Flight instructions (in half to form an L, then in half again to form a long rectangle with a point at the end, then in half lengthwise, then the point folded inwards, then rolled). The gores were then wound around the bundle per the instructions, but then, to make a more compact bundle, I folded the roll in half again before packing it in the tube. I think that folding it again after the gores were already rolled on the outside was a Bad Idea and caused the two halves to get tangled with each other. The next time I pack, I should try either folding the bundle in half before winding the gores around it (so they’re only going one direction) or coming up with another way to fold it so the gores are on the inside.
At any rate, it was a beautiful second flight and another very short recovery walk. Once I downloaded my altimeter data, I found that my altitude and speed had both exceeded my simulations, even without taking into account the 5% I expected to lose due to the camera. I have to assume that there is just that much variation in impulse between one motor and the next, and I happened to end up with an “overachiever.”
Wildman Dual Deploy “Home Alone” flight #2:
Motor: Cesaroni Pro54 1596K500-18A Red Lightning
Altitude: 7394 feet AGL
Max velocity: 573 MPH (Mach 0.76)
Motor burn time: 2.44 sec
Peak acceleration: 13.8 G
Descent rate: 74.90 ft/s (51 mph) under drogue streamer, 21.81 ft/s (15 mph) under main chute
Flight duration: 133 sec
Result: Landed in field very close to spectator area; apogee and main recovery deployment nominal except main seemed to be tangled until ~300 feet AGL; successful recovery, no damage