First the narrative, and then the data:
Saturday morning, I turned on the Blue Ravens and trackers in the sustainer and the booster, and they both were adequate for battery state of charge. I knew I wanted to go early because of the predicted rising wind, so Vic Davis and I got first in line to go out to my tower which we set up the day before. I turned on the sustainer tracker outside of the tower so it would get a good lock on a bunch of satellites. With the Blue Raven confirmed off, I installed the sustainer nozzle and then we got the rocket loaded in no problem. It's a 12' tower but the rails slide out at the bottom so we could do everything upright. I angled the tower a smidgen downwind, to the Northwest, to reduce the effect of weathercocking. I turned on the sustainer Blue Raven, got the expected main and Apogee continuity voltages, turned on the booster and did the same. Now the rocket was safe to arm the airstart, so I screwed in the screw switch, and.... the continuity voltages didn't change. the sustainer igniter was not connected for some reason. Time to recycle.
Back at camp, I had to take everything apart to find the ignition wire problem, which was that a wire broke where I had stripped it with the wrong setting on my wire strippers and then somehow put a bunch of twists on the motor connection. I re-connected the wires, re-inserted the motor (sans nozzle) and av-bay, re-connected the deployment wires, re-arranged and re-taped the deployment harnesses around the chute cannon, and fiddled with that, adding more and more tape as needed until I could get the nosecone fully seated. Finally we got back out to the pad, got everything set up the same way, and this time when I turned the screw switch to close it, the 3rd and 4th channels went to the battery voltage. With everything else done, I armed the channels through the app and walked away, keeping an eye on the tracker performance.
Back at the LCO table, things were busy well-organized. I bet there were over 1000 flights through the weekend. Matt and all the volunteers did a great job. When my turn came, the Loki J474 lit up with that brilliant purple laser flame out at the 500' pad area and it looked like a clean, straight boost. I sort of saw the rocket separate, and then it was gone, time to watch the GPS. After a few seconds I started getting good-looking GPS data and I watched the vertical velocity go down, down, down below 300 feet/second. 15 seconds from liftoff is a long time. Just when I thought the motor wasn't going to light, the velocity numbers started to go up again and I looked up and saw the nice white trail going nearly straight up, but with some obvious corkscrewing. The altitude went through 26,000, 27,000, 28,000 and 29,000 feet and I was overjoyed. The downward velocity went to 40 feet/second, and I was relieved that the apogee charge deployment worked. Yay! Wait, the velocity is still only 40 feet/second. Uh oh, the main chute came out somehow. I saw how slowly the altitude was coming down, and nervously watched the horizontal position as Saturday's 45 knot upper level winds took it to the northeast toward Alamosa. I briefly switched the phone and ground station over to look at the booster, and I saw that I was getting packets from it, but there was no GPS lock yet. I went back and forth a couple more times with the same result, and before long, the booster was down and I didn't know where. Meanwhile, the sustainer kept drifting away. After it landed, I copied the coordinates into Google Maps and drove off to get it. It was just to the east of one of the North-south roads. I was picturing it hung up on one of the overhead wires, or in some of the trees that border the road around there, but I lucked out, and it landed cleanly in the brush, with everything intact. I didn't see it until I was within about 10 feet:
Sustainer body showing the chute, chute cannon, and nosecone ejector piston
Here's the nosecone (in the bush) and the road. If the overhead wires were on the other side of the road I could have been in trouble.
I checked out the flight summary data and saw immediately that the main chute charge fired at 793 seconds into the flight, at low altitude. So the problem of the early main deployment wasn't software. On Sunday when I was prepping the upper stage for another flight, I saw that I had tied on the nosecone ejection piston to the harness going to the nosecone rather than the chute, and I figured that when the nosecone was ejected, it pulled the nosecone ejection piston with it, and then a bunch of the rest of the main chute harness it was taped to, and pulled the main chute out. In the landing photo you can also see the nosecone ejection piston tied to the harness that leads back to the nosecone. But today I looked closely at the electrical data, and the main chute continuity voltage didn't look right for that:
The main charge continuity voltage does go to 0V for 1 second at the main deployment altitude when it should, but starting it apogee the continuity voltage dropped to about 2V. Normally that kind of drop happens after a charge has fired, and if it were intact I would have expected it to stay at 4V. Then I just remembered that I saw a hole burned in the chute, which normally never happens, but could happen if the nosecone were still on when the main charge went off. If it had gotten pulled out of the chute cannon before the main charge went off, it wouldn't have gotten burned. So maybe I swapped the wires when I connected everything back up? But in that case, the apogee ejection charge wires would have broken before the main channel fired, and there was definitely charge residue I cleaned out the nosecone piston afterward. Now I think I pinched some wires when I screwed down the chute cannon, and the apogee and main wires were connected and fired together. The view photo below is from Balls rather than from this flight, but it gives the idea:
Lots of opportunity for pinching, when the bolt is tightened down, especially near the central bolt or on top of either the main or apogee threaded rod tops.
When the chute cannon charge fired and the apogee piston was yanked off, the apogee wires were broken by the nosecone piston getting blown off of the end of the main chute cannon, which would explain why the main channel is has a different continuity voltage than the apogee channel after apogee.
Once last year when I was doing a ground test with this setup I also had both charges go off simultaneously. I couldn't pin that one down (no altimeter there to record continuity voltages) and that problem never repeated since then, but I'm convinced now that's what happened Saturday.
The acceleration data around the apogee charge doesn't give a lot of insight into the cause but doesn't rule out the pinched wire and simultaneous firing:
In the plot above, I reversed the signs of the raw data so that the X axis is pointed up along the rocket. When the initial charge(s) fired, there is a pretty big spike downward, but it's not the clean single spike I'm used to. The next spike is when the nosecone takes the slack out of its shock cord, and then I think the next chaotic part is when the chute inflates. There aren't any more large acceleration events during the length of the high rate data, which ends 6.4 minutes into the flight when that memory allocation is full.
So I think that explains the main chute deployment. Let's look at the rest of the flight:
The GPS and baro sensors had their normal lag, but when the GPS figured out what was up, it matched the inertial navigation altitude up until the second burn. At that point, the roll gyro measurement got saturated at 2200 degrees/second so the inertial navigation would not be expected to match very well after that.
Interesting how the roll rate ramps up quickly during the initial burn and then goes up even faster after immediately after sustainer separation, and that the rotation rate goes up and down after the 2nd burn, maybe because of Mach transition effects?. Here is the velocity:
The GPS horizontal velocity was only 14-18 feet/second during the first coast. Here is the tilt:
The GPS flight path angle is going to be different from the tilt because of the crosswind. If the rocket is tilted into a crosswind, it can have a tilt even if the flight path angle is perfectly vertical. I think some of that was going on here. The upper level winds were expected to be about 45 knots. The horizontal velocity measured by the GPS when it was coming down on the main chute was around 80 feet/second at the higher elevations:
(BTW, James Russell just texted me that my booster has been found!)
I'll start another post so I can add more images....
