Tim51
Well-Known Member
So I finally launched Clear Air Turbulence yesterday, after a series of cancellations due to freakish weather over the past few months. Tracker was an Egg Finder 'classic'. Apogee was 3215'. As stated earlier, the original plan was to fly on a J449 core with two I55 outboards igniting at 3.5s, but there was some concern over whether two long burn motors with a relatively heavy rocket would lead to the rocket arcing under power, and landing outside the range, so I swapped the I55's for 2 x H225s, and reprogrammed the mDACS for airstart ignition at 2.9s, immediately after the J449 burnout. At first sight it seemed everything had gone perfectly - straight boost, good dual deploy recovery. The obligatory DRP:
And a nicer one:
Conditions were ideal with wind at around 2mph. The initial boost:
Airstarting took longer than expected, but produced a satisfying throaty roar. I was surprised how loud even an H motor can sound when the noise is coming from over head - and I say 'an' deliberately, because it became clear afterwards that only one had ignited...
Apogee event. I used a Loc Angel 24" drogue
And here's the main (Rocketman 6') inflated after deploying at 800':
Why exactly only one of the two H225s ignited is still something I'm looking at. At first I thought perhaps one of the motors had come up to pressure before the other, ripping out both wires.. or was there too much power drain on the 9V battery to ignite both ? Curiously the nozzle cap was still on the unburned motor when it landed, albeit somewhat melted, but the igniter wire (finger loop and all) had been whipped away. You can see in the onboard footage they broke away at apogee.
The second problem was internal damage to the MMT CR/ Bulkhead. I admit I was liberal with the BP, and used 4g. I had to remove the motor charges anyway, relying on electronics, and I added a bit extra to all my charges from those. I'd also shear pinned the booster section, which was necessary because of the extra weight of 3 motors, and I thought I had calibrated correctly. However the resulting punch broke the CR:
This is going to be tricky to fix. Normally I would simply saw the airframe below the CR, and use a coupler to connect a new section of airframe. However, the outboard 'nosecone' fairings extend beyond the damaged CR point, and would make this difficult. I will try - I hope to fly this again, this time using a larger core motor, with the I55s, hopefully at IRW in Scotland in late August.
And a nicer one:
Conditions were ideal with wind at around 2mph. The initial boost:
Airstarting took longer than expected, but produced a satisfying throaty roar. I was surprised how loud even an H motor can sound when the noise is coming from over head - and I say 'an' deliberately, because it became clear afterwards that only one had ignited...
Apogee event. I used a Loc Angel 24" drogue
And here's the main (Rocketman 6') inflated after deploying at 800':
Why exactly only one of the two H225s ignited is still something I'm looking at. At first I thought perhaps one of the motors had come up to pressure before the other, ripping out both wires.. or was there too much power drain on the 9V battery to ignite both ? Curiously the nozzle cap was still on the unburned motor when it landed, albeit somewhat melted, but the igniter wire (finger loop and all) had been whipped away. You can see in the onboard footage they broke away at apogee.
The second problem was internal damage to the MMT CR/ Bulkhead. I admit I was liberal with the BP, and used 4g. I had to remove the motor charges anyway, relying on electronics, and I added a bit extra to all my charges from those. I'd also shear pinned the booster section, which was necessary because of the extra weight of 3 motors, and I thought I had calibrated correctly. However the resulting punch broke the CR:
This is going to be tricky to fix. Normally I would simply saw the airframe below the CR, and use a coupler to connect a new section of airframe. However, the outboard 'nosecone' fairings extend beyond the damaged CR point, and would make this difficult. I will try - I hope to fly this again, this time using a larger core motor, with the I55s, hopefully at IRW in Scotland in late August.