Getting closer to 2-stage HPR

Chad said:

This is my two-stage build launching on a J250 without a motor in the sustainer. The booster is the bottom portion of a 4" Madcow DX3 with a scratch build sustainer based on bluetube and PML fiberglass fins. ISC is scratch based on a PML urethane 4" tailcone.

Flight went well, apogee at about 3k feet, I had an issue with a chute not fully inflating which was due to a tangled shock cord but there was no airframe damage. I need Santa to bring me some more featureful flight controllers before i feel comfortable igniting the sustainer (plan is redundant EasyMegas in the sustainer with tilt-lockout and redundant StratologgerCFs in the booster).

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JimJarvis50 said:

I would suggest not using two flight computers to redundantly light the sustainer. Using one flight computer for this task, and doing it safely, is tough enough. There is no reason to increase the complexity of this. I have never had an altimeter not try to fire the igniter when it was appropriate to do so**. Thus, I think the effect of using two is to raise the odds of the sustainer igniter firing from 98 to 99 percent. Not worth the added risk IMO.

Jim

** Actually, I did have this happen once due to an EasyMega firmware bug. But, using two EasyMega's would not have prevented the problem.

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Chad said:

My main worry is the sustainer igniting when conditions are not right. But, after that, my next thought is getting at least the drogue deployed safely no matter what. So, consider a power failure on booster ignition (maybe a wire comes loose). The sustainer won't ignite which is good but no recovery deployment means a dangerous trip back to the ground. A standard dual deployment altimeter with a separate power source would take care of that. Maybe I'll put one of the Stratologgers in the sustainer and use motor ejection as the backup deployment mechanism in the booster and save some money.

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mbeels said:

Nice, did you leave the stages connected? Drag separate? Or other?

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Chad said:

drag separation this time but i sort of regret it. When it all comes together I'll use a charge for stage separation, I should have tested that this time. I have a MT4 timer that i could have used but didn't.

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