cfb_rolley
Well-Known Member
Happy to hear this. Hopefully they'll approve the regular canisters.
Agreed, that would be absolutely awesome. There’s a few micro-hybrid flyers here and I don’t think we can get aluminium bulbs. But I've done well over 50 flights now and they’re quite safe. I’ve done all sorts from drilling out to a way oversized injector to putting in completely untested grains with way more pre-heater than needed and found that it’s very hard to break. you can’t cause a runaway overpressure unless you’re using oxidised grains (turbo APCP or bi-hybrid) because the oxidiser flow reduces when chamber pressure increases.
The biggest (only) “failure” I have had is with a printed grain that wasn’t thick enough at the top - the grain regressed enough to expose the o-ring and burned through and allowed hot gasses to pass the injector housing.
On a mono-tube hybrid that would normally be very bad. But since the oxidiser is inside the bulb, those gasses don’t reach the rest of the oxidiser and there is no damage at all. I noted that the nitrous bulb only had soot on the outside up to where the tape was too, which tells me you could probably add an extra safeguard against blow-by from just adding a second o-ring groove halfway up the injector housing (or by making sure there’s enough meat on your printed grain haha)
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