Found this comment of yours while searching on the forum for airstart methods:
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Nov 9, 2018
#54
Steve Shannon
Is it really possible to accomplish that with HEI systems? I can't quite wrap my head around how you'd assemble a motor using HEI without having the igniter/ignition system in place. For a second I thought the unit Tony linked to earlier would be install-able in the field after motor assembly but after looking at the pictures I'm not quite sure.
You’ve hit the nail on the head. It’s simply not possible with any existing amateur head end ignition system to install the initiator after the motor is in the rocket and the rocket is on the pad and pointed in a safe direction. The RCS/Aerotech head end system (the one Tony referenced) at least allows the motor to be fully assembled before inserting the head end initiator.
That’s also the problem with all traditional multiple stage amateur rocket vehicles. The booster is the only stage which allows the initiator to be installed after the entire rocket is assembled, on the pad, and pointing in a safe direction.
That’s the problem that should be solved before working on how to make air starts more reliable.
This obviously doesn’t apply to parallel staged rockets where all of the initiators can be installed on the pad.
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https://www.rocketryforum.com/threa...lty-with-airstarts.148953/page-2#post-1830143
Perhaps parallel staging could be used to solve the problem of high altitude ignition. You could use side rockets that ignite on the ground around a central rocket that doesn’t ignite until after the side rockets jettison.
This would solve the issue of how to safely install a head end igniter.
Alternatively, you could have also the central rocket ignite at the same time as the side rockets. BUT the central rocket would be given a very slow burning propellant formation so that it burns even after the side rockets have finished burning and are jettisoned. Ideally it would be arranged to burn slowly at first then more rapidly after the side rockets jettison.
Bob Clark