I have another question about my 2-stage rocket project that I hope some
experienced people can help me with. This is separate from the 3D
coupler / rail buttons thing, and from the PET2+ vs. altimeter safety
question, so I figured I should start a new thread.
For the airstart of the sustainer, it seems that ignition failures are a
common problem -- after all, consider how many times we burn an igniter
in a rocket on the pad. They just don't work 100% of the time. So,
what can be done to make this more reliable or provide some redundancy?
The obvious solution seems to be to have multiple igniters, so if the
first one fails the second one might get the sustainer started. My
question is, what's the best way to wire this up?
Option 1: Use 2 separate pyro channels on the altimeter, with separate
wires connecting to the igniters. Set the channels to fire, say, 0.5
second apart so that the rocket is still coasting upwards when the
second igniter fires. Pro: complete redudancy. Con: more complex wiring
& altimeter setup, and if the first igniter burns out, it might take out
the 2nd igniter with it.
Option 2: Use only 1 pyro channel. Put both igniters on the same
channel, wired in parallel, so they both ignite at the same time. We'll
call this the "big bang" approach :). Pro: simpler wiring and altimeter
setup. Con: less redundancy (igniters but not channels); single pyro
channel is a single point of failure.
Option 3: ???
Any advice?
Also I read that it's a good idea to rough up the sustainer grains to
make them more likely to ignite. Is that true?
I even saw someone saying to spread some Pyrogen on top of the sustainer
grains. I feel unsure about that (and I don't have any Pyrogen
anyway). Seems like that could cause an explosion, like black power,
rather than a controller burn. Is this is valid / recommended idea?
Thanks!
Terry McKiernan
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