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Using the Proton for Airstarting Clusters
Another cool thing you can do is to have a cluster of motors in your rocket, but instead of lighting
them all on the pad you light some of them in the air. Some rockets lend themselves to doing this...
anything with sidepods, for example (think Titan IIIC or Falcon Heavy). You can use this to get
some neat effects, like having a "sparky" main engine with "smokey" airstarted motors. You can
also use it to get the rocket going with a higher thrust main motor then airstart some long-burn
motors in the air.
You'll notice that we say "motors" and not "motor". That's because when you airstart a cluster,
you'll always need more than one motor, symmetrically arranged around the center. Otherwise,
when you light them the rocket will go very nicely off-axis for a long, long ways, possibly heading
into the ground. That's also the primary risk factor with an airstarted cluster... that one or more of
the motors doesn't light. We've had it happen, and although the resulting power prang from low
altitude is spectacular to watch we do not recommend it! For safety sake, you need to use motors
that light easily, and/or a really good igniter. CTI motors with the black powder pellet in the top
grain are a good choice, as are white/blue/smoky motors. Most long-burn motors work fine, too.
Avoid colored motors (red/green/pink), they generally take awhile to light and/or come up to
pressure.
The setup for the Proton is the same as you would use for lighting the sustainer of a two-stage
rocket, except you don't have a separation charge. That leaves another channel free for something
else, possibly redundant igniters or a charge that releases the pods after burnout (you'd use motor
deploy for their chutes). As with a two-stage build, you need to simulate everything thoroughly to
make sure that you have the correct timing (and altitude/velocity if you're using the qualifications).
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