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Appendix B: Using the Proton for Airstarts
A Brief Word About Airstarts...
The techniques in the manual are intended for use by relatively advanced rocketry hobbyists,
generally with a NAR or TRA high-power certification. A lot of the discussion assumes that you
have some experience with electronic deployments, high-power rocketry building techniques, the
basic physics of rocketry flight, and a good working knowledge of the safety procedures
involved in flying high-power rockets. It is not a complete course in these subjects, nor can any
short manual like this be.
We strongly recommend that if you do not have experience in electronic deployments that you
tackle that first BEFORE you try airstarts. A lot of things can go wrong with airstarts, even with
low-power motors. Remember that YOU are responsible for YOUR actions and the
consequences thereof. We help provide you with the tools you need for your projects, but it's up
to YOU to know how to use them correctly.
An Overview of Airstarts and the Eggtimer Proton
One of the coolest (and most complex) things you can do in hobby rocketry is to electronically
ignite a motor while you're in flight. This is called an "airstart". Airstarts are typically of two
types... you can ignite extra motors while in flight, or you can have multiple stages and
separate/ignite them in flight. These have different flight characteristics and requirements, but
from the electronics point of view it's the same... you're triggering something at a certain time
in the flight while going up. That's a much different requirement than a deployment controller,
which typically will trigger something (generally, parachutes) while you're going down,
generally at a relatively slow velocity.
The Eggtimer Proton performs this function by acting as a timer, triggered by the same launch
detect mechanism as the deployment functions (Launch Detect Altitude, or Accelerometer
Launch Detect). Since the Proton keeps track of about 2,000 altitude/accelerometer readings
prior to reaching LD, it "knows" when you actually started the flight by seeing when you first
started moving off the pad, so it can accurately time your flight from that point. That time is the
Start of Flight, of SOF.
Each output channel on the Proton is an independent timer, triggered by the SOF. They can be
used for igniting a motor, firing a charge to separate stages, or just about anything else you can
think of. Since these functions may have some serious safety ramifications (i.e. you don't want a
high-power rocket motor firing when you don't want it to fire) there are several safety features
and qualifications built into the Proton's airstart software. Those are discussed below.
In addition to the timer functions, you also get the usual Proton features... 14-flight memory,
remote WiFi interface for configuring, arming/disarming, downloading, and testing, and your
choice of single or dual battery operation. Since the Proton uses a unique dual-ended
deployment circuit, the airstart igniter is basically "dead" until you arm it, and you're well into
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