how about an infrared

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Well-Known Member
Sep 20, 2003
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actuated launch system? Seems like the electronics are practically "off the shelf". Can any EE chime in here?

Wireless launch controllers have been advised against many times and Justy gives some good advice in this thread

I beleive the interference issues still affect infra red, its just another form of light wave on the same spectrum as radio frequency.

The cost seems exceptionally high when compared to wire!
Wow, one of my posts got referenced in another conversation! :D

That wireless pyrotechnic igniter looks pretty slick, and it's considerably cheaper than the homebuilt system I'd described for doing the same job (passing a coded signal over a radio link to arm, and another coded signal to launch). You might be able to say that the keyfob is the safety key, since the system cannot be armed & launched when it is removed. It's kind of iffy though.

If you really wanted to you could do it with IR, but potential problems include:
a) bright sunlight, the type that's often present on good rocket launching days, may interfere with the signal getting through
b) if your system is looking for a simple flash of IR, it could be triggered by sunlight, a backfiring car, the glint off a pair of sunglasses... a system looking for a coded signal will have the same design & cost problems as a radio link
c) the reciever will have to be mounted on a structure to keep it above the grass, since a single blade of grass could block the signal
d) you'll have to clean the reciever's lens thoroughly after every flight, since it'll get coated in rocket exhaust gunk

For the price you would pay for any wireless launch system -- radio or IR, homebrew or commercial -- you could buy a spool of wire, a nice rocket kit, and a whole bunch of motors. A wireless launch system could be very cool if designed and built safely, and rocketry is all about cool, but a rocket and a pile of motors is cooler than a wireless launcher.

On a related subject...
Unconfirmed Rumour: A friend of mine insists that a powerful radio control airplane transmitter is capable of setting off an Estes igniter that's attached to a WIRED launch system. I can almost believe it, if the launch leads were exactly the right length to act as an antenna, but it seems real unlikely. My plan to prove/disprove this involves launch leads cut to a length matched for the frequency I'd broadcast, a CB radio, and an HF amplifier several times more powerful than any R/C airplane pilot has ever used. :D

There are two problems with an IR system.

The first is the range, and the second is the relative cost.

I doubt that you would get a range greater than ~30 ft without having a directional system thats going to cost more than an equivalent length of wire, and wire is going to win out for cost below that distance.

A more important issue is safety. You have to be concerned about accidental firings by extraneous IR/RF sources, so a simple on-off signal source shouldn't be used for any wireless system whether it be IR or RF. Within this limitation, you are restricted to either a multiple frequency, multiple level modulation technique or a truely digital one.

In the first case, at minimum you need modulation circuitry in the launch controller and demodulation circuitry at the pad. A better choice is to have a microprocessor in both the launcher and at the pad that requires a 5 command sequence before launching. You would send a command from the controller to arm the pad, have the pad confirm receipt of that command and reply that it is armed, have the controller send a command to the pad to launch, have the pad ask for a launch request confirmation, and have the launcher resend the the fire command which would then ignite the pyrotechnics.

It's hard for me to believe that this is simpler and cheaper than wire for most folks.

Bob Krech