I have to agree! use of extension cords and AC components is really not a wise decision John.
The decision to use AC extension cords wasn't John's, it was mine. I built the system he is using more than 5 years ago and with only minor maintenance, it's still working.
BTW: The extension cords we use are bright orange and they still get tripped over and the controller gets knocked to the ground a couple of times each launch but it keeps working because the connectors are rugged.
I did it that way for all the practical reasons given already, namely cost, reliability, ruggedness and availability. I've seen a lot of very high tech launch equipment fail in the middle of a Texas cow pasture just because someone tripped over a nearly invisible CAT 5 cable and broke the connectors or it got how and the microcontroller failed, etc. With the club launch controller is disabled in the middle of the launch folks have to bring out their personal Estes Electron Beam controllers with their skinny 15 foot cord just to keep the launch going.
Yes there is always a remote possibility of hooking something up to a 120 VAC source, but if you're setting up a rocket launching system and you're so "zoned out" you would make such a mistake, then you should consider staying home to begin with.
These things (AC extension cords) aren't made with built-in homing devices to seek out a power outlet at all costs. It takes a human being making a conscious choice. This is what you do at rocket launches at ever step. If you don't have your head IN the game then you're going to get hurt in a dozen other ways and probably hurt someone else in the process.:bangpan:
The choices for many small rocket clubs are either an unreliable launch system, no system or a system that can be build and maintain inexpensively by using what is readily available. After all, the point is to have a safe ROCKET launch not host a NEC convention. In a hobby as unpredictable and risky as rocketry, you can always find many, very good reasons not to do something. That's why there are so few people involved in amateur rocketry as it is and it's so hard to find a place to fly.
BTW: I'm thinking of offering a 4 pad version of the system John is using as a kit if anyone is interested. It uses AC extension cords (not included, it cheaper to buy them at Walmart than to mail them) between the controller and pads, AC Duplex outlets for connectors at the launch controller. Common AC wall switches for pad selection. For wiring at the pad, it uses 3 prong AC plugs, 3 feet of zip cord, banana plugs and slip-on (easily replaceable) alligator clips. It is housed in a plastic tackle box. :jaw:
Art Applewhite
Chief Rocket Scientist
If you build something that is truly fool-proof, then only a fool would use it.