Wear a face shield like this one
There are a lot of different designs around for these things, and mine is pretty much the easiest and simplest. The stupidest one I ever saw was like this: "Get a concrete pipe that is a little bigger than a Mosquito Estes rocket. Then cut grooves in the concrete pipe on the inside to put the rocket fins in for guidance. Now blow up your neighbors!" I actually saw this! If you plan to use pyrotechnic payloads, make sure to test it with dummy payloads first to make sure it won't go off in the tube.
Materials:
1. PVC, ABS, or HDPE tube, preferably HDPE, 2nd choice is ABS. I used a 5-foot length of 2-inch diameter ABS.
2. Momentary switch, get one at radio shack or something. Momentary
switch isn't nearly as high tech as it sounds. It just means that the
circuit is connected when you are pushing to button, and not connected
when you let go of it.
3. Some wire, it doesn't need to be all fancy or anything, just
insulated wire that's not too fat (just because fat wire is annoying).
4. Battery, I use a 9V with clip and holder so it is very easy to take
the battery out. Always leave it out when you are not using it! You
don't want it to shoot when its not supposed to.
5. End cap, to partially block the end. I use a metal lid taped to the end.
6. Alligator clips are not required, but it's a lot easier than twisting the wires to the igniter.
Procedure:
1. Wiring is the most
complicated part, but still easy. From the battery there are two wires.
One goes directly to an alligator clip to the igniter and one goes to
the switch first so you control when current goes through to the
igniter.
2. Attach all the parts to the tube with electrical tape or something.
3. For the end cap, I used a metal jar lid. Poke a hole in it that is
big enough to easily fit your alligator clips though. Tape it so it is
like a hinge for loading the rocket.
To use:
1. Put the rocket in with an electric igniter.
2. Run alligator clips through the hole in you end cap and hook them to the igniter.
3. Close the end cap, you can just tape it shut, but make sure it is secure.
4. Connect your battery.
5. Push the button! Make sure you have full-face protection or you
could get seriously burned. Cheap face shields can be bought from any
hardware store.
Wear a face shield like this one