My son was inspired to scare the neighbors. (Thanks Tom =)

So he has built an autonomous robot rocket launcher (no remote control; he programs it ahead of time, and off it goes).

The runtime program uses various trigger events to move the launch platform, raise the rocket into position (like a slow hydraulic rail, but using gears) and launch it. We are still working on that last part, but I suspect we will use the current from the LED light module to flip a relay to connect a fresh 9V battery to the igniter. And we may need to add the second NXT motor controller for ignition control and a second rocket rail. Should be able to aim in any direction and angle…