Build a water pressure or air pressure powered rocket. This combines elements of both pump and rocket design and construction. Finding an expert might be tricky. Judge by measuring altitude. Requiring a recoverable payload would be a bit much on top of the rest.

-- tBoy (tcornish@uiuc.edu), March 06, 2001

Answers

Look up plastic bottle rockets like these! http://www.h2orocket.com/ These people are crazy, multi-staging, discarding boosters, using several sizes of bottles and even plastic tubes intended for impact guards on fluorescent light tubes. I haven't looked around for a while but a year or so ago one builder was going to attempt a water rocket flight to 1,000 feet.

-- Gregg Eshelman (gregg1@valint.net), March 07, 2001.

As far as water pressure and air pressure I'm afraid I'm a bit of an expert in both those areas. Been dealing with the water pressure my entire life, it often wakes me in the middle of the night. As far as air pressure, it's hot air that people say I'm often filled with.

I used to love that airpump bottle rocket I had when I was a kid. It would squirt you but living in Florida a little squirt of water often felt good as a way to beat the heat.

Me thinks they will have to do some of the more popular challenges over again, like drag racers and things like that. Some ideas are just too good to use only once.

-- Richard James Retey (theswampie@cs.com), March 08, 2001.