Soda Bottle Water Rocket

I've been reading the GeekDad blog recently, looking for cool ideas of things to do with my kids this summer.  I came across their entry for making soda bottle water rockets.  It looked simple, cheap, and fun.  So we hopped over to Wal-Mart to buy a bike pump and an inner-tube.  It took us a bit, but Ann and I finally built a cork that would fit snugly in the bottle.  We were sorta testing it out and, uh, well, we accidentally launched in the kitchen.  Ooops.  Got water everywhere.  But it worked!  I can't wait till we try it outside tomorrow.