  Nothing could be simpler: attach the fins to an empty plastic soft-drink bottle (one quarter filled with water) attach the hose to a bicycle pump and start pumping. Slowly the pressure builds until the end of the hose is ejected and the force of the water being expelled (about 25psi theoretically developing 3.9lbs of thrust) carries the rocket up 100 feet into the air. Re-use it again and again. No rocket engines, no pyrotechnics and little risk of personal injury: even with miss-fires. Great for a sunny day at the local park, beware of trees and buildings or you're liable to lose it. Link: Google Search 
