As part of my introductory engineering class this year, I have to work with a group to build a small vehicle (no bigger that 2ftx2ftx3ft) that can carry some water up to 250 ft. However, we cannot use any electricity, anything flammable or solid rockets. So right now I'm at a loss as to how to give this thing enough power to carry 1/2 lb. of water 100 ft. (my goal right now). Compressed air, CO2, and chemical reactions are fine, but I haven't found any good resources on how to make use of any of those for a car type thing that needs to carry something. Any ideas or resources I could look into?