Useful links:
=> http://www.aircommandrockets.com/flying_higher.htm
=> http://www.sciencetoymaker.org/waterRocket/buildWaterRocketLauncher.htm
=> https://www.youtube.com/watch?v=1t663D_gErg
=> http://www.waterrocketmanual.com/how_they_work.htm
=> http://www.txsnapper.eezway.org/txsnapper/tips.html