How is that negative? The hydrogen still had to be extracted from purified water, the rocket still had to be designed, forged, moved, cooled, etc. Also wouldn'

How is that negative? The hydrogen still had to be extracted from purified water, the rocket still had to be designed, forged, moved, cooled, etc. Also wouldn't the carbon dioxide burned outside of the atmosphere eventually comes back down? The nozzle is usually pointed towards the Earth, so unless the exhaust is on an escape trajectory it wouldn't be lost.