this post was submitted on 29 Jul 2026
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yeah it's called a water bottle rocket i think and i've seen one like 2 months ago.
also you can't reach orbit that way. the rocket equation says that you'd need exponentially more fuel the higher you want to go, simplified. precisely, it's a bit more like: m~0~ / m~f~ = exp(Δv/v~e~) where v~e~ is the effective exhaust velocity (how quickly the water is thrown out behind) and Δv is constant 7 km/s for going to orbit, so if v~e~ is sth like 20 m/s you can see how that's difficult. chemical fuel has v~e~ of 3 km/s so Δv/v~e~ is sth around 2.3 and exp(2.3) ≈ 10 so that's doable.