This memory randomly came back to me when I woke up in the middle of the night and it’s been bothering me since. When I was a kid in the early 90s, I remember telling my dad about a rocket concept where the rocket would scoop up dust and gas from the space environment around it and use that as a propellant. His response was to make a face and go “cool” and that was the last time I thought about it. I think I might have seen it talked about in a library book and have a vague memory of a cartoonish illustration of a rocket with a funnel on the front.
At the time, the concept exited me, but it felt like a really long stretch to make something like that work. I haven’t really thought about it since. Is this concept still bouncing around? It doesn’t really sound that viable, but I don’t know crazy ideas sometimes work.
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: m0 / mf = exp(Δv/ve) where ve 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 ve is sth like 20 m/s you can see how that’s difficult. chemical fuel has ve of 3 km/s so Δv/ve is sth around 2.3 and exp(2.3) ≈ 10 so that’s doable.