[k7sune]

Humm the next logical step would be to pressurize the rocket before igniting it. Or maybe to add some water in the bottle to increase the propelled mass. They just need a way to ignite the alcohol fume from the top……

[neuroelectron]

I would think the next logical step would be pressurizing a stainless steel thermos with liquid methane and mating it to a 3d printed copper prototype manifold and turbine pump.