Water Rocket Thrust - Explanation - Draft 1

[@jacquev6]

Thanks for this video! I'm used to your very good explanation of how to build rockets, and I'm looking forward to more good explanation of the theory! Thank you for taking the time to film, produce and share your videos with us!

[@AirCommandRockets]

Thank you for following along :)

[@MrBellda]

Thanks for sharing George. Another great video.

[@AirCommandRockets]

Cheers Dave :)

[@prietjepruck]

I would be curious to know how much of the kinetic energy is caused by the air phase. Thanks for these interesting video's.

[@AndrewMerts]

There's one thing that I've always wondered about water rocket nozzle design. Water is an incompressible fluid so a de Laval nozzle isn't going to help for the water phase, but what if you got rid of the water phase and instead added a tube going into the tank with inlets and an orifice such that even at the very start you'd be getting compressed air entrained with the water right at liftoff with the aim being to try to minimize the length of the air phase? You're wasting your propellant mass at the beginning by not using the stored energy from the compressed air to accelerate it faster. Wouldn't this substantially increase the total impulse of the rocket if you could balance out using the energy from the compressed air with the mass flow from the water?

[@AirCommandRockets]

Does that mean that as the pressure drops, since you are letting some of the air out early, that there is less pressure to accelerate the rest of the water that is still left in the rocket? There have been a couple of proposed nozzles where the geometry of the nozzle changes when the water runs out. That way you get the best of both worlds. One of them was a simple insert that drops away at the end of the water phase.

[@danielkemp4860]

Commenting to help the algorithm 💪

[@AirCommandRockets]

Cheers :)

[@ptonpc]

Very interesting.

[@johndonaldson3619]

Hi George, just a novice question, do other liquids (or water variations with additives like saline etc) offer better performance options? Thank you

[@AirCommandRockets]

Hi John, good question. Yes it does affect performance but not necessarily the way you would expect. Although with a denser liquid you generate more thrust, you also have a heavier mass to lift with that thrust because of the heavier liquid still in the rocket, and so you may in fact end up flying to a lower altitude. Here is the experiment where we tried various liquid densities: kzbin.info/www/bejne/fKaWo3yfhd6SZ5o

[@ROCKETKNIGHT-ph7xp]

Very informative 👍

[@m7mds91]

nice

[@mstreich]

Air evacuates at the speed of sound? Is that for any type of nozzle? 1:40

[@oldmatebattle2905]

First like