Basic but very effective bottle rockets

 I'v always had a fascination for rockets, and a friend and I had the chance of devoting a saturday to having some fun with bottle rockets. We wanted to build a very simple, but impressive, bottle rocket, with hardly any parts. Check the video at the end to see how it goes!

Step 1 Concept

 Basically, for our rocket, the concept is very simple. A bottle has water and pressurized air sealed inside. The bottle is turned upside down  for launch, so that the water sits at the bottle cap end. When the cap is spun off, the highly pressurized air pushes the water out of the bottle neck with great force, and this creates the thrust.

Comments

[JohnR]

So . . . in your video . . . exactly what was that air-to-water mixture in the very "last" sendoff? Thanks for the instructions.

[ruktion]

water, air and a little special ingredient haha

[rocketree2000]

The optimum water/air ratio is about 35-40% water. Hold the bottle level and sideways, cup your hand at the nozzle and have water flow into the bottle from your hand, when it starts to backflow, it is just about perfect. Some of my students paint their rocket and needed a way to get the right amount of water without looking so we found this technique. We tested this ratio by computer simulation and actual launches and it seems to be the "sweet spot" for 60-90 psi launches. More than 90, we didn't test. I would be a bit careful launching like this, while fun on a hot day, you need to protect your eyes, the water exits at about 70mph. Otherwise it looks like you are having a great time with it, enjoy! My daughters and I spend many summer afternoons launching water rockets.

[DJ Radio]

That first picture in the intro looks very very wrong.  jk =P

[TheChemiker]

Someone got too horny......jk