Creating a "Coke Bottle" Rocket with Volatile Fuel

[Cummings]

Had a little project a while back, created some 'coke bottle' rockets.

The ideais simple, use compressed air to push out an incompressible liquid, water creating some thrust for the bottle rocket to fly into the sky.

there are plenty of tutorials for making bottle rockets out there, but i wanted a more realistic effect of a rocket.

Here is where some physics comes in. I personaly don't see this effecting lift off performence but i am no professor.

I want to replace the water, with a volatile liquid. And, when launched, the air forces the liquid out as it would do to water thus creating some thrust, but then the fuel coming out is ignighted, creating a rocket like effect on the ground and while it flies into the air.

As its ignighted outside the bottle, it wouldn't increase the thrust would it? If it were ignighted inside the bottle (well that's a generalisation), it would, as the expansion of gases would make a good little rocket.

Just somthing i want to test out to make the bottle rockets a tad more interesting. I fear that each rockets lifetime would drop dramaticly. That and i would be replacing launch pads quite a few tmes before i upgraded to a copper.

 

[LURCH]

Actually, igniting fuel outside the bottle should still generate thrust. The expansion of gases as they cumbust should send a pressure wave out in all directions, including the direction from which the fuel just came. This would send pressure, and therefore thrust, upward into the bottle. However, it might also bad instability as the thrust would be coming at the very tail of the rocket.

 

[NatSusan]

That sounds like a really cool project! I've seen some videos of people using dry ice and water to create a similar effect with their bottle rockets, but using a volatile liquid would definitely take it to the next level.

I think you're right in that the ignition of the fuel outside the bottle wouldn't really add much extra thrust, but it would definitely make for a more visually impressive rocket. And, as you mentioned, the rocket's lifespan may be shorter with the use of a volatile liquid, but it would definitely be worth it for the added excitement and realism.

Have you tried experimenting with different types of volatile liquids to see which one produces the best effect? I imagine certain liquids would ignite more easily and produce a bigger "rocket" effect.

I'm definitely interested to see how your project turns out. Keep us updated!