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Not sure if this is too much chemistry, but I'll try:

If I fill a plastic bottle with a small amount of rubbing alcohol, shake it around and hold a match to the bottle neck, I'll get a flame wooshing out of the opening. This can easily be used to propel the bottle upwards, like a rocket. I tried it already, there are lots of youtube videos about this, and NASA has instructions for the experiment as well.

When trying to go for maximum speed or height of the rocket, there are a few factors influencing this experiment. Here are the ones that I can think of:

Some related to the bottle:

volume, shape, aerodynamics, weight, size of opening, possibly shape of the bottle (long and thin or short and fat) When the bottle neck is smaller it creates a stronger thrust.

Others related to the propellant:

How fast does it burn, how dense is it (especially compared to air), how heavily does it vaporize. If the vapor is denser then air it all floats out of the opening of my bottle before I can light it and I don't have as much fuel.

As you might be able to see, I don't know a lot about the propellants.

So here's my question:

What are the factors related to the propellant, that influence the launch height and speed of the woosh rocket.

What's the best propellant to choose for a woosh rocket, and why?

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    $\begingroup$ Interesting question, but maybe better for chemistry - or chemical engineering - depends on burn speed etc. etc. - and frankly for this home experiment SAFETY. Alcohol is a good choice as it has a relatively cool flame $\endgroup$ – tom Jul 7 '15 at 0:03
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    $\begingroup$ The post has been flagged as belonging on Chemistry, but my feeling is that it is on-topic here, so I'm not moving it without the OP's say-so. Another possible location is Space Exploration where they may have more people with practical rocket experience. But I don't know how they would react over there. $\endgroup$ – dmckee Jul 7 '15 at 0:34
  • $\begingroup$ Since no one seems to know here, I asked in Space Exploration and Chemistry. Thanks for keeping this up for so long! :) $\endgroup$ – olli Jul 20 '15 at 0:17

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