Here is my instructable for making and setting off a bottle rocket. It doesn't require any launchers, pumps etc. Once made it can be used again and again. It does make a brilliant woosh sound and shoots across with flames (very cool in low light). Please read the safety and hints at the end as you will be shooting a flaming bottle a fair distance.
I regularly use this one in my Science lab in school so I have included some pointers for teachers who may want to try it in school.
Before publishing this instructable I got my 13 year old to follow it, she managed to make one and set it off. But I must admit I wish I hadn't shared this with her now as I am worried about her setting someone's house on fire.
All you need are:
A 2 litre drinks bottle (doesn't have to be 2 litres I have done it with 1.5 and 1 litre bottles, but 2 litres works best)
A Screw driver (or anything you can heat and melt plastic with), in school I use tong.
Fuel: Methylated spirit, or any liquid that is volatile (evaporates quickly) and is flammable (catches fire easily). In school I use Ethanol.
A lighter, the longer the better. In school I use a splint at the end of a meter rule, this is in my lab so no breeze to blow the flame out, keeps my hand out of the way and gives the pupils a better view.
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Step 1: Make a Hole in the Bottle Top
Heat the screwdriver in a flame and use it to melt a hole in the bottle top.
Take your time, heat the screwdriver a couple of times if you need to.
The hole should be about 7 to 10mm wide (a third of the top's diameter). There is no exact measurement as the rocket will work without a lid but it's more impressive with one.
Place the hot screwdriver somewhere safe to cool.
In school you can use tongs for the hole, heating it with a Bunsen burner and allow it to cool on a heatproof mat afterwards, you can prepare the lid well in advance.
Step 2: Add Fuel
Pour the fuel into the bottle.
You don't need much, just enough to fill the bottom bumpy bits.
In school I use about 20 ml of ethanol (should be cm cubes, but I can't find the superscript button).
Step 3: Shake
Block the hole in the lid with your hand/finger and shake the bottle for a good minute or two, to allow some of the liquid to evaporate.
You could use a spare lid during shaking.
In school for this step, I use the pupil that needs to be kept busy (check for allergy to alcohol first). I don't straight up ask "are you allergic to alcohol?" because I don't want the little darling to be tempted into drinking the ethanol, so I ask if they are allergic to swabs they have before injections or hand sanitisers and then ask them about alcohol, making sure to mention that there are lots of types of alcohol only one of which is in alcoholic drinks and if they drink this one it'll make them blind, followed by organ failure, peeing blood and then death/detention (I like to keep it light). I also take the bottle from them quickly so they don't breath in the alcohol vapour.
Step 4: Important: Empty the Excess Fuel
Pour whatever liquid that hasn't evaporated out of the bottle.
In school I have a separate bottle for this demonstration, so I don't contaminate the stock solution, (this avoids annoying the Chemists and more importantly the Technician). Put it somewhere safe so it doesn't "disappear" while your attention is elsewhere.
Step 5: Shoot the Rocket
Place the rocket on its side on a stable surface and place a flame near the hole.
The vapour catches fire with a woosh, there will be flames in the bottle and it'll shoot away in a blink of an eye.
(See video clip included)
Be patient with this part, it can take some time for the fire to catch, it'll help if the bottle lid is wet with a bit of the fuel. I sometimes squish the bottle a little to allow for some of the vapour to leave the bottle and be nearer to the flame.
Important thing to noteis that the flight path of the rocket is unpredictable, so anyone in front of the bottle (at any angle) is at risk, I've hit plenty of lights, monitors, taps and dented a couple of ceiling tiles, Please read the safety suggestion on the final step.
Step 6: Recover the Bottle
Go and pick up the bottle (this is a precaution, the flame should be out and the bottle is only warm to the touch).
You can't use the bottle immediately again, as the oxygen in the air in the bottle is used up during combustion, producing water and carbon dioxide (you'll be able to see condensation inside the bottle once it cools slightly), quickest way to repeat would be to have multiple bottles (only need one lid) or to fill the bottle with water and drain it, this will replace the "stale" air inside with fresh air containing the Oxygen needed. Don't be tempted to blow into the bottle as the fumes coming out could be an irritant.
Step 7: Safety and Helpful Hints
Important to remember:
You will be shooting a bottle with burning fuel inside it across a field/garden or lab so be sensible.
Pick your fuel carefully, most volatile, flammable liquids will work, but some liquids can dissolve the bottle, so if you're not sure pour a small amount in the bottle to check (do this outside or over a sink).
When melting the hole in the lid the hot screw driver will go through the lid suddenly, so have the lid on a heatproof surface and hold it in a way that the screwdriver will not go through the lid and into your hand.
You can use a drill insteadof the hot screwdriver, just make sure the surface under the lid is stable and it wouldn't matter if you went through the lid and marked the surface underneath. Sometimes the drill bit gets stuck in the lid and spins the lid out of your grip, just let it go and turn off the drill. If you have long hair (I don't) the chances are you will be holding the lid with one hand and the drill with the other and your lovely hair will be very close to the spinning drill with a potential risk of scalping (lots of youtube clips of this), so wear a hat.
Keep flames away from the fuel at all times. In the excitment it'll be easy to make mistakes, also remember that the vapour is even more flammable.
Shaking the bottle, chances are some of the fuel will get on hands, which is why you should check for allergies.
Don't breath in the vapour or fumes.
Before firing the rocket, put the bottle of fuel away from the flame and the rocket's path.
Guiding the rocket, I usually place the rocket on a piece of guttering about 18 inches long to help guide it, I have in the past placed books on either side of the bottle, just close enough to help guide the direction of the rocket over the first few inches.
Try it out first before showing off. This will help you know what to expect and also trouble shoot, you might decide it's too risky to do with "certain" people around. At work I have a couple colleagues who help me out with testing, improving, trouble shooting and risk assessments.
Don't do it if you have people (pupils) close that maybe upset by loud sudden sounds.
Don't be stupid. Can't risk assess for stupid, so...............
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