Fill the bottle so that the water is about 1







, This is where you will be able to see if you constructed the cap correctly. If you attach the pen to the bike pump and it doesn't leak when put upside down, it's ready to for your countdown.








If you are struggling with this step, you could secure the pump using tape or some gum. It'll still propel into the sky, and may even go higher if something is resisting it's flight.
 Don't be a jerk and point at somebody. Also, it's a good idea to steer clear of any neighboring windows. If your fins are secure and well portioned, the rocket should should upwards.
 You are creating a fuel by each pump you send to rocket. It can't fly with only a few pumps. Continue pumping air into the rocket until it takes off.









Be sure any kids or friends aren't too close while you pump.
The water will gurgle after each pump.
 Instead of using the pen cartridge in the plastic cap, you could just use the bike pump. Remove the cap. Wrap the bike pump with tape or until it seems like it will be a tight fit into the mouth of the bottle. Stick the pump directly into the water bottle.


If you did this correctly, you should have to really work for the bike pump's hose to fit into the bottle.
Add water into the bottle.
Attach to a bike pump.
Position your rocket.
Pump air into the bottle.
Use an alternative system.
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