During Dr Yuri Blashtov’s performance at Questacon, he’ll try and launch 10 rockets. Dr Yuri’s ‘rockets’ are not all rockets in fact, some are projectiles – they get given a push and then just fly through the air! Can you figure out which of the following are which?
1. Hydrogen Powered Rocket
A balloon contains the hydrogen gas fuel to launch Yuri’s first rocket with a small payload on top. When ignited, the hydrogen reacts explosively with oxygen from the air to produce a very loud noise. The force or thrust of the explosion is in all directions, only a little is directed upwards, so the payload doesn’t go very high!
2. Balloon Flight
The simple release of an inflated balloon demonstrates that air pushed out through the neck of the balloon in one direction pushes the balloon in the opposite direction. Directed thrust produces results although the flight path is wobbly.
3. Balloon Animal Rocket
Simple cardboard fins are added to a balloon rocket and demonstrate that the balloon now has direction without wobbles!
4. Finger Rockets
Energy is used to pull back elastic within the rocket. When the elastic is released the energy pushes the rocket forward. The flight path is wobbly until fins are added and help to stabilise the rocket.
5. Pump Rocket
A large pump rocket works by using a plunger to quickly squash air and build up the air pressure beneath the rocket. When the pressure is high enough, the force on the rocket is enough to launch it, and then it ‘flies’ through the air, hitting the wall before gravity brings it back to Earth.
6. Air Rocket
Using a foot pump, air is pushed into a plastic bottle until the pressure in the bottle is high. When the pressure is high enough the air escapes out of the narrow opening of the bottle rocket, pushing the rocket in the opposite direction. The rocket goes faster and faster until air stops escaping.
7. Water and Air Rocket
This bottle rocket contains some water, then air is added and compressed. On release, water is forced out of the bottom of the rocket by the compressed air above it, and the ‘reaction force’ pushes the rocket in the opposite direction. The water gives a bigger push than just air because a volume of water has more mass than the same volume of air.
As the water leaves the rocket gets lighter, so the push has more effect and the rocket accelerates at a faster and faster rate. This happens with space rockets too. As fuel is used, or stages discarded, the rocket becomes lighter and so accelerates faster.
8. Liquid Nitrogen Rocket
At -196°C, nitrogen is liquid. Above that temperature it becomes a gas and takes up 600 times as much space. A small plastic ball is filled with liquid nitrogen and floated in warm water. The liquid nitrogen warms and forms a gas which pushes like a jet stream through two small holes in the ball. The ball spins and rises high into the air. Dense white clouds are produced as the cold nitrogen gas freezes water in the atmosphere.
9. Pop off Rocket
A dissolving headache tablet, with a little water, is put in a film canister and tightly capped. The chemical reaction produces a gas which builds up enough pressure in the canister to pop off the canister. The canister travels high in the air as a result of the direct push, the lid gets pushed downwards, but doesn’t go very far because the table pushes back on it!
10. Kitchen Rocket
A chemical reaction between two common kitchen ingredients (baking soda and vinegar) produces a large amount of gas. When released, the gas pushes downwards out of the neck of the bottle, pushing the bottle in the opposite direction—similar to a space rocket where a chemical reaction produces gases which push out of a narrow opening and push the rocket in the opposite direction.