How Do Rockets Work?
Rockets work by expelling mass (hot gases) in one direction, which propels the rocket in the opposite direction (Newton's third law). Unlike airplanes, rockets do not need air - they carry both fuel and oxidizer to create combustion. The expanding gases are forced through a nozzle at high speed, generating thrust that pushes the rocket forward.
Key Takeaways
- Newton's third law explains rocket propulsion: every action has an equal and opposite reaction.
- Ion engines use electricity to accelerate ions and are more fuel-efficient but produce less thrust.
- Solid rocket boosters cannot be throttled or shut off once ignited.
Explanation
Newton's third law explains rocket propulsion: every action has an equal and opposite reaction. When a rocket expels gas downward at high velocity, an equal force pushes the rocket upward. This works in the vacuum of space because the rocket does not push against air - it pushes against its own exhaust.
Rockets carry both fuel (hydrogen, kerosene, or solid propellants) and oxidizer (oxygen) because there is no air in space. Chemical rockets burn these together in a combustion chamber, creating extremely hot gases that expand rapidly. A specially shaped nozzle accelerates these gases to very high speeds (thousands of meters per second).
The rocket equation (Tsiolkovsky equation) describes why rockets need so much fuel: to go faster, you need more fuel, but more fuel means more weight, requiring even more fuel. This is why rockets use multiple stages - dropping empty fuel tanks reduces weight, making the remaining fuel more effective.
Things to Know
- Ion engines use electricity to accelerate ions and are more fuel-efficient but produce less thrust.
- Solid rocket boosters cannot be throttled or shut off once ignited.
- Reusable rockets like SpaceX's Falcon 9 land and fly again, reducing costs.