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The parts of a rocket

Rockets and landing · level 2, lesson 6 of 6

A question to start

A big rocket can be as tall as a 30-storey building. Almost all of it is empty-looking tube. What is inside, and what is each part for?

The idea

nose cone, payload insidesecond stageoxygen tankfuel tankengines and nozzlesfinsstages split here
  • The payload is the reason for the trip: a satellite, a rover, or people in a capsule. It sits at the top.
  • The nose cone covers the payload, protecting it and helping the rocket slip through the air. Once the rocket is above the air, it splits open and falls away.
  • Tanks hold the fuel and the oxygen. They take up most of the rocket. Their walls are thin and light, as thin as a few coins stacked on top of each other, for their size.
  • Engines burn the fuel and oxygen. Pumps feed them, and the hot gas comes out of a bell-shaped nozzle, which helps the gas rush out fast and straight.
  • Fins, on some rockets, keep it pointing the right way in the air. Many big rockets steer by tilting their engines instead.
  • Stages. Big rockets are stacks of smaller rockets called stages. When the first stage runs out of fuel, it drops off and the next stage fires. There is no point carrying empty tanks.

Almost all of a rocket at launch is propellant (fuel and oxygen). In a big rocket like the Saturn V that flew to the Moon, about nine tenths of its mass at lift-off was propellant. The payload was only a few hundredths.

Worked examples

1. A rocket is mostly tank. If a rocket weighed 100 elephants at launch, about 90 of them would be fuel and oxygen, about 7 would be the tanks, engines and stages, and only about 3 would be the payload.

2. Dropping stages. The Saturn V had three stages. The first burned for about two and a half minutes and fell into the ocean; the second took over, then the third.

Try it

  1. Where on a rocket is the payload?
  2. What do the tanks hold?
  3. Why do big rockets drop their stages?
  4. About how much of a big rocket's launch mass is propellant?
Answers
  1. At the top, under the nose cone.
  2. Fuel and oxygen.
  3. So they do not have to carry heavy empty tanks and engines any more.
  4. About nine tenths.

Common mistake

"Most of a rocket is the spaceship." Most of it is propellant and the tanks to hold it. The part that reaches space, let alone Mars, is a small piece at the top.

Where it leads