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A rover's circuits

Electricity and magnetism · level 2, lesson 6 of 6

A question to start

Perseverance drives, steers, takes pictures and talks to Earth, all on Mars with nobody there to change a battery. How does the electricity get round it?

The idea

A rover is full of circuits, all joined to one power system.

  1. The power source. Perseverance has a nuclear generator that makes electricity from heat, day and night.
  2. The batteries. The generator charges two rechargeable batteries. They give extra power for the busy moments, when the rover needs more than the generator can make at once.
  3. The things that use it. Wires carry the electricity to motors, heaters, cameras, computers and radios.

There are lots of motors. Each of the six wheels has its own motor to drive it, and the four corner wheels have another motor each to steer.

The switches on a rover are electronic: its computer turns each circuit on and off, following commands sent from Earth.

generatorbatteries6 wheel motors4 steering motorsheaterscameras, radio

Worked examples

1. Counting motors. Six wheel motors plus four steering motors is ten motors just to move and turn.

2. Busy moments. Driving and using the arm at once needs more power than the generator makes. The batteries make up the difference, then the generator charges them again.

3. Switching from Earth. The team sends a plan. The rover's computer closes the circuit to a camera, takes a picture, then opens it again to save power.

Try it

  1. What makes Perseverance's electricity?
  2. Why does it need batteries as well?
  3. How many motors does it use to drive and steer?
  4. Who presses the switches on a rover?
Answers
  1. A nuclear generator that turns heat into electricity.
  2. For busy moments, when it needs more than the generator can make at once.
  3. Ten: six to drive and four to steer.
  4. Nobody: its computer opens and closes them, following commands from Earth.

Common mistake

"The generator drives the wheels directly." All the parts are on circuits joined to the batteries. The generator keeps the batteries charged.

Where it leads