# Temperature System

## Why do we have to control heat on a spacecraft if there are no people on board?

While it is far more important to control the heat on and around a space ship if there are people on board, it is also important to control heat on an unmanned space ship. Spacecraft have temperatures that they are comfortable at; this is usually called the operating temperature. The operating temperature is usually given as a range between two numbers like -10ºC to 60ºC. This means that the parts of the spacecraft have been tested and will work if the temperature in the spacecraft is between the two numbers.

A spacecraft has an operating temperature because the parts inside will only work at a certain temperature. If for example, your rocket thrusters use hydrazine as the rocket fuel then the tanks, plumbing, pumps, and rocket fuel needs to be kept at a certain temperature. Hydrazine freezes at 2ºC (35ºF) and boils at 113ºC (236.3ºF). If the temperature in the spacecraft goes outside of those temperatures, the hydrazine will either freeze out or boil off, leaving spacecraft with no fuel to turn.

What could go wrong on DS1 if it gets too cold?
What could go wrong on DS1 if there's too much heat?
What is heat?
How does heat move?

Will DS1 get heated directly by the Sun?
Does heat travel differently in space than it does on Earth?

What other forms of energy does a spacecraft releases into space?
What happens to the heat once it is released into space?