To change direction in space, spacecraft predominantly rely on thrusters, which are specialized propulsive devices.
The Role of Thrusters
In the vacuum of space, there's no air or surface to push against, unlike how vehicles work on Earth. Therefore, spacecraft must carry the means for propulsion with them. This is achieved using thrusters.
As outlined in the reference, "To change direction or move, rockets use propulsive devices called thrusters." These devices are crucial for maneuvering, adjusting orbits, and changing trajectory.
How Thrusters Work: Newton's Third Law
The fundamental principle behind how thrusters enable direction changes is Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction.
The reference explains: "Thrusters work by the principle of action a reaction which is based on Newton's Third Law."
Here's a simplified breakdown:
- Action: The thruster expels mass (often gas) in one direction.
- Reaction: An equal and opposite force is exerted on the spacecraft, pushing it in the opposite direction of the expelled mass.
Think of it like pushing off a wall or letting air out of a balloon – the air goes one way, and the balloon moves the other.
The reference further clarifies the action: "Releasing compressed gases provides a reaction in the direction opposite the outlet of the thruster and the reaction propels the rocket." By expelling gas or other propellant out of a nozzle, the spacecraft is pushed in the opposite direction.
Changing Direction vs. Changing Speed
Thrusters can be used not only to change speed (accelerate or decelerate) but also to change direction.
- To change speed: Fire the thrusters forward or backward along the direction of travel.
- To change direction: Fire thrusters perpendicular to the direction of travel, or use multiple thrusters strategically positioned around the spacecraft to rotate it or push it sideways.
Spacecraft are equipped with multiple thrusters pointing in different directions to allow for precise control over movement and orientation in three dimensions (up/down, left/right, forward/backward, and rotation).
Summary of Direction Change in Space
| Method | Principle | How it Works |
|---|---|---|
| Thrusters | Newton's Third Law | Expel mass (like compressed gas) one way. |
| Action/Reaction | Spacecraft moves/rotates the opposite way. |
In essence, changing direction in space is achieved by strategically firing thrusters to create a reaction force that pushes the spacecraft onto a new path or changes its orientation.
