How do direction work in space because north,east,west and south are bonded to earth? How does a spacecraft guide itself in the unending space?
In: Physics
Astronautical engineer here.
Spacecraft are equipped with a subsystem called Attitude Determination and Control System.
This subsystem can contain various tools including Star Trackers, Horizon Sensors, and Sun Sensors for navigation.
There are lots of stars in space, and a lot of them are so far away that they appear fixed, i.e. they do not seem to move.
A star tracker is basically a camera that scans the space for star patterns. Then it compares the image with the database to estimate its orientation.
Sun sensors find the Sun (obviously) and are generally used for solar panel pointing etc. Horizon sensors use infrared to find orientation based on the planet’s horizon line.
This is the navigation part. For control, there are reaction wheels, magnetorquers, reaction control thrusters, and more. RWs spin to generate a moment in the desired axis, so there are mostly 3 of them. Magnetorquers use magnetic field of the planet to change orientation. RTCs are small thrusters that are placed on large spacecraft to perform small correction/orientation maneuvers.
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