The Spacetime Beacon is a spatial positioning device used when building a base. It can send signals to receive supplies, and marks your territory over a radius of 125 meters.
When stocked with repair materials, it will automatically repair all structures within 50 meters.
On PVP servers, you can set the protection time for base structures at your Spacetime Beacon, preventing those structures from being attacked for a certain period of time.
The Spacetime Beacon can be unlocked from the Structures tab of the Tech interface [O].