I was reading a lot about the hypothetical orbital mega-structures that could potentially exist in the future if technology and manpower advances enough. A few of the more notable ones are the following (please post ones that aren't listed if you know about others):
Trans-orbital Structures
- Skyhooks - Orbital Transport Method
- Space Elevators - Orbital Transport Method
- Space Fountaions - Orbital Transport Method
- Launch Loops - Launching spacecraft into orbit
- Space Tethers - Orbital Propulsion
Orbital Structures
- Orbital Cable - Interstellar Launching after Geostationary Orbit
- Bernal Sphere - Stationary Orbital Habitat
- Rotating Wheel Space Station - Space Station with Artificial Gravity
- Bishop Ring - Same Basic Idea.
In addition to these seemingly non-fictional devices, there's tons of fictional mega structures like Dyson Spheres, Ring Worlds, Terraforming and other more "fictional", "long-term" or "planetary-scale" solutions are out of scope for this question.
The Question: Are any of these methodologies implemented currently at a "micro" scale for certain functions onboard existing spacecraft and are there any planned mega-structures (public or private) being built at the moment?