Orbital rings are extremely similar to launch loops, but have some differences.
They have the following advantages:
they have no high-g turnaround sections, so there's fewer problems to be solved in R&D, the cable/rotor has similar g-loading along its length
- they have less change in altitude on the active cable.
- they may be easier to start, it's theoretically possible to build the first one on the surface of the Earth around the equator including the ocean and then spin it up- it will lift off all by itself if the spokes are let out in a controlled way. Later ones may be built on orbit and lowered down.
- failure modes are mostly at altitude and this gives the energy a chance to dissipate in the upper atmosphere
- probably somewhat less susceptible to lighting as the magnetically active material is above the atmosphere (launch loop needs extra mass to deal with this)
- orbital rings can pass over more points on the Earth and can provide intercontinental transport.
They have the following disadvantages:
- the start up costs are higher as the minimum size/mass is several times larger than the launch loop in terms of magnetic material and linear cable length
- the motor to make the rotor turn has to be placed at altitude, rather than the ground
- if started from ground level, the cable is subject to accidental or deliberate attack from humans and animals (e.g. sharks) until it has left the ground (on the other hand cables are routinely laid anyway). If started on orbit, launching the materials is currently extremely expensive, but may be bootstrapped.
- orbital rings are much longer, and hence are more likely to be damaged by orbital debris.
The following things are notable, but are similar to launch loops
- a high altitude launch loop above 100km or so is highly susceptible to space debris
- orbital rings need the same sort of cable sheath as launch loops both to control the cable dynamics as well as to reduce air drag if used within the atmosphere.