Orbiting spaceport for efficient Earth-LEO and LEO-cislunar space transport

The orbiting spaceport envisioned in this concept is similar to a terrestrial airport in that it is a hub for arriving and departing flights. Like a terrestrial airport, it has "runways" for arriving and departing flights. However, the arrival and departure speeds for flights arriving at or departing from the orbiting spaceport are on the order of 50 times higher than speeds of aircraft landing or taking off from a terrestrial airport. The "runways" of the orbiting spaceport are consequently very much longer that those of an airport. As there is no atmosphere in LEO to provide lift nor gravitational force to hold arriving flights to the "runway", arriving flights are captured on the fly by "catcher sleds" that have been rapidly accelerated to match the speed and position of the arriving vehicle. The catcher sleds move on maglev tracks and are accelerated and decelerated by linear electric motor-generators. That avoids the need for arriving vehicles to carry their own complex systems to engage with the acceleration and braking fields of the linear motor-generators. Departing flights are similarly carried by "launcher sleds" that accelerate them to launch velocity and then release them. Following release of a departing flight, or as part of the release process, the launcher sled brakes at high acceleration, coming to rest at the far end of the launcher "runway". After each catch or launch of an arriving or departing flight, the sled involved is shuttled to the opposite end of its runway to be readied for its next catch or launch.

The arrival speed of a flight arriving at the orbiting spaceport subtracts directly from the rocket-supplied delta V that would be needed to rendezvous with the orbiting spaceport. Likewise, the launch speed for a flight departing for destinations in cislunar space subtracts directly from the rocket-supplied delta V that would be needed to reach its destination in cislunar space. For flights departing from the spaceport for a return to earth, the launch velocity subtracts from the reentry velocity into Earth's atmosphere, reducing demand on heat shields.

For flights incoming from cislunar space, the spaceport's ability to catch the flights at the perigee of their highly elliptical trajectories provides an attractive option to the technically challenging alternative of direct reentry to Earth's atmosphere at near escape velocity. It opens the possibility of efficient round-trip flights between LEO and cislunar space. The energy and momentum from capture of an incoming flight can balance the energy and momentum for launching an outgoing flight to the Moon or elsewhere in cislunar space.