A rocket or a gun carries cargo to an orbital coilgun. The coilgun converts some of the kinetic energy of the incoming cargo into the kinetic energy of flywheel generators. The orbital energy of the coilgun is replenished by electrodynamic tethers and by launching empty rockets backward. The orbital coilgun is prone to buckling unless it is segmented like the orbital loop. The minimum mass (for 1-ton cargo) is 105 tons.
Dandridge M. Cole and Donald W. Cox, Islands in space : the challenge of the planetoids, Philadelphia: Chilton Books 1964.
Roger Arnold and Donald Kingsbury, "The Spaceport, Part I," Analog Science Fiction/Science Fact, Vol. 99, No. 11, November 1979, pp. 48-67.
Roger Arnold and Donald Kingsbury, "The Spaceport, Part II," Analog Science Fiction/Science Fact, Vol. 99, No. 12, December 1979, pp. 60-77.