A rocket carries cargo from the Earth to a rotating orbital pipe. A magnet secured to the cargo generates eddy currents in the pipe and thereby accelerates the cargo. Half of the orbital energy of the tube is transferred to cargo, while the other half is wasted as heat. The electric current flowing in the pipe makes it act like an electrodynamic tether, so it can replenish its orbital energy. The pipe must be slender, because the cargo rides on the outside of the pipe. Buckling of the pipe makes the idea impractical. A similar idea called the electrotube is more promising. The minimum mass is only 100 tons.


C. S. Welch and C. Jack, "A Kinetic Tether System for Launching Payloads," Proceedings of 46th International Astronautical Congress, IAF-95-V.4.06, 1995.

Buckled pipe

If the pipe rotates slowly, the centrifugal force is too small to prevent buckling.

Bent pipe

If the pipe rotates fast and cargo moves slower than the speed of sound in the pipe (about 5 km/s), the pipe will bend.

Rough ride

If the pipe rotates fast and cargo moves faster than sound velocity in the pipe, it will be a rough ride, unless the pipe is perfectly straight.

Curator: Al Globus
NASA Responsible Official: Dr. Ruth Globus
If you find any errors on this page contact Al Globus.
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