Although it belongs to a class of propulsion systems known as ‘momentum exchange tethers’ it has radical and highly innovative features of its own ��" in particular the use of a precisely controlled motor drive to force the system to spin, and the use of symmetry.
The MMET fits into the current sustainability research theme because it is intended to be powered by solar energy and to use the absolute minimum of additional non-renewable fuel for station keeping, and orbit maintenance over a long life-time, and to be used for continuous interplanetary payload exchange, specifically for supplying terraforming and colonisation activities on local planetary bodies; activities which will inevitably go ahead in the future.
A detailed two-way Earth-Moon mission architecture for 1000 kg payloads, using nothing but tether propulsion from Low Earth Orbit to the Lunar surface and back, has recently been completed for Thales Alenia Aerospace, in Italy.
The system works on the principle of momentum transfer coupled to orbital mechanics. This is exploited to raise and lower the velocity of the payloads: for orbit raising or interplanetary transfer, and for retrieval of the incoming payload by a lower speed rocket or space plane.