Application of Symmetrical Motorised Momentum Exchange Tethers for Two-Way Earth–Mars Transportation

As we venture deeper into space and establish bases and orbital stations on celestial bodies, it is imperative to develop sustainable space transportation methods that minimise propellant usage. Space tethers represent one promising option in this endeavour. A space tether, in theory, can operate without the need for any propellant. This paper presents a novel strategy for the use of symmetrical motorised momentum exchange tethers for a 2-way continuous payload transfer system between Earth and Mars. Symmetrical tethers offer the advantage of not necessarily de-orbiting on payload capture and release because there is no change in the geometrical location of the centre of mass when in operation. A novel strategy is proposed requiring 2 tethers, whereby one rotates prograde and the other retrograde, and 2 dummy payloads in suitable parking orbits around each planet to provide overall mass balance. The analysis considers an idealised scenario where planets orbit the Sun in planar, concentric orbits, and no perturbational forces are present, in order to establish the concept. A methodology has been developed to calculate the orbits of the tethers and the dummy payloads around Earth and Mars based on the proposed strategy taking into consideration the reusability of the dummy payloads. A list of possible orbits around Earth and Mars is presented. Additionally, a drag perturbation analysis has been carried out on selected sets of results to determine the orbital decay. Finally, some major failure scenarios are discussed and some recovery options are proposed.