Embodied Energy Repurposing via Energy-Harvesting Electrodynamic Tethers

An electrodynamic-tether system in low Earth orbit has the possibility of transferring energy from its orbital potential energy to its electrical system. Thus, electrical energy can be made available for immediate use or stored for later use by transferring energy from the spacecraft's orbital energy. Reciprocally, stored electrical energy can be used to increase the altitude (that is, orbital energy) of the spacecraft. Using the energy stored in the "orbital battery" enables new design options that impact a spacecraft's power budget, orbital dexterity, and/or mission capabilities. In this paper, the concept of "energy repurposing" is introduced, which is the transfer of energy embodied in the orbital energy of unused spacecraft to the electrical subsystem of another spacecraft. The transfer of energy simultaneously powers the useful spacecraft while deorbiting the other. Embodied energy can also be used to extend mission lifetime. The "orbital energy density" is also defined, which relates the energy transferred from a spacecraft's orbit to the electrical subsystem for a given mass and change in altitude. Then, the orbital energy density is used to define a round-trip efficiency for deboost-boost scenarios. Simulation results support a value of approximately 1.08(W . h)/(kg . km) for the orbital energy density.