Recent and foreseen improvements in solar power generation and energy storage have opened the door for high-power SmallSat platforms with mission-enabling advances in electric propulsion, imaging payloads, or communications. As the power density grows, heat rejection and transport become increasingly critical. Thermal straps are inefficient for highly demanding applications, while heat pipes reach their limit for heat fluxes beyond 16 W/cm2. Alternatively, mechanically pumped loops have been considered for high-power density systems, but their increased thermal performance is balanced against the additional mass and reduced reliability associated with active pumps, which are the single most crucial component of the loop. This work proposes a SmallSat-scale active thermal control device consisting of a liquid metal loop powered by a magnetohydrodynamic (MHD) pump. The pump induces fluid motion without moving parts by exploiting the Lorentz force imposed on a single-phase liquid metal by permanent magnets and an applied electric current. Analytical estimations and benchtop tests indicate that the device is able to satisfy the need for miniaturized and low-power active SmallSat thermal systems by reducing the mass required per unit of transferred power by up to ~50% with respect to the state-of-the-art. This value applies to a LEO reference mission where a 60 W heat flux needs to be dissipated from a 60° C payload using a 1200 cm2 deployable radiator. Tests of the pump and power processing electronics indicate good agreement with analytical and numerical models. The absence of moving parts and the high electric conductivity of the liquid result in enhanced reliability and minimal power consumption in a small form factor. This low-mass and high-efficiency system provides a necessary alternative to current state-of-the-art thermal control technologies and will enable SmallSat missions to take full advantage of advances in high-power systems.
Hart et al. (Sun,) studied this question.