This month’s Acta Astronautica (vol. 227, February) is propulsion-relevant:
Deng, H. Sun, Y. Cheng, L. et al Study on the current stability and performances of electrospray thruster by coaxial capillary emitters of hybrid highly conductive ionic liquids P 1 .2024.11.049
Moriai, I. Fujimori, A. Sekine, H. et al. A water resistojet propulsion system on a 6U CubeSat EQUULEUS: Demonstration of reaction control in deep space P. 114 .2024.11.037
Electrospray thrusters are (depending on your choice of spray fluid) the simplest possible thruster, yet with very good Isp (propulsive efficiency). Therefore, electrospray thruster tech is very enabling for SmallSats and NewSpace. Attitude control becomes trivial; attitude control plus course correction is not much harder, being a slight scale-up. Therefore, deep-space missions by small, lightweight, robust probes (including daughtercraft and swarms) could be fully functional compared to traditional (‘OldSpace’) probes.
And speaking of OldSpace, the lunar mission EQUULEUS has field-demonstrated water resistojet thusters. Note, however, that Earth’s natural satellite has a deep gravity well. This strong acceleration (actually comparable to Earth gravity) means such minor thrusters are limited to attitude control. Around an asteroid, however, gravity is not Earthlike, not even a little. Ceres’ gravity is, not one-sixth Earth’s gravity, but one-sixth of one-sixth. And Ceres is the largest asteroid; more-typical mission targets would have, say, one-sixth of one-sixth of one-sixth. Therefore, an EQUULEUS trim thruster would be useful as an asteroid-bound primary engine.