Oops, forgot there was a mid-month Advances in Space Research. For Jan 15 (vol. 75 #2):
de Almeida, A. K. Vaillant, T. Santos, L. B. T. et al. Low-thrust transfer with Theory of Functional Connections: Application to 243 Ida with a solar sail p. 2108 .2024.09.069
Santos, L. Barros, L. Hiraki, K. et al. Potential of non-flat solar sail for higher characteristic acceleration p. 2289 .2024.11.041
When your target body has true microgravity (not one-sixth Earth level… not even one-sixth of one-sixth), entire new forms of travel open up. Because Earth-type, high-acceleration, high-thrust engines are no longer demanded. Solar sails are “free” propulsion (once built- there’s the trick) and can enable new mission scenarios, including final velocities beyond chemical propulsion. One proposal for a Halley mission included using solar sailing to “crank” the spacecraft orbit, and not fly by the (retrograde) comet at such a high, science-limiting flyby speed.
In this case, the use of solar sails to enable small-body science is still worthy and enabling. Here we see some of the details to be ironed out: skillful mission planning (versus today’s tools in dynamics) and the exact form of the solar sail (numerous designs have been proposed, much fewer actually flown by demonstrators). Every additional tool in our toolbox gets us one step closer to a new Age of Exploration: there are over a million asteroids in the Main Belt alone that beckon (including spectral types never seen up close), Kuiper Belt Objects never seen up close save for three (arguably four), and, oh… every single Centaur is a target, never before seen up close. The Lucy mission is the closest we’ll come to seeing a Centaur, and even then we won’t know what we won’t know. There is no guarantee that Jupiter Trojans will be ‘pretty much’ Centaurs closer to the Sun, and not something with a completely different origin.