Solar sailing seems like a simple concept—instead of being pushed along by the wind, as in a typical sailing ship, a spacecraft can use highly reflective said to be pushed along simply by sunlight. But as with almost all engineering challenges, that technique is much easier said than done. Sunlight can head up one side of a sail more than another, causing the ship to rotate unexpectedly. Other unforeseen situations could arise that can also have catastrophic consequences for any mission using this propulsion technology.

Luckily, there is a way to account for those situations, though it involves a lot of math. Control theory is common in system design, and now researchers at Beihang University have devised a control scheme that they think could help minimize the risk to solar sails.

Control systems are relatively easy to understand in concept. A system has a series of inputs; in the case of a solar sail, those inputs might be the solar force pushing on it from the sun and maybe the gravity of any nearby object.