Like most spacecraft, the CHEOPS mission launched last week uses a chemical propellant to adjust its position once in orbit. The high mass of such propellants has, however, prompted space scientists to explore alternatives such as “light sails” that enable spacecraft to navigate using the radiation pressure from light, much as old-fashioned sailing ships used wind to travel the high seas. A team of researchers in the US has now taken a step towards a more powerful light sail by testing a prototype design that uses lasers and diffraction gratings rather than the sunlight and mirrors employed previously.
The simplest light sail designs, such as that adopted by JAXA’s IKAROS mission or the privately-funded LightSail 2, use a large, thin mirror to reflect sunlight. Although the propelling force from sails of this type is small compared to that supplied by chemical fuels, spacecraft that rely on sails do not have to carry their own fuel supply. Another advantage is that their “fuel” will never run out as long as the sail is illuminated – making them good candidates for future long-haul space missions that require more energy than chemical propellants can supply.
A laser-based propulsion system ...