NASA Blazes the Trail

NASA had a more positive experience with solar sailing in 1974 when the Mariner 10 spacecraft ran low on attitude control gas. Because Mariner 10 was on a mission to Mercury, there was plenty of sunlight around and this gave mission controllers an idea. They angled Mariner's solar arrays into the Sun and used solar radiation pressure for attitude control. It worked. Though Mariner 10 was not a solar sail mission, and though the radiation pressure it used was incredibly small, this ingenious use of Mariner's solar arrays did demonstrate the principle of solar sailing.
Also in the 1970s, Dr Louis Friedman, then at NASA's Jet Propulsion Laboratory, led a project to try the first solar sail flight. Halley's Comet was to make its closest approach to Earth in 1986, and NASA conceived the exciting idea of propelling a probe via solar sail to rendezvous with the comet. Eventually, the project was scrapped. Still the year-long work on preliminary design demonstrated that, indeed, solar sailing was a feasible spacecraft-propulsion technique.