The fastest human-made spacecraft so far is NASA's Parker Solar Probe. After its launch in 2018, in November 2021 it skimmed the Sun's atmosphere and used the Sun's gravity to reach a maximum velocity of 586,864 km/h (364,660 mph). That might appear to be blazingly fast – yet it is only 0.06% of the speed of light (read more: "Have we made an object that could travel 1% the speed of light?"). However, exploring the outer solar system and interstellar space yet remains a slow, multi-year, if not multi-decade effort.
One promising way to get an object in space moving very fast is to use a solar sail. Solar sails are large, thin sheets of a reflective material attached to a spacecraft and designed so that the radiation pressure from sunlight can push on them, like wind in a normal sail. A few spacecraft have used solar sails to show that they work (such as NASA's NanoSail-D) (read more: "The physics behind solar sails"). An upcoming NASA solar sail spacecraft mission, the Near-Earth Asteroid Scout, will visit an asteroid estimated to be smaller than a school bus.
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