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A new spacecraft uses light as propulsion

Although the focus on the next generation of crewed spacecraft has been on the commercial companies like SpaceX and Boeing, as well as NASA’s new engine tests, there is another possible spacecraft in the works that uses a radically different type of propulsion.

The Planetary Society is preparing to test launch a new type of spacecraft into the upper atmosphere that uses a solar sail to create momentum. The craft is based off an idea from astronomer Carl Sagan, and according to Extreme Tech, the test will be held on May 20.

The design is one part brilliant and one part madness, but it has a very real shot at succeeding. The craft uses a massive mylar sail to capture light for propulsion. Light doesn’t have any actual mass, but its momentum can be harnessed and turned into an energy source.

The sail itself is designed to capture photons. What it can’t use, it reflects; this process creates pressure on the sail, which is enough to push the craft – similar, at least in the most basic sense, to wind pushing a sail.

The technology has already been proven to work, as both the US and Japan have successfully tested the theory, but the LightSail is significantly bigger. The sail being tested is 32 square meters, which is just large enough for the test craft to carry a comm system, batteries, solar panels, a computer, and flight hardware. The entire craft is about the size of a shoebox.

The acceleration of the craft in space will be directly proportionate to the size of the sails – the larger they are, the faster the craft will go. Some estimates claim that with a large enough sail made with current technologies, a space craft could eventually accelerate to around 20,000 meters per second. In theory, a large enough sail could take a craft a significant portion of the way towards reaching light speed.

This direct correlation between size and speed creates some serious issues though. To begin with, deploying a sail large enough to travel to other planets – or even the moon – is beyond our capabilities at the moment. It could be launched in several stages, but it would then need to be assembled in orbit.

A sail that large would also make maneuvering difficult. For the most part that wouldn’t be an issue given how massive space truly is, but the sail would likely be under near constant bombardment from micrometeoroids and similar types of space debris.

Despite that, this method of space travel has the benefit of being highly efficient. It would require no fuel, and very few moving parts. That would theoretically cut the costs of space travel significantly. As more and more commercial organizations are looking towards space, this may be a very real alternative to developing a costly spacecraft using conventional engines.

The test will be conducted on May 20 in the upper atmosphere. Assuming this mission is successful, the real test will begin in April 2016, when the solar sail is launched into orbit.

Update: This article has been updated to correct a typo.

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Founder and DBP boss. Ryan likes the Kansas Jayhawks, long walks on the beach, and high fiving unsuspecting people.
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