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An Anonymous Coward writes:

http://www.sciencealert.com/nasa-scientists-are-investigating-a-propulsion-system-that-could-reach-mars-in-3-days

NASA scientist Philip Lubin is working on a system where lasers propel spacecraft with giant sails to the Red Planet in as little as three days. Much like Bill Nye's much-hyped solar sail, this 'photonic propulsion' system relies on the momentum of photons - particles of light - to move forward. But instead of photons from the Sun's rays, Lubin's design would be given a push by giant Earth-based lasers.

[...] So how do photons work to propel something as big as a spacecraft? Despite not having any mass, particles of light have both energy and momentum, and when they reflect off an object, that momentum is transferred into a little push. With a large, reflective sail, it's possible to generate enough momentum to gradually accelerate a spacecraft.

While Lubin and his team haven't yet tried out their system, their calculations show that photonic propulsion could get a 100-kg robotic craft to Mars in just three days.

A larger craft, like the kind humans might travel in, would take around a month to get there - one-fifth of the time it would take the Space Launch System (SLS), the world's most powerful rocket currently being developed to take us to Mars.

Lubin also explains that in the 10 minutes it will take to get the SLS into orbit, photonic propulsion could propel a spacecraft to an unheard-of 30 percent the speed of light - and it would also use a similar amount of chemical energy (50 to 100 gigawatts) to do so.

But the real benefit of photonic propulsion comes over longer distances, where the spacecraft has more time to speed up, and could eventually take us outside our Solar System and to neighbouring stars.

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