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" In 2013, Y.K. Bae scored funding from NASA&amp;#039;s Innovative Advanced Concepts program to study an amazing new kind of propulsion: Thrust that comes not from liquid rockets but from lasers continuously fired at the spacecraft, which would steadily gain momentum in the frictionless vacuum of space. It&amp;#039;s called the Photonic Laser Thrust system, and it could drastically reduce the amount of fuel needed for space missions. And now, Bae has announced that lab tests of the technology were successful.  In the experiment, Bae fired a laser at a one-pound mock spaceship on a frictionless track and successfully produced thrust. The laser bounced continuously between two mirrors inside a cavity at the bottom of the simulated spaceship, building momentum of 1.1 milliNewtons. We&amp;#039;re not talking about a lot of thrust. For example, the full sized, 6.2-million-pound Saturn V rocket that sent the Apollo 11 moon mission to space needed about 34.5 million Newtons of thrust to lift off. It was many, many orders of magnitude more powerful. However, the goal of the laser system isn&amp;#039;t to get things off the ground. The goal is to boost a spacecraft&amp;#039;s momentum when it&amp;#039;s already in space\u2014which, if you can reach it, requires much less energy than getting a big, heavy hunk of metal off the ground.  Bae believes the Photonic Laser Thrust system eventually could push a craft to the moon in a matter of hours and to Mars in a matter of days. The system would first launch into orbit via conventional rockets. Once it&amp;#039;s in space it would fire the beam at the spacecraft ahead of it. That&amp;#039;s not to say it would be easy to push a ship to the moon or Mars. Laser spreading would degrade the light beam, and they&amp;#039;d still need an estimated 1 gigawatt of power, requiring energy sources that are still decades away. Thus, laser power is still a few decades from being ready for any kind of planetary exploration. But this first test confirms that it works \u2013 and that&amp;#039;s a big deal.      "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/space/a15545/photonic-laser-thrust-space-engine/>