Photonic laser thruster

A photonic laser thruster (PLT) is a concept for space propulsion that works on the principle of a photon-pushed sail, generating thrust directly from the momentum of a photon from a laser reflected from a mirror. The concept differs from other solar sail and laser propulsion concepts in that an amplification process is used, in which the incident beam is re-used by being reflected by a stationary mirror, with an amplification stage at each reflection. Because of the recycling of energy, the photonic laser thruster is more energy efficient than other laser-pushed sail concepts.

The concept was initially developed by Young Bae for use in nanometer precision spacecraft formation under a NASA Institute for Advanced Concepts (NIAC) grant in 2006, for forming space telescopes and radars. However, in this research Bae discovered that photonic laser thruster was stable against movements of laser mirrors and proved that it can be used for main propulsion. Initial proposed uses include high-precision and high-speed maneuver of small spacecraft, such as formation flying, orbit adjustments, and drag compensation. It can be used for beaming thrust from a conventional heavy "tanker" vehicle to a more expensive, lightweight mission vehicle, similar to aerial refueling. Recently in 2015 under another NASA program (NASA Innovative Advanced Concepts), Y.K. Bae Corporation demonstrated a photonic laser thruster with a thrust of 3.5 mN for the first time in history. In this demonstration, the amplified laser power of the photonic laser thruster was greater than 500 kW, which was powered by a 500 W laser.

The practical usage of the photonic laser thruster for main space propulsion would require laser powers and overcoming technological challenges in achieving the laser power and fabricating the required optics. Photonic laser thrusters have a very high specific impulse, and can permit spacecraft to reach much higher speeds that approach a fraction of the light speed, than with conventional rockets, which are limited by the Tsiolkovsky rocket equation.

The use of light for propulsion has been researched since the beginning of the 20th century, with the analysis of a sail pushed by the pressure of sunlight by Friedrich Tsander. Photon propulsion has been discussed for decades as a propulsion that could enable interstellar flight.

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