The performance of conventional rockets is limited by the amount of chemical energy in their fuel. One way to improve the performance of rocket engines is to separate the energy source from the rocket. This can be accomplished by using a laser beam to transfer energy from a stationary source to the rocket. In laser propulsion, the rocket carries a tank of reaction mass, but a stationary laser supplies the energy. The laser can either be located on the ground, and beamed upward at the rocket, or in orbit, and beamed downward.

A laser-propelled vehicle is tested in this image.

There are two approaches to laser propulsion to launch from the surface of Earth into space. In laser-thermal propulsion, a laser beam is used to heat a gas, which expands through a rocket nozzle to provide a thrust system. The laser beam is focused on a...