Beamed-energy propulsion is a method of propulsion that uses a remote energy source, such as a ground- or space-based laser or microwave transmitter, to send power to a space vehicle via a beam of electromagnetic radiation. If the energy to propel a spacecraft does not have to be carried on board the vehicle, significant weight reductions and performance improvements can be achieved. Presently, beamed-energy is one of the most promising technologies to lower dramatically the cost of space transportation. One form of beamed-energy propulsion is laser propulsion.