A conceptual microwave-propelled lightcraft receives microwave beams
from an array of microwave sources on the ground. Credit: Kevin Parkin
Instead of explosive chemical reactions on-board a rocket, the new concept, called beamed thermal propulsion, involves propelling a rocket by shining laser light or microwaves at it from the ground. The technology would make possible a reusable single-stage rocket that has two to five times more payload space than conventional rockets, which would cut the cost of sending payloads into low-Earth orbit.
NASA is now conducting a study to examine the possibility of using beamed energy propulsion for space launches. The study is expected to conclude by March 2011.
In a traditional chemical rocket propulsion system, fuel and oxidizer are pumped into the combustion chamber under high pressure and burnt, which creates exhaust gases that are ejected down from a nozzle at high velocity, thrusting the rocket upwards.
A beamed thermal propulsion system would involve focusing microwave or laser beams on a heat exchanger aboard the rocket. The heat exchanger would transfer the radiation's energy to the liquid propellant, most likely hydrogen, converting it into a hot gas that is pushed out of the nozzle.
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