This release of gas under pressure produces the required Thrust and leads in the propulsion of the jet engine.
During the nuclear reaction, high energy neutrons are produced.
…A specific impulse of 100,000 250,000 seconds may be provided.
As per the patent, Boeing may also use the laser engine to power rockets, spacecrafts and missiles.
The Laser and Nuclear fusion powered jet engine however is still on the paper or rather the patent documents.
source: www.techworm.net
