SoylentNews is people
SoylentNews
Boeing has patented a laser powered propulsion system for airplanes. A number of sites reported on the patent, with eye-rubbing headlines that told the story. BusinessInsider headline read, "Boeing just patented a jet engine powered by lasers and nuclear explosions." Benjamin Zhang said the US Patent and Trademark Office approved Boeing's application for a laser and nuclear-driven airplane engine.
Zhang noted that presently the Boeing Dreamliner is powered by multiple turbofan engines with their fans and turbines in place to compress air and ignite fuel to provide thrust. The engine presented in Boeing's patent application takes another route. Zhang said the laser engine may also be used to power rockets, missiles, and spacecraft.
The new engine would work "by firing high-power lasers at radioactive material, such as deuterium and tritium," said BusinessInsider. "The lasers vaporize the radioactive material and cause a fusion reaction—in effect a small thermonuclear explosion," said the article. "Hydrogen or helium are the exhaust byproducts, which exit the back of the engine under high pressure. Thrust is produced."
In this approach the inside wall of the engine's thruster chamber coated in uranium 238 reacts with the neutrons from the nuclear reaction and generates immense heat. "The engine harnesses the heat by running coolant along the other side of the uranium-coated combustion chamber," said Zhang. "This heat-energized coolant is sent through a turbine and generator that produces electricity to power the engine's lasers."
Three inventors named in the patent application are Robert Budica, James Herzberg and Frank Chandler of California. The applicant is listed as The Boeing Company in Chicago. The patent was filed in 2012.
Original Submission
(Score: 2) by Immerman on Tuesday July 14 2015, @04:40PM
>The fusion doesn't have to be energy-positive or even break-even as long as the total energy from the fusion, fission and decay is greater than the energy required for the fusion.
Exactly.
As for their engine, it has a rather different design goal - instead of generating energy efficiently, it's designed to produce thrust, which means you need high-velocity exhaust, which is what the fusion is providing. Fission doesn't do "fast" very well - the energy-to-mass ratio of the fragments just isn't high enough. Plus they tend to be locked into solid fuel pellets so that the energy is thermalized almost instantly. The fission is just there to power the lasers to sustain the fusion.
As for an "expensive" fusion method - for extended operation in a rocket chamber I can't really think of any better alternatives offhand. Farnsworth-style fusors are unlikely to provide an attractive energy density without vaporizing themselves, tokamaks are far too massive to incorporate into a rocket, and most other techniques are still unproven laboratory curiosities.