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June 11, 2013

John Slough preparing first nuclear fusion tests for the end of this summer

Last month at a NASA symposium, John Slough and his team from MSNW, presented their mission analysis for a trip to Mars, along with detailed computer modeling and initial experimental results.

Slough and his team have published papers calculating the potential for 30- and 90-day expeditions to Mars using a rocket powered by fusion, which would make the trip more practical and less costly.

But is this really feasible? Slough and his colleagues at MSNW think so. They have demonstrated successful lab tests of all portions of the process. Now, the key will be combining each isolated test into a final experiment that produces fusion using this technology.

The research team has developed a type of plasma that is encased in its own magnetic field. Nuclear fusion occurs when this plasma is compressed to high pressure with a magnetic field. The team has successfully tested this technique in the lab.




To power a rocket, the team has devised a system in which a powerful magnetic field causes large metal rings to implode around this plasma, compressing it to a fusion state. The converging rings merge to form a shell that ignites the fusion, but only for a few microseconds. Even though the compression time is very short, enough energy is released from the fusion reactions to quickly heat and ionize the shell. This super-heated, ionized metal is ejected out of the rocket nozzle at a high velocity. This process is repeated every minute or so, propelling the spacecraft.

In the video below, the plasma (purple) is injected while lithium metal rings (green) rapidly collapse around the plasma, creating fusion.

Thin hoops of metal are driven at the proper angle and speed for convergence onto target plasmoid at thruster throat. A target Deuterium FRC plasmoid is created and injected into thruster chamber.

Target FRC is confined by axial magnetic field from shell driver coils as it translates through chamber eventually stagnating at the thruster throat

Converging shell segments form fusion blanket compressing target FRC plasmoid to fusion conditions. The shell absorbs neutrons emitted during fusion.

Vaporized and ionized by fusion neutrons and alphas, the plasma blanket expands against the divergent magnetic field resulting directed flow of the metal plasma out of the magnetic nozzle.



The team had a sample of the collapsed, fist-sized aluminum ring resulting from one of those tests on hand for people to see and touch at the recent NASA symposium.

The team is working to bring it all together by using the technology to compress the plasma and create nuclear fusion. Slough hopes to have everything ready for a first test at the end of the summer.

The Plasma Dynamics Lab — where Slough and colleagues, including UW graduate students, build and conduct experiments — is filled wall-to-wall with blue capacitors that hold energy, each functioning like a high-voltage battery. The capacitors are hooked up to a giant magnet that houses the chamber where the fusion reaction will take place. With the flip of a switch, the capacitors are simultaneously triggered to deliver 1 million amps of electricity for a fraction of a second to the magnet, which quickly compresses the metal ring.


The fusion driven rocket test chamber at the UW Plasma Dynamics Lab in Redmond. The green vacuum chamber is surrounded by two large, high-strength aluminum magnets. These magnets are powered by energy-storage capacitors through the many cables connected to them. (Credit: University of Washington, MSNW)

The mechanical process and equipment used are reasonably straightforward, which Slough said supports their design working in space.

“Anything you put in space has to function in a fairly simple manner,” he said. “You can extrapolate this technology to something usable in space.”

In actual space travel, scientists would use lithium metal as the crushing rings to power the rocket. Lithium is very reactive, and for lab-testing purposes, aluminum works just as well, Slough said.

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