Lockheed Martin made a lot of news when they revealed their compact nuclear fusion project last week with promises of commercial nuclear fusion within ten years.
Recent criticism has forced project leader McGuire to provide more technical and project details. MIT Technology Review reports on the skepticism and critics of the Lockheed Martin approach. Ian Hutchinson, a professor of nuclear science and engineering at MIT and one of the principal investigators at the MIT fusion research reactor, says the type of confinement described by Lockheed had long been studied without much success.
McGuire acknowledged the need for shielding against neutrons for the magnet coils positioned inside the reactor vessel. He estimates that between 80 and 150 centimeters of shielding would be needed, but this can be accommodated in their compact design. Researchers contacted by ScienceInsider say that it is difficult to estimate the final size of the machine without more knowledge of its design. Lockheed has said its goal is a machine 7 meters across, but some estimates had suggested that the required shielding would make it considerably larger.
Lockheed has built its first compact fusion machine and has carried out 200 shots during commissioning and applied up to 1 kilowatt of heating, but McGuire declined to detail any measurements of plasma temperature, density, or confinement time—the key parameters for a fusion plasma—but said the plasma appeared very stable. He said they would be ramping up heating over the coming months and would publish results next year.
Lockheed has had a team of five to 10 people for the past 4 years and hopes to expand the team now that the project is in the open. This scale of project is about $1 million per year.
Superconductors inside magnetic rings will contain the plasma.Credit : Lockheed Martin
Magnetic Confinement with magnetic mirrors and recirculation of losses
Their magnetic confinement concept combined elements from several earlier approaches. The core of the device uses cusp confinement, a sort of magnetic trap in which particles that try to escape are pushed back by rounded, pillowlike magnetic fields. Cusp devices were investigated in the 1960s and 1970s but were largely abandoned because particles leak out through gaps between the various magnetic fields leading to a loss of temperature. McGuire says they get around this problem by encapsulating the cusp device inside a magnetic mirror device, a different sort of confinement technique. Cylindrical in shape, it uses a magnetic field to restrict particles to movement along its axis. Extra-strong fields at the ends of the machine—magnetic mirrors—prevent the particles from escaping. Mirror devices were also extensively studied last century, culminating in the 54-meter-long Mirror Fusion Test Facility B (MFTF-B) at Lawrence Livermore National Laboratory in California. In 1986, MFTF-B was completed at a cost of $372 million but, for budgetary reasons, was never turned on.
Another technique the team is using to counter particle losses from cusp confinement is recirculation.
Mirror Fusion Test Facility B
The Mirror Fusion Test Facility B followed the earlier Baseball II device, the facility was originally a similar system in which the confinement area was located between two horseshoe-shaped “mirrors”. During construction, however, the success of the Tandem Mirror Experiment (“TMX”) led to a redesign to insert a solenoid area between two such magnets, dramatically improving confinement time from a few milliseconds to over one second. Parts of the MFTF-B were reused. [A spheromak ignition experiment reusing Mirror Fusion Test Facility (MFTF) equipment].
What has previously been announced about Lockheed’s Compact Fusion
“Our [Lockheed’s] compact fusion concept combines several alternative magnetic confinement approaches, taking the best parts of each, and offers a 90 percent size reduction over previous concepts,” said Tom McGuire, compact fusion lead for the Skunk Works’ Revolutionary Technology Programs. “The smaller size will allow us to design, build and test the CFR in less than a year.”
After completing several of these design-build-test cycles, the team anticipates being able to produce a prototype in five years. As they gain confidence and progress technically with each experiment, they will also be searching for partners to help further the technology.
Aviation Week has some technical details
Initial work demonstrated the feasibility of building a 100-megawatt reactor measuring seven feet by 10 feet, which could fit on the back of a large truck, and is about 10 times smaller than current reactors.
The Lockheed 100MW compact fusion reactor would run on deuterium and tritium (isotopes of hydrogen).
Instead of the large tokomaks which will take until the mid-2040s or 2050s for the first one and which will be large (30,000 tons) and expensive have one that fit on a truck. Build on a production line like jet engines.
Aviation Week was given exclusive access to view the Skunk Works experiment, dubbed “T4,” first hand. Led by Thomas McGuire, an aeronautical engineer in the Skunk Work’s aptly named Revolutionary Technology Programs unit, the current experiments are focused on a containment vessel roughly the size of a business-jet engine. Connected to sensors, injectors, a turbopump to generate an internal vacuum and a huge array of batteries, the stainless steel container seems an unlikely first step toward solving a conundrum that has defeated generations of nuclear physicists—namely finding an effective way to control the fusion reaction.
The problem with tokamaks is that “they can only hold so much plasma, and we call that the beta limit,” McGuire says. Measured as the ratio of plasma pressure to the magnetic pressure, the beta limit of the average tokamak is low, or about “5% or so of the confining pressure,” he says. Comparing the torus to a bicycle tire, McGuire adds, “if they put too much in, eventually their confining tire will fail and burst—so to operate safely, they don’t go too close to that.”
The CFR will avoid these issues by tackling plasma confinement in a radically different way. Instead of constraining the plasma within tubular rings, a series of superconducting coils will generate a new magnetic-field geometry in which the plasma is held within the broader confines of the entire reaction chamber. Superconducting magnets within the coils will generate a magnetic field around the outer border of the chamber. “So for us, instead of a bike tire expanding into air, we have something more like a tube that expands into an ever-stronger wall,” McGuire says. The system is therefore regulated by a self-tuning feedback mechanism, whereby the farther out the plasma goes, the stronger the magnetic field pushes back to contain it. The CFR is expected to have a beta limit ratio of one. “We should be able to go to 100% or beyond,” he adds.
he Lockheed design “takes the good parts of a lot of designs.” It includes the high beta configuration, the use of magnetic field lines arranged into linear ring “cusps” to confine the plasma and “the engineering simplicity of an axisymmetric mirror,” he says. The “axisymmetric mirror” is created by positioning zones of high magnetic field near each end of the vessel so that they reflect a significant fraction of plasma particles escaping along the axis of the CFR. “We also have a recirculation that is very similar to a Polywell concept,” he adds, referring to another promising avenue of fusion power research. A Polywell fusion reactor uses electromagnets to generate a magnetic field that traps electrons, creating a negative voltage, which then attract positive ions. The resulting acceleration of the ions toward the negative center results in a collision and fusion.
Neutrons released from plasma (colored purple in the picture) will transfer heat through the reactor walls. Credit : Lockheed Martin
Breakthrough technology: Charles Chase and his team at Lockheed have developed a High Beta configuration, which allows a compact reactor design and speedier development timeline (5 years instead of 30).
* The magnetic field increases the farther that you go out, which pushes the plasma back in.
* It also has very few open field lines (very few paths for the plasma to leak out)
* Very good arch curvature of the field lines
* The Lockheed system has a beta of about 1.
* This system is DT (deuterium – tritium)
Credit : Lockheed Martin and Google Solve for X
McGuire said the company had several patents pending for the work and was looking for partners in academia, industry and among government laboratories to advance the work.
Currently a cylinder 1 meter wide and 2 meters tall. The 100 MW version would be about twice the dimensions.
Credit : Lockheed Martin and Google Solve for X
Credit : Lockheed Martin and Google Solve for X
SOURCES- Lockheed Martin, Youtube, Science Magazine, Aviation Week
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
Known for identifying cutting edge technologies, he is currently a Co-Founder of a startup and fundraiser for high potential early-stage companies. He is the Head of Research for Allocations for deep technology investments and an Angel Investor at Space Angels.
A frequent speaker at corporations, he has been a TEDx speaker, a Singularity University speaker and guest at numerous interviews for radio and podcasts. He is open to public speaking and advising engagements.