General Fusion has achieved a significant milestone by successfully generating plasma, a superheated state of matter necessary for fusion, within its prototype reactor. This accomplishment marks the beginning of a 93-week journey to demonstrate the viability of the company’s unique approach to fusion power.

The reactor, known as Lawson Machine 26 (LM26), is the latest iteration of General Fusion‘s devices, which have been testing various aspects of its distinctive approach. The company assembled LM26 in just 16 months and aims to achieve “breakeven” by 2026.

As one of the oldest fusion companies still in operation, General Fusion was founded in 2002 and has raised $440 million to date, according to PitchBook. Despite seeing competitors rise and fall, and failing to meet breakeven promises, including one made over 20 years ago, the company remains committed to its mission. It has witnessed the fusion industry’s struggles and has learned from its own experiences, including the challenges of achieving commercial breakeven.

In the context of fusion power, breakeven can refer to two distinct points. Commercial breakeven occurs when a fusion reaction produces more power than the entire facility consumes, enabling the power plant to supply electricity to the grid. Currently, no company has achieved this milestone. Scientific breakeven, on the other hand, is reached when the fusion reaction generates at least as much power as was directly delivered to the fuel, without considering the rest of the facility. This milestone is crucial for any fusion attempt, and so far, only the U.S. Department of Energy’s National Ignition Facility has achieved it.

General Fusion’s approach to fusion power differs significantly from other startups. Its magnetized target fusion (MTF) technique shares some similarities with inertial confinement, the method used by the National Ignition Facility in late 2022 to demonstrate that fusion reactions can produce more power than required to initiate them. However, instead of using lasers to compress a fuel pellet, General Fusion’s MTF reactor design relies on steam-driven pistons.

Within the chamber, deuterium-tritium fuel is electrified to generate a magnetic field, which helps contain the plasma. The pistons then drive a liquid lithium wall inward, compressing the plasma. As the fuel is compressed, its temperature increases until it sparks a fusion reaction, which heats the liquid lithium. The company plans to circulate the heated lithium through a heat exchanger to produce steam and power a generator.

The concept of MTF originated in the 1970s at the U.S. Naval Research Laboratory, where researchers were exploring compact fusion reactor designs. Although these efforts were unsuccessful, General Fusion believes that modern computers can now execute the complex choreography required for MTF, making it a viable approach.

While LM26 is an essential step forward, General Fusion still faces significant challenges. The device lacks a liquid lithium wall, instead relying on solid lithium compressed by electromagnets, which limits the number of test runs. Although the company has made progress on a liquid wall prototype, performing over 1,000 tests to assess its durability, integrating all the components will be a substantial engineering challenge.

Activating LM26 is a crucial step for General Fusion, which is now competing with a host of newcomers boasting significant funding and ambitious timelines. The company must navigate these challenges to deliver a power plant and prove the viability of its unique approach to fusion power.