At Commonwealth Fusion Systems (CFS), our mission is to widely deliver fusion’s clean, secure, steady, and affordable energy as soon as possible. A new $863 million B2 round in funding ensures we’re able to do just that.
Our top priority right now is completing SPARC — our machine that’ll demonstrate and refine our core technology at scale. Our new funding lets us continue to push forward on that while also advancing SPARC’s successor and commercial product — the ARC fusion power plant.
You might well ask, “How can CFS start ARC when it hasn’t even completed SPARC yet?” It’s important to note we’re not putting the cart before the horse. We have consciously structured our fundamental approach and architecture so that we aren’t constrained to working purely serially. We believe that the rate of progress is just as important as making progress, because that’s how you get to global scale and ultimately global impact.
We ardently believe the fastest path to fusion is the best path for humanity. Our approach lets us move at top speed in the race to fusion energy.
The B2 funding brings CFS to our next phase in that race. It’s the last funding we’ll raise before SPARC reaches its first key milestone: net fusion energy, denoted scientifically as Q>1, which means producing more energy from fusion than it takes to sustain the fusion process. That’ll be a big moment in the years-long shift in perception about fusion energy moving from “impossible” to “inevitable.”
Accelerating the ARC fusion power plant
At our headquarters in Devens, Massachusetts, we’re building SPARC now. It’s a tokamak — a donut-shaped machine that uses super-strong magnets to confine our fusion fuel at temperatures hotter than the center of the sun. Two forms of hydrogen fuel called deuterium and tritium will release enormous amounts of energy as they fuse together. With ARC, we’ll capture that energy as heat, convert it to electricity, and put the watts onto the power grid.
One of SPARC’s jobs is to prove our core fusion technology like high-temperature superconductors (HTS) that enable our magnets to be stronger and smaller than previously possible. SPARC is a fusion power plant demonstration device — the prototype for ARC.
SPARC’s core mission is to demonstrate industrial-scale fusion power in a commercially relevant package that demonstrates our ability to execute and to integrate a complex set of technologies into a plant. Along the way, we’ll get the final learnings that will inform key details on elements of the ARC design and on how to best operate ARC.
But we don’t have to be done with SPARC to start on ARC.
Why CFS can ramp up serious ARC work now
CFS deliberately designed and planned our SPARC and ARC projects so that we can work in parallel. By making certain architecture choices, we are able to decouple many parts of the work, proceeding on some elements without needing everything on SPARC to be complete.
Because much of ARC’s design is by design essentially the same as SPARC’s — not just most of the subsystems like magnets and heating and controls, but also the physics conditions inside the machine — developing SPARC has given us a head start on developing ARC.
That’s not possible without confidence, so we methodically established our faith in SPARC technology through peer-reviewed papers, modeling, prototypes, and real-world tests. SPARC also is a conservative design that operates largely within previously explored physics regimes we picked to minimize tangling with the sorts of new phenomena that have surprised fusion researchers in the past. Through its similarity to SPARC, ARC inherits our confidence.
We won’t know everything, though. Part of the point of SPARC is to teach us the rest. That’s where another facet of our parallel work comes into play: a “late lock” approach to pin down ARC’s final details. For example, SPARC’s results will help us settle the precise shape of ARC’s vacuum vessel, the chamber that houses the fusion process. But, because of the architecture we’ve selected, we do not need to know the precise shape today to scope the design of a large portion of the rest of ARC.
There are a few ARC systems that aren’t in SPARC, and for those we deliberately set up a path that let us develop them alongside our work to complete SPARC. That includes work on the “blanket,” the system that will capture ARC’s fusion energy so we can convert it to electrical power. We can, for example, build a demonstration system of this technology that doesn’t use fusion heat but that still gets the learnings and proof points.
But frankly, much of the power plant actually has nothing to do with fusion and we can start on much of it early.
For instance, we know how much power ARC will produce — 400 megawatts, or enough for about 280,000 average US homes — and that lets us begin sizing ARC’s balance of plant and cooling systems, and its interconnection to the grid. Now that we’ve selected our first ARC site in Chesterfield County, Virginia, with a strategic partnership with Dominion Energy and Google as our first ARC power customer, we can drive forward detailed permitting and project development. These are all things our new funding enables.
A history of working on parallel priorities at CFS
This isn’t the first time we’ve worked this way. It’s how we operate, when possible:
- CFS bought our campus land before we had completed our Toroidal Field Model Coil (TFMC) magnet prototype test in 2021. We started preparing that land for our offices, magnet factory, and SPARC facility, spending a relatively small amount of money early to ensure we could move imminently the minute the magnet test was done.
- We purchased SPARC’s cryoplant — the centerpiece of our magnet cooling system — almost immediately after raising our last funding round. That sophisticated system took about three years to obtain, but we did the detailed engineering up front to enable our readiness to procure it.
- We sped the arrival of our superconducting tape by purchasing SPARC’s supply before the TFMC project was done, enabling our suppliers to build out their production lines sooner and more steadily.
- Using prototype hardware, we took advantage of every opportunity to learn production techniques early, like welding magnet case halves together or fitting equipment into our vacuum vessel.
Not everything can be done in parallel, of course. But we always try to be intentional and to sequence our work based on first-principles thinking.
With that framework in place, and new funding in hand, now is the time to step on the gas.
