This startup wants to build a fusion reactor on a boat

There is only one fusion device on Earth that has been able to meet A The main scientific thresholdBut Maritime Fusion CEO Justin Cohen is already preparing to put a fusion reactor on a boat.

Stay with me, it’s not entirely far-fetched. Thanks to the progress In artificial intelligence, computing and superconducting magnetsThe power of fusion is closer to commercial reality than ever before. It increasingly looks as if nuclear fusion is a matter of “when” rather than “if.” When that happens, it promises to provide large amounts of clean energy from an abundant fuel source: water.

Putting a reactor on a ship isn’t necessarily unreasonable either. Today, submarines and aircraft carriers powered by nuclear fission reactors routinely patrol the seas. It’s quiet, powerful, and can operate for decades before needing to be refueled. Even the civil sector I played with this idea Nuclear-powered cargo ships of the 1960s and 1970s.

“Fission certainly paved the way in terms of nuclear power on ships,” Cohen, who co-founded it Marine fusionTechCrunch said.

A nuclear fusion program promises to give ships similar capabilities but without concerns about meltdowns, spread or radiation. Currently, the sector is focusing on building the first reactors on Earth. “I’m sure we’re the first to really look at what it means to put a tokamak on a ship,” Cohen said, referring to a pioneering fusion reactor design.

If nuclear fusion succeeds, Maritime’s leap into the seas will put it ahead. In addition, Cohen argues, it may be easier commercially to start offshore.

The first fusion power plants will not be cheap, and it will take some time before their cost comes down.

“Competing against things like solar and wind on the grid is very challenging from a cost perspective,” Cohen said.

At sea, economic matters look different. Ammonia and hydrogen are the main contenders to replace diesel and bunker fuel on cargo ships, but they are still expensive.

“These are some other very expensive fuels that may actually be the only other things that are as expensive as first-of-its-kind nuclear fusion,” Cohen said. “In those cases, we are actually competing, directly.”

To flesh out its concept and begin building parts for its first reactor, Maritime Fusion has raised $4.5 million in a seed round led by Trucks VC with participation from Aera VC, Alumni Ventures, Paul Graham, Y Combinator, and several angel investors, the startup exclusively told TechCrunch. The company was part of Y Combinator’s winter 2025 cohort.

Maritime has begun assembling high-temperature superconducting (HTS) cables from tape it buys from suppliers, mostly Japanese companies, Cohen said. These cables will eventually form the basis of the powerful magnets the tokamak will need to trap the plasma required for fusion reactions. It will also be sold to other companies to generate revenue as Maritime develops its own power plant, he said.

The startup expects its first power plant, named Yinsen, to generate about 30 megawatts of electricity.

Some of the biggest engineering challenges will be designing the support systems that harvest the energy and keep the tokamak running, Cohen said. To simplify the equipment on board, some additional tasks, such as fuel processing, will be performed ashore, he said.

The first marine tokamak will be about eight meters wide, and the startup expects it to become operational in 2032 and will cost about $1.1 billion.

By comparison, Commonwealth Fusion Systems (CFS), widely considered a leader in the fusion race, is building Spark, a smaller tokamak less than five meters wide. The company has almost raised 3 billion dollars And yet, much of it is gone Towards building the pilot factorywhich is expected to come online next year.

Sparc will not deliver power to the grid; Instead, his goal is to prove that tokamaks can generate more energy than they consume. CFS’s large-scale Arc reactor, which powers the grid, will not be ready until the early 2030s.

CFS has a big head start on several merger startups, including newcomer Maritime. However, Cohen is confident that this will not be an obstacle.

“We’re not going to spend billions on a break-even device that doesn’t produce power on the grid,” he said. “The first tokamak we build will be a tokamak that produces energy for the customer.”