this startup wants to build a fusion reactor — on a boat

The Vision of Fusion Power at Sea

Currently, only one fusion device globally has achieved a crucial scientific milestone. However, Maritime Fusion CEO Justin Cohen is already preparing for the deployment of a fusion reactor aboard a vessel.

This concept, while seemingly ambitious, is grounded in recent advancements. Progress in artificial intelligence, computational power, and superconducting magnet technology is bringing commercially viable fusion energy closer to realization. The prevailing outlook suggests that fusion power is a matter of “when,” rather than “if,” promising abundant clean energy derived from a readily available source – water.

Drawing Parallels to Fission Power

The idea of a reactor on a ship isn’t unprecedented. Nuclear fission reactors already power submarines and aircraft carriers, offering quiet, robust operation with decades-long intervals between refueling.

Even in the civilian sector, the possibility of nuclear-powered cargo ships was explored during the 1960s and 1970s. As Cohen, co-founder of Maritime Fusion, explained to TechCrunch, fission technology has laid the groundwork for nuclear power applications in maritime settings.

Fusion offers the potential for similar capabilities, but without the risks associated with meltdowns, nuclear proliferation, or radioactive waste. While current efforts are focused on establishing land-based fusion reactors, Cohen believes Maritime Fusion may be the first to investigate the feasibility of a ship-based tokamak – a leading fusion reactor design.

A Potentially Easier Path to Commercialization

Should fusion technology prove successful, Maritime’s focus on marine applications could provide a competitive advantage. Cohen also posits that launching operations at sea might be strategically simpler.

Initial fusion power plants are anticipated to be expensive, and cost reduction will take time. Competing with renewable sources like solar and wind on the traditional power grid presents significant economic challenges.

However, the economic landscape at sea is different. Alternatives to diesel and bunker fuel for cargo ships, such as ammonia and hydrogen, are currently costly.

“These alternative fuels are also expensive, potentially making them comparable in price to early-stage fusion,” Cohen stated. “This creates a direct competitive opportunity for us.”

Securing Funding and Building Capabilities

Maritime Fusion has secured $4.5 million in seed funding, led by Trucks VC, with contributions from Aera VC, Alumni Ventures, Paul Graham, Y Combinator, and various angel investors. The company participated in Y Combinator’s winter 2025 program, as exclusively reported to TechCrunch.

The company has begun assembling high-temperature superconducting (HTS) cables sourced primarily from Japanese suppliers. These cables are essential for constructing the powerful magnets needed to confine the plasma required for fusion reactions.

Maritime also intends to sell these cables to other organizations, generating revenue while developing its own power plant.

Project Yinsen: A 30-Megawatt Goal

The startup’s initial power plant, codenamed Yinsen, is projected to generate approximately 30 megawatts of electricity.

Significant engineering challenges remain, particularly in designing the systems to capture energy and maintain the tokamak’s operation. To streamline onboard systems, certain processes, like fuel processing, will be conducted onshore.

The first Maritime tokamak will measure around eight meters in diameter, with an anticipated operational date of 2032 and a projected cost of $1.1 billion.

Comparing with Commonwealth Fusion Systems

For context, Commonwealth Fusion Systems (CFS), a leading entity in the fusion field, is constructing Sparc, a smaller tokamak with a diameter of just under five meters. CFS has raised nearly $3 billion to date, primarily dedicated to building its demonstration plant, expected to come online next year.

Sparc’s primary objective is to demonstrate that tokamaks can produce more energy than they consume, rather than directly supplying power to the grid. CFS’s full-scale, grid-connected reactor, Arc, is slated for completion in the early 2030s.

Confidence in a Unique Approach

While CFS holds a considerable lead, Cohen remains optimistic. “We won’t invest billions in a breakeven device that doesn’t generate energy for the grid,” he emphasized. “Our first tokamak will be designed to produce energy for a customer.”