Maritime Fusion Raises $4.5M to Build Superconducting Tokamaks for Ships

Most fusion ventures design power plants intended for the electrical grid, facing strict economic requirements against cheap renewables. Maritime Fusion is taking a different route: adapting compact tokamak reactors to propel commercial cargo vessels and power off-grid defense operations.

The San Francisco startup raised $4.5 million in a seed round led by Trucks VC, with participation from Y Combinator, Alumni Ventures, Aera VC, and Paul Graham, according to PR Newswire. The company, which participated in YC's Winter 2025 batch, is using the funding to advance its high-temperature superconducting (HTS) magnet cable architecture and build its first low-power-density reactor.

Targeting Sea-Based Power and Near-Term Cables

Marine operations provide a distinct entry market for nuclear fusion. Commercial shipping relies on expensive heavy fuels or proposed zero-carbon alternatives like green hydrogen and ammonia. In an interview with TechCrunch, Chief Executive Officer Justin Cohen noted that high initial reactor costs can compete directly with expensive marine fuels, unlike grid applications where solar and wind set a lower price threshold.

Maritime Fusion's planned first-of-a-kind reactor, named Yinsen, is designed to generate 30 megawatts of electricity. The tokamak spans approximately eight meters across and features high-temperature superconducting magnets. The company projects an operational target date of 2032 with a first-of-a-kind cost around $1.1 billion, according to the American Nuclear Society.

To support development before ship deployment, Maritime Fusion is commercializing its patent-pending SHIELD (Superconducting High Integrity Energy Link & Distribution) cable technology. The assembly carried 5,000 amperes at 77K in a liquid-nitrogen-cooled bench test at the company's San Francisco lab. Alongside its reactor program, the company plans to sell these low-loss HTS cables to AI data center operators and power distribution grids.

To lead commercialization outside of fusion, Maritime Fusion is hiring a Business Development & Strategic Partnerships Lead in San Francisco, CA ($120,000–$200,000). The role involves identifying deployment opportunities for HTS cables across AI data centers, power distribution, maritime, and defense sectors.

Engineering Roots from Tesla and SpaceX

Maritime Fusion was co-founded by CEO Justin Cohen and Chief Technology Officer Jason Kaufmann. Cohen is a nuclear engineer and plasma physicist with previous experience at Tesla, SpaceX, Columbia University, Princeton Plasma Physics Laboratory, and NC State. Kaufmann studied physics and computer engineering at Penn before building AI hardware at Tesla and power systems for rockets at SpaceX.

The founding team has established research relationships to support its physics and engineering validation. A Sponsored Research Agreement with Columbia University focuses on pulse scenario development and time-dependent plant systems. The company also participates in experiments at the U.S. Department of Energy's DIII-D National Fusion Facility.

Maritime Fusion was also named to the 2026 Forbes 30 Under 30 list for Energy & Green Tech.

Hiring Technical Staff in San Francisco

With a team of six employees, Maritime Fusion is filling four onsite roles at its headquarters in San Francisco, California.

The team is expanding its hardware engineering capacity with a Member of Technical Staff - R&D Engineering ($120,000–$200,000), who will build and test REBCO conductors, high-current power supplies, and cryogenic cooling systems. Hands-on fabrication is supported by an R&D Technician ($100,000–$160,000) to assemble magnet test stands, cryogenic plumbing, vacuum systems, and custom power racks.

On the physics side, the company is recruiting a Member of Technical Staff - Plasma Physics ($120,000–$200,000) to model marine deployable tokamaks using simulation suites including POPCON, TokaMaker, ASTRA, TGLF, Fuse, CGYRO, and OpenMC.

See all open roles at Maritime Fusion