Maritime Fusion, a San Francisco fusion energy startup founded by former Tesla engineers, has raised $4.5 million in seed funding to accelerate development of its high-temperature superconducting cable architecture and its low-power-density tokamak reactor designed for maritime and other off-grid energy applications. Trucks VC led the financing with participation from Paul Graham, Alumni Ventures, Aera VC, Y Combinator, and several strategic angel investors.
The company is pursuing a commercialization pathway that differs from the majority of fusion ventures. Instead of targeting large, grid-scale electricity production, Maritime Fusion is engineering a compact tokamak optimized for lower power output, reduced uptime requirements, and rapid deployment in use cases such as commercial shipping. This strategy also helps avoid the most difficult material and confinement challenges typically encountered when scaling fusion reactors toward grid-level operation.
Maritime Fusion is progressing its reactor concept, Yinsen, with support from two major research collaborations. A Sponsored Research Agreement with Columbia University is enabling detailed work on pulse scenarios and time-dependent systems, and participation in the U.S. Department of Energy’s DIII-D National Fusion Facility is providing access to experiments aligned with the firm’s envisioned operating regime.
Central to Yinsen is the company’s SHIELD high-temperature superconducting cable. The cable, which has a diameter smaller than a quarter, excluding cryostat hardware, recently achieved a milestone by carrying 5,000 amps at 77K during a liquid nitrogen bench test. Maritime Fusion says SHIELD is modular, robust, and capable of supporting up to 8,000 amps at 77K with even higher performance expected under fusion-relevant conditions. The architecture is intended not only for use in fusion magnets but also for commercial high-power transmission needs, including AI datacenters where demand for dense, efficient electrical distribution is rapidly increasing.
The company notes that, compared to conventional copper, an HTS cable can reduce ohmic losses and deliver significant cost savings in data center operations, potentially exceeding $10 million annually in extensive facilities. While fusion applications require REBCO tape with advanced pinning to handle high magnetic fields, most features of the SHIELD architecture remain the same across markets.
The latest capital infusion will support the expansion of the company’s engineering, manufacturing, and business development teams as Maritime Fusion works toward early off-grid deployments ahead of grid-scale fusion adoption.
KEY QUOTES:
“Breakeven fusion is on the horizon, but the grid may not be the first place fusion achieves commercial success. By targeting applications that require lower power and lower uptime, we simultaneously reduce challenging physics problems from power exhaust to nuclear activation, while also decreasing the burden and cost impact of maintenance operations that are unavoidable in any first-of-a-kind deployment.”
Justin Cohen, Co-Founder and CEO of Maritime Fusion
“Fusion’s impact on transportation will be enormous, obviously for the grid, but also for large-scale applications like maritime. The team picked a smart first channel, allowing them to make a significant impact well before the largest barriers to grid fusion are fully solved.”
Jeffrey Schox, Partner at Trucks Venture Capital
