Fusion power is rediscovering its first customer. As climate-focused venture money stalls, laser fusion startups are signing defense deals — and the two fields turn out to need exactly the same component.

The clearest example arrived this week: RTX Ventures, the venture arm of the Raytheon parent, made a minority investment in Denver-based Xcimer Energy and signed a teaming agreement to explore integrating and containerizing Xcimer's multi-kilojoule-class pulsed excimer lasers into RTX air-defense systems. The Wall Street Journal put the development agreement at roughly $50 million.

The engineering overlap is the whole story. Whether you are driving a fusion target or shooting down a drone swarm, you need a laser that fires repeatedly and reliably, costs little per joule, is energy-efficient, maintainable and mass-manufacturable. Xcimer — which has raised nearly $200 million, won the largest Department of Energy milestone-programme award for laser fusion, and had its pilot power-plant design approved in June, targeting grid power in the mid-2030s — sells the same physics twice: as an energy source and as a weapon.

Xcimer is not alone. Pacific Fusion signed a memorandum of understanding with the National Nuclear Security Administration in late August and broke ground on a research and manufacturing campus in New Mexico, near Sandia and Los Alamos. Its high-yield experiments would be considerably more powerful than the shots the government currently uses for weapons physics. Co-founder Carrie von Muench has said defense applications were "always on our mind" — an unsurprising statement from a team whose technical leadership came out of Sandia, Lawrence Livermore and the NNSA.

The economic logic is straightforward. Venture funding for climate tech has cooled, and fusion is one of the most capital-hungry bets in the portfolio; investors are pleased when a portfolio company finds a second payer. Defense, meanwhile, has an urgent problem: traditional air defense was designed for crewed aircraft. Roughly a decade ago, a U.S. ally used a $3 million Patriot missile to down a $200 consumer drone — effective, as TechCrunch noted, but not efficient. Directed energy promises to change that arithmetic by firing cheaply from a generator or a ship's powerplant.

That history is also the awkward part. Fusion emerged from Cold War weapons research, and its national-security ties never fully disappeared — the 2022 ignition breakthrough happened at the National Ignition Facility, which has supported defense work for decades. The renewed embrace gives startups runway and validation. It also puts them back at the table where the technology's most consequential applications are decided.

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