Hephaestus exits stealth with $17.2M to make fusion magnets without rare earths
What's the deal? London-based Hephaestus has emerged from stealth with $17.2 million to develop rare-earth-free high temperature superconducting (HTS) magnets and build a low-cost fusion reactor. CiRi VenturesDealroom has a profile for this one. Try Dealroom → led the round, with Prescience Ventures, Teampact VenturesDealroom has a profile for this one. Try Dealroom →, Climate CapitalDealroom has a profile for this one. Try Dealroom →, and Unruly CapitalDealroom has a profile for this one. Try Dealroom → also taking part.
What's the endgame? Founded in 2019, Hephaestus wants to make fusion cheap enough to compete on the grid. Its AI plasma solver pointed to negative triangularity (NT) — a configuration that inverts the D-shaped plasma used in most tokamaks — as the most likely path to low-cost fusion.
The company has two targets: start HTS magnet manufacturing in 2027, and demonstrate net energy gain in an NT reactor by 2030.
Why rare-earth-free? Every HTS magnet in fusion today uses REBCO (rare-earth barium copper oxide), a superconductor that is slow and expensive to scale, and concentrated in regions of geopolitical risk. Hephaestus says its alternative is cheaper, more scalable, and less exposed to supply bottlenecks, positioning it as a supplier to the wider fusion sector as well as an energy provider.
Where's it expanding? The funding will fund HTS manufacturing at a new 70,000ft² New Jersey facility starting in 2027. Hephaestus is hiring across its New Jersey, London, and Rome sites, and has opened early-access talks with fusion developers seeking HTS supply.
"Fusion has the potential of adding tens of GW's per year of clean stable power to the grid, but that only happens if it becomes affordable and scalable," said founder and chief executive officer Jack Zamattio.
The signal: Hephaestus's raise is modest beside recent megadeals — Commonwealth Fusion Systems pulled in $1 billion in July, and Tokamak Energy secured $125 million in September. That contrast frames Hephaestus as an early-stage supplier bet rather than a financing peer; technical validation and manufacturing scale will decide whether its rare-earth-free claim holds up.
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Image credit: Generated with Gemini
