The Helium-3 Supply Gate

MetroVolt burns D-³He, so it needs helium-3 — scarce on Earth. Fleet-scale supply, including a lunar path, is an open program-level gate.

The fuel the burner needs

MetroVolt’s fuel is deuterium and helium-3. Deuterium is abundant. Helium-3 is not — it is scarce on Earth, available in small quantities from tritium decay and other limited sources. A single test unit can be fueled from existing supply; a commercial fleet cannot rely on that alone.

This is an open program-level gate. The breeder produces a helium-3 coproduct (near 1.97 kg/yr class), which contributes but does not by itself supply a large fleet. A credible fleet path considers lunar helium-3, which is a long-horizon source (roughly 2038–2040 in program planning) rather than a near-term one.

Why this gates the fleet, not the test

Fuel scarcity does not block the ~2032 test unit, which needs relatively little. It gates the fleet: many MetroVolt units burning D-³He imply a supply chain that does not fully exist today. Honest planning treats fleet-scale helium-3 as an unresolved dependency.