Doubling Time and Fleet Growth
Doubling time — how long a breeder takes to make enough surplus tritium to start another — falls as net TBR rises, linking breeding to fleet scale.
Turning surplus into more machines
Doubling time is the interval over which a breeder produces enough surplus tritium, beyond its own needs, to provide the full startup inventory for an identical new unit. It is a standard measure of how fast a breeding fleet can grow, borrowed from the same logic used for breeder reactors.
The controlling quantity is the net TBR above self-sufficiency. A machine breeding at net 1.1 has almost no surplus and a very long doubling time; a machine at net 1.5 or 1.8 accumulates a startup charge much sooner. Higher breeding and lower losses both shorten it.
What sets doubling time
- Net TBR above 1.0 — the surplus rate
- Startup inventory required per new unit
- Tritium losses and holdup that erode surplus
- Decay of stored surplus while it accumulates
Why the target is 1.8
The reference TBR target of 1.8 is chosen partly so that doubling time is short enough for a fleet to grow on a useful schedule — FOAK to NOAK to BOAK and beyond — rather than being throttled by fuel. This is the practical link between the breeding-ratio lever and the foundry's role as the fuel source for the wider program, including the burner's eventual helium-3 pathway.
Doubling time is a design-and-simulation projection contingent on net TBR and self-sufficiency, both of which remain open.
This page describes a design-and-simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind (FOAK) first tritium is targeted near 2030. No net-gain claim is made before FOAK.