How net power scales with length.

The burner's gain and cleanliness are fixed by its plasma; only its size decides how much power it makes. That makes length a dial — the same physics sells as a 440 m Aegis or a 1400 m MetroVolt.

Length-independent

Q_E, f_n, ion temperature — set by plasma conditions

Length-dependent

Fusion power and net electric — set by central-cell length

Aegis

440 m → +850 MWe

MetroVolt

1400 m → +2832 MWe

In a tandem mirror the central cell is a uniform channel of burning plasma. Double its length and you roughly double the fusion power — but the intensive physics (the gain Q_E, the neutron fraction, the ion temperature) is unchanged, because those depend on conditions, not on how much of the channel there is. Kronos freezes this as the "free capital dial."

55 m — reference

0.54 GW fusion → +104 MWe

440 m — Aegis

4.3 GW fusion → +850 MWe

1400 m — MetroVolt

13.7 GW fusion → +2832 MWe

This is the physical reason there are two burner products rather than two burner designs. Aegis is the shorter machine, sized for fixed-site installations; MetroVolt is the long machine, sized for cities and data centers. They are the same physics at two lengths — which is why proving the closing point once proves both.

The dial is "free" in the sense that length adds capacity without changing the underlying physics risk: the hard requirement (plug density) is the same at 55 m as at 1400 m. What length changes is the capital and the market, not the plasma.