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Physics & Fusion Science

Fusion Gain (Q) and Engineering Gain

Q is the number everyone quotes — but it is not the number that keeps the lights on. Kronos is careful to distinguish scientific gain from the plant-level gain that matters commercially.

Physics & Fusion ScienceUpdated 2026-08-11
Breeder Q
3.076
Breeder P_fus
85.0 MW
Breeder P_aux
25.9 MW
Burner Q_E
1.31
DEC efficiency
0.70

Fusion gain Q is the ratio of fusion power produced to external heating power supplied. Q = 1 is scientific break-even; Q → ∞ is ignition. The HYPERION breeder is designed for Q = 3.076 — its 85.0 MW of fusion power against 25.9 MW of auxiliary heating.

Scientific vs engineering gain

Q measures the plasma. The plant-level engineering gain counts net electricity delivered to the grid against every watt the facility consumes — magnets, cryogenics, heating, pumps, controls. A machine can have an impressive Q and still not be a net electricity producer. Kronos reports the plant-level ledger separately for each product housing rather than letting a high plasma Q stand in for commercial viability.

The burner's direct advantage

The D–³He burner is quoted at an engineering gain QE = 1.31 because it converts charged-particle energy straight to electricity via direct energy conversion at about 0.70 efficiency, skipping the thermal cycle's losses.

Requirement-class resultThe burner's net-positive engineering gain is a requirement: it depends on achieving a plug-to-central density ratio of about 16. Until a plug demonstration reaches it, net power is a target, not a measured outcome.

Q measures the plasma; the plant-level engineering gain measures the business. HYPERION's plasma Q of 3.076 is comfortably net-positive, while the burner quotes a plant-level QE of 1.31 thanks to direct conversion. Kronos reports both separately and per product housing, refusing to let a headline plasma Q stand in for grid electricity.

Common questions

What is the difference between Q and Q_E?

Q is plasma gain (fusion power ÷ heating power); HYPERION's is 3.076. QE is plant-level engineering gain (net electricity ÷ all plant power); the burner's is 1.31. Kronos reports both separately and never lets a high plasma Q stand in for net electricity.

Does Kronos claim ignition?

No. Both machines are driven — continuously heated — and quote finite gain with the heating power stated. That is a complete, checkable claim.

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Content reviewed August 2026 · design-and-simulation stage