We mapped every combination of density and temperature around the frozen point — 667 coupled evaluations per posture through the full eight-constraint systems code (S80). The answer: 36% of the scanned plane runs the plant at positive net power.
Below the design point, the window is wide: density can fall 37% and ion temperature 38% before the plant stops closing — it degrades gracefully, shedding output rather than tripping a cliff. Above the point, the story is one-sided: MetroVolt rides the no-wall β limit, so there is no headroom at βN = 4.5. The wall-stabilised limit (βN = 5.0, adjudicated by the deposited MHD decks S22/S25) opens +10% density room above the point.
The near-thermal posture fails this particular 0-D gate everywhere on the plane — a convention gap the study reports rather than hides: its feasibility rests on the profile-resolved accounting, and its break-even H98 (2.24 at the deposited 42 keV reference) is computed and emitted, not asserted.
Operators buy windows, not points. A −37%/−38% graceful envelope means startup, ramp, and off-normal operation have somewhere to live; a mapped edge means control systems know exactly which boundary they defend. Publishing the one-sided upside is the marketing: it tells sophisticated readers we measured our room instead of imagining it.
| Feasible fraction of scanned plane | 36% (with P_net > 0) |
| Graceful room below point | −37% density / −38% temperature |
| Upside at no-wall limit | none (βN binding) |
| Upside with wall stabilization | +10% density (βN 5.0) |
| Grid | 29 × 23 = 667 evaluations / posture |