biome · fountain & sun — looking down the axis (8 km habitat, 10 km hull)

The cross-section, drawn right: a 10 km outer hull, a 1 km foam rind, the 8 km habitat wall (1 g, ω≈0.035, 480× Earth). The linear sun glows at the axis (irradiance ∝ 1/r); a diurnal column runs in the background, so the fog ring blooms each night and burns off by day. A fountain rises from inside each lake and throws pond water inward — at this spin the Coriolis force rivals gravity, curving it into a sheet. The chevrons trace the wind it induces in the air (a gale at the nozzle, a breeze at the inversion). Engage it and its momentum mixing feeds back into the column. ← M1 · M2 ↗

The jet (Fond du Lac)

Lower the floor gravity (1 g lives at the outer radius) and the spin eases, so the axis-reaching speed ωR drops — the fountain throws farther for free. Ventilation needs only ~48 m/s; sonic is only for crossing the whole bore, and waterjet cutters already run >3000 bar. The symmetric fan ignores the aim and broadcasts a balanced sheet.

Cross-section — axis/sun at centre, canopy at the 8 km wall

day 0 · —

The axial sun — luminous flux

Momentum coupling → the column

Day-phased is the sweet spot: the jet ventilates the canopy when photosynthesis needs CO₂ (and the sun is burning the fog anyway), then backs off at night so the cool surface breeds free dew irrigation. That is the phase separation.

Systems ledger — reactors & water

Power is almost all light — the jets are <0.1%. Three jets irrigate the three forests; three lakes (at the ratchet low points — see the ratchet topology ↗) buffer the water and grow fish.