Power in space · Generation, transmission, storage, use · Government and first-party sources
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Image of the Day · 2026-05-19

Held in Rotation

Under Mars the day is not kept as heat or charge but as turning, and one hall of identical wheels holds it until dark.

An artistic imagining, not real hardware. A dark cyan scene underground: a rank of heavy composite flywheel drums stands in a rock tunnel on Mars, receding to the right toward a pale glow far down the hall. Each drum is turned away from the viewer, so it reads as a thick ellipse rather than a full circle, and each sits in a low containment cradle with a drive can and a horizontal shaft entering from the left and disappearing behind the wheel. Nothing is drawn at the axis. A bright arc of light wraps part of every rim, long on some wheels and short on others, and the faces carry soft tangential smears where the mass is turning. A lit power line runs along the floor from the lower left, and a short feeder drops from each cradle down onto it. The rock roof and floor are modelled in tone only, warm basalt washed cyan by the machines, with no drawn outline anywhere.
An artistic imagining of kinetic storage under Mars: a hall of magnetically levitated composite flywheels in a lava tube, each rim arc showing how much of the day that wheel is still holding. Flywheel storage on magnetic bearings in vacuum is real technology and Martian lava tubes are inferred from orbital imaging of collapsed pit chains and skylights, but a hall like this one does not exist. Image: poweringspace.com. Artistic imagining.
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