🛰️ Spinning for Gravity

About this simulation

Without a planet underfoot, a spacecraft can only manufacture "gravity" by spinning. Anything riding on the inside of a rotating ring or cylinder is constantly accelerated toward the axis — centripetal acceleration — and the structure's floor pushes back on your feet just like a real planet's surface would, so it feels exactly like weight. Push outward on that floor and, by Newton's third law, it pushes back.

How it works

• Spin gravity — a = ω²R, where ω is the angular velocity (rad/s) and R the radius. Shown here as a fraction of Earth g (9.81 m/s²).
• Rim speed — the tangential velocity of the floor, v = ωR.
• Head–foot gradient — gravity is weaker near the axis, so a standing crew member feels noticeably less "weight" at the head than at the feet when R is small. Below roughly 100m this becomes uncomfortable.
• Coriolis effect — anything moving relative to the rotating floor (walking, throwing a ball, pouring a drink) appears to curve sideways. Push off from the zero-g hub and you travel in a perfectly straight line in the outside, non-rotating frame — but the ring rotates underneath you, so you land offset from the point you aimed at.

Controls

• Habitat radius — the real radius of the ring or cylinder, 50–500m.
• Rotation rate — spin speed in revolutions per minute (RPM).
• Habitat shape — a single rotating ring/torus, or a paired O'Neill-style cylinder.
• Push-off speed — how fast a crew member launches from the central hub toward the rim; used in the Coriolis drop test.
• Show "down" vectors — toggles arrows showing the local "floor-ward" direction at points around the habitat.
• Drop test object — launches a marker from the hub and shows exactly how far it lands from its "aimed-at" target due to the Coriolis effect.

Did you know?

Engineers generally target 2–4 RPM as the comfort sweet spot: fast enough to need a manageable radius, slow enough that the inner ear's vestibular system doesn't fight the Coriolis forces produced every time a crew member turns their head. NASA's 1970s studies suggested most people can adapt to spins as high as 6 RPM with a few days' practice — but nobody has ever tested it on a station large enough to matter.