Flywheel Energy Storage for Satellites

Flywheel Aerospace develops flywheel energy storage systems (FESS) for satellite power management and attitude control. Unlike chemical batteries (which degrade with charge-discharge cycles), flywheel systems store energy in spinning composite rotors with virtually unlimited cycle life — ideal for LEO satellites that experience 15 charge-discharge cycles per day over a 5–10 year mission.

Satellite flywheels serve dual purposes: as energy storage (absorbing solar panel power during illumination and releasing it during eclipse periods) and as reaction wheels (exchanging angular momentum with the spacecraft to control attitude). This ‘integrated power and attitude control system’ (IPACS) concept eliminates dedicated battery and separate reaction wheel sets, reducing total mass and improving reliability through fewer components.

Flywheel rotors for space use are made from high-strength carbon fiber composite operating in vacuum (eliminating air drag) at speeds of 10,000–100,000 RPM. Magnetic bearings eliminate mechanical wear and lubrication requirements. Flywheel energy density is increasing as composite materials improve, but still lags behind modern lithium-ion batteries by 3–5×, making the cycle life and dual-function advantages the primary value proposition for long-life LEO missions.