Item from Project Hail Mary by Andy Weir
An engine that tricks starlight-eating microbes into pushing a spaceship — 1,009 of them strapped to the Hail Mary, burning six grams of impossible fuel per second.
The spin drive is Komorov's genius made mechanical. It exploits Astrophage biology in a three-phase cycle: first, low-intensity light at 4.26μm and 18.31μm attracts Astrophage to coat one side of a transparent triangular mechanism. Then the coated surface rotates to face space and light intensity increases — the Astrophage push against the surface (imparting momentum to the ship) as they try to move toward the light. Finally, the surface rotates back, dead Astrophage are scraped off, and the cycle repeats. It's propulsion through biological manipulation — using a living organism's instincts as a thrust mechanism. The Hail Mary burns 6.045 grams of Astrophage per second across all 1,009 drives, achieving acceleration of 1.5g and a cruising velocity near the speed of light. The irony is inescapable: the organism killing Earth's sun is the only thing powerful enough to send a ship to save it.
Small triangular mechanisms — each spin drive is individually modest in size but collectively they number 1,009 across the Hail Mary's propulsion array. The active surface is transparent, designed to manipulate Astrophage behavior through controlled light exposure.
Also known as: Spin Drive, Spin Drives