Kite Flying API

Kite-flying maths as an API, computed locally and deterministically — the line-pull, altitude and minimum-wind numbers a kite flyer, festival organiser or kite app works a flight out with. The line-pull endpoint gives the tension a kite puts on the line ≈ ½ × air density × wind speed² × sail area × a force coefficient (~0.8 for a typical flat or delta kite): because it rises with the square of the wind, doubling the wind quadruples the pull — a 1.5 m² kite holds about 47 N (nearly 5 kgf) at 8 m/s but four times that in a strong blow, so the line and your grip must be sized to the gusts, not the average. The altitude endpoint gives the flying height = the line let out × the sine of the line angle above the horizontal, with the downwind distance from the cosine: 100 m of line at a 45° angle reaches about 71 m up and 71 m downwind, while a heavy or under-flown kite sags to a low angle and never climbs. The min-wind endpoint gives the lightest wind that lifts off, where the aerodynamic lift just equals the weight: min wind = √(2 × mass × g ÷ (air density × area × lift coefficient)), so a 200 g, 1.5 m² kite needs only about 1.6 m/s (6 km/h) — lighter sails and bigger area drop the threshold. Everything is computed locally and deterministically, so it is instant and private. Ideal for kite-flying and festival apps, hobby and STEM-education tools, and outdoor calculators. Pure local computation — no key, no third-party service, instant. Flat-kite estimates — combine with real wind readings. 3 compute endpoints. For drag and terminal velocity use a drag API; for structural wind load a wind-load API.