feat: polish & windviz & deploy

internal/numerics/atmosphere.go

@@ -0,0 +1,25 @@
+package numerics
+
+import "math"
+
+// NasaDensity returns air density in kg/m^3 at the given altitude in metres,
+// using the NASA piecewise standard-atmosphere model.
+// See https://www.grc.nasa.gov/WWW/K-12/airplane/atmosmet.html.
+//
+// The model is split into three altitude bands (troposphere, lower
+// stratosphere, upper stratosphere); density is pressure / (0.2869 * T_K).
+func NasaDensity(alt float64) float64 {
+	var temp, pressure float64
+	switch {
+	case alt > 25000:
+		temp = -131.21 + 0.00299*alt
+		pressure = 2.488 * math.Pow((temp+273.1)/216.6, -11.388)
+	case alt > 11000:
+		temp = -56.46
+		pressure = 22.65 * math.Exp(1.73-0.000157*alt)
+	default:
+		temp = 15.04 - 0.00649*alt
+		pressure = 101.29 * math.Pow((temp+273.1)/288.08, 5.256)
+	}
+	return pressure / (0.2869 * (temp + 273.1))
+}