ksp tool

diff --git a/tools/game/ksp_planet_transfer_calculator.go b/tools/game/ksp_planet_transfer_calculator.go
new file mode 100644 (file)
index 0000000..dbc3ebb
--- /dev/null
+++ b/tools/game/ksp_planet_transfer_calculator.go
@@ -0,0 +1,95 @@
+/*
+ * ------------------------------------------------------------------------
+ *   File Name: ksp_planet_transfer_calculator.go
+ *      Author: Zhao Yanbai
+ *              2017-07-23 10:29:09 Sunday CST
+ * Description: 计算 Kerbal Space Program 在天体间轨道转移的相位角
+ * ------------------------------------------------------------------------
+ */
+package main
+import (
+       "fmt"
+       "math"
+)
+
+type AstronomicalObject struct {
+       name                    string
+       parent                  string
+       radius                  float64 // 天体半径
+       sma                             float64 // Semi-major axis 轨道半长轴
+       inclination             float64 // 轨道倾角
+       eccentricity    float64 // 轨道偏心率,没有使用
+       u                               float64 // 标准重力参数
+       soi                             float64 // Sphere of influence 势国作用范围
+}
+
+var objects = map[string]AstronomicalObject {
+       "Kerbol" : {
+               "Kerbol",
+               "",
+               261600000,
+               0,
+               0,
+               0,
+               1.1723328e18,
+               math.MaxFloat64,        // 应该是infinity
+       },
+       "Duna" :
+       {
+               "Duna",
+               "Kerbol",
+               320000,
+               20726155264,
+               0.06,
+               0.05,
+               3.0136321e11,
+               47921949,
+       },
+       "Kerbin" :
+       {
+               "Kerbin",
+               "Kerbol",
+               600000,
+               13599840256,
+               0,
+               0,
+               3.5315984e12,
+               84159271,
+       },
+}
+
+func getAstronomicalObjectOrbitalPeriod(sma float64, u float64) float64 {
+       return 2*math.Pi*math.Sqrt(math.Pow(sma, 3) / u)
+}
+
+func main() {
+       defer fmt.Println("Program Exited...")
+
+
+       // 轨道周期的计算公式为 T=2*Pi*sqrt(sma^3/u)
+       // 设源和目标轨道半轴长分别为Rs, Rd
+       // 则转移轨道周期为 Tt = 2*Pi*sqlrt(((Rs+Rd)/2)^3/u)
+       // 则源，目标和平均转移角速度分别为 Ws = 1/Ts, Wd = 1/Td, Wt = 1/Tt
+       // 设转移时间为t
+       // 则有 t*Wt = Pi   ===> t = Tt*Pi
+       // 则有 Wd*t + PhaseAngle = Pi (即经过t时间目标+相位角=霍曼转移经过Pi弧度后会合)
+       // ===> (1/Td)*Tt*Pi + PhaseAngle = Pi
+       // ===> PhaseAngle = Pi - Tt*Pi/Td 
+
+       aos := objects["Kerbin"]
+       aod := objects["Duna"]
+       if aos.parent != aod.parent || aos.parent == "" || aod.parent == "" {
+               fmt.Println("invalid astronomical object");
+               return
+       }
+
+       u := objects[aos.parent].u
+       Ts := getAstronomicalObjectOrbitalPeriod(aos.sma, u)
+       Td := getAstronomicalObjectOrbitalPeriod(aod.sma, u)
+       Tt := getAstronomicalObjectOrbitalPeriod((aos.sma+aod.sma)/2, u)
+
+       PhaseAngle := math.Pi - Tt*math.Pi/Td
+
+       fmt.Printf("%.6f %.6f\n", Ts, Td)
+       fmt.Printf("phase angle %.2f°\n", PhaseAngle*180/math.Pi);
+}