From: Ace <ace@Aces-MacBook-Pro.local>
Date: Sun, 23 Jul 2017 14:39:58 +0000 (+0800)
Subject: ksp tool
X-Git-Url: http://zhaoyanbai.com/repos/Bv9ARM.ch06.html?a=commitdiff_plain;h=7fcf5e1fd53d660c87bb514049c8970152ca5e00;p=acecode.git

ksp tool
---

diff --git a/tools/game/ksp_planet_transfer_calculator.go b/tools/game/ksp_planet_transfer_calculator.go
new file mode 100644
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);
+}