From ac93b44dc14e0c863c86c0ad6650cccb47287106 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sat, 14 Dec 2019 17:38:48 +0900
Subject: [PATCH 01/18] [add] environment/earth dir

---
 src/environment/{earth.hpp => earth/ellipsoid.hpp} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename src/environment/{earth.hpp => earth/ellipsoid.hpp} (100%)

diff --git a/src/environment/earth.hpp b/src/environment/earth/ellipsoid.hpp
similarity index 100%
rename from src/environment/earth.hpp
rename to src/environment/earth/ellipsoid.hpp

From 50972b6c6d2ab70a6b996b5e2d6b8e6489390307 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sat, 14 Dec 2019 17:47:29 +0900
Subject: [PATCH 02/18] [fix] include path

---
 src/coordinate/earth.hpp            |  2 +-
 src/environment.hpp                 | 31 +++++++++++++++++++++++++++++
 src/environment/earth/ellipsoid.hpp |  6 +++---
 src/simulation.cpp                  |  3 +--
 4 files changed, 36 insertions(+), 6 deletions(-)
 create mode 100644 src/environment.hpp

diff --git a/src/coordinate/earth.hpp b/src/coordinate/earth.hpp
index 6df1a63..e1324ba 100644
--- a/src/coordinate/earth.hpp
+++ b/src/coordinate/earth.hpp
@@ -22,7 +22,7 @@
 #ifndef COORDINATE_EARTH_HPP_
 #define COORDINATE_EARTH_HPP_
 
-#include "../environment/earth.hpp"
+#include "../environment/earth/ellipsoid.hpp"
 
 namespace trochia::coordinate::earth {
 	using namespace environment::earth;
diff --git a/src/environment.hpp b/src/environment.hpp
new file mode 100644
index 0000000..044622b
--- /dev/null
+++ b/src/environment.hpp
@@ -0,0 +1,31 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *    Copyright (C) 2019 sksat <sksat@sksat.net>
+ *
+ *    This file is part of Trochia.
+ *
+ *    Trochia is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Trochia is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You Should have received a copy of the GNU General Public License
+ *    along with Trochia.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * ----------------------------------------------------------------------- */
+
+#ifndef ENVIRONMENT_HPP_
+#define ENVIRONMENT_HPP_
+
+#include "environment/air.hpp"
+#include "environment/earth/ellipsoid.hpp"
+//#include "environment/earth/geodesy.hpp"
+#include "environment/gravity.hpp"
+#include "environment/launcher.hpp"
+
+#endif
diff --git a/src/environment/earth/ellipsoid.hpp b/src/environment/earth/ellipsoid.hpp
index 0ba84ff..2a43399 100644
--- a/src/environment/earth/ellipsoid.hpp
+++ b/src/environment/earth/ellipsoid.hpp
@@ -19,10 +19,10 @@
  *
  * ----------------------------------------------------------------------- */
 
-#ifndef ENVIRONMENT_EARTH_HPP_
-#define ENVIRONMENT_EARTH_HPP_
+#ifndef ENVIRONMENT_EARTH_ELLIPSOID_HPP_
+#define ENVIRONMENT_EARTH_ELLIPSOID_HPP_
 
-#include "../math.hpp"
+#include "../../math.hpp"
 
 namespace trochia::environment::earth {
 	namespace ellipsoid {
diff --git a/src/simulation.cpp b/src/simulation.cpp
index 0e38782..51ce786 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -23,8 +23,7 @@
 #include "math.hpp"
 #include "simulation.hpp"
 #include "solver.hpp"
-#include "environment/launcher.hpp"
-#include "environment/gravity.hpp"
+#include "environment.hpp"
 
 auto trochia::do_simulation(Simulation &sim) -> void {
 	const auto &timeout = sim.timeout;

From 9970a80400f762ddd9936895c1c63dc4b224daf2 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sat, 14 Dec 2019 19:37:03 +0900
Subject: [PATCH 03/18] [add] Fundamental Physical Constants header

---
 src/environment.hpp         |  1 +
 src/environment/gravity.hpp |  9 ++---
 src/environment/physics.hpp | 67 +++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 7 deletions(-)
 create mode 100644 src/environment/physics.hpp

diff --git a/src/environment.hpp b/src/environment.hpp
index 044622b..1756518 100644
--- a/src/environment.hpp
+++ b/src/environment.hpp
@@ -22,6 +22,7 @@
 #ifndef ENVIRONMENT_HPP_
 #define ENVIRONMENT_HPP_
 
+#include "environment/physics.hpp"			// fundamental physical constants
 #include "environment/air.hpp"
 #include "environment/earth/ellipsoid.hpp"
 //#include "environment/earth/geodesy.hpp"
diff --git a/src/environment/gravity.hpp b/src/environment/gravity.hpp
index bf9a17d..42bbd5a 100644
--- a/src/environment/gravity.hpp
+++ b/src/environment/gravity.hpp
@@ -23,15 +23,10 @@
 #define ENVIRONMENT_GRAVITY_HPP_
 
 #include "../math.hpp"
+#include "physics.hpp"
 
 namespace trochia::environment {
 	namespace constant {
-		// 2018 CODATA recommended values
-		constexpr math::Float G		= 6.6743015e-11;
-
-		// standard acceleration of gravity(definition)
-		constexpr math::Float gn	= 9.80665;
-
 		// Chronological Scientific Tables 2014
 		constexpr math::Float re	= 6.3781366e6;
 	}
@@ -43,7 +38,7 @@ namespace trochia::environment {
 
 	inline auto gravity(const math::Float &altitude) -> const math::Float {
 		const auto tmp = constant::re / (constant::re + altitude);
-		return constant::gn * tmp * tmp;
+		return physics::g0 * tmp * tmp;
 	}
 }
 
diff --git a/src/environment/physics.hpp b/src/environment/physics.hpp
new file mode 100644
index 0000000..3f0ceb2
--- /dev/null
+++ b/src/environment/physics.hpp
@@ -0,0 +1,67 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *    Copyright (C) 2019 sksat <sksat@sksat.net>
+ *
+ *    This file is part of Trochia.
+ *
+ *    Trochia is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Trochia is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You Should have received a copy of the GNU General Public License
+ *    along with Trochia.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * ----------------------------------------------------------------------- */
+
+#ifndef ENVIRONMENT_PHYSICS_HPP_
+#define ENVIRONMENT_PHYSICS_HPP_
+
+#include "../math.hpp"
+
+namespace trochia::environment::physics {
+	using math::Float;
+
+	// standard acceleration of gravity(definition value)
+	// The third General Conference on Weights and Mesures(1901)
+	constexpr Float g0 = 9.80665;
+
+	inline namespace CODATA2018 {
+		// 2018 CODATA recommended values
+		// https://physics.nist.gov/cuu/pdf/wall_2018.pdf
+
+		// speed of light in vacuum
+		constexpr Float c	= 299792458;
+
+		// Newtonian constant of gravitation
+		constexpr Float G	= 6.6743015e-11;
+		
+		// molar gas constant
+		constexpr Float R	= 8.314462618;
+	}
+
+	namespace CODATA2014 {
+		// 2014 CODATA recommended values
+		// https://physics.nist.gov/cuu/pdf/wallet_2014.pdf
+
+		constexpr Float c	= 299792458;
+		constexpr Float G	= 6.6740831e-11;
+		constexpr Float R	= 8.314459848;
+	}
+
+	namespace CODATA2010 {
+		// 2010 CODATA recommended values
+		// https://physics.nist.gov/cuu/pdf/all_2010.pdf
+
+		constexpr Float c	= 299792458;
+		constexpr Float G	= 6.6738480e-11;
+		constexpr Float R	= 8.314462175;
+	}
+}
+
+#endif

From 4fff1c888879d9d2ad8966625076721e082029f1 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sat, 14 Dec 2019 19:58:43 +0900
Subject: [PATCH 04/18] [add] environment/earth.hpp

---
 src/environment.hpp                 |  5 ++--
 src/environment/earth.hpp           | 36 +++++++++++++++++++++++++++++
 src/environment/earth/ellipsoid.hpp |  4 +---
 src/environment/gravity.hpp         |  8 ++-----
 4 files changed, 41 insertions(+), 12 deletions(-)
 create mode 100644 src/environment/earth.hpp

diff --git a/src/environment.hpp b/src/environment.hpp
index 1756518..5b0849e 100644
--- a/src/environment.hpp
+++ b/src/environment.hpp
@@ -23,10 +23,9 @@
 #define ENVIRONMENT_HPP_
 
 #include "environment/physics.hpp"			// fundamental physical constants
-#include "environment/air.hpp"
-#include "environment/earth/ellipsoid.hpp"
-//#include "environment/earth/geodesy.hpp"
+#include "environment/earth.hpp"
 #include "environment/gravity.hpp"
+#include "environment/air.hpp"
 #include "environment/launcher.hpp"
 
 #endif
diff --git a/src/environment/earth.hpp b/src/environment/earth.hpp
new file mode 100644
index 0000000..d661d67
--- /dev/null
+++ b/src/environment/earth.hpp
@@ -0,0 +1,36 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *    Copyright (C) 2019 sksat <sksat@sksat.net>
+ *
+ *    This file is part of Trochia.
+ *
+ *    Trochia is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Trochia is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You Should have received a copy of the GNU General Public License
+ *    along with Trochia.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * ----------------------------------------------------------------------- */
+
+#ifndef ENVIRONMENT_EARTH_HPP_
+#define ENVIRONMENT_EARTH_HPP_
+
+#include "../math.hpp"
+
+namespace trochia::environment::earth {
+	using math::Float;
+
+	// Chronological Scientific Tables 2014
+	constexpr Float re = 6.3781366e6;
+}
+
+#include "earth/ellipsoid.hpp"
+
+#endif
diff --git a/src/environment/earth/ellipsoid.hpp b/src/environment/earth/ellipsoid.hpp
index 2a43399..50ea1c2 100644
--- a/src/environment/earth/ellipsoid.hpp
+++ b/src/environment/earth/ellipsoid.hpp
@@ -22,12 +22,10 @@
 #ifndef ENVIRONMENT_EARTH_ELLIPSOID_HPP_
 #define ENVIRONMENT_EARTH_ELLIPSOID_HPP_
 
-#include "../../math.hpp"
+#include "../earth.hpp"
 
 namespace trochia::environment::earth {
 	namespace ellipsoid {
-		using math::Float;
-
 		class Ellipsoid {
 		public:
 			constexpr Ellipsoid(Float a, Float f_inv) : a(a), f_inv(f_inv),
diff --git a/src/environment/gravity.hpp b/src/environment/gravity.hpp
index 42bbd5a..9f1f240 100644
--- a/src/environment/gravity.hpp
+++ b/src/environment/gravity.hpp
@@ -24,20 +24,16 @@
 
 #include "../math.hpp"
 #include "physics.hpp"
+#include "earth.hpp"
 
 namespace trochia::environment {
-	namespace constant {
-		// Chronological Scientific Tables 2014
-		constexpr math::Float re	= 6.3781366e6;
-	}
-
 	// TODO
 	// latitude model(Helmert equation, WGS-84)
 	// gravitation model
 	// other planet
 
 	inline auto gravity(const math::Float &altitude) -> const math::Float {
-		const auto tmp = constant::re / (constant::re + altitude);
+		const auto tmp = earth::re / (earth::re + altitude);
 		return physics::g0 * tmp * tmp;
 	}
 }

From a887a037aa0810ac61940b5d12812c08b0f2636f Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sat, 14 Dec 2019 20:39:05 +0900
Subject: [PATCH 05/18] [fix]

---
 src/environment/earth.hpp           | 4 +---
 src/environment/earth/ellipsoid.hpp | 4 +++-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/environment/earth.hpp b/src/environment/earth.hpp
index d661d67..00cfc08 100644
--- a/src/environment/earth.hpp
+++ b/src/environment/earth.hpp
@@ -25,10 +25,8 @@
 #include "../math.hpp"
 
 namespace trochia::environment::earth {
-	using math::Float;
-
 	// Chronological Scientific Tables 2014
-	constexpr Float re = 6.3781366e6;
+	constexpr math::Float re = 6.3781366e6;
 }
 
 #include "earth/ellipsoid.hpp"
diff --git a/src/environment/earth/ellipsoid.hpp b/src/environment/earth/ellipsoid.hpp
index 50ea1c2..2a43399 100644
--- a/src/environment/earth/ellipsoid.hpp
+++ b/src/environment/earth/ellipsoid.hpp
@@ -22,10 +22,12 @@
 #ifndef ENVIRONMENT_EARTH_ELLIPSOID_HPP_
 #define ENVIRONMENT_EARTH_ELLIPSOID_HPP_
 
-#include "../earth.hpp"
+#include "../../math.hpp"
 
 namespace trochia::environment::earth {
 	namespace ellipsoid {
+		using math::Float;
+
 		class Ellipsoid {
 		public:
 			constexpr Ellipsoid(Float a, Float f_inv) : a(a), f_inv(f_inv),

From d7e760883b3f91e28bb202f88408cc97934f226e Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sat, 14 Dec 2019 21:20:10 +0900
Subject: [PATCH 06/18] [add] geodesy header

---
 src/environment/earth.hpp         |  1 +
 src/environment/earth/geodesy.hpp | 41 +++++++++++++++++++++++++++++++
 src/simulation.cpp                |  3 ++-
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 src/environment/earth/geodesy.hpp

diff --git a/src/environment/earth.hpp b/src/environment/earth.hpp
index 00cfc08..e14dae3 100644
--- a/src/environment/earth.hpp
+++ b/src/environment/earth.hpp
@@ -30,5 +30,6 @@ namespace trochia::environment::earth {
 }
 
 #include "earth/ellipsoid.hpp"
+#include "earth/geodesy.hpp"
 
 #endif
diff --git a/src/environment/earth/geodesy.hpp b/src/environment/earth/geodesy.hpp
new file mode 100644
index 0000000..33538d4
--- /dev/null
+++ b/src/environment/earth/geodesy.hpp
@@ -0,0 +1,41 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *    Copyright (C) 2019 sksat <sksat@sksat.net>
+ *
+ *    This file is part of Trochia.
+ *
+ *    Trochia is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Trochia is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You Should have received a copy of the GNU General Public License
+ *    along with Trochia.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * ----------------------------------------------------------------------- */
+
+#ifndef ENVIRONMENT_EARTH_GEODESY_HPP_
+#define ENVIRONMENT_EARTH_GEODESY_HPP_
+
+#include "../earth.hpp"
+
+namespace trochia::environment::earth::geodesy {
+	// geopotential height
+	// U.S. Standard Atmosphere, 1976: https://ntrs.nasa.gov/search.jsp?R=19770009539
+	auto potential_height(const math::Float &height) -> math::Float {
+		// the adopted, effective earth's radius, 6356.766km
+		// used for computing g(Z) for 45-degree north latitude,
+		// and used for relating H and Z at that latitude
+		constexpr math::Float r0 = 6356766;
+		constexpr math::Float gamma = 1.0;
+
+		return (r0 * height) / (gamma * r0 - height);
+	}
+}
+
+#endif
diff --git a/src/simulation.cpp b/src/simulation.cpp
index 51ce786..f3d7704 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -88,7 +88,8 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 		if(step % output_rate == 0){
 			std::cout << time << " "
 				<< rocket.pos.altitude() << " "
-				<< environment::gravity(rocket.pos.altitude()) << std::endl;
+				<< environment::earth::geodesy::potential_height(rocket.pos.altitude())
+				<< std::endl;
 		}
 
 		if(step > 100 && rocket.pos.altitude() <= 0.0)

From d10104e9d63e64a1790d50eb6db94de84647978c Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 00:48:04 +0900
Subject: [PATCH 07/18] [add] temperature header

---
 src/environment.hpp             |  1 +
 src/environment/temperature.hpp | 52 +++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 src/environment/temperature.hpp

diff --git a/src/environment.hpp b/src/environment.hpp
index 5b0849e..82fc587 100644
--- a/src/environment.hpp
+++ b/src/environment.hpp
@@ -23,6 +23,7 @@
 #define ENVIRONMENT_HPP_
 
 #include "environment/physics.hpp"			// fundamental physical constants
+#include "environment/temperature.hpp"
 #include "environment/earth.hpp"
 #include "environment/gravity.hpp"
 #include "environment/air.hpp"
diff --git a/src/environment/temperature.hpp b/src/environment/temperature.hpp
new file mode 100644
index 0000000..79ae5de
--- /dev/null
+++ b/src/environment/temperature.hpp
@@ -0,0 +1,52 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *    Copyright (C) 2019 sksat <sksat@sksat.net>
+ *
+ *    This file is part of Trochia.
+ *
+ *    Trochia is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Trochia is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You Should have received a copy of the GNU General Public License
+ *    along with Trochia.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * ----------------------------------------------------------------------- */
+
+#ifndef ENVIRONMENT_TEMPERATURE_HPP_
+#define ENVIRONMENT_TEMPERATURE_HPP_
+
+#include "../math.hpp"
+
+namespace trochia::environment::temperature {
+	class thermodynamic {
+	public:
+		constexpr thermodynamic() : t(0.0) {}
+		constexpr thermodynamic(const math::Float &t) : t(t) {}
+
+		virtual operator math::Float() {
+			return t;
+		}
+	protected:
+		math::Float t;
+	};
+
+	using kelvin = thermodynamic;
+
+	class celsius : public thermodynamic {
+		constexpr celsius(const thermodynamic &t) : thermodynamic(t) {}
+		constexpr celsius(const math::Float &t)   : thermodynamic(t + 273.15) {}
+
+		operator math::Float() {
+			return this->t - 273.15;
+		}
+	};
+}
+
+#endif

From f964d45af156794afb284922bf8305b82b96f200 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 00:59:44 +0900
Subject: [PATCH 08/18] [fix]

---
 src/environment/temperature.hpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/environment/temperature.hpp b/src/environment/temperature.hpp
index 79ae5de..b13cc79 100644
--- a/src/environment/temperature.hpp
+++ b/src/environment/temperature.hpp
@@ -40,6 +40,8 @@ namespace trochia::environment::temperature {
 	using kelvin = thermodynamic;
 
 	class celsius : public thermodynamic {
+	public:
+		constexpr celsius() : thermodynamic(273.15) {}
 		constexpr celsius(const thermodynamic &t) : thermodynamic(t) {}
 		constexpr celsius(const math::Float &t)   : thermodynamic(t + 273.15) {}
 

From cd430607a7197687567e8aaf007a993dda87eb59 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 01:29:22 +0900
Subject: [PATCH 09/18] [add] simple temperature change

---
 src/environment/air.hpp | 7 ++++++-
 src/simulation.cpp      | 9 +++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/environment/air.hpp b/src/environment/air.hpp
index 55718f9..32d819d 100644
--- a/src/environment/air.hpp
+++ b/src/environment/air.hpp
@@ -23,8 +23,13 @@
 #define ENVIRONMENT_AIR_HPP_
 
 #include "../math.hpp"
+#include "temperature.hpp"
 
-namespace environment::air {
+namespace trochia::environment::air {
+	auto temperature(const math::Float &height) -> temperature::kelvin {
+		const auto height_km = height * 0.001;
+		return environment::temperature::celsius(15.0 - 6.5*height_km);
+	}
 }
 
 #endif
diff --git a/src/simulation.cpp b/src/simulation.cpp
index f3d7704..d1a130f 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -86,9 +86,14 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 
 		// log
 		if(step % output_rate == 0){
+			const auto altitude		= rocket.pos.altitude();
+			const auto geo_height	= environment::earth::geodesy::potential_height(altitude);
+			const auto temperature = environment::air::temperature(geo_height);
+
 			std::cout << time << " "
-				<< rocket.pos.altitude() << " "
-				<< environment::earth::geodesy::potential_height(rocket.pos.altitude())
+				<< altitude << " "
+				<< geo_height << " "
+				<< (math::Float)environment::temperature::celsius(temperature)
 				<< std::endl;
 		}
 

From 64c484867f67ea06416f882133155de2f28e0f1b Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 01:51:49 +0900
Subject: [PATCH 10/18] [fix] enable cast if temperature is const

---
 src/environment/temperature.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/environment/temperature.hpp b/src/environment/temperature.hpp
index b13cc79..11b93b3 100644
--- a/src/environment/temperature.hpp
+++ b/src/environment/temperature.hpp
@@ -30,7 +30,7 @@ namespace trochia::environment::temperature {
 		constexpr thermodynamic() : t(0.0) {}
 		constexpr thermodynamic(const math::Float &t) : t(t) {}
 
-		virtual operator math::Float() {
+		virtual operator math::Float() const {
 			return t;
 		}
 	protected:
@@ -45,7 +45,7 @@ namespace trochia::environment::temperature {
 		constexpr celsius(const thermodynamic &t) : thermodynamic(t) {}
 		constexpr celsius(const math::Float &t)   : thermodynamic(t + 273.15) {}
 
-		operator math::Float() {
+		operator math::Float() const {
 			return this->t - 273.15;
 		}
 	};

From a0d4438a5101c8d15de078620a6ee1a5e65e30a7 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 01:56:06 +0900
Subject: [PATCH 11/18] [add] pressure

---
 src/environment/air.hpp | 10 +++++++++-
 src/simulation.cpp      |  3 ++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/environment/air.hpp b/src/environment/air.hpp
index 32d819d..bcb5fa0 100644
--- a/src/environment/air.hpp
+++ b/src/environment/air.hpp
@@ -26,9 +26,17 @@
 #include "temperature.hpp"
 
 namespace trochia::environment::air {
+	// from FROGS (return kelvin)
 	auto temperature(const math::Float &height) -> temperature::kelvin {
 		const auto height_km = height * 0.001;
-		return environment::temperature::celsius(15.0 - 6.5*height_km);
+		return temperature::celsius(15.0 - 6.5*height_km);
+	}
+
+	// from FROGS (return Pa)
+	auto pressure(const temperature::kelvin &t) -> math::Float {
+		math::Float tmp = (math::Float)t;
+		tmp = 288.15 / tmp;
+		return 101325.0 * std::pow(tmp, -5.256);
 	}
 }
 
diff --git a/src/simulation.cpp b/src/simulation.cpp
index d1a130f..caeac62 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -93,7 +93,8 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 			std::cout << time << " "
 				<< altitude << " "
 				<< geo_height << " "
-				<< (math::Float)environment::temperature::celsius(temperature)
+				<< (math::Float)environment::temperature::celsius(temperature) << " "
+				<< environment::air::pressure(temperature) / 100.0
 				<< std::endl;
 		}
 

From db68cb7fff05afbd53714533c4aef2cccd8e241e Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 02:03:11 +0900
Subject: [PATCH 12/18] [add] density

---
 src/environment/air.hpp | 11 ++++++++---
 src/simulation.cpp      |  3 ++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/environment/air.hpp b/src/environment/air.hpp
index bcb5fa0..21f1753 100644
--- a/src/environment/air.hpp
+++ b/src/environment/air.hpp
@@ -34,9 +34,14 @@ namespace trochia::environment::air {
 
 	// from FROGS (return Pa)
 	auto pressure(const temperature::kelvin &t) -> math::Float {
-		math::Float tmp = (math::Float)t;
-		tmp = 288.15 / tmp;
-		return 101325.0 * std::pow(tmp, -5.256);
+		const math::Float t_ = t;
+		return 101325.0 * std::pow((288.15 / t_), -5.256);
+	}
+
+	// from FROGS (Don't use this equation over 11km)
+	auto density(const temperature::kelvin &t) -> math::Float {
+		const math::Float t_ = t;
+		return (0.0034837 * pressure(t)) / t_;
 	}
 }
 
diff --git a/src/simulation.cpp b/src/simulation.cpp
index caeac62..9eefb2c 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -94,7 +94,8 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 				<< altitude << " "
 				<< geo_height << " "
 				<< (math::Float)environment::temperature::celsius(temperature) << " "
-				<< environment::air::pressure(temperature) / 100.0
+				<< environment::air::pressure(temperature) / 100.0 << " "
+				<< environment::air::density(temperature)
 				<< std::endl;
 		}
 

From 30cfdd6f9e2689415e559bcde9ad0ced11e6a972 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 02:46:43 +0900
Subject: [PATCH 13/18] [fix] function return type

---
 src/coordinate/local.hpp            | 62 ++++++++++++++---------------
 src/engine.hpp                      |  6 +--
 src/environment/earth/ellipsoid.hpp |  6 +--
 src/environment/gravity.hpp         |  2 +-
 src/environment/launcher.hpp        |  2 +-
 src/math.hpp                        | 10 ++---
 src/object.hpp                      | 18 ++++-----
 src/rocket.hpp                      |  4 +-
 8 files changed, 55 insertions(+), 55 deletions(-)

diff --git a/src/coordinate/local.hpp b/src/coordinate/local.hpp
index c711a07..66473a5 100644
--- a/src/coordinate/local.hpp
+++ b/src/coordinate/local.hpp
@@ -29,42 +29,42 @@ namespace trochia::coordinate::local {
 
 		Vector3 vec;
 
-		inline auto operator+(const Base &b) const -> const Base {
+		inline auto operator+(const Base &b) const -> Base {
 			Base ret;
 			ret.vec = this->vec + b.vec;
 			return ret;
 		}
-		inline auto operator-(const Base &b) const -> const Base {
+		inline auto operator-(const Base &b) const -> Base {
 			Base ret;
 			ret.vec = this->vec - b.vec;
 			return ret;
 		}
 
-		inline auto operator*(const math::Float &b) const -> const Base {
+		inline auto operator*(const math::Float &b) const -> Base {
 			Base ret;
 			ret.vec = this->vec * b;
 			return ret;
 		}
-		inline auto operator/(const math::Float &b) const -> const Base {
+		inline auto operator/(const math::Float &b) const -> Base {
 			Base ret;
 			ret.vec = this->vec / b;
 			return ret;
 		}
 
-		inline auto operator+=(const Base &b) -> const Base& {
+		inline auto operator+=(const Base &b) -> Base& {
 			this->vec += b.vec;
 			return *this;
 		}
-		inline auto operator-=(const Base &b) -> const Base& {
+		inline auto operator-=(const Base &b) -> Base& {
 			this->vec -= b.vec;
 			return *this;
 		}
 
-		inline auto operator*=(const math::Float &b) -> const Base& {
+		inline auto operator*=(const math::Float &b) -> Base& {
 			this->vec *= b;
 			return *this;
 		}
-		inline auto operator/=(const math::Float &b) -> const Base& {
+		inline auto operator/=(const math::Float &b) -> Base& {
 			this->vec /= b;
 			return *this;
 		}
@@ -74,23 +74,23 @@ namespace trochia::coordinate::local {
 	public:
 		NED() : Base() {}
 
-		auto north() const -> const Float { return vec.x(); }
-		auto east()  const -> const Float { return vec.y(); }
-		auto down()  const -> const Float { return vec.z(); }
+		auto north() const -> Float { return vec.x(); }
+		auto east()  const -> Float { return vec.y(); }
+		auto down()  const -> Float { return vec.z(); }
 
-		auto south() const -> const Float { return -1.0*north(); }
-		auto west()  const -> const Float { return -1.0*east();  }
-		auto up()    const -> const Float { return -1.0*down();  }
+		auto south() const -> Float { return -1.0*north(); }
+		auto west()  const -> Float { return -1.0*east();  }
+		auto up()    const -> Float { return -1.0*down();  }
 
-		auto altitude() const -> const Float { return up(); }
+		auto altitude() const -> Float { return up(); }
 
-		auto north(const Float &n) -> void{ vec.x() = n; }
-		auto east(const Float &e)  -> void{ vec.y() = e; }
-		auto down(const Float &d)  -> void{ vec.z() = d; }
+		auto north(const Float &n) -> void { vec.x() = n; }
+		auto east(const Float &e)  -> void { vec.y() = e; }
+		auto down(const Float &d)  -> void { vec.z() = d; }
 
-		auto south(const Float &s) -> void{ north(-1.0*s); }
-		auto west(const Float &w)  -> void{ east(-1.0*w);  }
-		auto up(const Float &u)    -> void{ down(-1.0*u);  }
+		auto south(const Float &s) -> void { north(-1.0*s); }
+		auto west(const Float &w)  -> void { east(-1.0*w);  }
+		auto up(const Float &u)    -> void { down(-1.0*u);  }
 
 		template<typename Frame>
 		operator Frame() {
@@ -106,19 +106,19 @@ namespace trochia::coordinate::local {
 	public:
 		ENU() : Base() {}
 
-		auto east()  const -> const Float { return vec.x(); }
-		auto north() const -> const Float { return vec.y(); }
-		auto up()    const -> const Float { return vec.z(); }
+		auto east()  const -> Float { return vec.x(); }
+		auto north() const -> Float { return vec.y(); }
+		auto up()    const -> Float { return vec.z(); }
 
-		auto west()  const -> const Float { return -1.0*east();  }
-		auto south() const -> const Float { return -1.0*north(); }
-		auto down()  const -> const Float { return -1.0*up();    }
+		auto west()  const -> Float { return -1.0*east();  }
+		auto south() const -> Float { return -1.0*north(); }
+		auto down()  const -> Float { return -1.0*up();    }
 
-		auto altitude() const -> const Float { return up(); }
+		auto altitude() const -> Float { return up(); }
 
-		auto east(const Float &e)  -> void{ vec.x() = e; }
-		auto north(const Float &n) -> void{ vec.y() = n; }
-		auto up(const Float &u)    -> void{ vec.z() = u; }
+		auto east(const Float &e)  -> void { vec.x() = e; }
+		auto north(const Float &n) -> void { vec.y() = n; }
+		auto up(const Float &u)    -> void { vec.z() = u; }
 
 		template<typename Frame>
 		operator Frame() {
diff --git a/src/engine.hpp b/src/engine.hpp
index e6c3c1b..885f24c 100644
--- a/src/engine.hpp
+++ b/src/engine.hpp
@@ -82,16 +82,16 @@ namespace trochia {
 			itr = data.cbegin();
 		}
 
-		inline auto progress(const math::Float &time) const -> const math::Float {
+		inline auto progress(const math::Float &time) const -> math::Float {
 			return time / time_max;
 		}
 
-		inline auto weight(const math::Float &time) const -> const math::Float {
+		inline auto weight(const math::Float &time) const -> math::Float {
 			const auto prop = math::lerp(weight_prop, 0, this->progress(time));
 			return weight_total - weight_prop + prop;
 		}
 
-		auto thrust(const math::Float &time) -> const math::Float {
+		auto thrust(const math::Float &time) -> math::Float {
 			const auto &next = itr+1;
 			const auto &time_now	= itr->first;
 			const auto &thrust_now	= itr->second;
diff --git a/src/environment/earth/ellipsoid.hpp b/src/environment/earth/ellipsoid.hpp
index 2a43399..2e80077 100644
--- a/src/environment/earth/ellipsoid.hpp
+++ b/src/environment/earth/ellipsoid.hpp
@@ -46,17 +46,17 @@ namespace trochia::environment::earth {
 				e2= f_tmp / (f_inv * f_inv);
 			}
 
-			constexpr auto W(const Float &lat) const -> const Float {
+			constexpr auto W(const Float &lat) const -> Float {
 				const auto sin  = math::sin(lat);
 				const auto sin2	= sin*sin;
 				return math::sqrt(1.0 - e2*sin2);
 			}
 
-			constexpr auto N(const Float &lat) const -> const Float {
+			constexpr auto N(const Float &lat) const -> Float {
 				return a / W(lat);
 			}
 
-			constexpr auto M(const Float &lat) const -> const Float {
+			constexpr auto M(const Float &lat) const -> Float {
 				const auto w = W(lat);
 				const auto W2= w*w;
 				return N(lat) * (1.0 - e2) / W2;
diff --git a/src/environment/gravity.hpp b/src/environment/gravity.hpp
index 9f1f240..b76c4a2 100644
--- a/src/environment/gravity.hpp
+++ b/src/environment/gravity.hpp
@@ -32,7 +32,7 @@ namespace trochia::environment {
 	// gravitation model
 	// other planet
 
-	inline auto gravity(const math::Float &altitude) -> const math::Float {
+	inline auto gravity(const math::Float &altitude) -> math::Float {
 		const auto tmp = earth::re / (earth::re + altitude);
 		return physics::g0 * tmp * tmp;
 	}
diff --git a/src/environment/launcher.hpp b/src/environment/launcher.hpp
index fcde7ca..5186eb9 100644
--- a/src/environment/launcher.hpp
+++ b/src/environment/launcher.hpp
@@ -36,7 +36,7 @@ namespace trochia::environment {
 		math::Quaternion angle;
 
 	public:
-		auto get_angle() const -> const math::Quaternion { return this->angle; }
+		auto get_angle() const -> math::Quaternion { return this->angle; }
 
 		auto set_angle(const math::Vector3 &euler) -> void {
 			this->set_angle(euler.x(), euler.y(), euler.z());
diff --git a/src/math.hpp b/src/math.hpp
index 7e42aeb..78550a1 100644
--- a/src/math.hpp
+++ b/src/math.hpp
@@ -77,15 +77,15 @@ namespace trochia::math {
 		return series;
 	}
 
-	constexpr auto deg2rad(const Float &deg) -> const Float {
+	constexpr auto deg2rad(const Float &deg) -> Float {
 		return deg * (pi / 180.0);
 	}
-	constexpr auto rad2deg(const Float &rad) -> const Float {
+	constexpr auto rad2deg(const Float &rad) -> Float {
 		return rad * (180.0 / pi);
 	}
 
 	[[deprecated("please use AngleAxis")]]
-	inline auto euler2quat(const Float &roll, const Float &pitch, const Float &yaw) -> const Quaternion {
+	inline auto euler2quat(const Float &roll, const Float &pitch, const Float &yaw) -> Quaternion {
 		using Eigen::AngleAxisd;
 
 		Quaternion q;
@@ -95,11 +95,11 @@ namespace trochia::math {
 		return q;
 	}
 
-	inline auto quat2euler(const Quaternion &q) -> const Vector3 {
+	inline auto quat2euler(const Quaternion &q) -> Vector3 {
 		return q.toRotationMatrix().eulerAngles(0, 1, 2);
 	}
 
-	inline auto lerp(const Float &a, const Float &b, const Float &t) -> const Float {
+	inline auto lerp(const Float &a, const Float &b, const Float &t) -> Float {
 		return a + t*(b - a);
 	}
 }
diff --git a/src/object.hpp b/src/object.hpp
index af7a949..ebbadf6 100644
--- a/src/object.hpp
+++ b/src/object.hpp
@@ -42,7 +42,7 @@ namespace trochia::object {
 			return ret;
 		}
 
-		virtual auto weight() const -> const math::Float {
+		virtual auto weight() const -> math::Float {
 			return 0.0;
 		}
 
@@ -52,45 +52,45 @@ namespace trochia::object {
 		}
 
 		// operator
-		auto operator+=(const Object &o) -> const Object {
+		auto operator+=(const Object &o) -> Object {
 			this->pos += o.pos;
 			this->vel += o.vel;
 			return *this;
 		}
-		auto operator-=(const Object &o) -> const Object {
+		auto operator-=(const Object &o) -> Object {
 			this->pos -= o.pos;
 			this->vel -= o.vel;
 			return *this;
 		}
 
-		auto operator*=(const math::Float &a) -> const Object {
+		auto operator*=(const math::Float &a) -> Object {
 			this->pos *= a;
 			this->vel *= a;
 			return *this;
 		}
-		auto operator/=(const math::Float &a) -> const Object {
+		auto operator/=(const math::Float &a) -> Object {
 			this->pos /= a;
 			this->vel /= a;
 			return *this;
 		}
 
-		auto operator+(const Object &o) const -> const Object {
+		auto operator+(const Object &o) const -> Object {
 			Object ret = *this;
 			ret += o;
 			return ret;
 		}
-		auto operator-(const Object &o) const -> const Object {
+		auto operator-(const Object &o) const -> Object {
 			Object ret = *this;
 			ret -= o;
 			return ret;
 		}
 
-		auto operator*(const math::Float &a) const -> const Object {
+		auto operator*(const math::Float &a) const -> Object {
 			Object ret = *this;
 			ret *= a;
 			return ret;
 		}
-		auto operator/(const math::Float &a) const -> const Object {
+		auto operator/(const math::Float &a) const -> Object {
 			Object ret = *this;
 			ret /= a;
 			return ret;
diff --git a/src/rocket.hpp b/src/rocket.hpp
index d804c7d..ec7f7dd 100644
--- a/src/rocket.hpp
+++ b/src/rocket.hpp
@@ -47,11 +47,11 @@ namespace trochia::rocket {
 			return object::Object<LocalFrame>::dx(t, r);
 		}
 
-		auto lcg() const -> const math::Float {
+		auto lcg() const -> math::Float {
 			return math::lerp(lcg0, lcgf, engine.progress(this->time));
 		}
 
-		auto weight() const -> const math::Float {
+		auto weight() const -> math::Float {
 			return 10.0 + engine.weight(this->time);
 		}
 	};

From b33899fa8f3b3cb6b8c0ea0c22e1bd7210f158ae Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 03:35:00 +0900
Subject: [PATCH 14/18] [add] calc angle of attack, side-slip

---
 src/simulation.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/simulation.cpp b/src/simulation.cpp
index 9eefb2c..8986193 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -61,6 +61,18 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 		const auto &time = s.t;
 		rocket.time = time;
 
+		const coordinate::local::NED vel_ned = rocket.vel;
+		const auto vab_ned = vel_ned.vec;
+
+		// Body座標系での対気速度ベクトル
+		const auto vab = coordinate::dcm::ned2body(rocket.quat) * vab_ned;
+		const auto va = vab.norm();
+
+		// tan(attack) = z/x
+		// arctan(z/x) = attack
+		const auto angle_attack		= std::atan(vab.z() / vab.x());
+		const auto angle_side_slip	= std::atan(vab.y() / va);
+
 		// thrust
 		const auto thrust = rocket.engine.thrust(time); // first stage only
 
@@ -95,7 +107,8 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 				<< geo_height << " "
 				<< (math::Float)environment::temperature::celsius(temperature) << " "
 				<< environment::air::pressure(temperature) / 100.0 << " "
-				<< environment::air::density(temperature)
+				<< environment::air::density(temperature) << " "
+				<< angle_attack
 				<< std::endl;
 		}
 

From 18e6285ddaf44543a2d7d260d8588534084973c8 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 03:38:53 +0900
Subject: [PATCH 15/18] [update] example configuration

---
 config-example.toml | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/config-example.toml b/config-example.toml
index 961febf..2de6aee 100644
--- a/config-example.toml
+++ b/config-example.toml
@@ -1,11 +1,11 @@
 [simulation]
 dt			= 0.01
-output.dt	= 0.1
+output.dt	= 0.01
 
 [launcher]
 length	= 5
-angle	= 86
-# angle.start = 86
+angle	= 85
+# angle.start = 85
 # angle.end = 89
 
 [rocket]
@@ -13,9 +13,11 @@ name	= "example rocket"
 type	= "hybrid"
 
 [[rocket.stage]]
-engine	= "larkspur_xp_300.resm"
+engine	= "K240.eng"
 length	= 1.1540
 diameter= 0.112
 mass	= 5.679
 Cd		= 0.450
+lcg0	= 0.913
+lcgf	= 0.905
 parachute= {condition = "top", delay = 2.5}

From 5a1431df54127b915ff46e45f2045490208c1c64 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 04:02:27 +0900
Subject: [PATCH 16/18] [add] drag force

---
 src/io/config.cpp  |  4 ++++
 src/rocket.hpp     |  2 ++
 src/simulation.cpp | 13 ++++++++++++-
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/io/config.cpp b/src/io/config.cpp
index ad5b466..00415a6 100644
--- a/src/io/config.cpp
+++ b/src/io/config.cpp
@@ -56,8 +56,12 @@ auto load(const std::string &fname, std::vector<Simulation> &sims) -> void {
 		const auto engine = stage[0].at("engine");
 		sim.rocket.engine.load_eng(engine.as_string());
 
+		sim.rocket.diameter = stage[0].at("diameter").as_floating();
+
 		sim.rocket.lcg0 = stage[0].at("lcg0").as_floating();
 		sim.rocket.lcgf = stage[0].at("lcgf").as_floating();
+
+		sim.rocket.Cd = stage[0].at("Cd").as_floating();
 	}
 
 	sims.push_back(sim);
diff --git a/src/rocket.hpp b/src/rocket.hpp
index ec7f7dd..99e27d0 100644
--- a/src/rocket.hpp
+++ b/src/rocket.hpp
@@ -41,7 +41,9 @@ namespace trochia::rocket {
 		std::string name;
 		Engine engine;
 
+		math::Float diameter;		// 直径(m)
 		math::Float lcg0, lcgf;		// 重心位置
+		math::Float Cd;				// 抗力係数
 
 		static auto dx(const math::Float &t, const Rocket &r) -> const Rocket {
 			return object::Object<LocalFrame>::dx(t, r);
diff --git a/src/simulation.cpp b/src/simulation.cpp
index 8986193..4816e06 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -73,11 +73,22 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 		const auto angle_attack		= std::atan(vab.z() / vab.x());
 		const auto angle_side_slip	= std::atan(vab.y() / va);
 
+		// 代表面積
+		const auto S = rocket.diameter * rocket.diameter * math::pi / 4;
+
+		const auto altitude = rocket.pos.altitude();
+		const auto geo_height = environment::earth::geodesy::potential_height(altitude);
+		const auto temperature = environment::air::temperature(geo_height);
+		const auto rho = environment::air::density(temperature);
+
+		// 空気抵抗
+		const auto D = 0.5 * rocket.Cd * rho * va*va*S;
+
 		// thrust
 		const auto thrust = rocket.engine.thrust(time); // first stage only
 
 		const auto force = coordinate::body::Body(
-			thrust,
+			thrust - D,
 			0.0,
 			0.0
 		);

From 357d0ca53ed702d708636e1fd4fb372788cf013e Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 04:45:31 +0900
Subject: [PATCH 17/18] [add] side,normal force

---
 config-example.toml | 3 ++-
 src/io/config.cpp   | 1 +
 src/rocket.hpp      | 1 +
 src/simulation.cpp  | 9 ++++++---
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/config-example.toml b/config-example.toml
index 2de6aee..9018b40 100644
--- a/config-example.toml
+++ b/config-example.toml
@@ -17,7 +17,8 @@ engine	= "K240.eng"
 length	= 1.1540
 diameter= 0.112
 mass	= 5.679
-Cd		= 0.450
+Cd		= 0.440
+Cna		= 7.840
 lcg0	= 0.913
 lcgf	= 0.905
 parachute= {condition = "top", delay = 2.5}
diff --git a/src/io/config.cpp b/src/io/config.cpp
index 00415a6..076fcd6 100644
--- a/src/io/config.cpp
+++ b/src/io/config.cpp
@@ -62,6 +62,7 @@ auto load(const std::string &fname, std::vector<Simulation> &sims) -> void {
 		sim.rocket.lcgf = stage[0].at("lcgf").as_floating();
 
 		sim.rocket.Cd = stage[0].at("Cd").as_floating();
+		sim.rocket.Cna= stage[0].at("Cna").as_floating();
 	}
 
 	sims.push_back(sim);
diff --git a/src/rocket.hpp b/src/rocket.hpp
index 99e27d0..4badab6 100644
--- a/src/rocket.hpp
+++ b/src/rocket.hpp
@@ -44,6 +44,7 @@ namespace trochia::rocket {
 		math::Float diameter;		// 直径(m)
 		math::Float lcg0, lcgf;		// 重心位置
 		math::Float Cd;				// 抗力係数
+		math::Float Cna;
 
 		static auto dx(const math::Float &t, const Rocket &r) -> const Rocket {
 			return object::Object<LocalFrame>::dx(t, r);
diff --git a/src/simulation.cpp b/src/simulation.cpp
index 4816e06..d6da721 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -82,15 +82,18 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 		const auto rho = environment::air::density(temperature);
 
 		// 空気抵抗
-		const auto D = 0.5 * rocket.Cd * rho * va*va*S;
+		const auto q = 0.5 * rho * va * va; // 動圧
+		const auto D = rocket.Cd  * q * S;
+		const auto Y = rocket.Cna * q * S * std::sin(angle_side_slip);
+		const auto N = rocket.Cna * q * S * std::sin(angle_attack);
 
 		// thrust
 		const auto thrust = rocket.engine.thrust(time); // first stage only
 
 		const auto force = coordinate::body::Body(
 			thrust - D,
-			0.0,
-			0.0
+			-1.0 * Y,
+			-1.0 * N
 		);
 
 		rocket.force(force.to_local<rocket::LocalFrame>(rocket.quat));

From 7ac396ca20bcc86a889d6eb09f11caf6780f5910 Mon Sep 17 00:00:00 2001
From: sksat <sksat@sksat.net>
Date: Sun, 15 Dec 2019 05:00:49 +0900
Subject: [PATCH 18/18] [fix] dividation by zero

---
 src/simulation.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/simulation.cpp b/src/simulation.cpp
index d6da721..cf85ff0 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -70,8 +70,8 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 
 		// tan(attack) = z/x
 		// arctan(z/x) = attack
-		const auto angle_attack		= std::atan(vab.z() / vab.x());
-		const auto angle_side_slip	= std::atan(vab.y() / va);
+		const auto angle_attack		= (vab.x()!=0.0 ? std::atan(vab.z() / vab.x()) : 0.5*math::pi);
+		const auto angle_side_slip	= (va!=0.0 ? std::atan(vab.y() / va) : 0.5*math::pi);
 
 		// 代表面積
 		const auto S = rocket.diameter * rocket.diameter * math::pi / 4;
@@ -122,7 +122,8 @@ auto trochia::do_simulation(Simulation &sim) -> void {
 				<< (math::Float)environment::temperature::celsius(temperature) << " "
 				<< environment::air::pressure(temperature) / 100.0 << " "
 				<< environment::air::density(temperature) << " "
-				<< angle_attack
+				<< angle_attack << " "
+				<< Y
 				<< std::endl;
 		}