Spacecraft.m

classdef Spacecraft < handle
	properties
		m; % mass [kg]
		L; % characteristic length or diameter [m]
		R; % nose radius [m]
		S; % reference surface area [m^2]
		I; % inertia matrix [kg.m^2]
		db; % struct with aerodynamic coefficients f(alpha, M, Kn)
		deploy; % altitude at which to deploy drogue/parachutes [m]
		CG; % nominal center of gravity location (in negative nominal body axes) [m]
		damp; % damping coefficient/s to represent control RCS thrusters [1x1 or 3x1]
		hold; % attitude hold coefficient/s [1x1 or 3x1]
		tref; % array of times in which to perform bank angle rotation [s]
		maxW; % angular velocity rate-limiter for bank angle rotations [rad/s]
		F; % high-performance interpolants for db
	end

	properties (Constant, Access = protected)
		datadir = 'constants/';
	end

	methods
		% Constructor
		function self = Spacecraft(data)
			if nargin
				% Note: data *will* have the following properties since they are taken from defaults if not provided
				self.m = data.mass;
				self.L = data.length;
				self.R = data.nose;
				self.deploy = data.deploy;
				self.CG = data.cg;

				% Inertia can be either diagonal or full tensor
				I = data.inertia;
				if numel(I) == 3
					% [Ixx; Iyy; Izz]
					self.I = diag(data.inertia);
				elseif numel(I) == 6
					% [Ixx; Iyy; Izz; Ixy; Iyz; Ixz]
					self.I = diag(I(1:3)) + diag(I(4:5), 1) + diag(I(4:5), -1) + diag(I(6), 2) + diag(I(6), -2);
				elseif numel(I) == 9
					% [Ixx; Ixy; Ixz; Ixy; Iyy; Iyz; Ixz; Iyz; Izz]
					self.I = reshape(I, [3 3]).';
				else
					util.exception('Unexpected length of inertia vector');
				end

				% Controls
				self.damp = data.damping;
				self.hold = data.holding;
				self.tref = [data.times; NaN]; % append NaN to increase array length
				self.maxW = deg2rad(data.maxbank); % [deg/s] -> [rad/s]

				% Store database as struct
				self.db = util.open(data.database, 'DataDir', self.datadir);

				% Create interpolants for high performance
				keys = fieldnames(self.db);
				Cn = keys(strncmp(keys, 'C', 1));
				self.F = struct();
				for i = 1:numel(Cn)
					self.F.(Cn{i}) = griddedInterpolant(self.db.alpha, self.db.M, self.db.Kn, self.db.(Cn{i}));
				end
			end
		end

		% Aerodynamic coefficients interpolant
		function Cx = Cx(self, str, AoA, M, Kn)
			Cx = self.F.(str)(AoA, M, Kn);
		end
	end
end