Пример #1
0
 def findTerminalThrust():
     # above the top of the atmosphere, there is no limit!
     if alt >= TOA: return 1e30
     v_term = planet.terminalVelocity(alt, dragCoefficient)
     a = timestep * timestep
     v_noTX = v_nothrust[0] * cos(phi) + v_nothrust[1] * sin(phi)
     b = 2 * timestep * v_noTX
     c = v_noTX - v_term * v_term
     soln = physics.quadratic(a,b,c)
     return max(soln)
Пример #2
0
    def determineOrbit(self, h, velocity):
        """
        Given distance from the planet's core, and current velocity vector,
        return the apsides in meters from the planet's core.

        If one of them is negative, the orbit is hyperbolic.

        h is in meters relative to the core
        velocity is in polar coordinates (m/s, radians) where the angle is
            relative to the tangent to the surface.
        """
        # http://forum.kerbalspaceprogram.com/showthread.php/36178-How-to-predict-my-apoapsis-given-altitude-and-velocity
        # Plugging in Horn Brain's derivation (which is the same as Jason
        # Patterson's, but seems a bit easier to follow):
        # We use two equations, twice each:
        # vis viva:     v^2 = mu (2/r - 1/a) where a is the semimajor axis
        # momentum:     p = r v cos(theta) where theta is the angle of v to
        #               the surface tangent.
        # Momentum is preserved, so p is the same value at all points of
        # the orbit.
        #
        # Steps:
        # 1. vis viva with r=h, v=v, solve for 1/a.
        # 2. momentum from the parameters: p = rv cos theta
        # 3. momentum at the apses to relate r_apsis and v_apsis
        # 4. vis viva with r being the apses.
        #    Substitue 1/a from before, and substitute v_apsis from
        #    momentum.
        # 5. Solve quadratic equation:
        #    0 = (1/a) r_apsis^2 - 2 r_apsis + p^2 / mu
        #
        # We get two solutions, which are the apoapsis and periapsis
        # (measured from the center of the planet), in that order.
        #
        (v, theta) = velocity
        ainv = (2 / h) - (v*v / self.mu)
        p = h * v * cos(theta)
        return quadratic(ainv, -2, p*p / self.mu)