User Guide

Using a Solver

Each Lambert’s problem algorithm in lamberthub is a Python function with the same interface:

from lamberthub import authorYYYY

v1, v2 = authorYYYY(
    mu, r1, r2, tof, M=0, is_prograde=True, is_low_path=True,  # Type of solution
    maxiter=35, atol=1e-5, rtol=1e-7, full_output=False        # Iteration config
)

Replace authorYYYY with the solver author’s surname and its publication year. For example, import the Izzo solver as izzo2015. The lamberthub.ALL_SOLVERS list contains every available solver.

Parameters

Parameter	Type	Description
mu	float	Gravitational parameter, which is the mass of the attracting body multiplied by the gravitational constant.
r1	numpy.ndarray	Initial position vector.
r2	numpy.ndarray	Final position vector.
tof	float	Time of flight between the initial and final position vectors.
M	int	Number of revolutions. A value of zero, the default, selects a direct transfer.
is_prograde	bool	Controls the inclination of the final orbit. True selects an inclination between 0 and 90 degrees. False selects an inclination between 90 and 180 degrees.
is_low_path	bool	Selects the path when more than two solutions are available. Neither path has an advantage unless the mission has specific constraints.
maxiter	int	Maximum number of iterations allowed when computing the solution.
atol	float	Absolute tolerance for the iterative method.
rtol	float	Relative tolerance for the iterative method.
full_output	bool	Returns iteration details when set to True.

Returns

Return	Type	Description
v1	numpy.ndarray	Initial velocity vector.
v2	numpy.ndarray	Final velocity vector.
numiter	int	Number of iterations. This value is returned only when full_output is True.
tpi	float	Time per iteration. This value is returned only when full_output is True.