Welcome!

Astrohelion (Astro - heel - eon) is a set of C++ tools that facilitiate multi-body trajectory design. Specifically, analysis in the circular restricted three-body problem (CR3BP), the CR3BP with low-thrust (CR3BP-LT), and bi-circular restricted four-body problem (BC4BP) is supported.

Capabilities

So, what can Astrohelion do? There are several key functionalities:

• Numerical Integration Astrohelion leverages the ordinary differential equation (ODE) solvers in the GSL library to numerically integrate the equations of motion associated with a few common multi-body astrodynamical systems. This propagation is controlled by a SimEngine object that possesses many of the same features as Matlab's ODE solvers, such as event detection. The engine creates a trajectory object that can then be operated on for further analysis.

• Differential Corrections Continuous trajectories may be discretized into a series of nodes, and constraints can be applied to the nodes, segments between nodes, and the trajectory as a whole. A multiple shooting differential corrections algorithm is then applied to the constrained "arcset" with the goal of satisfying all constraints. The algorithm itself, contained in the MultShootEngine object, is problem-independent and can be applied to CR3BP, CR3BP-LT, or BC4BP arcsets using the same set of commands.

• Continuation Once a desirable trajectory has been computed (and possibly corrected to meet certain constraints), continuation algorithms can be applied to generate a continuous family of similar solutions. Both natural parameter continuation (see NatParamEngine) and psuedo-arclength continuation (see PseudoArcEngine) are avaiable, both of which are agnostic to dynamical model.

• Export to File Trajectories are easily saved to file in MATLAB binary format for further analysis or visualization.

Limitations

This software has been developed to support MS and PhD research. Thus, while the tools are fully operational and have been tested fairly well, they are not as flexible or extensible as they could be. Please submit feedback via issue reports if you encounter problems so that we can continue to improve this software! However, note that we make no guarantee that we'll be able to offer support; this software is provided as is, without any quality guarnatee.

Installation

The following steps describe a general installation process.

1. Copy the installDeps.sh script into the main directory from the build directory.
2. Open installDeps.sh and set the INSTALL_DIR, CONFIG_DIR, and SPICE_DIR variables to point to locations you have write access to.
3. Additionally, set the SPK and TLS variables to the names of SPICE kernels you want to download to use for ephemeris data.
4. Run the installation script, i.e., sh installDeps.sh. This will download, build, and install the libraries required to run Astrohelion
5. Copy makefile out of the build directory into the main directory and adjust the INSTALL_DIR variable to point to the same directory as the INSTALL_DIR variable in installDeps.sh
6. Compile the project source, i.e., run make
7. Install the Astrohelion libriaries and headers, i.e., run make install

Documentation

Astrohelion documentation is available at http://adcox.github.io/astrohelion/. To build the latest documentation (which is stored in docs/api/html), run the command make docs. Document generation requires the doxygen package.