Adding a new propellant

HallThruster allows users to add new propellants beyond those provided by the code. For instance, if you wanted to implement Neon, you first create an appropriate Gas, like so:

using HallThruster: HallThruster as het

Neon = het.Gas("Neon", "Ne"; γ = 5/3, M = 20.1797)

Next, you need to find some reactions. Ionization reactions are mandatory, while elastic collisions and excitation reactions are optional. We recommend you check the LXCat database for appropriate cross sections.

You must then convert cross sections must be converted into ionization rate coefficients by integrating over a Maxwellian electron energy distribution for a number of energies. You can do this manually, or use a tool like BOLSIG+ to do it for you.

Then, you must place the resulting table of electron energy versus rate coefficient in an appropriately-named file. The expected formats for these filenames and files can be seen by examining the tables for the built-in propellants.

If you want to run a simulation with Z as the maximum charge state, HallThruster requires at least one reaction containing each species, including the mandatory first ionization reaction (i.e. neutral -> singly-charged ion). For example, for Neon with ncharge = 3, the following ionization reaction sets would suffice.

• [ionization_Ne_Ne+.dat, ionization_Ne_Ne2+.dat, ionization_Ne_Ne3+.dat]
• [ionization_Ne_Ne+.dat, ionization_Ne+_Ne2+.dat, ionization_Ne2+_Ne3+.dat]

While excitation reactions (excitation_Ne.dat) and electron-neutral elastic collisions (elastic_Ne.dat) are optional, they are strongly encouraged to improve the physical fidelity of your simulations.

With these files created, you can now run a simulation using Neon as a propellant by passing Neon to Config, along with a list of directories that HallThruster should search in order to find your reaction files.

using HallThruster: HallThruster as het

Neon = het.Gas("Neon", "Ne"; γ = 5/3, M = 20.1797)

config = het.Config(
    propellant = Neon,
    reaction_rate_directories = ["~/reactions/neon_reaction_dir"]
    ... # other arguments
)

simparams = het.SimParams(...)

solution = het.run_simulation(config, sim_params)

These directories will be checked, in order, before the HallThruster.jl directory is checked. For example, if we passed reaction_rate_directories = ["reactions", "more_reactions"], the code will first look in "reactions", then in "more_reactions", before finally checking "HallThruster.jl/reactions". An error will be emitted if the reaction rate files cannot be found.

Note that you may need to tweak other settings in the Config and SimParams struct to get simulations using non-built-in propellants working well, as thrusters running on these propellants may exhibt very different stability and physical characteristics than the default parameters were designed to handle.