The chemistry of the low-temperature plasma discharge in electric propulsion devices is introduced for atomic and diatomic substances, and the related reactions are implemented in a particle/fluid multi-dimensional simulation code. For atomic substances: elastic, excitation and ionization collisions are considered. Excitation and de-excitation to and from metastable states can be state-selective, and thus it is possible to model stepwise ionization. For diatomic substances: in addition, vibrational and rotational excitations, dissociation and dissociative ionization are considered. Chemistry of the wall interaction is also modeled considering ion recombination, associative wall recombination, and the wall accommodation processes. Applications to two cases of interest are shown for an electrodeless plasma thruster. First, the effects of the stepwise ionization from metastable states operating with Xe are analyzed. Simulations are run for several operation conditions (on mass flow and electric power) to find regimes where stepwise ionization is important, and how it impacts on the plasma response. Second, the air-breathing concept is assessed. Simulations are run with air substances (nitrogen and oxygen) for various operation conditions to find the best thrust efficiency, and the plasma discharge characteristics and thruster performances obtained are compared with those of Xe.

This paper reports about the upcoming release of a professional plasma simulation software targeting specifically plasma engineering and design work in the electric propulsion industry. It describes the plasma engineering issues that are addressed by this software, how these issues are addressed, which market players do support it already, and how users can get involved to maximize the added value provided to them. The targeted readers are EP developers regardless of their host institution, and decision makers in charge of keeping competitivity at high levels.

Molecular dynamics calculations of inelastic collisions of atomic oxygen with molecular nitrogen are known to show orders of magnitude discrepancies with experimental results in the range from room temperature to many thousands of degrees Kelvin. In this work, we have achieved an unprecedented quantitative agreement with experiments even at low temperature, by including a non-adiabatic treatment involving vibronic states on newly developed potential energy surfaces. This result paves the way for the calculation of accurate and detailed databases of vibrational energy exchange rates for this collisional system. This is bound to have an impact on air plasma simulations under a wide range of conditions and on the development of Very Low Earth Orbit (VLEO) satellites, operating in the low thermosphere, objects of great technological interest due to their potential at a competitive cost.

An investigation on the influence of relevant parameters on an annular Hall effect thruster plasma discharge is performed using a radial particle-in-cell simulation code with secondary electron emission from the walls and prescribed axial electric and radial magnetic fields. A simulation with true-secondary electrons only is taken as reference. First, the near-wall conductivity effects on the magnetized secondary electrons are illustrated by doubling the E x B, allowing a further code validation. Second, when secondary backscattered electrons are included, the enhanced secondary emission yields lower sheath potential drops and primary electron temperature. Moreover, the dominant backscattered electrons increase the average secondary electrons emission energy, greatly affecting its temperature anisotropy ratio and increasing the replenishment level of the wall collectable tails of the primary electrons velocity distribution function. Third, the effect of the true-secondary electrons emission energy on the potential profile is shown to be negligible, the latter being mainly set by the dominant magnetic mirror effect. Finally, a planar case featuring symmetric plasma profiles permits to confirm the validity of the large cylindrical asymmetries present in the reference case, induced by the combined effects of the geometric expansion, the magnetic mirror and the centrifugal force (due to the E x B drift). A smaller deviation of the primary electron momentum equation from the Boltzmann relation along the magnetic lines is still found in the planar case, induced by the parallel temperature non-uniformity.

The new era of space exploration has begun with the intent of expanding the frontiers of knowledge, capability, and opportunities in space, to bring humans back to the Moon before sending them to Mars. One of the first milestones is represented by the settlement of the Deep Space Gateway by the mid 2020's in the lunar proximity, thanks to the exploitation of key technologies such as high-power Solar Electric Propulsion, which will be the propulsive core of the Gateway. In compliance with the current plans of efficiently reduce the number of development and validation efforts, designing and exploiting same elements for multiple missions, this paper proposes an innovative high-power electric space tug to support the replenishment of the Station, which should be flexible enough to be adopted in different phases of the Gateway lifetime. Exploiting a tailored MATLAB design tool, the main mission, mass and power budgets are provided for several spacecraft configurations and electric propulsion subsystem architectures. Moreover, the impact of adopting this cornerstone technology on the platform design is investigated with respect to different thruster working points. Then, the optimal LST configuration able to support the Gateway crew for different resupply needs is selected and its design is presented in detail.