Research
We research propulsion solutions that enable new classes of space missions, working at the intersection of propulsion hardware and mission design. We research high efficiency electric propulsion systems for spacecraft to improve upon their designs and feasibility of mission integration. Our long term goals are to enable sustainable exploration of the solar system starting with propellant depots in Earth and lunar orbits and extending to interplanetary architectures.
Research Areas:
Molecular dynamics simulations of propellant-propellant interactions.
Electrospray thrusters represent an attractive technology for micropropulsion of small satellites. They produce thrust
by ejecting charged molecules at high velocities using strong electric fields.However, the molecules present in the plume are susceptible to collision, chemical reaction, and fragmentation, which may introduce different new species with various mass-to-charge ratios inside the plume. Prediction of the byproducts that appear upon collisions is of prime importance to predicting the evolution of the plume and estimating the performance and the lifetime expectancy of the thruster. In this work, we use molecular dynamics simulations to investigate monomer-neutral collisions at different impact configurations, impact energies, and impact parameters, and provide the mass spectra of the resulting species [1].
Fragmentation due to EMI-Neutral Collisions
[1] Bendimerad, R., Tahsin, A. T. M., Yonas, A., Colucci, C., & Petro, E. M. (2023, January). Investigating the Chemical Stability of Electrospray Plumes During Particle Collisions. In 2023 AIAA SciTech Forum and Exposition.
Molecular dynamics simulations of propellant-surface interactions.
Electrospray thrusters are of particular interest for micropropulsion because of their compactness and high specific impulse. However, due to off-axis emission and narrow extractor grid apertures, a non-negligible fraction of the plume collides with the extractor grid, and therefore, reduces the efficiency and limits the lifetime of the electrospray thruster. This phenomenon is investigated using molecular dynamics (MD) simulations with the Large-scale Atomic Molecular Massively Parallel Simulator (LAMMPS) program. MD simulations allow the determination of the thermodynamic properties of the colliding molecule (EMI-BF4) and the extractor grid surface (Au) as well as the characterization of the behavior of the molecule after the collision. Three different regimes are characterized: deposition at low impact energies, reflection without fragmentation at medium impact energies and reflection with fragmentation at high impact energies [1].
Fragmentation of the molecule EMI-BF4 after collision.
[1] Cidoncha, X. G., Lozano, P. C., Bendimerad, R., Petro, E. M., & Hampl, S. K. (2022, March). Modeling and Characterization of Electrospray Propellant-Surface Interactions. In 2022 IEEE Aerospace Conference (AERO) (pp. 1-11). IEEE.
Designing Propulsion systems for In-Situ Resource Compatability
We have been studying the efficacy of replacing traditional noble gas propellants used in plasma propulsion devices with gaseous water. We have analyzed plasma generation efficiency which is applicable to a range of propulsion devices [1] and the efficiency of various non-contact plasma acceleration schemes [2,3]. Methods we have used include plasma-chemical analyses coupled with particle-in-cell modeling and quasi-1D plasma flow approximations. Our current research focus involves the study of dual-mode devices for flexible mission architectures using a shared propellant and efficiency improvements for water-plasma devices.
[1] Petro and Sedwick, Effects of Water Vapor Propellant on Electrodeless Thruster Performance, AIAA Journal of Propulsion and Power, 2017.
[2] Petro, Brieda, and Sedwick, PIC Simulations of Chemistry Effects in an Electrodeless Water Plasma Thruster, Proceedings of AIAA Propulsion and Energy Forum, 2019.
[3] Petro and Sedwick, Effects of Water Vapor Propellant on Helicon Thruster Performance, Proceedings of AIAA Propulsion and Energy Forum, 2016.
Kinetic Ion Beam Modeling for Electrospray Thrusters
Sustainable space exploration requires longevity and flexibility in satellite platforms. For small satellites, compact electric propulsion devices such as electrospray thrusters can significantly extend lifetime and capability. As these devices operate under different principles and with more complex propellants than traditional plasma thrusters, fundamental modeling of the ion emission process and plume-spacecraft interactions are required. Towards this end, we have developed a kinetic model of the plume evolution of an electrospray ion source that tracks processes at the individual ion level. This model can be used to predict the trajectory of plume ions and neutral bi-products and their impact on performance. As a spacecraft-integrated device would have thousands of emission sites, further research will include the physics of the composite plume.
[1] Petro, Miller, Schmidt, and Lozano, Development of a Fragmentation Model for Kinetic Plume Modeling, Proceedings of the International Electric Propulsion Conference, 2019.
Electric Propulsion and Mission Design
The choice of propulsion system is deeply tied to mission objectives and spacecraft properties. Electric propulsion systems often enable missions that are otherwise infeasible with less fuel-efficient propulsion architectures. For these missions, the propulsion system, spacecraft, and trajectory are closely coupled throughout the formulation and design process. We are interested in exploring new ways that electric propulsion and other revolutionary architectures can enable new solar system science and we are working to develop tools to explore this design space more efficiently.
[1] Petro and Sedwick, Survey of Moderate-Power Electric Propulsion Systems, Journal of Spacecraft and Rockets, Vol. 54, No. 3, 2017.
[2] Sheerin, Petro, Lozano, and Lubin, Fast Solar System Transportation with Electric Propulsion Powered by Directed Energy, Acta Astronautica, vol. 179, 2021.
[3] MacKensie, et. al., THEO Concept Mission: Testing the Habitability of Enceladus’s Ocean, Advances in Space Research, Vol. 58, No. 6, 2016.
