Electrospray Thruster Plume Impingement Study Shows 7% Error, Achieving 100% Thrust Efficiency for CubeSat Arrays

Electrospray thrusters represent a promising propulsion technology for CubeSats, offering efficient operation with low power demands, but their divergent ion plumes pose a challenge to spacecraft performance. Ethan Kahn, unaffiliated and based in Z̈urich, Switzerland, leads a study that investigates how these plumes interact with CubeSat solar arrays, potentially causing contamination and reducing thrust efficiency. The research team develops a validated particle-tracking simulation to quantify the effects of thruster placement on various CubeSat sizes, revealing a significant correlation between platform dimensions and contamination levels. Their findings demonstrate that strategic thruster positioning, particularly side-mounted configurations with deployable arrays, can virtually eliminate impingement and maintain high efficiency, offering crucial design guidelines for optimising CubeSat missions based on specific power and propellant constraints.

Researchers employed a validated particle-tracking simulation to model the thruster plume and its interaction with the arrays, confirming its accuracy against experimental data with less than 7% divergence angle error. A parametric study evaluated nine different thruster configurations across three CubeSat sizes, 1U, 3U, and 6U, and two solar array types, quantifying the amount of thruster plume material impacting the arrays and directly affecting performance. Results demonstrate that larger CubeSats (3U) experience significantly higher contamination, 2.

8times more, compared to 1U platforms for the same thruster placement. Deployable solar arrays reduce contamination by 77% compared to body-mounted designs. Side-mounted thrusters achieve near-perfect efficiency, 98-100%, but require more spacecraft volume. Corner-mounted thrusters, angled at 30 degrees, provide a good balance between efficiency and contamination. The optimal thruster placement depends on mission requirements, such as power and mass constraints.

For most missions, deployable solar arrays with rear-mounted thrusters are recommended. Mass-constrained missions benefit from side-mounted or corner-mounted thrusters to maximize efficiency. The 1U CubeSat can accept rear-axial mounting due to limited options. Maintaining 85% efficiency provides optimal performance. Future research should incorporate electrostatic effects, varying droplet sizes, plasma-surface interactions, and long-term accumulation over the mission lifetime. On-orbit validation with CubeSat telemetry is also recommended. This research provides valuable insights and quantitative data for designing electrospray propulsion systems for CubeSats, helping engineers optimize thruster placement, minimize contamination, and improve the performance and reliability of small satellite missions.

Ion Plume Simulation Quantifies Thruster Performance

This study pioneers a particle-tracking simulation to meticulously quantify the impact of electrospray thruster placement on CubeSat performance, addressing potential contamination and thrust efficiency losses caused by divergent ion plumes. Researchers developed a detailed plume model based on established electrospray physics, emitting particles from a point source with velocities determined by a directional vector and a cosine power distribution with an exponent of 1. 8. This distribution, calibrated against experimental data, accurately reproduces observed plume profiles, capturing the forward-peaked nature of the ion emission with a maximum divergence angle of 46 degrees.

Velocity magnitudes were sampled from a normal distribution with a mean of 2500m/s, mirroring typical ion energies, and particle masses were assigned to simulate a consistent mass flow rate over a one-second emission duration. To accurately represent spacecraft interactions, the team modeled three standard CubeSat form factors, 1U, 3U, and 6U, and two solar array configurations: body-mounted and deployable. Body-mounted arrays were integrated directly onto the spacecraft body, while deployable arrays extended 15cm from the body on booms, increasing separation from the plume. Nine distinct thruster mounting configurations were then evaluated, including rear-axial, side-mounted, and corner-mounted placements, tested across all CubeSat sizes and array types.

A robust collision detection algorithm, based on ray-plane intersection, determined when particles impinged upon the solar arrays, flagging them for removal from the simulation. Researchers defined two key performance metrics: thrust efficiency, representing the fraction of propellant contributing to spacecraft acceleration, and contamination fraction, quantifying the ratio of impinged particles to the total. The simulation incorporates a sticking coefficient of 0. 8 to estimate deposited mass on the arrays, providing a comprehensive assessment of thruster performance. Validation of the plume model involved comparing simulated divergence angle distributions to experimental data, ensuring the accuracy and reliability of the results.

Thruster Placement Optimizes CubeSat Performance and Efficiency

This work presents a validated particle-tracking simulation quantifying the impact of electrospray thruster placement on CubeSat performance, specifically thrust efficiency and surface contamination. Researchers systematically evaluated nine thruster mounting configurations across 1U, 3U, and 6U CubeSat sizes, utilizing both body-mounted and deployable solar arrays. The plume model accurately reproduces experimental divergence data, achieving errors below 7% and employing a cosine power distribution with an exponent of 1. 8 and half-angle of 46 degrees. Results demonstrate a correlation between thruster placement and performance.

Thrust efficiency ranges from 53. 6% for rear-mounted thrusters on 3U CubeSats with body-mounted arrays, to 100% for side-mounted configurations utilizing deployable arrays. CubeSat size also impacts contamination levels; 3U platforms experience 46. 4% contamination with rear-mounted thrusters, compared to 16. 6% for 1U platforms.

Deployable solar arrays dramatically reduce contamination, achieving a 77% reduction compared to body-mounted designs. Furthermore, side-mounted thrusters completely eliminate impingement on spacecraft surfaces, incurring only a 1. 6% loss in thrust efficiency. Corner-mounted configurations, canted at 30 degrees, provide intermediate performance, delivering 88. 9% efficiency with 11.

1% contamination. Statistical analysis confirms the reliability of the simulation, with uncertainty below 0. 15% across all configurations. These quantitative results provide mission planners with crucial design guidelines for optimizing thruster integration based on power and propellant constraints, enabling efficient and reliable CubeSat operations.

CubeSat Contamination, Size, and Array Design

This research presents the first systematic quantification of how electrospray thruster plumes affect CubeSat solar arrays, offering crucial design guidelines for small satellite missions. Using validated particle-tracking simulations, scientists evaluated nine thruster configurations across three CubeSat sizes and two types of solar arrays, achieving a robust convergence with statistical uncertainty below 0. 15%. Results demonstrate a strong correlation between CubeSat size and contamination levels, with 3U platforms experiencing 2. 8times more impingement than 1U platforms for equivalent thruster placement.

The study reveals that deployable solar arrays significantly reduce contamination, decreasing it by 77% compared to body-mounted designs, while side-mounted thrusters virtually eliminate impingement with minimal efficiency loss. Corner-mounted thrusters offer a practical compromise, achieving 88. 9% efficiency with 11. 1% contamination.