ADR system in action
Theoretical use of an e-beam in the ionosphere to disperse debris.
Credit: Osaka Metropolitan University
Scientific Frontline: Extended "At a Glance" Summary
The Core Concept: A proposed method for clearing space debris using remotely transmitted electron beams to induce ablation and propulsion, serving as a high-efficiency alternative to laser-based systems.
Key Distinction/Mechanism: Unlike lasers, electron beams (e-beams) theoretically offer higher overall energy efficiency and momentum transfer. However, the system relies on transmitting the beam through the ionosphere's plasma, where it faces challenges like beam divergence and instability (turbulence) that must be managed to maintain focus over long distances.
Major Frameworks/Components:
- Active Debris Removal (ADR): The overarching strategy of actively removing defunct satellites and fragments from orbit.
- Particle-in-Cell (PIC) Simulation: The numerical method used to model the complex behavior of charged particles in the ionosphere.
- Two-Stream Instability: A specific plasma instability identified as the source of turbulence that disrupts the electron beam.
- Laminar-to-Turbulent Transition: The critical threshold where the beam loses cohesion, which determines the effective range and focus of the system.
Branch of Science: Aerospace Engineering, Plasma Physics, Thermophysics.
Future Application: The development of ground-based or orbital systems capable of "pushing" hazardous space junk out of orbit more effectively than current theoretical laser models.
Why It Matters: As low Earth orbit becomes increasingly crowded, the risk of catastrophic collisions (Kessler Syndrome) grows; this research provides crucial data on how to stabilize the high-energy beams necessary to clean up the space environment efficiently.
A possible alternative to the active debris removal (ADR) by laser is the ablative propulsion by a remotely transmitted electron beam (e-beam). The e-beam ablation has been widely used in industries, and it might provide higher overall energy efficiency of an ADR system and a higher momentum-coupling coefficient than the laser ablation. However, transmitting an e-beam efficiently through the ionosphere plasma over a long distance (10 m–100 km) and focusing it to enhance its intensity above the ablation threshold of debris materials are new technical challenges that require novel methods of external actions to support the beam transmission.
Therefore, Osaka Metropolitan University researchers conducted a preliminary study of the relevant challenges, divergence, and instabilities of an e-beam in an ionospheric atmosphere, and identified them quantitatively through numerical simulations. Particle-in-cell simulations were performed systematically to clarify the divergence and the instability of an e-beam in an ionospheric plasma. The major phenomena, divergence and instability, depended on the densities of the e-beam and the atmosphere. The e-beam density was set slightly different from the density of ionospheric plasma in the range from \(10^{10}\) to \(10^{12}\) m\(^{-3}\). The e-beam velocity was changed from \(10^{6} \text{ m/s} \text{--} 10^{8} \text{ m/s}\), in a nonrelativistic range.
Results revealed that nonrelativistic e-beams of density from \(10^{10}\) to \(10^{12}\) m\(^{-3}\) emitted in ionospheric plasmas of density from \(10^{10}\) to \(10^{12}\) m\(^{-3}\) experience the laminar-to-turbulent transition. The turbulence should originate from the beam electron/ion two-stream instability because the transition length can be approximated by the theoretical formula of the two-stream instability. In the laminar region, the lateral expansion of the electron beam was suppressed in the plasma. The beam compression factor was quantified for the first time. These results indicate that for the use of e-beams for ADR applications, the laminar region with suppressed divergence can be beneficial for efficient focusing and ablation, but the turbulence due to plasma instabilities needs to be considered in ADR system design.
Published in journal: Journal of Thermophysics and Heat Transfer
Title: Particle-In-Cell Study of Electron Beam Propagation Through Ionospheric Plasma
Authors: Keita Nishio, and Koichi Mori
Source/Credit: Osaka Metropolitan University
Reference Number: phy020926_01