Zhen He

Ablative pulsed plasma thruster (APPT)-induced fluorocarbon contamination severely degrades microsatellite optics and solar panels, but the spatial heterogeneity of its chemo-optical properties and underlying plasma-film mechanisms remain poorly understood. In this work, X-ray photoelectron spectroscopy (XPS), scanning probe microscopy (SPM), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) spectrophotometry were used to characterize the chemical structure, morphology, thickness, and chemo-optical properties of PTFE-derived fluorocarbon films, while high-speed imaging and triple Langmuir probe diagnostics were used to map plume conditions governing film formation. The film F/C ratio (0.6–1.0) is far lower than that of pristine PTFE (2.0), controlled by competition between energetic ion sputtering and delayed neutral C₂F₄ deposition. In the electrode-perpendicular plane, the F/C ratio reaches a minimum ~0.6 at 30°, corresponding to a transmittance of F/C ratios and transmittance yet higher reflectance than cathode-side counterparts. Films in the electrode-parallel plane show quasi-symmetric bond distributions and higher F/C ratios and transmittance, with F/C minima at ±15°. By correlating plasma anisotropy (cathode-biased electron density and anode-biased electron temperature) with film chemistry and optics, we identify this ion–neutral competition as the origin of angle-dependent film properties. This work provides design guidelines: optics within 30° of the thruster axis in the perpendicular plane require active protection, enabling quantitative anisotropic contamination risk assessment for microsatellites.

To address the issue of spark plug erosion in gas-fed pulsed plasma thrusters, a spark plug-free, self-igniting gas-fed pulsed plasma thruster with parallel-plate electrodes was designed. Ignition tests were conducted on four gas-fed pulsed plasma thrusters with different electrode gaps. The results demonstrate that all four thrusters achieved reliable ignition with a 100% success rate. Furthermore, breakdown does not occur immediately after ammonia injection into the discharge channel; instead, a distinct breakdown late time is observed. Both experimental and simulation results indicate that under consistent ammonia mass bit and electrode voltage conditions, an increase in the electrode gap prolongs the breakdown late time. While a smaller gap leads to faster breakdown, this reduces the propellant utilization efficiency of the gas-fed pulsed plasma thruster with parallel-plate electrodes. A larger electrode gap may be more favorable for enhancing thruster performance.

This study explores the thermodynamic and kinetic properties of CeO₂ nano-fuels, with a particular focus on the influence of nanoparticle additives on the diffusion and thermal conductivity of C14-based fuel systems. Using molecular dynamics simulations and the COMPASS force field, we model the interactions between C14 molecules and CeO₂ nanoparticles, varying nanoparticle size and concentration. Our results reveal that the inclusion of CeO₂ nanoparticles leads to significant enhancements in both thermal conductivity (increasing by 9.8–23.6%) and diffusion coefficients (increasing by approximately 140%) within the 20 °C to 100 °C temperature range. These improvements are attributed to the interactions between nanoparticles and fuel molecules, which facilitate more efficient energy and mass transport. Notably, nanoparticles with smaller sizes (0.2 nm and 0.5 nm) exhibit more pronounced effects on both the thermodynamic and kinetic properties than larger nanoparticle analogs (20 nm and 50 nm). The study also highlights the temperature-dependent nature of these properties, demonstrating that nanoparticle additives enhance the fuel’s thermal stability and diffusion behavior, particularly at elevated temperatures. This work provides valuable insights into the optimization of nano-fuel systems, with potential applications in enhancing the performance and efficiency of diesel combustion and heat transfer processes.

The accuracy of the laser sparking time interval measurement plays a key role in the measurement results when the projectile velocity is measured by shadow photograph system with three-sequence laser sparking. By comparing with the original single-chip measurement results, it was found that there was a certain deviation in the measurement results of the laser sparking time. Then the principle of the laser sparking time measurement circuit is introduced in detail, and the reasons for this error phenomenon are summarized. And analyze the original laser sparking time measurement data column and the data column accurately measured with an oscilloscope, use the Pearson correlation coefficient to describe the correlation between the two data columns, and obtain the sample correlation coefficient, the first laser sparking interval coefficient r₁=0.50, the second laser sparking interval coefficient r₂=0.52. According to the three-level division rule, when 0.4≤|r|1= 0.238μs, Δ₂= 0.201μs. Comparing the compensated data with the original data, The standard deviation of the measured columns of the first flash interval decreased from 0.117μs to 0.022μs after compensation, and the second decreased from 0.102μs to 0.014μs. This shows that the two columns error of compensated data are significantly reduced, which is important for the improvement of the velocity measurement accuracy of the target channel.