In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g⁻¹, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N₂O, CH₂O, CO₂ and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH₂ and –NO₂ within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (E_a) of 115.6 kJ·cm⁻³. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models.

Power generation can be realized in space when current is induced on a bare electrodynamic tether system. The performance of power generation is discussed based on a debris mitigation mission by numerical simulation in the paper. A Li-ion battery subsystem is used to complete the energy conversion—harvest and supply the energy. The battery can provide 10–300 W average electric power continuously during several hundred hour mission time. The energy conversion efficiency ranges from 1% to a maximum value 30%. With constant power consumption on board, the battery operation generally experiences a discharging phase, a charging phase, and a stable phase. The first two phases determine the mission risk coefficient. The heating problem in the stable phase cannot be ignored. The optimization of battery design and tether design should be considered for each debris mitigation mission. An extra control circuit or small battery voltage with large capacity for battery design is suggested to eliminate the stable phase. Wide or long tether designs are more appropriate for mission with high or low power demands on board, respectively. The power generation is affected by the system mass and the mission orbit parameters.

The jet interaction flow field generated by a subsonic circular jet exhausting into a transonic cross-flow over a convergent–divergent nozzle is investigated using numerical simulations. The simulations use the three-dimensional large eddy simulation and Reynolds-averaged Navier–Stokes equations coupled with the standard k-ε turbulence model. The numerical method is verified via cold-flow and schlieren experiments. The vortex structures are identified via the Liutex–Omega method, and the flow details of various pressure ratios and injection angles are studied. The numerical results capture the main vortex structures of a jet in cross-flow, such as the trailing upper vortex and trailing major vortex. The trailing top vortex, which is difficult to capture, and a new vortex structure, named the longitudinal shear vortex, are both observed when the momentum flux is sufficiently large. This study identifies the longitudinal shear vortex for restricted flow, which to some extent facilitates the mixing of the cross-flow and the jet. The results presented in this paper indicate that the vortex structure distribution of a subsonic jet and transonic cross-flow in the restricted region can be optimized. The main vortex structures are analyzed in detail.

Purpose: Traditional ion optics manufacturing processes are complex and costly. The purpose of this paper is to study the feasibility of using selective laser melting (SLM) to produce additively manufactured ion optics. Design/methodology/approach: An SLM machine was used to generate Ti6Al4V screen grids. The output was separated through wire cutting from the build platform and studied through a scanning electron microscope. To increase the geometrical accuracy of the original grid, samples consisting of nine-aperture arrays were fabricated with different parameter combinations, increasing the energy density. An empirical method to correlate the energy density applied in the fabrication process with the dimensional accuracy of the hole array positioning was developed through the analysis of multiple samples. Findings: The SLM machine generated grids with optimal microstructure, the apertures fell within the specified tolerances and tolerances of slightly less than 10 µm can be guaranteed for the hole array positioning. The grids’ upper surfaces presented good-quality surface finish, and the lower surface quality was acceptable when the wire cutting process that separated the grid from the build platform performed slowly. Regardless of the build strategy, the stresses generated in the separation process caused the warping of the ion optic, so a flattening operation was necessary in all cases. Originality/value: This research proved that SLM is a viable solution for ion optics fabrication, faster (less than 24 h) and less expensive (order of US$300) than traditional fabrication methods (with fabrication times from 24 to more than 400 h and costs from US$500 to US$5,000, depending on the material, size and shape).