A parachute is a kind of decelerator that requires very high reliability. Inflation is a primary step that causes the failure of a parachute structure, especially for a slot parachute. If success/failure data from the airdrop experiment or numerical simulation are to be used for assessing the reliability of a parachute, a series of experiments or simulations is necessary. However, this process is unacceptable in engineering because of the high cost required. A new assessment method is proposed in this paper, and a novel simulation method of slot-parachute inflation is investigated to obtain strength test data. In the assessment method, strength test data are used as the prior information and integrated with inflation simulation information to assess parachute reliability using the Bayesian theory. This method is derived from a strict mathematical theory. The assessment results are consistent with the parachute's actual performance. The simulation results demonstrate the effectiveness of the proposed approaches.

Micro and sub-micro-spherical copper powder slurries were elaborately prepared to fabricate different types of porous coating surfaces. These surfaces were further treated with low surface energy modification to obtain the superhydrophobic and slippery capacity. The surface wettability and chemical component were measured. The results showed that both the micro and sub-micro porous coating layer greatly increased the water-repellence capability of the substrate compared with the bare copper plate. Notably, the PFDTES-fluorinated coating surfaces yielded superhydrophobic ability against water under 0 °C with a contact angle of ~150° and a contact angle of hysteresis of ~7°. The contact angle results showed that the water repellency of the coating surface deteriorated with decreasing temperature from 10 °C to −20 °C, and the reason was probably recognized as the vapor condensation in the sub-cooled porous layer. The anti-icing test showed that the ice adhesion strengths of the micro and sub-micro-coated surfaces were 38.5 kPa and 30.2 kPa, producing a 62.8% and 72.7% decrease compared to the bare plate. The PFDTES-fluorinated and slippery liquid-infused porous coating surfaces both produced ultra-low ice adhesion strengths of 11.5–15.7 kPa compared with the other non-treated surfaces, which showed prominent properties for anti-icing and deicing requirement of the metallic surface.

We introduce a circle rolling method (CRM) for boundary extraction from 2D point clouds. The core idea is to create a circle that performs pure rolling on the perimeter of the point cloud to obtain the boundary. For a 3D point cloud, a plane adsorbs points on both sides to create a 2D point cloud, and the CRM is used to extract the boundary points and map them back into space to obtain 3D boundary points. Continuously moving this plane can obtain a complete boundary, which is called the moving adsorption rolling method (MARM). In this paper, we solve the interference problems in our method caused by unidirectional overlapping points and porous structures and successfully validate the solutions in practical examples. Our point cloud boundary extraction method is faster in 2D and better for surface concavities extracted in 3D compared to existing methods, and it is unaffected by sparse points within the point cloud.

The growing risk of falling debris from outer space as well as the atmospheric interaction effect makes the orbit decay prediction of large spacecraft in very low earth orbit (VLEO) increasingly significant. Focusing on the aerodynamic perturbation effects under multiscale and nonequilibrium states on the orbit decay of the large spacecraft in VLEO at the end of its lifetime, we developed a novel perturbation prediction model covering the entire altitude range before reentry to perform long-term and short-term predictions of the large-scale spacecraft. A unified local rapid engineering algorithm for aerodynamic force and moment coefficients covering all flow regimes is proposed. The orbit perturbation models, combining the components of aerodynamics solved by the engineering algorithm, are built for the large-scale spacecraft. For altitudes ranging from 350 km to 250 km, which we defined as the slow descending stage (SDS), the two-line orbital elements (TLEs) and simplified general perturbation 4 (SGP4) model were used for long-term prediction, whereas for altitudes from 250 km to 120 km, which we defined as the rapid falling stage (RFS), Kepler two-body motion dynamics with acceleration perturbations were applied. All the relevant orbital elements were analytically solved and numerically simulated by the Runge–Kutta integration method. Thus, the decay orbit for large spacecraft from 350 km to 120 km altitudes can be evaluated by the platform we built. All the predicted results were broadly consistent with the measurement data. The findings in this paper can be further applied into the orbit determination of noncooperative spacecraft.

This study examines boundary layer control and pressure recovery in low Reynolds number supersonic flow with chemical reactions in a chemical laser system. Our work prescribes a novel boundary layer control method for the optical cavity of a chemical laser system, and a design of a supersonic diffuser is compared and proposed to make a stable flow for the system. The flow characteristics of a low Reynolds number and internal reaction heat release were analyzed. Three types of experimental pieces were designed to passively control the boundary layer in the optical cavity. An active booster-type supersonic diffuser is proposed to study the pressure recovery problem of a low Reynolds number and chemical reaction supersonic flow generated by an optical cavity. A supersonic chemical reaction platform (SCRP) was established to conduct experimental research on boundary layer control and docking the active booster supersonic diffuser with the SCRP. The experimental results indicate that increasing the boundary layer pumping capacity within a certain range can reduce both the boundary layer thickness and the pressure on the optical cavity while simultaneously enhancing the SCRP energy power. The supersonic diffuser based on active gas pressurization can create the necessary conditions for the normal chemical reaction and improve the ability of the SCRP to resist high back pressure and airflow disturbance. Moreover, the chemical reaction energy release was full and stable with the docking of supersonic diffuser test pieces, resulting in energy power increases, which could be a significant improvement for the design of chemical laser systems.