Low-thrust trajectory optimization of asteroid sample return mission with multiple revolutions and moon gravity assists

Near-Earth asteroids have gained a lot of interest and the development in low-thrust propulsion technology makes complex deep space exploration missions possible. A mission from low-Earth orbit using low-thrust electric propulsion system to rendezvous with near-Earth asteroid and bring sample back is investigated. By dividing the mission into five segments, the complex mission is solved separately. Then different methods are used to find optimal trajectories for every segment. Multiple revolutions around the Earth and multiple Moon gravity assists are used to decrease the fuel consumption to escape from the Earth. To avoid possible numerical difficulty of indirect methods, a direct method to parameterize the switching moment and direction of thrust vector is proposed. To maximize the mass of sample, optimal control theory and homotopic approach are applied to find the optimal trajectory. Direct methods of finding proper time to brake the spacecraft using Moon gravity assist are also proposed. Practical techniques including both direct and indirect methods are investigated to optimize trajectories for different segments and they can be easily extended to other missions and more precise dynamic model.

Ejection Separation Characteristic Analysis of Parachute Container Cover from Return Capsule for Lunar Exploration

The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system,which is related to the success of a recovery system.Adopting the computational fluid dynamics(CFD)simulation and flight dynamics coupling method,the parachute container cover ejection separation is simulated.The rationality of the ejection separation speed and dynamic characteristics of the separation process is analyzed.Meanwhile,the influences of angle of attack,Mach number and ejection separation speed on the parachute container cover ejection are also investigated.Results show that the ejection separation speed design is reasonable.It has a certain design margin for parachute container cover to escape from the wake region,and to pull out the drag parachute completely.The results may provide a theoretical basis for recovery system engineering design of the lunar exploration project.

Patent Analysis and Research on Mars Sampling Technology

This article reviews Mars sampling and return technology,by retrieving and analyzing the patents of domestic and foreign sampling equipment and mechanism technology,Mars surface removal technology and ultra-highspeed light and small sample return technology.It conducts patent analysis from the macro-technical view down to the micro-specific content view using statistical,quantitative and qualitative analysis methods.In the process of macro-analysis,it analyzes patent data from multiple perspectives such as time,region,technical composition,and applicants,and establishes the development trends for Mars sampling and return technology at home and abroad.In the process of micro-analysis,through the analysis and interpretation of key patents,we can learn the development priorities and development direction of foreign Mars sampling and return technology.This paper also proposes China’s Mars sampling and return technology development suggestions.

Analysis of Chang’e-5 lunar core drilling process

Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface.This study analyzed the lunar core drilling process based on the telemetry data,image information,and returned samples to optimize the sampling device design and enhance the understanding of the lunar regolith.In particular,a prediction method for the projected drilling path and local terrain fitting of drilling dip angle was proposed based on the flight events recorded during the core drilling process and the image information acquired before,during,and after sampling.The results revealed that the drilling dip angle of Chang’e-5 was approximately2.3.,and the deviation of the drilling length and depth was less than 2 mm.For continuous drilling,a fusion method based on telemetry data and image information was applied to determine the demarcation point of drilling with and without the lunar soil.The position of the demarcation point implied that the drilling point remained at approximately 6 mm loose soil,thereby lagging the action of the force response.Additionally,a characteristic parameter comparison method was proposed for the lunar and ground drilling to analyze the status of the lunar soil.Furthermore,the analysis results revealed that the majority of the Chang’e-5 drilling samples were derived from 0–73.8 cm below the lunar surface and few samples were extracted below 73.8 cm,as the drilling encountered several rocky regions.Moreover,the drilling point exhibited two prominent stratification variations at~28.7 cm and~70 cm below the lunar surface.Ultimately,the preliminary relationship between sample dissected position in soft tube and drilling displacement was analyzed.The segmented estimation results can support research on subsurface lunar soil.

Rendezvous to asteroid with highly uncertain ephemeris: Hayabusa2’s Ryugu-approach operation result

This paper describes the guidance and navigation technique used by Hayabusa2 for the asteroid rendezvous operation to reach Ryugu.The operation results,including the achieved guidance and navigation performance,are also summarized.Multiple assessment and navigation teams worked closely to provide reliable navigation solutions with a short solution delivery cycle.Although the uncertainty of the Ryugu’s ephemeris was considerable before Hayabusa2’s arrival,a combination of radiometric-optical hybrid navigation and a stochastic-constrained optimum guidance method was able to achieve an accuracy of less than 100 m and 1 cm/s,and the arrival was precisely timed.

Management innovation of Chang'e-5 project

1 Overview of Chang'e-5 project As the final step of the"three-step''development strategy(i.e.,orbiting,landing and sample returning)of the Chinese Lunar Exploration Program,the Chang,e-5 project aims to achieve moon surface sampling and retrieving for the first time in China.It was initiated with the approval of the State Council in January 2011.

Mineral chemistry and 3D tomography of a Chang’E 5 high-Ti basalt:implication for the lunar thermal evolution history

In December 2020, Chang’E-5(CE-5), China’s first lunar sample return mission, successfully collected samples totaling 1731 g from the northern Oceanus Procellarum. The landing site was located in a young mare plain, a great distance from those of Apollo and Luna missions. These young mare basalts bear critical scientific significance as they could shed light on the nature of the lunar interior(composition and structure) as well as the recent volcanism on the Moon. In this article, we investigated a CE-5 basalt sample(CE5 C0000 YJYX065) using a combination of state-of-art techniques, including high resolution X-ray tomographic microscopy(HR-XTM), energy dispersive X-ray spectroscopy(EDS)-based scanning electron microscope(SEM), and electron probe microanalysis(EPMA) to reveal its 3 D petrology and minerology.Our results show that this sample has a fine-to medium-grained subophitic texture, with sparse olivine phenocrysts setting in the groundmass of pyroxene, plagioclase, ilmenite and trace amounts of other phases. It has an extremely high ilmenite modal abundance(17.8 vol%) and contains a significant amount(0.5 vol%) of Ca-phosphate grains. The mineral chemistry is in excellent agreement with that of Apollo and Luna high-Ti basalts. The major phase pyroxenes also display strong chemical zoning with compositions following the trends observed in Apollo high-Ti basalts. Based on current data, we came to the conclusion that CE5 C0000 YJYX065 is a high-Ti mare basalt with a rare earth element(REE) enriched signature. This provides a rigid ground-truth for the geological context at the CE-5 landing site and clarifies the ambiguity inferred from remote sensing surveys.