ENGINEERING TECHNOLOGY

Explore the vast universe, free to travel to and from home – a special issue on space entry deceleration and landing technology


Space entry deceleration and landing technology is the use of deceleration and buffer devices, through specific control means, so that spacecraft or other aircraft entering the extraterrestrial body at high speed or re-entering the earth’s atmosphere can land safely according to the predetermined procedure and purpose. For entry/return spacecraft, space entry deceleration and landing technology is the key to determining the success or failure of the entire space mission, and is an indispensable core technology for promoting the development of space technology, which is of great significance to the development of China’s space science and technology and the modernization of national defense and the army. With the development of the space industry, China’s space entry deceleration and landing technology from scratch, from weak to strong, especially through the baptism of re-entry satellites, manned spacecraft, lunar exploration, Mars exploration and other projects, has now become one of the advanced technologies in China’s aerospace field, and plays a decisive role in China’s space technology entering the world’s advanced ranks.

In the planning of China’s space industry, major special projects such as manned spaceflight and deep space exploration, as well as advanced space-to-earth shuttle systems, higher performance strategic and tactical missile weapons, etc., have an increasingly urgent demand for space entry deceleration and landing technology, and the main trends include: Meet more diverse engineering needs, Achieve entry deceleration and landing with larger load, adapt to faster entry speed, adapt to more complex environments such as space, high altitude, and extraterrestrial objects, Achieve higher descent and landing accuracy, The reliability and safety of entry deceleration and landing systems continue to improve, enabling spacecraft reuse, etc.

In 2019, China Aerospace Science and Technology Corporation Co., Ltd., relying on the 508 institutes of the Fifth Academy of Aeronautics and Astronautics, and Nanjing University of Aeronautics and Astronautics established the Space Entry Deceleration and Landing Technology Laboratory, positioned in: Closely focusing on the strategic needs of China’s major tasks such as manned spaceflight, deep space exploration, and space-ground round-trip transportation, carry out exploratory and innovative application basic research and key technology research on entry and landing technology, and cultivate and cultivate a high-level research team. Since the establishment of the laboratory, together with Tsinghua University, Beihang University and other universities and relevant scientific research institutes, under the guidance of the academic committee of which Academician Ye Peijian is the director, fruitful results have been achieved in the field of space entry deceleration and landing technology, and breakthroughs have been made in key technologies such as large-scale parachute recovery and landing technology of a new generation of manned transport spacecraft, and fixed-point recovery of large-scale wing parachute in the landing area of launch vehicle booster control.

In order to actively promote the development of space entry deceleration and landing technology, with the strong support of the editorial board of Tsinghua University (Natural Science Edition), the Space Entry Deceleration and Landing Technology Laboratory of China Aerospace Science and Technology Corporation Co., Ltd. carefully organized this special issue, which received a positive response from domestic scholars. This special issue selects 17 papers, covering the design, simulation analysis, test verification and other contents of the space entry deceleration and landing system, which shows the latest progress in this technology field in recent years for the reference of domestic and foreign researchers.

For details, please read Journal of Tsinghua University (Natural Science Edition) Issue 3, 2023, identify the QR code below or click on ithttp://jst.tsinghuajournals.com/CN/1000-0054/current.shtmlto view the full article.

01

Space parachute tear belt test device and its dynamic cable response characteristics

LI Dongxing,HOU Senhao,SUN Haining,LI Fan,TANG Xiaoqiang

In this paper, a space parachute tear belt test device is proposed to test the working performance of the tear zone. Based on the test device, the dynamic cable force response of rope under high-speed impact load is studied. The mechanical system is simplified to a spring damping system, the system dynamics equation is derived based on the second type of Lagrange equation, and the model is solved by the Runge-Kutta method to obtain the rope stress state during the tear zone test. The mechanism of rope damping under high-speed shock load was studied. The influence of elastic modulus, damping and mass ratio at both ends of rope on cable force was further studied, and finally the data of theoretical model and verification experiment were compared. The results show that the rope end force calculated by the theoretical model is consistent with the trend of experimental results, which verifies the correctness of the theoretical model and has guiding significance for the design and control of the tear belt test device.

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02

Design and performance analysis of inflatable film ball with omnidirectional resistance increase and derailment

WEI Jianzheng, ZHANG Yi, HOU Yixin, TAN Huifeng

Drag-enhanced de-orbit is one of the most efficient ways to avoid space debris after the failure of small satellites. Aiming at the deorbiting problem of inflatable unfolded drag enhancing film balls, firstly, the omnidirectional resistance enhancement design scheme of inflatable unfolded film balls is given, and a fusion folding method of closed three-dimensional spherical deformation and shrinkage into compact star shape and star flap Z-shape is proposed, and a dense cube shape is formed by folding with zero line width and variable thickness. Secondly, based on the deformation assumption of the small deflection spherical shell, the instability critical pressure of the drag increasing film ball when it is subjected to the maximum gas resistance at the limit height of 200 km is analyzed, and the critical pressure change of the film ball under room temperature and high temperature conditions is compared and verified by vacuum environmental chamber. Finally, the relationship between the surface-to-mass ratio of different fragments and the diameter of the bulge-increasing film ball on the deorbiting time was analyzed. The results show that the polyimide film sphere can be used as a spherical structure of omnidirectional resistance increase and de-orbit design of space debris, and its critical pressure decreases exponentially with the increase of the diameter of the sphere. At the same orbital altitude, the larger the surface-to-mass ratio of the fragments, the shorter the deorbiting time; Under the same surface-to-mass ratio conditions, the higher the orbital height of the fragments, the longer the deorbiting time.

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03

Simulation of the effect of angle of attack effect on the parachute straightening process

WANG Guangxing, FANG Guanhui, LI Jian, LIU Tao, HE Qingsong, JIA He

The ejection straightening process of the parachute is the first key action of the parachute work, which can create conditions for the smooth inflation of the subsequent parachute. The ejection straightening process of the parachute is generally in the wake area of the aircraft, and the wake characteristics have an important influence on the process. The altitude, Mach number, angle of attack, etc. of the aircraft during parachute opening will affect the wake of the aircraft, and the angle of attack of the aircraft during parachute opening is an important consideration in parachute design. In this paper, the three-dimensional unsteady Reynolds averaged Navier-Stokes (URANS) equation coupled with six degrees of freedom (6DoF) equation is used to study the influence of angle of attack effect on the straightening process of parachute ejection. The results show that the angle of attack effect will significantly change the wake characteristics of the aircraft, and compared with the 0° angle of attack, the wake of the non-0° angle of attack return module presents asymmetric flow characteristics, which leads to the inconsistency between the wake direction and the initial velocity direction of ejection. Asymmetric wake will have a great influence on the trajectory and attitude of the isolate. The angle of attack effect causes the position of the separator to change relative to the wake, which affects the straightening process time, that is, as the angle of attack increases, the ejection straightening time decreases. The method and conclusion have important reference value for the design of parachute system.

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04

Effect of the change of fullness of the sail structure on the aerodynamic performance of the circumferential parachute

GAO Chang, LI Yanjun, YU Li, NIE Shunchen

Based on the aerodynamic shape of the circumferential parachute under the steady descent state, a numerical model of the circumferential flow field of the parasail is established, and the influence of the sail structure on the deceleration and stability performance of the parasail is analyzed by studying the wake of the circumferential parasail under different sail exhaust directions, the seam jet of the parachute jacket and the surface pressure of the parachute, and the influence of the change of fullness on the aerodynamic performance of the parachute is explored. The results show that the axial resistance of the upward exhaust structure is reduced by the action of the downstream air column through the crescent gap, but the recovery moment is obtained when the umbrella deviates from the equilibrium position, so the drag coefficient is reduced and the stability is enhanced compared with the downward exhaust umbrella. With the increase of the fullness of the sail structure, the resistance coefficient of the upward exhaust parachute increases, and the drag coefficient of the downward exhaust parachute decreases. Both venting directions have stable and optimal fullness values. The research results provide a theoretical reference for improving the design of parasailing.

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05

Umbrella fabric microporous jet breathability characteristics

SUN Zhihong, QIU Bowen, YU Li, LI Yanjun, NIE Shunchen

In order to study the jet characteristics of the microporous breathable structure of the umbrella coat, a microscopic model of two fabrics is established based on TexGen, and computational fluid dynamics (CFD) technology is used to study the pore jet flow field under different pressure differences, and the change law of velocity and pressure along the central axis of pores is explored. The results show that different pore structure fabrics have similar flow field distribution rules, and there are four regions of pore jet: velocity increase area, velocity attenuation area, wake attenuation zone and wake transition zone. The velocity and pressure gradients along the axial direction mainly appear in the velocity increase zone and the velocity attenuation zone. The maximum velocity point and the minimum pressure point of the central axis are located about 0.145t behind the pore throat (t is the fabric thickness); The flow characteristics of the wake attenuation zone are not affected by the internal and external pressure difference, and when the pressure difference is greater than 200 Pa, the change of flow characteristic parameters in the fabric pores and wake field is only determined by the fabric structure. Combined with the exponential attenuation relationship between the length of the jet zone and the air permeability of the fabric, a universal jet influence domain model is proposed. This research method is of great significance to explore the fine wake structure of breathable parachutes and improve the accuracy of the flow field model of permeable parachutes.

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06

Design of a round umbrella with lateral movement ability

CHEN Guanhua,CHEN Yaqian,ZHOU Ning,JIA He,RONG Wei,XUE Xiaopeng

As an important deceleration tool, parachute usually has vertical deceleration ability, if it has a certain stable and controllable lateral movement ability, it will greatly expand the application range of parachute. Asymmetrical seams and holes on the umbrella jacket are simple and effective ways to achieve level flight. In this paper, an umbrella with asymmetric hole and slit structure is designed based on a planar circular umbrella, and the results of comparing the flow field structure, resistance coefficient and transverse force coefficient are calculated by numerical simulation method to verify whether it has lateral motion ability. Through calculation, it can be seen that the ring seam deceleration effect is best at 30° from the corresponding circle angle at the bottom of the umbrella. On this basis, the length of the ring seam of the umbrella is shortened by half, and the radial hole is gradually added to achieve asymmetrical slit and hole. In all calculation models, the design of the U-shaped parachute slit will greatly improve the deceleration performance and lateral movement performance of the parachute, and the best stability of the parachute with the change of angle of attack.

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07

Design and test of a large stamped wing parachute

WU Zhuo,ZHANG Wenbo,WANG Zhiguo,FENG Jiarui,REN Yali

The ramjet wing is a parachute with high glide ratio and controllable flight ability, which has broad application prospects in the field of precision airdrop and recovery. The design technology of foreign large-scale stamped wing parachutes is relatively mature, and stamping wing parachutes have also been widely used; The domestic design technology still stays on small and medium-sized stamped wing parachutes, and the design and application of large stamped wing parachutes are less. In this paper, a design method of large ramjet wing parachute is proposed, a structural design method is given, the engineering calculation method of aerodynamic performance is corrected, and a large ramjet wing parachute is designed for recovery of launch vehicle boosters, and the calculation results and test data of the aerodynamic performance value of the parachute are analyzed. The revised engineering calculation method can calculate the stall angle of attack of the parachute system, which can explain the phenomenon that the parachute system cannot be trimmed at a small installation angle, and the aerodynamic performance data of the large parachute system obtained are also close to the data of the airdrop test, which is an effective auxiliary method for the design of large rampage. The success of airdrop and flight tests also proved that the design method of this large ramjet wing was plausible.

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08

Influence of material elasticity on the mechanical properties of parachute inflatable expansion

WANG Qi,JIANG Wei,WANG Wenqiang,LEI Jiangli,ZHANG Zhang,ZHAO Miao

The parachute inflatable unfolding process involves a high degree of coupling between the nonlinear deformation of the flexible structure and the flow field. In order to study the influence of different elastic zonal reinforcement bands on the mechanical properties of parachute inflation and unfolding, the inflatable unfolding process of three elastic zonal reinforcement belt configurations was simulated based on fluid-solid interaction (FSI) methodThe key parameters such as aerodynamics, weft reinforcement belt tension and stress distribution of the parachute jacket during the inflatable unfolding process were obtained, the influence of fabric material elasticity on the dynamic load and local force of the parachute opening was analyzed, and the aerodynamic changes of the inflatable unfolding process of the parachute were tested by wind tunnel test, which verified the feasibility of using the FSI method to predict the dynamic mechanics and local force characteristics of the parachute. The simulation and experimental results show that the elastic modulus of the zonal reinforcement zone has little effect on the overall aerodynamic force during the inflated unfolding of the parachute, and has a significant effect on the stress distribution of the parachute jacket and the zonal reinforcement zone itself. Compared with the aromatic III. weft reinforcement belt with high elastic modulus, the maximum stress of the weft reinforcement belt and the umbrella jacket was reduced by 83.3% and 22.8%, respectively.

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09

Strength verification method for parachute materials for aerospace recycling

SUI Rong, ZHANG Wenbo, JIA He, JIANG Wei

In order to simulate the real working state of the parachute as much as possible and improve the design verification method of the parachute, the experimental research of the common fabric materials of parachute under fatigue load, biaxial tensile load and vertical plane load was carried out according to the actual application conditions of the parachute, and the load calculation method of the fabric under the vertical plane load was proposed. The results show that fatigue loading reduces the elongation at break of nylon, a fabric material commonly used for parachutes, makes the tensile breaking work smaller, and reduces the dynamic load bearing capacity of the fabric. Under the action of biaxial tensile load, the tensile strength of the nylon plain fabric materials commonly used in the two parachutes did not have obvious differences from the uniaxial tensile strength. Under the vertical plane load, the breaking strength of the nylon fabric is less than the nominal breaking strength of the material, and the strength loss is up to about 16%, and the test results can be applied to the calculation of the parachute strength design coefficient to guide the product design.

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10

Dynamics of the main parachute package of a manned spacecraft

WANG Yongbin, ZHANG Yajing, HUANG Xuejiao, YIN Sha, CHEN Dianhao, WANG Qi, LEI Jiangli, JIA He, CHEN Jinbao

The aerodynamic deceleration system of China’s new generation manned spacecraft test ship consists of 2 parachutes and 3 main parachutes, which separate and pull the main parachute bag out of the spacecraft after achieving the first stage of deceleration. As an important working link of the parachute system, the main parachute bag exit capsule has always been one of the key technical and design difficulties of the recovery landing system, because this instantaneous highly dynamic process involves multi-body contact and force coupling such as sling, parachute bag and hatch, so it is difficult to accurately describe the process by theoretical calculation method based on simplified dynamic model. In this paper, a coupled aerodynamic-dynamic analysis method based on finite element model is proposed, the dynamic model of the main parachute bag out of the cabin is established, and the dynamic transmission of the parachute from aerodynamic load to the dynamic model is realized by using the aerodynamic load dynamic matching control method, and the dynamic characteristics such as load, speed and overload of the main parachute package exit process are obtained by comprehensively analyzing and comparing the factors affecting the initial speed, heat protection layer tension and hatch quality of the hatch out, and the dynamic process of the main parachute bag out of the cabin is intuitively and realistically described. This method effectively guides the design of a new generation of manned spacecraft test ship recovery system scheme, and provides theoretical support for subsequent formal missions.

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11

Thermochemical non-equilibrium simulation of flow fields of tapered deceleration structures

LIU Yu,ZHAO Miao,ZHANG Zhang,JIA He,HUANG Wei

In this paper, the flow field of conical deceleration structure used in inflatable reentry and descent technology (IRDT) is calculated by aerothermal simulation. The computational model solves the N-S (Navier-Stokes) equation based on the finite volume method, and uses the non-equilibrium dual-temperature model to calculate the flow field thermochemical reaction. In order to verify the accuracy of the algorithm, the blunt body standard model ELECTRE was simulated and calculated, and the calculation results were basically consistent with the flight test and literature results. The simulation results show that the vibration temperature is activated after the shock and gradually increases to the translational temperature, while the concentration of dissociation components in the air gradually increases. The heat flow and pressure on the surface of the structure decrease rapidly in the radial direction near the standing point, and then the heat flow decreases linearly, and the pressure is approximately constant. The simulation results of four different half-cone angle conical deceleration structures are compared, and the results show that the position and surface heat flow of the 50°, 55° and 60° half-cone angle shock waves are basically the same, and the 65° half-cone angle shock is farther from the leading edge point, and the surface heat flow is lower. The standing point pressure of the four half-cone angles was basically the same, and the peripheral pressure increased linearly with the increase of the half-cone angle. The simulation results can provide a reference for IRDT scheme design.

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12

Aeroelastic dynamic response characteristics of space-filled returner

ZHANG Zhang,WU Jie,ZHAO Miao,WANG Qi,LIU Yu

Aiming at the aeroelastic dynamic response of space-filled returner under supersonic flow field, a fluid-structure interaction model considering the action of internally charged gas is established, which reveals the influence of deformation of spatial re-inflatable flexible inflatable structure on the flow field more realistically than the existing methods. At the same time, the flight trajectory of the supersonic stage was corrected by using six-degree-of-freedom flight dynamics, which effectively realized the two-way coupling between flight dynamics and gas dynamics. The results show that under supersonic conditions, the pitch moment derivative of the aircraft is negative when the angle of attack is less than 50°, and its structure has the ability to maintain a static stable state. The aircraft will produce violent vibration in the supersonic flow field, which is essentially the jitter effect under the action of large-scale turbulent wake, and this phenomenon is more serious in the case of transsonic speed and asymmetric flow, and there is a risk of inducing low-frequency resonance of the structure. This study provides a reference for the design and evaluation of structural safety of space-inflatable returners under supersonic conditions.

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13

Gravity unloading system for ground contact simulation testing of Mars landers

SUI Yi, SUN Haining, HUANG Wei, DONG Qiang, LI Guangyu, ZHANG Jianyong, ZHANG Yajing

Reliable and rapid verification tests on the ground are key to a successful landing. Based on the zero-free length spring simulating the gravity unloading system of the Mars landing of “Tianwen-1”, this paper provides the spacecraft with the gravity environment on the surface of Mars in the ground contact stage, solves the technical problem of stable and constant output of unloading force during ground contact and violent collision, and uses the truncation ability of the spring to high-frequency interference such as impact force to maintain a stable output of the gravity unloading system in the process of violent dynamics. The test results show that the maximum average error of the constant force output of the system is 1.5%, which can effectively guarantee the application of constant unloading force under large stroke, heavy load, high speed and impact conditions. The load-adjustable design of the system can adapt to the gravity environment of different target planets, which improves the test efficiency of related ground contact simulation.

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14

Numerical study on aerodynamic characteristics of continuous flow zone during rocket fairing half-hood re-entry process

FENG Rui,LIU Yu,ZHANG Zhang,HE Qingsong,WU Zhuo,TENG Haishan,JIA He

Aiming at the problem that it is difficult to predict the re-entry landing point after the fairing half-hood is separated from the launch vehicle, combined with the measured flight trajectory data of reentry, the aerodynamic characteristics of the re-entry process of a certain type of commonly used rocket fairing half-hood in the continuous flow area are comprehensively studied by computational fluid dynamics (CFD), and the aerodynamic parameters of the re-entry speed in the range of Ma 0.20~5.95 and angle of attack are 0°~360°. The calculation results show that there are two trim angles of attack in the half-hood reentry process, and the first trim angle of attack in the supersonic and subtransonic basins is about 95° and 88°, respectively, and the angle of attack of the second trim is about 255°. At the first and second trim angles of attack, the half-hood exhibits static stability and non-static stability in the rolling direction at 0°, respectively. Adjusting the position of its center of mass along the axis of the half-hood can effectively change its trim flight angle of attack, thereby significantly changing the trim flight lift-to-drag ratio. The research results are of great value for the reliable prediction of the half-cover re-entry landing zone of the launch vehicle or the adjustment and control of the landing area within a certain range.

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15

Design and topology optimization of single wing configuration of combined UAV

ZHANG Qingsong, JIA Shan, CHEN Jinbao, XU Yingshan, SHE Zhiyong, CAI Chengzhi, PAN Yihua

Lightweight is a key indicator of aircraft design and optimization, which directly affects the combat efficiency of aircraft. Aiming at the design of load-bearing structure and lightweight design of single UAVs in combined UAVs with large aspect ratio, this paper establishes a single wing frame model of combined UAVs, and proposes an overall design optimization method for topology optimization of the main force transmission components of the wing under the constraints of aerodynamic cyclic load action and fatigue life: firstly, the aerodynamic load under the full working condition of the wing is analyzed by the finite element method; Secondly, the fatigue life characteristics of the whole wing are analyzed under the action of ultimate load cycle. Finally, the volume optimization design of the single wing load-bearing frame is carried out through topology optimization technology, and the weight of the optimized wing frame is reduced by 35%, which effectively realizes the lightweight design goal of the wing frame.

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16

Lunar dust transport anomalies at the junction of light and dark in the lunar environment

DONG Tailang, FENG Yulong, HUANG Wei, REN Depeng, WANG Zhihao, WANG Jianshan, CUI Yuhong

In the lunar surface environment, lunar dust transport anomalies occur in mountains or in the vicinity of detectors and rovers. In this paper, by establishing two global and local light and dark junction models, using the particle grid method and frog jumping method, based on the amount of lunar dust measured by Apollo detector, the abnormal phenomenon of lunar dust transport in the two models is studied. The results showed that there were very significant lunar dust transport anomalies in the overall light and dark junction area, and the moon dust transport path showed the shape of a trumpet mouth or a flaky parabola, and a large amount of moon dust accumulated above the light and dark junction, and the moon dust transport phenomenon had obvious horizontal transport characteristics. In the local light and dark junction area, there are very significant lunar dust transport anomalies on the left and right sides of the detector, with two-way horizontal transport characteristics, and there are large or small double moon dust vortices, which cause local “moon dust storms” around the detector. The abnormal phenomenon of lunar dust transport in the overall light-dark junction area can indirectly verify the “glow” phenomenon, and the abnormal phenomenon of lunar dust transport in the local light-dark junction area may also be one of the main reasons for the deposition of a large amount of lunar dust on the lunar surface detector. Lunar dust transport anomalies are not only potentially harmful to active lunar rovers and probes, but also one of the key problems that cannot be avoided in future lunar exploration activities. The results of this study have important reference value for the selection of lunar probe landing sites and rover walking routes, which is helpful to reduce the impact of lunar dust pollution on human lunar exploration activities.

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17

Three-dimensional follow-up system of spacecraft low-gravity simulation test platform

DONG Qiang, CHEN Qiang, HUANG Ke, XING Wei, SHEN Bing

In order to verify the adaptability of spacecraft to land and take off on the surface of the target celestial body under low-gravity environmental conditions, the three-dimensional follow-up system adopts the two-level linkage drive technology of large-range follow-up and fast and accurate tracking to construct a low-gravity environment, and conducts the landing and take-off test of the spacecraft on the ground. The test method overcomes the difficulties of technical indicators such as large test space requirements and high control accuracy requirements, and solves many key technical problems such as multi-degree-of-freedom linkage of three-dimensional follow-up system and high-speed and high-precision collaborative control of large inertia electromechanical equipment. Through the drive technology of parallel cable system, the rapid follow-up platform movement is controlled to complete the large-scale follow-up tracking during the spacecraft test. Apply high-precision rope pull control to the spacecraft through the fast follow-up platform device, and follow the spacecraft movement in the horizontal direction while maintaining the absolute inclination of the rope; By improving the horizontal stiffness of the fast follower platform, the adverse effect of coupling shaking of two-stage linkage equipment on spacecraft test is overcome. The system has been successfully applied to a series of ground real working conditions verification tests such as hovering, obstacle avoidance, slow descent and landing, and takeoff of Chang’e-3, Chang’e-5 and Mars-1 spacecraft in China’s lunar exploration project, which provides key technical means for the verification and optimization of comprehensive performance parameters of spacecraft.

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