Airdrop Test Research Articles

Inflation process of radially closed parachute

Parachute closing technology can effectively control the parachute deployment process and overload and is an important technology to ensure the safe opening and normal use of the parachute. Radially closed parachutes are more effective in achieving faster and more consistent canopy inflation than traditional circumferential closing parachute technology. This study is based on numerical simulation technology and explores the working mechanism of the intake control system through comparison of experimental data. The ALE method (arbitrary Euler–Lagrangian penalty function method and multi-medium arbitrary Lagrangian–Euler algorithm) is used to construct the incompressible flow field and the coupled dynamic model of the radially closed and circumferentially closed parachute structures. Combined with the inflated shape of the airdrop test, the simulation results of the two types of closed parachutes are compared and analyzed. The study found that the radially closed parachute forms a high-pressure area through the inner parachute and a low-speed vortex area inside the canopy, which increases the pressure difference between the inside and outside of the canopy, makes the inflation more full, the stress distribution more uniform, and the parachute opening overload and speed better. It is suitable for the delivery and recovery of heavy-duty materials at low altitude and lays the foundation for further improved design and engineering application of the air intake control system.

Aerodynamic prediction for flight dynamics simulation of parafoil system and airdrop test validation

Aerodynamic prediction for flight dynamics simulation of parafoil system and airdrop test validation

Dynamic modelling of parafoil system based on aerodynamic coefficients identification

This study focuses on the identification of aerodynamic coefficients through airdrop data based on a known six-degree-of-freedom (6-DOF) model. Since the precise modelling of the parafoil system is a prerequisite for design of guidance, navigation and control systems, the accurate calculation of aerodynamic coefficients is vital. This paper first presents a rigid 6-DOF nonlinear model and simplifies it by linearizing the equations around the equilibrium point, which facilitates the acquisition of aerodynamic parameters next. Then, the recursive weighted least square method is applied to identify roll and yaw coefficients from airdrop test data. At last, simulations in the wind environment are implemented to analyse the dynamics of gliding and turning. The airdrop experiment also verifies the effectiveness of the dynamic model and the accuracy of identification.

New general correlations for opening shock factor of ram-air parachute airdrop system

The attainability of the opening process directly determines the success of a ram-air parachute airdrop system. The opening shock is the most concerned parameter for designers. Focusing on the parachute opening process, the peak load is evaluated using the opening shock factor, which is obtained using the dynamic model and the Momentum Impulse theory. Comparisons with airdrop test results show that the two methods can accurately predict the peak load. In the similarity analysis of parachutes, the criteria for flexibility, elasticity, and air permeability are summarized, and the dimensionless numbers affecting the opening shock are identified as the mass ratio, the Froude number, and the Strouhal number. The frame design of the ram-air parachute airdrop system is completed, and a database of opening shock factors including airdrop test data and numerical results is established. New general correlations for the opening shock factor are presented for vertical and horizontal opening utilizing the Levenberg-Marquardt method for regression analysis, with R2 of 0.9935 and 0.9880, and MAPE of 3.45% and 2.64%, respectively. The new correlations can quickly and accurately predict the opening shock for ram-air parachute airdrop systems.

Prediction and effect analysis for equilibrium profile of flexible porous canopy fabric

Parachute is decelerator constructed of flexible porous fabrics that changes the motion state of the payload, aerodynamic characteristic in steady descent of which largely depends on equilibrium profile. A novel analytical method to predict the equilibrium profile of flexible porous canopy fabrics in steady decelerating stage is presented. This method introduces Forchheimer’s law and Ergun theory into Ross mechanical equilibrium model, and further considering both the flight status and the materials properties. The prediction error of projection radius of gore centreline is 3.83% compared with the airdrop test results, and the prediction errors of the projection radius of cord and gore centreline are 1.09% and 0.66% respectively compared with Fluid-Structure Interaction method. Results indicate that this proposed method can be an efficient way to obtain an accurate canopy profile with much less computation cost. Finally, some illustrative examples are given to evaluate the effect of structural parameters on the parachute equilibrium profile. It is found that the length of the suspension line should be somewhat longer than the nominal diameter and the spacing of suspension lines should be slightly longer than 1m. And it is recommended that the radius of apex vent should be 0.04 ∼ 0.1 times of the nominal radius of the parachute. The Young’s modulus of materials has little effect on the equilibrium profile. Overall, the new approach could predict the canopy profile quickly for the parachute design and provide an accurate shape basis for the subsequent aerodynamic research based on CFD method.

TuSeSy: An Intelligent Turntable Servo System for Tracking Aircraft and Parachutes Automatically

Tracking aircraft and parachutes plays a vital role in airdrop experiments. It is necessary to study a parachute’s open state and flight trajectory. More scholars are looking into how to efficiently and accurately obtain parachute deformation data and trajectory data. At present, the actual data collection primarily involves experimenters holding high-definition high-speed cameras to track and shoot parachutes to obtain the image sequences of the parachutes during the airdrop process. However, these methods cannot obtain the trajectories of the parachutes and they are susceptible to interference from human factors. In this paper, we designed TuSeSy, an intelligent turntable servo system that can track the aircraft and parachutes in airdrop tests automatically. Specifically, TuSeSy generates the control commands according to the differences between the actual taken images and the inferred images by tracking algorithms (so as to actually track the target). In addition, we propose an effective multi-target tracking switch algorithm based on the image frame difference and optical flow, to achieve real-time switching from the aircraft to the parachute in an airdrop test. To evaluate the performance of TuSeSy, we conducted extensive experiments; the experimental results show that TuSeSy not only solves the problem of wrong target tracking, but it also reduces computational overhead. Moreover, the multi-target tracking switch algorithm has higher computing efficiency and reliability compared to other tracking switch approaches, ensuring the practical applications of the turntable servo system.

Design and verification of parachute deceleration subsystem of Tianwen-1 Mars probe

<p indent="0mm">The main parameters of the parachute deceleration system for the Mars probe include the special environment, mission requirements, and parachute opening conditions. The parachute deceleration subsystem of the Tianwen-1 Mars probe includes one parachute for deceleration, one motor deployment system, and one passive separation apex cap. The parachute deceleration subsystem has been fully and effectively verified by fluid-structure interaction (FSI) simulations, airdrop tests, and high-altitude parachute opening tests. On May 15, 2021, Tianwen-1 successfully landed on Mars, and all flight data of the parachute deceleration subsystem were in line with expectations.

Design improvement of air deployable parachute for high altitude launch ofpayload based on investigationand experimentation

Purpose The purpose of this paper is to improve the design of a solid square canopy of a parachute. The design improvements are brought out by providing minor slits in the canopy area. Proper designing of the parachute was carried out using theoretical investigation coupled with experimentation. This parachute is designed for launch of sonobuoy from fixed wing aircraft. Design/methodology/approach Literature review was carried out on the design of such parachutes for the launch of a sonobuoy from a high altitude to the water entry. Computational fluid dynamics (CFD) analysis provided the value of the coefficient of drag for the slit-cut square canopy parachute, with and without sonobuoy for different lengths of the slit. Besides the theoretical investigation, experimentation was also carried out to validate the design. Findings The experimentation was carried out on 58 and 75 gsm fabric canopies with the slit edge plain-cut with thermally sealed edges, stitched and strengthened. In the case of plain-cut slits on the canopy made of 75 gsm fabric, no tearing of the slit edge was observed in dynamic and flight tests. Research limitations/implications The present work has been carried out considering various assumptions and limited trial data specific to precision drop of 9 kg payload. The work can be adopted for bigger parachute for dropping of higher payloads. Originality/value Lab strength test, track dynamic and flight trials were conducted to acquire useful data for the present analysis. Besides the theoretical investigations and CFD analysis inherently based on numerous assumptions, experimentation was carried out as the sonobuoy deployment conditions are full of uncertainty. Dynamic and airdrop tests were conducted for this reason to determine design changes in the slits, both at the material level and on improvisations.

Fluid–structure interaction-based aerodynamic modeling for flight dynamics simulation of parafoil system

Prediction of aerodynamic force is a crucial issue for parafoil canopy as the strong nonlinear fluid–structure interaction (FSI) between the flexible canopy material and flow field. Flight tests and wind tunnel experiments are difficult to analyze the aerodynamics of parafoil because of the limitation and difficulty of data measurement in an unknown environment. The objective of this study was to computationally derive the aerodynamic characteristics of parafoil, as an alternative to expensive and unrepeatable test regimes. Different from previous works that assume canopy structure as a rigid body and serve for the design of parafoil, this study focused on the precise dynamic modeling of parafoil based on FSI simulations. To investigate the aerodynamic performance of the full-scale canopy with stabilizers for better control, the strong coupling FSI simulations were performed using the incompressible computational fluid dynamics techniques. The highlight of this paper is to explore the effects of canopy inflation and trailing edge deflections on aerodynamic performance. Then the aerodynamic coefficients are identified by a linear regression method using the obtained database of high fidelity lift and drag forces. Furthermore, an accurate six-degree-of-freedom dynamic model of the parafoil system is implemented based on the estimated coefficients. Simulations are conducted to prove the dynamic stability of the model and the feasibility of trajectory tracking. At last, simulation results of basic motions are compared with airdrop testing data, which demonstrates that the established model is capable of accurately predicting the flight behaviors of the parafoil system.

Design, Development and Flight Performances of Deceleration System

Human Spaceflight Programme (HSP) of Indian Space Research Organisation is proposed with the objective of carrying two crew members to low Earth orbit and bring them back safely to a predetermined location on Earth. The deceleration system for the programme has been designed for a 4-tonne class payload and shall cater to the requirements of nominal as well as abort missions. In order to finalize the parachute configurations and deployment sequence, detailed studies and development tests, starting from wind tunnel tests to full-scale air-drop tests were carried out. After successful structural and functional qualification of the parachutes and the various subsystems, the system was used to safely recover the module in the Crew Module Atmospheric Re-entry Experiment, the first unmanned spaceflight of HSP. This article provides details on the system configurations, deployment sequence and numerous tests that have been carried out till now in order to make the system worthy of manned flights in future.

Design and Realization of Recovery System of Chang’e-5 Reentry Spacecraft

On December 17, 2020, the Chang’e-5 reentry spacecraft landed safely and brought back the lunar sample without damage. This paper describes the recovery system that has critically contributed to the scientific success of the Chang’e-5 missions and presents the technical requirements and constraints of the recovery system for the Chang’e-5 reentry spacecraft and discusses the design process of the recovery system, including the system composition, working procedure, and some other key aspects. Finally, the ground cover rejection tests and air drop and flight tests were carried out to confirm the design configuration. The results showed that the Chang’e-5 reentry spacecraft recovery system was designed correctly, and its functions and performances met the design requirements. A breakthrough in the recovery technology of the reentry spacecraft was achieved for Chinese first lunar sample-return mission.

Numerical investigation of ram-air parachutes inflation with fluid-structure interaction method in wind environments

A novel nonlinear numerical model for folded ram-air parachutes inflation in wind environments is proposed based on graphical deformation and arbitrary Lagrange-Euler method. The Constrained Free-Form Deformation algorithm is introduced to implement the spanwise modeling of folded ram-air parachutes. The finite mass inflation simulation adopts Time-step Motion Method. The convection of flow field is set up by initial and boundary conditions to introduce the wind speed. This method is used to study the fluid-structure interaction dynamic characteristics of the folded ram-air parachutes inflation process in wind environments, and the transient 3D canopy shapes, surrounding flow field and opening load are obtained. The results show that the numerical result of opening load is consistent with the airdrop test. There exists a wake recontact phenomenon at the initial inflation stage. Besides, wind environments affect the inflation performance. Under upwind, the parachute inflates well and keeps a certain elevation angle. However, in the downwind or crosswind state, the payload-parachute system is unstable and unable to work. The maximum opening load in wind environments is larger than that without wind. And the stress concentration occurs at the leading edge and the stability fins. This manuscript can provide a reference for ram-air parachutes design and inflation performance optimization.

Flight Trajectory Simulation and Aerodynamic Parameter Identification of Large-Scale Parachute

In this paper, the multibody parachute-payload system is simplified and analyzed. A six-degree-of-freedom rigid body flight dynamic model is established to calculate the flight trajectory, attitude, velocity, and drop point of the parachute-payload system. Secondly, the random interference factors that may be encountered in the actual airdrop test of the parachute system are analyzed. According to the distribution law of the interference factors, they are introduced into the flight dynamic model. The Monte Carlo method is used to simulate the target and predict the flight trajectory and landing point distribution of the parachute system. The simulation results can provide technical support and theoretical basis for the parachute airdrop test. Finally, the genetic algorithm is used to identify the aerodynamic parameters of the large-scale Disk-Gap-Band parachute. The simulation results are in good agreement with the test results, which shows that the research method proposed in this paper can be applied to study practical engineering problems.

Research on Cumulative Damage Evaluation Method for Structural Impact on Airborne Armored Vehicle in Landing Process

Since it was very costly and complicated to analyze cumulative damage caused by structural impact on airborne armored vehicle in landing process using real equipment airdrop test, finite element method(FEM) was taken to build a finite element(FE) model of airborne armored vehicle and airbag system to simulate the landing impact process of airborne armored vehicle. In combination with Lemaitre Damage Model and the damage evolution law of materials, the cumulative damage caused by structural impact of vehicle was calculated. The cumulative damage of structure of airborne armored vehicle in multiple landing processes was assessed, results of which were expected to provide theoretical guidance for the operational use and maintenance of airborne armored vehicle.

Analysis on Characteristics of Structural Impact Response of Airborne Armored Vehicle in Landing Process

For such problems as high cost and complex implementation in analyzing the characteristics of the structural impact response of airborne armored vehicle in landing process by real equipment airdrop test, finite element method(FEM) was taken to build the finite element(FE) model of airborne armored vehicle and airbag system to simulate the landing impact process of airborne armored vehicle and that under different typical airdrop conditions of airborne armored vehicle, including different altitude and different vertical landing speed. In addition, comprehensive quantitative analysis was conducted on the characteristics of the structural impact response of airborne armored vehicle to provide theoretical guidance for the design, development, operational use and maintenance of airborne armored vehicle.

Modeling and control of parafoils based on computational fluid dynamics

• Leading-edge incision and trailing-edge deflection are incorporated into the calculation of aerodynamic coefficients . • A flexible dynamic model with eight degrees of freedom is established. • A characteristic modeling method is used to reduce the order of the dynamic model. • Generalized predictive control based on a characteristic model is applied to the parafoil system. The determination of aerodynamic parameters of parafoil canopies has been a crucial issue because it affects the model precision. To calculate the aerodynamic coefficients of a canopy, the lifting-line theory has been used in the traditional method. However, because of the existence of leading-edge incisions, there are some restrictive assumptions in lifting-line theory when one is calculating the aerodynamic coefficients of a canopy. Therefore in this article we calculate the aerodynamic coefficients on the basis of computational fluid dynamics . As an improvement, the effects of a leading-edge incision and trailing-edge deflection are considered. Firstly, lift and drag coefficients are obtained by use of computational fluid dynamics. Then the least-squares method is used to identify incision and deflection factors. Furthermore, an eight-degrees-of-freedom mathematical model of a parafoil system is established on the basis of the parameters obtained. Finally, a novel control algorithm, generalized predictive control based on a characteristic model, is applied to the system. The precision of the model established and the effectiveness of the proposed control method are validated by simulation and airdrop testing.

Dynamic Modeling and Simulation of Whipping Phenomenon for Large Parachute

This paper establishes the multibody dynamic model of the deployment process of a large parachute and adopts the mass-spring-damper model to simulate the suspension line and canopy. In the model, the factors of the stack sequence of the suspension line and the canopy as well as the pullout process of the bridle segments and constraint of the binding rope were considered. The model was validated by an airdrop test video. The reason for the formation of the whipping phenomenon was analyzed and validated through theoretical modeling and simulation. This paper also studies the influencing factors of the whipping phenomenon and evaluates the effect of the attached apex drogue that prevents the whipping phenomenon from forming. The research of this paper provides an analytical method to model and simulates the deployment process and the whipping phenomenon for a large parachute.

Accurate calculation of aerodynamic coefficients of parafoil airdrop system based on computational fluid dynamic

Accurate calculation of canopy aerodynamic parameters is a prerequisite for precise modeling of a parafoil airdrop system. This investigation analyses the aerodynamic performance of the canopy in airdrop testing combining the leading-edge incision and the trailing-edge deflection. Aerodynamic parameters of the canopy are obtained using the computational fluid dynamic simulations, and then, the output data are used to estimate the deflection and incision factors. The estimated lift and drag coefficients instead of the traditional parameters based on lifting-line theory are incorporated into the eight degrees of freedom dynamic model of an airdrop system and make some simulations. The effectiveness of the proposed method for calculating aerodynamic coefficients is verified by actual airdrop testing.

In-flight wind identification and soft landing control for autonomous unmanned powered parafoils

ABSTRACTFor autonomous unmanned powered parafoil, the ability to perform a final flare manoeuvre against the wind direction can allow a considerable reduction of horizontal and vertical velocities at impact, enabling a soft landing for a safe delivery of sensible loads; the lack of knowledge about the surface-layer winds will result in messing up terminal flare manoeuvre. Moreover, unknown or erroneous winds can also prevent the parafoil system from reaching the target area. To realize accurate trajectory tracking and terminal soft landing in the unknown wind environment, an efficient in-flight wind identification method merely using Global Positioning System (GPS) data and recursive least square method is proposed to online identify the variable wind information. Furthermore, a novel linear extended state observation filter is proposed to filter the groundspeed of the powered parafoil system calculated by the GPS information to provide a best estimation of the present wind during flight. Simulation experiments and real airdrop tests demonstrate the great ability of this method to in-flight identify the variable wind field, and it can benefit the powered parafoil system to fulfil accurate tracking control and a soft landing in the unknown wind field with high landing accuracy and strong wind-resistance ability.

Computational fluid dynamics based dynamic modeling of parafoil system

The calculation of aerodynamic coefficients has been one of the key issues when modeling parafoil systems, that directly affects model precision. This study relates to investigate limitations of traditional calculation methods. As a result, we achieve aerodynamic parameters of a parafoil using computational fluid dynamics simulations. Also we employ the least square method as a tool for the rapid identification of deflection factors of aerodynamic coefficients. The estimated aerodynamic coefficients of the system were incorporated into the dynamic equations of the parafoil to implement a six degree of freedom model of a parafoil system according to the Kirchhoff equations. Numerical results generated by simulation and airdrop testing demonstrate that the established model can accurately describe the flight characteristics of the parafoil system.