Reentry Capsule Research Articles

Design and realization of configuration and layout for lunar-earth high-speed reentry capsule

Circumlunar return and reentry capsule is Chinas first high-speed semi-ballistic reentry leaping return spacecraft, with technical difficulties of space compact, space strong coupling, centroid location strict requiring, and precision high setting. This paper describes the configuration and layout design technique of circumlunar return and reentry capsule, including light and small enclosed cabin configuration and layout technology, engine layout technology, high-precision centroid trim design and implementation, pivotal product layout and precision maintenance technology, accurate precision measurement method and implementation, which is the basis for the system integration of reentry vehicle. The technology described in this paper, through ground and flight test validation, is a reference to the configuration and layout design of other light reentry vehicles.

Aerodynamic design and verification technology for the circumlunar free return and reentry flight vehicle

Compared to LEO reentry vehicles, the flow effect of the circumlunar free return and reentry flight vehicle is much more complex, and the aerodynamic data with high precision is required. The correctness and completeness of the aerodynamic design and verification is vital to the success of the lunar return mission. The aerodynamic characteristics of the mission is summarized, and the aerodynamic design method, calculations and experiments, data analysis method and its results for the reentry capsule, several specific aerodynamic problems and the research conclusious are also presented in this paper. The flight results show that the data achieved by areodynamic design and verification is well satisfied with the requirements of the mission.

Aerodynamic Design Optimization of a Kind of Reentry Capsule Based on CFD and Multi-objective Genetic Algorithm

This paper presents a new kind of aerodynamic shape for reentry capsule, called spherical cap cubic curve segment(SCCS) shape, which is modeled by replacing the reversing cone segment of the traditional spherical cap segment-reversing cone(SCSC) shape with a more various cubic curve segment, however the spherical cap section is retained. In the assumed allowable axial range of centroid under a designed Mach number, a multi-point/objective design optimization mathematical programming model was established against aerodynamic static longitudinal stability characteristics, hypersonic lift-to-drag ratio characteristics under trim angle of attack and off-set location placement of gravity center for the above reentry capsule. Then the aerodynamic design optimization problem of the proposed reentry capsule was investigated through multi-objective genetic algorithm(MOGA) combined numeric parallel field simulation methods, and finally the optimal Pareto front was given. Comparing with the results of the SCSC shape in the literature[1], it shows that the optimal Pareto front of the current cubic curve shape has a wider distribution range relative to the counterparts of the segment-reversing cone shape, however both are relatively close in the overlapping area.

Effect of Recession on the Re-entry Capsule Aerodynamic Characteristic

Numerical simulation and analysis of aerodynamic characteristics of Soyuz ablation shape is carried out in this paper for the adverse influence coming from recession. The result indicates that the shape change caused by the recession will increase absolute value of trim angle of attack and trim lift-drag ratio. The conclusion offers reference for the aerodynamic layout design and improve of the Soyuz re-entry capsule.

Aerodynamic and aerothermodynamic analysis of high-speed earth re-entry capsule

This paper deals with the computational fluid dynamics analysis of a capsule entering the earth atmosphere at the end of a sample return mission. Several numerical simulations have been carried out to assess the flowfield environment past a sphere-cone capsule, by using non-equilibrium reacting gas approximations. Heat shield ablation and effects of flow plasma radiation on capsule aeroheating are also accounted for in the flowfield analysis. The issue of aerodynamic and aerothermodynamic performance of the entry spacecraft in the framework of a super-orbital re-entry scenario is addressed.

127 不確定性を考慮したカプセルカバー分離挙動のCFD解析

127 不確定性を考慮したカプセルカバー分離挙動のCFD解析

Earth re-entry capsule CFD simulations taking into account surface roughness and mass injection at the wall

Future space exploration missions will likely use capsule type ballistic re-entry vehicles that will re-enter the earth atmosphere at very high speed (velocities in the order of 11.7 km/s or higher, this compared to 7.5 km/s for the US Space Shuttle). Passive concepts will be employed for the deceleration, and the thermal protection system (TPS) needs to be dimensioned to protect the vehicle and samples from the effects of the aerodynamic heating. The technology readiness level of these passive concepts is today still rather low, leading to large design margins. This paper is concerned with the design of a possible earth re-entry capsule, it discusses the re-entry trajectory and heat loads encountered during descent. Detailed CFD simulations were made for three selected points on the re-entry trajectory. The ablation of the TPS material was taken into account through a mass injection boundary condition. The turbulence models employed in the study were modified to account for surface roughness due to ablation. Calculated heat fluxes and shear stresses for a smooth wall are compared with results from empirical correlations and showed a fairly good agreement. For rough walls, the CFD results show a substantial increase in convective heat flux, while the injection of mass at the wall reduces the convective heat flux.

Aerodynamic design of a re-entry capsule for high-speed manned re-entry

Aerodynamic configuration of the capsule for manned re-entry at the second cosmic speed requires a relatively higher lift-to-drag ratio compared to the configuration for manned re-entry at the first cosmic speed. The present capsule configurations with high lift-to-drag ratio, for instance, the Apollo and the Orion, have secondary statically stable trim points, which is highly undesirable since it would cause disastrous result once the vehicle flies at the secondary trim point during re-entry. In the present study, effective design methodology for improving the monostability characteristics of re-entry capsules without compromising the lift-to-drag ratio is revealed based on flow field characteristics analysis. As a result, aerodynamic configuration design of a capsule with high lift-to-drag ratio and monostable characteristics is proposed. And the aerodynamic characteristics of the capsule ranging from subsonic to hypersonic speed are predicted by numerical simulations.

Effects of gradient density on thermal protection performance of AVCOAT composites under varied heat flux

Effective heat capacity is a key index to estimate the performance of the thermal protection system of reentry vehicles subjected to aerodynamic heating. To explore the effect of gradient density on the effective heat capacity in this paper, considering variable density we develop the one‐dimensional pyrolysis interface model with surface ablation, and design two kinds of the gradient density of AVCOAT composites. The computer codes are written to simulate the thermal behavior of a homogeneous AVCOAT composites and that of two types of gradient AVCOAT composites under aerodynamic heat flux during Apollo capsule reentry. Numerical results indicate that gradient density can improve the thermal protection performance of homogeneous AVCOAT composites, e.g. the piecewise linear and the parabola designs have larger effective heat capacity than homogeneous AVCOAT composites, which owe to exceptional thermal response of gradient density. This study will be helpful for the design of the thermal protection system in re‐entry vehicles. POLYM. COMPOS. 37:1034–1041, 2016. © 2014 Society of Plastics Engineers

Fluorescence Imaging of Reaction Control Jets and Backshell Aeroheating of Orion Capsule

Planar laser-induced fluorescence of nitric oxide was used to visualize the interaction of reaction control system jet flows on the afterbody of a hypersonic capsule reentry vehicle at the Calspan-University at Buffalo Research Center’s Large Energy National Shock Tunnel I reflected shock tunnel facility. The interaction of pitch and roll jets with the flowfield was investigated. Additionally, thin-film sensors were used to monitor heat transfer on the surface of the model to detect localized heating resulting from the firing of the reaction control system jets. Visualizations of the capsule shear layer using both planar laser-induced fluorescence and schlieren imaging compared favorably. The structure of the roll jet was found to be significantly altered due to interactions with the flowfield. Additionally, the presence of the roll jet appeared to change the nature of the shear layer from steady laminar to unsteady. The pitch jet structure was only disturbed in the far field. Comparison of the planar laser-induced fluorescence jet-fluid visualizations and the surface heat flux distributions indicate that the regions of enhanced aeroheating are not caused by the jet fluid itself impinging on the surface, but rather by the presence of jet-induced horseshoe vortices and shock wave/boundary-layer interactions.

Inverse analysis for transient thermal load identification and application to aerodynamic heating on atmospheric reentry capsule

A transient inverse heat conduction analysis enables the identification of the unknown boundary heat flux from finite number of temperature data obtained, e.g., in the high temperature structural tests or in the actual operation. Since the prediction of thermal load (heat flux) is difficult, the inverse analysis is expected to improve structural design of high temperature components. The present study develops a computational method of transient inverse heat conduction analysis. The developed code is applied to problems of a simple two-dimensional plate and of an atmospheric reentry capsule. Sequential Function Specification (SFS) method and Truncated Singular Value Decomposition (TSVD) are employed to improve the stability of the inverse analysis. Effects of these regularization methods are numerically discussed.

Ablative Heat Shield Design for Reentry Vehicle Using Numerical Analysis

At this paper, the thermal behavior of ablative materials as heat shields for reentry vehicles is investigated numerically. A one-dimensional finite difference solver is developed to simulate governing mass and energy equations. Four ablative materials; AVCO 5026-HCG, Carbon-Phenolic, Nylon-Phenolic, and Silica-Phenolic; are considered as a heat shield material for a reentry capsule with the diameter 2.8 meter. A heat flux profile from a simulated trajectory of a reentry capsule is used for investigation the performance and essential thickness of these four ablative materials. The only restriction for this simulation is the ultimate temperature of the backup structure which is beneath the ablative heat shield. At all simulations, the final thickness is defined by reaching the interface temperature, the temperature of the border between the ablative heat shield and solid shell, to 80±0.5 degrees Celsius. In addition, the sensitivity analysis is carried out to investigate the effect of properties variations on Carbon-Phenolic’s thickness for this specific heat flux profile.

Evolution of Plasma Species and Heat–Shield Temperatures from Hayabusa Reentry Observation

Emission signatures of the Hayabusa capsule reentry, acquired by the Australian Ultraviolet Spectrograph instrument on the NASA DC-8 mission over the South Australian Woomera landing site on 13 June 2010, are analyzed to identify thermal characteristics of the shock layer and the ablative heat-shield performance. The spectral range 330 to 470 nm of the Australian Ultraviolet Spectrograph instrument contains signatures of the air plasma species nitrogen and the ablation-related species cyanogen. The time-resolved evolution of averaged species number densities, vibrational and rotational plasma temperatures, and the heat-shield surface temperature are deduced through a multiparameter error-minimization analysis based on the European Space Agency plasma radiation database PARADE. The plasma temperatures indicate nonequilibrium conditions for cyanogen at altitudes above 70 km and equilibrium conditions after peak heating. Two separate thermal protection system activity periods are identified by the analysis. Early pyrolysis activity is indicated by a peak in cyanogen and nitrogen–hydrogen emissions at altitudes around 80 km. Broader peaks in the number of cyanogen molecules and reduced nitrogen–hydrogen emissions were identified around the time of peak heating at an altitude of about 57 km and elevated surface temperatures, above 3000 K.

English

This paper presents an implementation of the modified Newton method for the aerodynamic analysis of Planetary Reentry Capsules. A straightforward method is employed, such that a CATIA model and its hybrid surface mesh are used as input. Reference capsules are analyzed and results are compared to other similar codes. Future improvements of the code consider the Busemann correction of the wall pressure, heat flux evaluation and unsteadiness in order to enable the analysis of the hypersonic portion of trajectory and to assess the vehicle's stability.

Analytical solutions for Prandtl–Meyer wave–oblique shock overtaking interaction

The interaction between oblique shock and preceding expansion or compression Prandtl–Meyer wave of the same direction are studied theoretically. Two reliable analytical solutions for overtaking Prandtl–Meyer wave–oblique shock interaction were obtained. The criteria of reflected wave type change, shock inflection and degeneration, occurrence of subsonic flow pockets and influence of ratio of gas specific heats are established analytically.The results obtained can be used for the design of re-entry capsules, supersonic inlets, and supersonic nozzles, where wave interactions considered in the present paper take place.

Near-Infrared Spectroscopy of Hayabusa Sample Return Capsule Reentry

As part of the 2010 airborne observational campaign for the Hayabusa capsule reentry, a system of four colocated cameras was deployed to track and measure the spacecraft fragmentation and sample return capsule descents. These instruments included an intensified video camera for narrow-field tracking, an intensified video camera for visible and near-infrared spectral measurements from 400 to 900 nm, and a near-infrared spectrograph for high-resolution measurements from 980 to 1080 nm. The latter was configured to monitor the spectral evolution of capsule emissions during descent, seeking evidence of possible carbon signatures due to ablation of the heat shield. The data complement previous Stardust capsule observations in which distinct 1069 nm emission signatures were measured, likely associated with carbon ablation from the Phenolic Impregnated Carbon Ablator heat shield. The Hayabusa capsule spectra also exhibited 1069 nm line emissions, appearing intermittently at , persisting from approximately 13:52:10 to 13:52:20 as the capsule approached peak heating, and weakening to undetectable levels after . Continuum emission and nitrogen line emissions were detected simultaneously. The evolutions of these signatures over the course of reentry are investigated, in comparison with model predictions and complementary campaign data.

Trajectory Optimization of Reentry Capsule

Abstract Reentry vehicles are required to meet stringent boundary conditions and path constraints, while minimizing certain cost functional. Parameter optimal control is easier and faster to solve than indirect methods for complex problems, such as the problem of re-entry trajectory optimization subject to multiple path constraints. In this paper, a direct transcription method is applied for finding optimal trajectory of 2 problems. Firstly, Newtonian method is used for finding aerodynamic coefficients of blunt nose conical re-entry capsule in hypersonic regime. Using these coefficients, trajectory satisfying path constraints corresponding to heat influx, G-load and control angles is generated while minimizing the vehicle manoeuvres. In the second problem Apollo capsule's multiphase optimization problem is solved based on the aerodynamic coefficients obtained from wind tunnel test data.

821 重心オフセットを有するカプセルの低速風洞内動的試験

821 重心オフセットを有するカプセルの低速風洞内動的試験

Thermal analysis of charring materials based on pyrolysis interface model

Charring thermal protection systems have been used to protect hypersonic vehicles from high heat loads. The pyrolysis of charring materials is a complicated physical and chemical phenomenon. Based on the pyrolysis interface model, a simulating approach for charring ablation has been designed in order to obtain one dimensional transient thermal behavior of homogeneous charring materials in reentry capsules. As the numerical results indicate, the pyrolysis rate and the surface temperature under a given heat flux rise abruptly in the beginning, then reach a plateau, but the temperature at the bottom rises very slowly to prevent the structural materials from being heated seriously. Pyrolysis mechanism can play an important role in thermal protection systems subjected to serious aerodynamic heat.

S1910202 回収カプセル着水時の動的応答計測と簡易解析([S191-02]大気突入・減速技術(2),宇宙工学部門)

S1910202 回収カプセル着水時の動的応答計測と簡易解析([S191-02]大気突入・減速技術(2),宇宙工学部門)