Entry Capsule Research Articles

Fusion of In-Flight Aerothermodynamic Heating Sensor Measurements Using Kalman Filtering

On February 18th, 2021, the Mars 2020 entry system successfully delivered the Perseverance rover to the surface of Mars at Jezero Crater. The entry capsule carried instrumentation installed on the heatshield and backshell, named “Mars Entry, Descent, and Landing Instrumentation 2.” The instruments were used to measure the aerodynamic and aerothermodynamic performance of the entry vehicle. Five sensors at two locations (three sensors at one location and two sensors at the second location), including a thermocouple plug, heat flux gauge, and a radiometer, were co-located on the backshell. The sensors were exposed to roughly the same aerodynamic heating but measured these environments in different ways, each with its own set of modeling and measurement error complications. This paper develops a method for blending each of these measurements together in a single algorithm to produce estimates of the aerothermodynamic environments at each backshell location. The approach makes use of the Kalman–Schmidt filter/smoother methodology, where systematic measurement error parameters are modeled as multiplicative states that are estimated by the filter along with the aerothermal states. The results of the sensor fusion approach are expected to be used to inform and improve aerothermal modeling for future Mars entry capsules.

Electronics Design and Testing of the KREPE Atmospheric Entry Capsule Avionics

Electronics Design and Testing of the KREPE Atmospheric Entry Capsule Avionics

Large-Eddy Simulation of the unsteady supersonic flow around a Mars entry capsule at different angles of attack

Time-evolving high-fidelity simulations of an entry capsule in a supersonic flight regime have been performed at different angles of attack (0∘,5∘,10∘ and 15∘) in Mars' atmosphere. The aim is to contribute to the understanding of the critical unsteady phenomena that arise during the descent phase, gaining insights on the optimal design choices to ensure a safe atmospheric entry and a successful landing procedure. Turbulent structures effectively solved via Implicit Large-Eddy Simulation technique allow us to evaluate the flow properties and the capsule's response both in space and time, placing special attention to the analysis of the turbulent motions responsible for the oscillatory and unsteady dynamics. Ultimately, Proper Orthogonal Decomposition is employed to provide a low-order model of the wake dynamics.

Aerodynamic Analysis of an Entry Capsule at Titan in Transition Regime

The interest of the scientific community in Titan, Saturn’s largest moon, is still strong. In fact, after the successful Cassini–Huygens mission, which landed the Huygens capsule on Titan, other missions are planned in the coming years. The aims of this work are to provide the extent of global aerodynamic force, to provide thermal and aerodynamic loads on a capsule entering Titan atmosphere, and to evaluate the effects of chemistry on 1) flowfield parameters, 2) surface catalyticity, 3) temperature and pressure distributions on a heat shield, and 4) global aerodynamic force. To develop this study, the authors used the Huygens capsule and related entry trajectory. The study was carried out in the altitude interval of 295–470 km by means of the direct simulation Monte Carlo codes: DS2V for the solution of two-dimensional/axisymmetric flowfields, and DS3V for the solution of three-dimensional flowfields. The Titan atmosphere is a mixture of nitrogen, methane, and argon. The chemical model is made of 221 reactions, making gas around the capsule a mixture of 18 species. Chemistry strongly influences local aerodynamic quantities, both in the flowfield and on the capsule surface; whereas the chemical effects on the global aerodynamic force are negligible. Our computations also verified the lack of ionization.

Mars Entry, Descent, and Landing Instrumentation 2 Trajectory, Aerodynamics, and Atmosphere Reconstruction

On February 18th, 2021, the Mars 2020 entry system successfully delivered the Perseverance rover to the surface of Mars at Jezero Crater. The entry capsule carried a set of instrumentation installed on the heat shield and backshell, named the “Mars Entry, Descent, and Landing Instrumentation 2.” The instruments include pressure transducers, thermocouples, heat flux gauges, and radiometers to measure the aerodynamic and aerothermodynamic performance of the entry vehicle. This paper describes the trajectory and atmosphere reconstruction results based on the pressure sensor measurements. The process uses a Kalman filter approach to estimate the freestream atmospheric properties from the pressure measurements combined with a model of the pressure distribution of the heatshield and other sensor inputs, including an inertial measurement unit and other on-board navigation sensors, and several external atmospheric observations. The results indicate that the upper altitude density was up to 150% higher than nominal, which is consistent with the observed early entry guidance start time. The density below 40 km was within 12% of the preflight predictions. The reconstructed axial force coefficient was approximately 2% lower than the preflight prediction across the flight range.

Simulations of Dusty Flows over Full-Scale Capsule During Martian Entry

Suspended dust particles can have adverse effects on heat shields during Mars atmospheric entry. For instance, they can increase both surface heating and surface recession. Current studies on this subject often make many simplifications, focus on a specific physical process, or include flow conditions different from those on Mars. To address this, we perform computational fluid dynamics simulations of hypersonic dusty flows over a full-scale entry capsule based on a realistic flight trajectory. The simulations are performed with an Euler–Lagrange methodology in which the carrier gas solution is obtained with a discontinuous Galerkin method. We employ a recently developed physics-based drag correlation that obtains better agreement with experimental data than popular existing correlations. To improve understanding of the relevant physical processes, which are still not very well understood, the effects of various factors, such as particle size distribution, angle of attack, and two-way coupling, on dust-induced heating augmentation and erosion are assessed.

Experimental study of dynamic stability for a entry capsule in supersonic flow

experimental study of dynamic stability for a entry capsule in supersonic flow

MC-New: A Program to Calculate Newtonian Aerodynamic Coefficients Based on Monte-Carlo Integration

A computer program, MC-New, to calculate Newtonian aerodynamics is presented. The aerodynamic coefficients of a geometry expressed by an analytic function are calculated in a Monte-Carlo integration manner, in which the local forces on the randomly chosen sample points are summed up. The verification study and the accuracy analysis show that the program can provide good approximations of exact solutions. The example results of the parametric study on the Apollo-like entry capsule geometry are presented, showing the potential capability of the MC-New program as an efficient open-source tool for designing hypersonic vehicles.

Influence of the gas model on the boundary layer characteristic parameters and transition prediction for the Mars entry capsule

<p indent="0mm">Turbulent transition is an important factor affecting the thermal environment of spacecraft. A boundary layer transition prediction method was developed for both smooth and rough thermal protection system surfaces of a large-scale entry capsule in the process of entering the Martian atmosphere. The effects of the gas model and wall temperature constraints on the boundary layer characteristic parameters and transition features were analyzed. The results indicate that the dissociation reaction of carbon dioxide and its thermodynamic non-equilibrium effect will lead to increases in the momentum thickness Reynolds number and the roughness-height-based Reynolds number of the boundary layer. The radiative-equilibrium wall temperature constraint also results in a higher momentum thickness Reynolds number and roughness-height-based Reynolds number compared to those of the cold wall conditions. Therefore, the thermochemical non-equilibrium and radiative-equilibrium wall temperature boundary condition should be included in the analysis model to obtain the actual transition features.

High-Order Spectral/-Based Solver for Compressible Navier–Stokes Equations

High-order spectral element methods are becoming more established for solving problems in computational fluid dynamics. In this paper, we introduce new stabilization parameters for the solution of compressible Navier–Stokes equations in conjunction with high-order spectral element methods. We previously defined a new set of stabilization parameters for Euler equations in a high-order spectral/ framework. In this paper, we examine the definition of these stabilization parameters in the context of solutions of full Navier–Stokes equations, and we report good agreement with previously published results in the literature. We establish spectral convergence of errors for Kovasznay flow. We then validate the definition of the stabilization parameter for Couette flow, flat plate, and compression corner problems. In a later example, we solve the flow past a cylinder and benchmark results with previously published results obtained with low-order methods and other approaches in compressible flow computations. We further solve hypersonic flow past a wedge and supersonic flow past a Flight Investigation of Re-Entry program (FIRE) entry capsule. We explore the definition of the shock-capturing parameter based on the parameter. The introduced definitions are found to provide excellent results for the full Navier–Stokes equations.

Corrigendum to “Thermal Environment and Aeroheating Mechanism of Protuberances on Mars Entry Capsule”

Corrigendum to “Thermal Environment and Aeroheating Mechanism of Protuberances on Mars Entry Capsule”

Ocean Recovery Design and Drift Analysis for Atmospheric Entry Capsule with Inflatable Deployable Aeroshell

Ocean Recovery Design and Drift Analysis for Atmospheric Entry Capsule with Inflatable Deployable Aeroshell

Attitude Control of a Low L/D Re-entry Module with Multiple Equilibrium Points

The paper describes the development of attitude control system of a low L/D atmospheric entry capsule with multiple equilibrium points. The critical phase of flight occurs during the atmospheric aborts where the capsule gets separated from the abort vehicle at an unfavorable angle of attack and traverses multiple equilibrium points to reach the desired trim angle of attack. The nonlinear nature of aerodynamics and control law makes the problem challenging. The objective of this paper is to describe the challenges encountered and solution proposed in the development of control law for the crew capsule during re-entry. Phase plane analysis is extensively used as a tool to develop the control strategy. Performance of the proposed RCS control law is established using 6- DoF simulations for different flight conditions.

Experimental study of dynamic stability for a entry capsule in supersonic flow

Due to the lack of existence of control surfaces in entry capsules, the subject of static and dynamic stability is always important. In this paper, these coefficients are investigated experimentally for the case of forced oscillation at supersonic flow. In this experimental study, the effects of freestream Mach number, mean attack angle and pitch frequency on dynamic stability coefficients were evaluated. According to the results, in Mach 1.8, the geometry starts to be dynamically unstable. One approach to overcome this problem is to change the average attack of angle of the model. This change in the mean attack of angle, similar to the results presented for the five-degree mean angle, will lead to dynamic stability.

Development of a particle collision algorithm for discontinuous Galerkin simulations of compressible multiphase flows

This paper discusses the development of algorithms for simulating compressible, four-way coupled, particle-laden flows with discontinuous Galerkin methods. Specifically, the algorithmic developments focus on the treatment of hard-sphere collisions. First, we aim to reduce the computational effort devoted to inspecting pairs of particles for collisions during the given time step. This is often one of the most expensive stages of four-way coupled particle-laden flow simulations. The proposed algorithm exploits information about relative particle positions provided by the geometric mapping of a physical element to a reference element commonly employed in discontinuous Galerkin and other finite-element-based solvers. Second, we develop an enhanced particle-wall collision methodology that better accounts for finite particle size than previously developed schemes. A particular feature of the particle-particle and particle-wall collision algorithms is compatibility with arbitrary, curved, unstructured elements. Finally, we apply the resulting framework to a number of test cases, including hypersonic dusty flow over an entry capsule and surface erosion by sandblasting.

Thermal Environment and Aeroheating Mechanism of Protuberances on Mars Entry Capsule

Mars has only thin atmosphere composed mainly of carbon dioxide that differs significantly from the atmosphere of Earth in terms of characteristics of reentry flows. To connect with the orbiter, the Mars entry capsule is provided with titanium pipes and other units installed on the heat-shield. These units will create significant local interaction flow on the surface of the capsule and cause additional heating on the surface of the shield during the entry of the capsule. With a view to interaction thermal environment issues for the surface of the shield, in this paper, the characteristics of protrusion interaction flow on different location of the shield were studied by means of numerical simulation. Heating mechanisms of protuberances on different location were derived by analyzing characteristic parameters such as local flow velocity, pressure, and Mach number. The results show that the interaction thermal environment of protuberances in the windward area is smaller than that of protuberances in the leeward area, mainly because subsonic flow dominates in the windward area, and the interaction is weak, while in the leeward area, the direction of flow intersects with protuberances to form a boundary layer shear flow, which results in a stronger interaction before the protuberances.

Ballistic Range Testing Data Analysis of Tianwen-1 Mars Entry Capsule

A typical blunt body such as Tianwen-1 Mars entry capsule suffers dynamic instability in supersonic regime. To investigate the unstable Mach range of flight and to confirm the design of aerodynamic shape and mass properties, a ballistic range test was carried out aiming at capturing supersonic dynamic characteristics of Tianwen-1. Aerodynamic coefficients of free-flight scaled models were derived by modified linear regression method based on position and attitude data, while the dynamic coefficients were established under the assumption of small angle linearization. The static moment coefficients and dynamic derivatives were identified thereafter. Results show that models in untrimmed configuration are dynamically unstable at certain Mach numbers, whereas models in trimmed configuration are dynamically stable at other Mach numbers tested. Both trimmed and untrimmed configurations are statically stable in all testing cases.

CFD design capabilities for next generation high-speed aircraft

Current design requirements are shaping advanced and efficient supersonic or hypersonic aircraft concepts, capable of flying between distant parts of the globe within hours, and making affordable and safe access-to-space transportation. To achieve this challenge, reliable design tools, like Computational Fluid Dynamics, are strongly integrated in multidisciplinary design procedures. In this framework, the present paper deals with the importance and capabilities of Computational Fluid Dynamics investigations, especially those involved in vehicle aerodynamic and aerothermodynamic appraisal, to support and feed the design of high-speed aircraft. At first the Computational Fluid Dynamics support in various phases of design is addressed. Furthermore, an overall vision on methodologies used in a high speed flow computation is also given, addressing advantages and drawbacks of classical methodologies versus modern hybrid RANS methods ones. Then, a brief overview on either numerical schemes and tools, routinely adopted in an hypersonic simulation, is presented with reference to the multi-scale accuracy required by high supersonic/hypersonic flow regime. Finally, to provide a complete template for future numerical experiments, several Computational Fluid Dynamics activities, performed for a number of high-speed aircraft in different flow regimes, ranging from subsonic up to hypersonic speed, are reported and discussed. Computational methodology, domain discretization, and the support to design activity are provided for the CIRA USV1 and USV3, ESA-IXV, HEXAFLY-INT, a space launcher, and a Mars entry capsule. These examples show that Computational Fluid Dynamics can no longer be considered only an analysis tool, but it allows great advantages in all design stages, from conceptual up to detailed design level.

Modeling Heat-Shield Erosion due to Dust Particle Impacts for Martian Entries

Heat-shield design for spacecraft entering the atmosphere of Mars may be affected by the presence of atmospheric dust. Particle impacts with sufficient kinetic energy can cause spallation damage to the heat shield that must be estimated. The dust environment in terms of particle size distribution and number density can be inferred from ground-based or atmospheric observations at Mars. Using a Lagrangian approach, the particle trajectories through the shock layer can be computed using a set of coupled ordinary differential equations. The dust particles are small enough that noncontinuum effects must be accounted for when computing the drag coefficient and heat transfer to the particle surface. Surface damage correlations for impact crater diameter and penetration depth are presented for fused silica, AVCOAT, shuttle tiles, cork, and Norcoat® Liège. The cork and Norcoat Liège correlations are new and were developed in this study. The modeling equations presented in this paper are applied to compute the heat-shield erosion due to dust particle impacts on the ExoMars Schiaparelli entry capsule during dust storm conditions.

VSL Analysis of Atmospheric Entry Capsule with Electrodynamic Heat Shield

VSL Analysis of Atmospheric Entry Capsule with Electrodynamic Heat Shield