Inflatable Aerodynamic Decelerator Research Articles

Inflatable aerodynamic decelerators for CubeSat reentry and recovery: Surface properties

In this investigation, Direct Simulation Monte Carlo Method is used to compute the surface properties of inflatable aerodynamic decelerators (IAD) applied for the reentry, recovery, and reuse of cubeSats. Surface properties calculation is of fundamental importance for flexible thermal protection system materials selection that withstand the harsh reentry environment. Furthermore, simulations are extremely important to detect possible hot spots at the IAD before design and flight. In this work, three IAD configurations are exposed to a rarefied hypersonic flow with freestream conditions that correspond to those found at reentry conditions at 105 km altitude. All geometries are assumed to be axisymmetric and have a maximum radius of 0.3 m from the center line to the shoulder edge. The main differences between the geometries are the angle between the IAD and cubeSat body and the IAD curvature for geometry 3. According to the results, all IAD geometries are effective in protecting the cubeSat during the reentry phase. It is shown that the IAD geometry has a significant influence on the heat transfer, pressure, and skin friction coefficient distribution over the flexible heat shield. The maximum heat transfer coefficient computed for geometry 1, 2, and 3 is 0.90, 0.97, and 0.84, respectively.

Analysis of Stem Assembly of Inflatable Aerodynamic Decelerator (IAD) that Failed During Spin Test

Analysis of Stem Assembly of Inflatable Aerodynamic Decelerator (IAD) that Failed During Spin Test

Inflatable aerodynamic decelerator for CubeSat reentry and recovery: IAD geometrical effects on the flowfield structure

In this investigation, Direct Simulation Monte Carlo computations were carried out to assess the influence of Inflatable Aerodynamic Decelerator (IAD) geometrical configurations on the flowfield during the atmospheric reentry. The non-reacting hypersonic rarefied flow over three IAD configurations coupled to a CubeSat was simulated considering a 0∘ angle of attack at an altitude of 105 km. According to the results, it was observed the formation of a strong and diffuse shock wave for all geometries considered in this investigation. However, a lower inflatable aeroshell angle is associated with a thinner shock wave and a maximum shock wave temperature closer to the shield's surface. These differences decrease in the flow expansion over the IAD shoulder. In the rear of the inflatable shields, a low-temperature and low-velocity region is observed, indicating that the IADs geometries successfully mitigate the harsh reentry conditions experienced by the payload. Finally, it was noticed that the wake region is larger for aerodynamic elongated shapes, in contrast to blunt geometries with the expense of slightly higher gas temperature closer to the front surface of the shield. No recirculation zone was observed in any of the simulated IAD configurations considered in this investigation.

Simulation and analysis of drag for inflatable aerodynamic decelerator

Inflatable aerodynamic decelerator, as a novel deceleration and recovery technology, has received attention due to its lightweight and freedom from the launch vehicle fairing size constraints for the space mission. Aimed at the aerodynamic characteristics of the inflatable aerodynamic decelerator, this work studied the effect of the cone angle on its drag and discussed the drag varied with the angle of attack under the different cone angles. The simulation showed that the drag was affected by the cone angle and increased locally with the angle of attack. Furthermore, the larger cone angle was beneficial to the stability of the flow field on its leeward in the case of a high Mach number. The math model of drag with the Mach number and the angle of attack was obtained by fitting the data, which provided favorable support for the prospective discussion of the flight dynamics characteristics.

Inflatable aerodynamic decelerator for CubeSat reentry and recovery: Altitude effects on the flowfield structure

In the present investigation, numerical simulations are conducted in order to characterize the flowfield structure of Inflatable Aerodynamic Decelerators (IAD) for CubeSat reentry and recovery. IAD may inflate to its full size before the reentry procedure, and it can be used to reduce the velocity and protect the CubeSat against the harsh reentry environment. In addition, by protecting the CubeSat during the reentry, it will be possible to recover and reuse part of it in several missions. In the present investigation, a CubeSat coupled with an IAD system is investigated for altitudes ranging from 115 to 95 km. Due to the considerable degree of rarefaction at these altitudes, the Direct Simulation Monte Carlo Method was employed to compute the macroscopic properties around the nanosatellite. According to the computational results, it was observed the formation of a highly diffuse shock wave upstream of the IAD at 115 km. As the CubeSat moves through an ever-thickening atmosphere, a significant increase in the shock wave temperature, pressure, and density measured along the stagnation streamline was noticed. As the flow expands over the IAD shoulder, the wake region is characterized by a significant decrease in the macroscopic properties, and no recirculation region was formed for the altitudes considered in the present investigation.

Effect of Shear Modulus on the Inflation Deformation of Parachutes Based on Fluid-Structure Interaction Simulation

Parachutes and other inflatable aerodynamic decelerators usually use flexible fabrics due to their lightweight and high load-carrying capacity. The behavior of fabrics during complex deformations is mainly influenced by their shear properties. The shear properties of fabric can be explained by the shear stiffness or shear modulus. The design optimization of these inflatable structures relies on a detailed knowledge of the mechanical properties of the fabric material. To investigate the effect of shear modulus on the inflatable shapes of parachute canopies, an arbitrary Lagrangian–Eulerian coupling method based on the incompressible computational fluid dynamics solver and structural solver LS-DYNA is proposed. Finite element methods are used to describe continuous materials such as fabrics and airflow fields. The effects of the shear modulus on the inflated parachute shapes are investigated from the macroscopic and microscopic scales. A comparison analysis reveals that different shear moduli have little effect on the overall shape and in-plane shear strain of the parachute, while they have significant effects on the in-plane stress distribution and wrinkles of the parachute. The methods and conclusions of this paper can provide some reference for the materials design of parachutes in preforming stage.

The Effect of Roll Rate on Simulated Entry Vehicle Ballistic Range Tests

Free-flight computational fluid/rigid-body dynamics simulations are now being explored as a way to augment physical experiments for characterizing the dynamic behavior of blunt-body atmospheric entry vehicles. Initializing these simulations with accurate initial conditions is critical to achieving validation against experimental results and characterizing vehicle behavior. This paper explores the impact of a nonnegligible initial roll rate on numerical free-flight simulations of ballistic range tests using the FUN3D Navier–Stokes flow solver and POST2 trajectory propagator. These ballistic range shots were performed on a model of the Supersonic Inflatable Aerodynamic Decelerator at the NASA Ames Hypervelocity Free-Flight Aerodynamics Facility. In the absence of measured roll data, a method for reconstructing the initial roll rate is developed assuming that a nonnegligible roll rate accounts for the exchange in amplitude between the experimental pitch and yaw data. Simulations of three shots spanning a range of initial roll rates are executed to evaluate the new method. Results are validated against the physical ballistic range tests. Simulations with the reconstructed roll rate are more accurate to the experimental data than those assuming a negligible initial roll rate. Direct calculation of the pitch damping coefficient also captures the effect of roll rate on pitching moment.

Application of improved k-ω-γ model to deformed hypersonic Inflatable Aerodynamic Decelerator aeroshell

The scalloping surface of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) promotes flow transition. Precise prediction of flow transition and surface aeroheating over the HIAD is imperative to the design of thermal protection system. In this paper, the improved k-ω-γ model considering the separation instability is first applied to the deformed HIAD aeroshell under various angles of attack to assess and verify its performance on such complex configuration, where multiple transition mechanisms coexist and interact. The results of the original k-ω-γ model are also provided for comparison and the prediction mechanisms of the improved model are further dissected. The results reveal that the flow separation and crossflow caused by the scalloping surface are highly sensitive to the angle of attack (α). With the α increasing, an opposite tendency between them can be found, that is, larger α causes stronger and earlier crossflow, but much later flow separation, which leads to the alternation of dominant instabilities for transition in turn. At the relatively high angle of attack, the crossflow becomes critical, at a small angle of attack, however, the separation instability is dominant. The first-mode disturbance can also accelerate the flow instability, while the influence of second-mode disturbance can be neglected due to relatively low post-shock Mach numbers. As a result, the original k-ω-γ model, not attempting to incorporate separated flow transition, predicts an opposite tendency to the experiments. While the transition onset, extent and shape simulated by the improved k-ω-γ model compare quite well with the experiments.

Assessment and improvement of k-ω-γ model for separation-induced transition prediction

The purpose of this work is to improve the k-ω-γ transition model for separation-induced transition prediction. The fundamental cause of the excessively small separation bubble predicted by k-ω-γ model is scrutinized from the perspective of model construction. On the basis, three rectifications are conducted to improve the k-ω-γ model for separation-induced transition. Firstly, a damping function is established via comparing the molecular diffusion timescale with the rapid pressure-strain timescale. The damping function is applied to prevent the effective length scale from incorrect distribution near the leading edge of the separation bubble. Secondly, the pressure gradient parameter λζ, is proposed as an indicator for local susceptibility to the separation instability. Additionally, λζ,-based separation intermittency γsep is constructed to accelerate the substantial growth of turbulent kinetic energy after flow separation. The improved model appropriate for both low- and high-speed flow has been calibrated against a variety of diverse and challenging experiments, including the subsonic T3L plate, Aerospatial A airfoil, transonic NLR-7301 airfoil and deformed hypersonic inflatable aerodynamic decelerator aeroshell. The improved model is strictly based on local variables and Galilean invariance. Besides, the proposed improvement for k-ω-γ model can be fairly convenient to incorporate into other existing intermittency-based transition models.

Investigation into The Influences of Turbulence Models on Heating Prediction of Hypersonic Inflatable Aerodynamic Decelerator

With the increasing demand for larger payloads for manned spaceflight and planetary exploration missions, hypersonic inflatable aerodynamic decelerator has gradually great application potentiality. The work presents the numerical simulations of hypersonic inflatable aerodynamic decelerator by the compressible Reynolds averaged Navier-Stokes equations with different turbulence models (such as SA, BSL, wilcox1988, SST). The pressure, eddy viscosity and heat flux under three Reynolds numbers (6.89E+6, 9.94E+6, 12.73E+6) are analyzed. The results demonstrate that the surface pressure distributions have slight difference, whereas the surface heating distributions appear remarkable diversity. In addition, compared with one equation turbulence model, two-equation turbulence models maybe more suitable for hypersonic heating predictions.

Design and Mathematical Modelling of Pressurisation System for Inflatable Aerodynamic Decelerator

The paper depicts design philosophy of a pneumatic pressurization system configured for Inflatable Aerodynamic Decelerator (IAD). The objective is to fine tune parameters in conjunction with mathematical model allowing a better understanding of process. System configuration has been discussed and mathematical model is formulated for estimating thermodynamic properties and mass flow of gas transferring from high pressure storage to IAD through orifice. Theoretical analysis and calculations were made and compared with the simulations carried out in LMS AMESim platform. Experiments were conducted in vacuum conditions to verify pressure change in high pressure storage and in IAD and this experimental data is used for validation of mathematical model.

Multifidelity Turbulent Heating Prediction of Hypersonic Inflatable Aerodynamic Decelerators with Surface Scalloping

The objective of this work was to investigate a multifidelity modeling approach to accurately and efficiently predict the turbulent convective heating on hypersonic inflatable aerodynamic decelerators with both smooth and scalloped walls. A previously developed co-kriging-based multifidelity modeling approach was used to model the turbulent and laminar convective heat fluxes on smooth wall vehicles. The smooth wall turbulent and laminar multifidelity heating models were then combined to create a multifidelity model of the augmented turbulent heat flux on scalloped vehicles. The smooth wall turbulent heat-flux multifidelity model was found to have a mean convective heat rate error of approximately 7% when compared to high-fidelity computational fluid dynamics (CFD) simulations. The scalloped augmented turbulent heat-flux multifidelity model was found to have a mean convective heat rate error of approximately 10% when compared to high-fidelity CFD simulations. Compared to a single-fidelity model, the multifidelity model required approximately one-quarter the number of high-fidelity model evaluations to obtain the same accuracy level. The computational cost of evaluating the multifidelity model was approximately five orders of magnitude less than one high-fidelity model simulation.

Temperature state of the housing and shell for an inflatable aerodynamic decelerator

Space debris is a growing concern that becomes more urgent with the increase in space exploration. This is the reason for equipping spacecraft with disposal systems. One of the methods for space debris removal is deorbiting a small spacecraft by using a decelerator. This paper presents issue analysis related to a selection of design and technology solutions and temperature analysis for inflatable aerodynamic decelerator of small spacecraft.

An improved local correlation-based intermittency transition model appropriate for high-speed flow heat transfer

An improved local correlation-based intermittency transition model is developed for high-speed flow heat transfer in this paper. Based on the intermittency transition model, two improvements have been proposed. One is introducing a new correlation of the momentum thickness Reynolds number for high-speed boundary layer into the transition onset function. In this new correlation, the free stream Mach number and the free stream Reynolds number are used to reflect the compressible effects. The other improvement is the modification of the intermittency factor transport equation to include physical information regarding the transition processes. Several test cases containing supersonic and hypersonic flat plates, a slender cone at different Reynolds numbers, the X-51A forebody, and the Hypersonic Inflatable Aerodynamic Decelerator are conducted to assess the applicability of the improved intermittency transition model. The numerical results show the ability of the improved model to describe the high-speed boundary layer transition processes. However, further research is needed to reproduce the overshoot phenomena and verify the capacity of the improved model on complex cases.

On the way to the optimal design of an inflatable aerodynamic decelerator of space debris removal system for CubeSat nanosatellites

In order to avoid pollution of the near-Earth space out-of-service small spacecrafts could be transferred to the disposal orbits in dense atmosphere with the help of inflatable decelerator. The issues of aerodynamics and heat transfer are of key importance for such systems design. The movement conditions in a low Earth orbit of a spherical inflatable aerodynamic decelerator designed for small spacecrafts removal are considered. The preliminary results of thermal analysis of the decelerator made of polymer film with the surface metallization are presented.

The heat transfer features of the thin-walled shell of an inflatable aerodynamic decelerator for CubeSat nanosatellites

Small spacecraft, first of all, nanosatellites of a CubeSat standard have a relatively small operational life. After their operational lives have expired, they turn into space debris. Disabled spacecraft can be transferred to the disposal orbit in the dense atmosphere using inflatable decelerators in order to avoid pollution of the near-Earth space. Decelerator’s temperature state is formed under the action of thermal radiation from the Sun and the Earth and kinetic heating caused by movement in a free-molecular medium. The specific features of heat transfer of inflatable decelerator’s thin-walled spherical shell are considered. The inflatable decelerator is designed for spacecraft removal during moving in the low-earth orbit.

Numerical study of the cone angle effects on transition and convection heat transfer for hypersonic inflatable aerodynamic decelerator aeroshell

The inevitable boundary-layer transition and severe heating argumentation of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) pose challenge for survivability of a Thermal Protection System (TPS). In the current study, the effects of sphere-cone angle on hypersonic heating and boundary-layer transition of stacked tori HIADs with 60°, 65° and 70° sphere-cone are demonstrated minutely by solving compressible Navier-Stokes equations with k-ω-γ transition model. Transition and heating augmentation triggered on the leeward where the shape deformation causes crossflows and local flow separations are sensitive to the cone angle. Smaller cone angle withstands severer heating flux. The study reveals that the first-mode disturbance and crossflow instability are dominators to the transition. Whereas the contribution of second-mode disturbance could be negligible. Larger cone angle postpones transition onsets as a result of weaker crossflow and more limited affected region of the first-mode disturbance. The 70° sphere-cone model, whose crossflow is lower than the critical value is only determined by the first mode, and thus has a quite smaller transition zone as compared to the other two models.

Anisotropic thermal conductivity under compression in two-dimensional woven ceramic fibers for flexible thermal protection systems

Flexible thermal protection materials made from two-dimensional woven ceramics fibers are of significant interest for hypersonic inflatable aerodynamic decelerators being developed by NASA for future missions on Mars and other planets. A key component of the thermal shield is a heat-resistant outer ceramic fabric that must withstand harsh aero-thermal atmospheric entry conditions. However, a predictive understanding of heat conduction processes in complex woven-fiber ceramic materials under deformation is currently lacking. This article presents a combined experimental and computational study of thermal conductivity in 5-harness-satin woven Nextel 440 fibers, using the hot-disk transient plane source method and computational thermo-mechanical modeling by finite-element analysis. The objective is to quantify and understand the effect of compressive strain on anisotropic heat conduction in flexible two-dimensional ceramic materials. We find, both experimentally and theoretically, that thermal conductivity of woven fabrics rises in both in-plane and out-of-plane directions, as the transverse load increases. Air gap conduction and fiber-to-fiber contacts are shown to play a major role in this behavior. Our finite-element simulations suggest that the thermal conductivity anisotropy is strong because heat transfer of air confined between fibers is reduced compared to that of free air. The proposed modeling methodology accurately captures the experimental heat conduction results and should be applicable to more complex loading conditions and different woven fabric materials, relevant to extreme high temperature environments.

New Method for Systems and Cost Analysis of Human Mars Entry Vehicles

Cost is one of the biggest obstacles to sending humans to Mars. However, spacecraft costs are typically not estimated until after the preliminary vehicle and mission concepts have been designed. By automating the cost estimation process, the effect of any change in vehicle or mission design on the mission cost can be determined more efficiently. This paper describes an extension to the systems analysis for planetary entry, descent, and landing tool. This extension integrates the cost modeling software SEER-H (which stands for system estimation and evaluation of resources hardware) with a number of systems analysis tools. This new method is used to analyze several tradespaces of a hypersonic inflatable aerodynamic decelerator entry vehicle for human Mars missions. Key findings include quantifying the impacts of the ballistic coefficient, the main engine specific impulse, and the thrust-to-weight ratio on the overall cost of the vehicle; as well as how the payload per lander and the number of landers affect the cost of a campaign to Mars.

Hypersonic aerodynamics of a deformed aeroshell in continuum and near-continuum regimes

The flexible inflatable aeroshell naturally deforms under aerodynamic loads during atmospheric entry. In this paper, we investigate the hypersonic aerodynamics of an inflatable aeroshell forebody with undulated surface deformation in the continuum and near-continuum flow regimes, where flow physics is complex involving rarefaction and thermochemical nonequilibrium effect. The aeroshell forebody shape is originated from a model of 8.3 m diameter stacked-tori hypersonic inflatable aerodynamic decelerator, and a series of surface deflections is generated by a parametric method based on the consistency of undulation with underlying structure. The trajectory points of 90, 80, and 68 km altitudes in a low Earth orbit reentry are considered. The thermochemical nonequilibrium Navier-Stokes equations with slip and no-slip boundary conditions are numerically solved to characterize flowfields and provide aerodynamic predictions. The results demonstrate that the undulated surface deflection induces local fluctuations of pressure and local Knudsen number, while the local variations of aerodynamic quantities create minor difference in total drag. The surface friction and drag are dependent on boundary conditions, i.e., either slip or no-slip model. The results also indicate that it is required to employ slip boundary conditions for the accurate prediction of friction and drag in the near continuum regime.