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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

A Cellular Backshell Concept for a Planetary Entry Vehicle

The development of an alternative, novel backshell concept to replace the traditional approach for the backshell of a planetary entry vehicle, was initiated in this study. The motivation was to determine if the novel concept, with the potential to provide significant improvements compared to the traditional approach, would be feasible. In initiating this effort, two cellular-type structures were chosen for evaluation. Preliminary structural finite element analysis models of just a single backshell panel were created for both a traditional design and the cellular concepts. Structural results revealed similar behavior for all the models. Although these initial results predicted higher mass values for the cellular structures, eventually adding more variables to the cell structure to further tailor the cellular concept, may significantly lower the mass predicted, and is justification for further study. Additionally, a novel approach to the thermal protection system of the cellular structures was proposed that included the use of advanced thermal blanket insulation. Thermal sizing analysis was performed for a simplified planetary entry heating condition producing a preliminary thermal design. However, further development and testing will be needed to determine if the proposed novel thermal protection approach, in conjunction with the cellular structure, would be an attractive alternative candidate backshell concept for future planetary entry vehicles.

Krings, Ethan↗
NASA NTRS2021

VAPRE: A tool to support the design optimization of planetary entry probe missions

The importance of the atmospheric data collected by planetary entry probes has been emphasized since the results of Galileo in 1995 and are reflected in the interest . The results add to our fundamental understanding about the formation and the evolution of our solar system. Of special interest are the Outer Planets Saturn, Uranus and Neptune, serving as missing puzzle pieces to the existing data sets. In order to maximize the data and science return from those missions, the tool VAPRE is developed to facilitate the design optimization of planetary entry probe missions by increasing the trade-space. Using a data set of interplanetary trajectories, it assesses the change in availability and accessibility of entry sites on the planets with respect to their latitudes depending on the hyperbolic arrival velocity. In this paper, we introduce the motivation behind the implementation of VAPRE, the science and engineering input gathered to bridge the knowledge between both fields, the design structure of the implementation as well as the significance and future development and potential of the tool VAPRE for future mission concept developments for planetary probe and lander missions.

Simon, Amy↗
NASA NTRS2010

Challenges to Computational Aerothermodynamic Simulation and Validation for Planetary Entry Vehicle Analysis

Challenges to computational aerothermodynamic (CA) simulation and validation of hypersonic flow over planetary entry vehicles are discussed. Entry, descent, and landing (EDL) of high mass to Mars is a significant driver of new simulation requirements. These requirements include simulation of large deployable, flexible structures and interactions with reaction control system (RCS) and retro-thruster jets. Simulation of radiation and ablation coupled to the flow solver continues to be a high priority for planetary entry analyses, especially for return to Earth and outer planet missions. Three research areas addressing these challenges are emphasized. The first addresses the need to obtain accurate heating on unstructured tetrahedral grid systems to take advantage of flexibility in grid generation and grid adaptation. A multi-dimensional inviscid flux reconstruction algorithm is defined that is oriented with local flow topology as opposed to grid. The second addresses coupling of radiation and ablation to the hypersonic flow solver - flight- and ground-based data are used to provide limited validation of these multi-physics simulations. The third addresses the challenges of retro-propulsion simulation and the criticality of grid adaptation in this application. The evolution of CA to become a tool for innovation of EDL systems requires a successful resolution of these challenges.

Gnoffo, Peter A.↗
NASA NTRS2010

Challenges to Computational Aerothermodynamic Simulation and Validation for Planetary Entry Vehicle Analysis

Challenges to computational aerothermodynamic (CA) simulation and validation of hypersonic flow over planetary entry vehicles are discussed. Entry, descent, and landing (EDL) of high mass to Mars is a significant driver of new simulation requirements. These requirements include simulation of large deployable, flexible structures and interactions with reaction control system (RCS) and retro-thruster jets. Simulation of radiation and ablation coupled to the flow solver continues to be a high priority for planetary entry analyses, especially for return to Earth and outer planet missions. Three research areas addressing these challenges are emphasized. The first addresses the need to obtain accurate heating on unstructured tetrahedral grid systems to take advantage of flexibility in grid generation and grid adaptation. A multi-dimensional inviscid flux reconstruction algorithm is defined that is oriented with local flow topology as opposed to grid. The second addresses coupling of radiation and ablation to the hypersonic flow solver--flight- and ground-based data are used to provide limited validation of these multi-physics simulations. The third addresses the challenges of retro-propulsion simulation and the criticality of grid adaptation in this application. The evolution of CA to become a tool for innovation of EDL systems requires a successful resolution of these challenges.

Gnoffo, Peter A.↗
NASA NTRS1982

A vectorized, finite-volume, adaptive grid algorithm applied to planetary entry problems

An adaptive grid, finite-volume method has been applied to problems in planetary entry for computing complete flowfields. The adaption algorithm is implicit in nature and is keyed to resolve user specified gradients. The finite-volume algorithm is explicit, utilizing a maximum time step advancement at each grid point to accelerate convergence to the steady state. The present version of the code is for the laminar flow of a perfect gas. The role of the adaption algorithm in resolving various features of blunt body/wake flow for planetary entry conditions is emphasized.

Gnoffo, P. A.↗
NASA NTRS2011

Multidisciplinary Tool for Systems Analysis of Planetary Entry, Descent, and Landing

Systems analysis of a planetary entry (SAPE), descent, and landing (EDL) is a multidisciplinary activity in nature. SAPE improves the performance of the systems analysis team by automating and streamlining the process, and this improvement can reduce the errors that stem from manual data transfer among discipline experts. SAPE is a multidisciplinary tool for systems analysis of planetary EDL for Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Titan. It performs EDL systems analysis for any planet, operates cross-platform (i.e., Windows, Mac, and Linux operating systems), uses existing software components and open-source software to avoid software licensing issues, performs low-fidelity systems analysis in one hour on a computer that is comparable to an average laptop, and keeps discipline experts in the analysis loop. SAPE uses Python, a platform-independent, open-source language, for integration and for the user interface. Development has relied heavily on the object-oriented programming capabilities that are available in Python. Modules are provided to interface with commercial and government off-the-shelf software components (e.g., thermal protection systems and finite-element analysis). SAPE currently includes the following analysis modules: geometry, trajectory, aerodynamics, aerothermal, thermal protection system, and interface for structural sizing.

Samareh, Jamshid A.↗
NASA NTRS2007

Aerocapture Inflatable Decelerator for Planetary Entry

Forward Attached Inflatable Decelerators, more commonly known as inflatable aeroshells, provide an effective, cost efficient means of decelerating spacecrafts by using atmospheric drag for aerocapture or planetary entry instead of conventional liquid propulsion deceleration systems. Entry into planetary atmospheres results in significant heating and aerodynamic pressures which stress aeroshell systems to their useful limits. Incorporation of lightweight inflatable decelerator surfaces with increased surface-area footprints provides the opportunity to reduce heat flux and induced temperatures, while increasing the payload mass fraction. Furthermore, inflatable aeroshell decelerators provide the needed deceleration at considerably higher altitudes and Mach numbers when compared with conventional rigid aeroshell entry systems. Inflatable aeroshells also provide for stowage in a compact space, with subsequent deployment of a large-area, lightweight heatshield to survive entry heating. Use of a deployable heatshield decelerator enables an increase in the spacecraft payload mass fraction and may eliminate the need for a spacecraft backshell.

Reza, Sajjad↗
NASA NTRS2011

Combined Structural and Trajectory Control of Variable-Geometry Planetary Entry Systems

Some of the key challenges of planetary entry are to dissipate the large kinetic energy of the entry vehicle and to land with precision. Past missions to Mars were based on unguided entry, where entry vehicles carried payloads of less than 0.6 T and landed within 100 km of the designated target. The Mars Science Laboratory (MSL) is expected to carry a mass of almost 1 T to within 20 km of the target site. Guided lifting entry is needed to meet these higher deceleration and targeting demands. If the aerodynamic characteristics of the decelerator are variable during flight, more trajectory options are possible, and can be tailored to specific mission requirements. In addition to the entry trajectory modulation, having variable aerodynamic properties will also favor maneuvering of the vehicle prior to descent. For proper supersonic parachute deployment, the vehicle needs to turn to a lower angle of attack. One approach to entry trajectory improvement and angle of attack control is to embed a variable geometry decelerator in the design of the vehicle. Variation in geometry enables the vehicle to adjust its aerodynamic performance continuously without additional fuel cost because only electric power is needed for actuating the mechanisms that control the shape change. Novel structural and control concepts have been developed that enable the decelerator to undergo variation in geometry. Changing the aerodynamic characteristics of a flight vehicle by active means can potentially provide a mechanically simple, affordable, and enabling solution for entry, descent, and landing across a wide range of mission types, sample capture and return, and reentry to Earth, Titan, Venus, or Mars. Unguided ballistic entry is not sufficient to meet this more stringent deceleration, heating, and targeting demands. Two structural concepts for implementing the cone angle variation, a segmented shell, and a corrugated shell, have been presented.

Quadrelli, Marco B.↗
NASA NTRS1973

Characteristics of Coupled Nongray Radiating Gas Flows with Ablation Product Effects About Blunt Bodies During Planetary Entries

A computational method was developed for the fully-coupled solution of nongray, radiating gas flows with ablation product effects about blunt bodies during planetary entries. The treatment of radiation accounts for molecular band, continuum, and atomic line transitions with a detailed frequency dependence of the absorption coefficient. The ablation of the entry body was solved as part of the solution for a steady-state ablation process. The method was applied by results at typical conditions during entry to Venus. The radiative heating rates along the downstream region of the body can exceed the stagnation point value. The radiative heating to the body is attenuated in the boundary layer at the downstream region of the body and at the stagnation point of the body. A study of the radiation, inviscid flow about spherically capped, conical bodies during planetary entries shows that the nondimensional, radiative heating distributions are nonsimilar with entry conditions. Caution should be exercised in attempting to extrapolate results from known distributions to other entry conditions for which solutions have not yet been obtained.

Sutton, K.↗
NASA NTRS1974

Performance of convolutional codes on fading channels typical of planetary entry missions

The performance of convolutional codes in fading channels typical of the planetary entry channel is examined in detail. The signal fading is due primarily to turbulent atmospheric scattering of the RF signal transmitted from an entry probe through a planetary atmosphere. Short constraint length convolutional codes are considered in conjunction with binary phase-shift keyed modulation and Viterbi maximum likelihood decoding, and for longer constraint length codes sequential decoding utilizing both the Fano and Zigangirov-Jelinek (ZJ) algorithms are considered. Careful consideration is given to the modeling of the channel in terms of a few meaningful parameters which can be correlated closely with theoretical propagation studies. For short constraint length codes the bit error probability performance was investigated as a function of E sub b/N sub o parameterized by the fading channel parameters. For longer constraint length codes the effect was examined of the fading channel parameters on the computational requirements of both the Fano and ZJ algorithms. The effects of simple block interleaving in combatting the memory of the channel is explored, using the analytic approach or digital computer simulation.

Modestino, J. W.↗
NASA NTRS1976

Planetary/DOD entry technology flight experiments. Volume 3: Planetary entry flight experiments handbook

The environments produced by entry into Jupiter and Saturn atmospheres are summarized. Worst case design environments are identified and the effect of entry angle, type of atmosphere and ballistic coefficient variations are presented. The range of environments experienced during earth entry is parametrically described as a function of initial entry conditions. The sensitivity of these environments to vehicle ballistic coefficient and nose radius is also shown. An elliptical deorbit maneuver strategy is defined in terms of the velocity increment required versus initial entry conditions and apoapsis altitude. Mission time, ground track, and out of plane velocity penalties are also presented. Performance capabilities of typical shuttle launched boosters are described including the initial entry conditions attainable as a function of paylaod mass and apoapsis altitude.

Christensen, H. E.↗
NASA NTRSDate not supplied

Radiative Heating Under Particulate-Laden Conditions During Hypersonic Planetary Entry

An important consideration while designing for hyper-sonic planetary entry is the interaction between the multitude of physical phenomena that manfist them-selves at these extreme conditions. This fact is also true for a Martian landing where in addition to thermo-chemical non-equilibriurm, vehicular predictions are impacted by radiative heating and potentially atmos-pheric dust. Previous studes have indicated that infra-red (IR) radiation emanating from CO2 and CO mole-cules constitute a significant fraction, especially in the backshell, of the total surface heat flux. In similar vein, dust particles, which can be present even under quiescent conditions, have been shown to increase the erosion rate of the heatshield. However, what remains relatively unquantified is the possible modification of the radiative environment due to the presence of dust. The present study is expected to provide the most de-tailed assessment to date of particles introducing changes to the radiative energy transfer both through the attenuation of existing shocked gas-induced radia-tion and additional emission.

Radiation↗
NASA NTRSDate not supplied

Evaluation of Magnet Configurations for Magnetohydrodynamic Trajectory Control during Planetary Entry

Magnetohydrodynamics is a phenomenon that can be harnessed during planetary entry to augment aerodynamic drag and may enable higher mass payloads to safely reach the surface. The magnetohydrodynamic force is quantified over a wide range of freestream conditions using computational fluid dynamics results from a previous study. The force is calculated for an array of small electromagnets, a large non-superconducting magnet, a large superconducting magnet, and a uniform field. The superconducting magnet produces a magnetohydrodynamic force within an order of magnitude of aerodynamic drag for velocities higher than 10 km/s, indicating that it may have a reasonable impact on the trajectory for some cases. The array of small magnets and non-superconducting magnet produced a magnetohydrodynamic force that is less than 1% of the aerodynamic drag, so their magnetic fields are not strong enough to affect an entry trajectory. Additionally, the magnet placement plays an important role in magnetohydrodynamic force magnitude, with a magnet located near the shoulder producing approximately eight times more force than a magnet placed on the axis of symmetry. A mass and power budget for each magnet configuration is given assuming current state-of-the-art magnet technology. This study also discusses implementation challenges for each type of magnet on a spacecraft.

Magnetohydrodynamics↗