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Results for “Atmospheric Entry Vehicle”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Mars Exploration Rover Heatshield Observation Campaign

For the first time ever, engineers were able to observe a heatshield on the surface of another planet after a successful entry through the atmosphere. A three-week heatshield observation campaign was conducted in December 2004 after the Mars Exploration Rover Opportunity exited "Endurance Crater." By utilizing the rover's scientific instruments, data was collected to make a qualitative assessment of the performance of the heatshield. This data was gathered to gain a better understanding of how the heatshield performed during entry through the Martian atmosphere. In addition, this unprecedented look at the heatshield offered engineers the opportunity to assess if any unexpected anomalies occurred. Once a survey of the heatshield debris was completed, multiple targets of interest were chosen for the collection of imaging data. This data was then used to assess the char depth of the thermal protection material, which compared well with design and post-flight computational predictions. Extensive imaging data was collected and showed the main seal in pristine conditions, and no observable indications of structure overheating. Additionally, unexpected vehicle dynamics during the atmospheric entry were explained by the observation of thermal blanket remnants attached to the heatshield.

Mars Exploration Rovers↗
NASA NTRS1997

Transient Ablation of Teflon Hemispheres

For high-speed entry of space vehicles into atmospheric environments, ablation is a practical method for alleviating severe aerodynamic heating. Several studies have been undertaken on steady or quasi-steady ablation. However, ablation is a very complicated phenomenon in which a nonequilibrium chemical process is associated with an aerodynamic process that involves changes in body shape with time. Therefore, it seems realistic to consider that ablation is an unsteady phenomenon. In the design of an ablative heat-shield system, since the ultimate purpose of the heat shield is to keep the internal temperature of the space vehicle at a safe level during entry, the transient heat conduction characteristics of the ablator may be critical in the selection of the material and its thickness. This note presents an experimental study of transient ablation of Teflon, with particular emphasis on the change in body shape, the instantaneous internal temperature distribution, and the effect of thermal expansion on ablation rate.

Arai, Norio↗
NASA NTRSDate not supplied

Instrumentation for Measuring Entry Radiative Heating - Past, Present, and Future

Radiative heating can be a significant contributor to the total heat load during atmospheric entry, especially for large vehicles with high entry velocties. For example, the stagnation region heat load derived from thermocouples embedded in the thermal protection system (TPS)of the Mars Science Laboratory (MSL) heatshield did not match the unmargined pre-flight predictions. This was at least partially attributed to the fact that radiative heating was not accounted for in the unmargined pre-flight predictions [2].Since MSL, significant work has been done to update radiative heating models and test how the models perform compared to ground-based test facilities such as shock tubes. The models and ground-based tests have shown that radiative heating can be significant for entry into the atmospheres of Venus, Earth, Mars, and Titan, among other planetary bodies. However, there are still discrepancies between the models and the test data, which is where the desire for flight data comes in to play. Missions that have had or are currently planned to have instrumentation to measure radiative heating during atmospheric entry are listed in Table 1.

R A Miller↗
NASA NTRS1974

Planetary entry aerothermodynamics. I - Technology requirements and experimental facilities

Consideration has been given to the entry of vehicles into the atmospheres of all planets with the exception of Pluto and to missions for returning samples to Earth from all the planets (excepting Pluto), the satellites of Mars, Jupiter, and Saturn, the Moon, the asteroids, and certain comets. The efficient planning of the space missions including the appropriate design of the spacecraft requires that operational and environmental parameter values for the large range of mission options included be adequately known. The need to obtain the data required as a basis for the computational studies involved makes it necessary to conduct a comprehensive experimental research program. Details concerning the experimental facilities employed in this program are discussed, giving attention to shock tubes, the planetary-entry radiation facility, ballistic ranges, an expansion tube, a hypersonic tetrafluoromethane tunnel, and arcjet facilities.

Olstad, W. B.↗
NASA NTRS1968

Ablation sensor Patent

Ablation sensor for measuring surface ablation rate of material on vehicles entering earths atmosphere on entry into planetary atmospheres

Russell, J. M., III↗
NASA NTRS1983

Thermal response of advanced high temperature ceramic-composite insulation to a convectively heated environment

The Space Shuttle uses currently fibrous high temperature, reusable surface insulation (HRSI) as a Thermal Protection System (TPS) at 1260 C for normal-design mission operation. Higher density material of a similar type extended the maximum temperature to 1480 C. However, a surface temperature capability exceeding 1540 C is desired for future space vehicles, such as the Orbital Transfer Vehicle (OTV). A TPS providing such a capability would permit future entry vehicles to enter the atmosphere at a much higher velocity than the Space Shuttle. The present investigation is concerned with arc-jet test data obtained from a family of fibrous refractory-composite insulation (FRCI) materials developed to meet the future TPS requirements. FRCI materials containing between 20 and 80 percent aluminoborosilicate fibers with the balance composed of silica fibers were studied.

Stewart, D. A.↗
NASA NTRS2004

Fact Sheet: Range Complex

NASA Ames has a long tradition in leadership with the use of ballistic ranges and shock tubes for the purpose of studying the physics and phenomena associated with hypervelocity flight. Cutting-edge areas of research run the gamut from aerodynamics, to impact physics, to flow-field structure and chemistry. This legacy of testing began in the NACA era of the 1940's with the Supersonic Free Flight Tunnel, and evolved dramatically up through the late 1950s with the pioneering work in the Ames Hypersonic Ballistic Range. The tradition continued in the mid-60s with the commissioning of the three newest facilities: the Ames Vertical Gun Range (AVGR) in 1964, the Hypervelocity Free Flight Facility (HFFF) in 1965 and the Electric Arc Shock Tube (EAST) in 1966. Today the Range Complex continues to provide unique and critical testing in support of the Nation's programs for planetary geology and geophysics; exobiology; solar system origins; earth atmospheric entry, planetary entry, and aerobraking vehicles; and various configurations for supersonic and hypersonic aircraft.

Cornelson, C.↗
NASA NTRSDate not supplied

Discrete Rotational Energy for Polyatomic Molecules in Direct Simulation Monte Carlo

The environments experienced by vehicles upon entry into planetary atmospheres generally result in severe aerothermodynamic loading. These flows are characterized by the formation of strong shock waves, behind which high temperatures and non-equilibrium environments are generated, and the accurate prediction of internal energy relaxation and chemical kinetics becomes important. This manuscript focuses on the internal relaxation of the rotational energy of polyatomic molecules. Previous work has described the implementation of a discrete rotational energy model for diatomic molecules (linear rotators). Later, Gimelshein et. al extended this model to include polyatomic molecular internal energies. However, they did not include details on how to generate the particles at equilibrium conditions and centrifugal distortion was not included in their model. The purpose of the present study is to extend the afore-mentioned models to the treatment of discrete rotational energy in polyatomic molecules with the addition of centrifugal distortion. An overview of the background theory needed for the implementation of the model will be given followed by the model itself and verification of the model. For example, sampled versus Boltzmann distributions are compared in Figure 1 for CH3 (oblate rotator – two quantum numbers) and examples of thermal relaxation behavior for linear and non-linear rotators are presented in Figure 2. In addition, comparisons of thermophysical properties will be presented, as well as examples of adiabatic relaxation and application to hypersonic flow.

Rarefied Gas Dynamics↗
NASA NTRS1994

Grid resolution and solution convergence for Mars Pathfinder forebody

As part of the Discovery Program, NASA Plans to launch a series of probes to Mars. The Mars Pathfinder project is the first of this series with a scheduled Mars arrival in July 1997. The entry vehicle will perform a direct entry into the atmosphere and deliver a lander to the surface. Predicting the entry vehicle's flight performance and designing the forebody heatshield requires knowledge of the expected aerothermodynamic environment. Much of this knowledge can be obtained through computational fluid dynamic (CFD) analysis.

Nettelhorst, Heather L.↗
NASA NTRS1980

Generic aerocapture atmospheric entry study, volume 1

An atmospheric entry study to fine a generic aerocapture vehicle capable of missions to Mars, Saturn, and Uranus is reported. A single external geometry was developed through atmospheric entry simulations. Aerocapture is a system design concept which uses an aerodynamically controlled atmospheric entry to provide the necessary velocity depletion to capture payloads into planetary orbit. Design concepts are presented which provide the control accuracy required while giving thermal protection for the mission payload. The system design concepts consist of the following elements: (1) an extendable biconic aerodynamic configuration with lift to drag ratio between 1.0 and 2.0; (2) roll control system concepts to control aerodynamic lift and disturbance torques; (3) aeroshell design concepts capable of meeting dynamic pressure loads during aerocapture; and (4) entry thermal protection system design concepts to meet thermodynamic loads during aerocapture.

Source record↗
NASA NTRS1972

PAET entry heating and heat protection experiment.

A description is given of the thermal characterization of two low-density (270 and 450 kg/cu cm) elastomeric silicone ablators determined during the entry of the NASA Ames Planetary Atmosphere Experiments Test (PAET) vehicle into the earth's atmosphere. The spacecraft configuration, entry parameters, and associated trajectory variables are presented. Measurements of both the surface convective heat transfer rate and pressure on the beryllium nose cap are shown to be within 5% of theory. The predicted and measured internal temperatures are compared at various depths in the forebody and afterbody heat shields. Significant differences observed between experiment and theory for the afterbody thermal response are examined in relation to existing laboratory data.

Vojvodich, N. S.↗
NASA NTRS2012

Thermal Protection Materials: Development, Characterization and Evaluation

Thermal protection materials and systems (TPS) are used to protect space vehicles from the heat experienced during entry into an atmosphere. The application for these materials is very specialized as are the materials. They must have specific properties to withstand conditions during specific entries. There is no one-size-fits-all TPS as the conditions experienced by a material are very dependent upon the atmosphere, the entry speed, the size and shape of the vehicle, and the location on the vehicle. However, all TPS must be reliable and efficient to ensure mission safety, that is to protect the vehicle while ensuring that payload is maximized. Types of TPS will be reviewed in relation to types of missions and applications. Both reusable and ablative materials will be discussed. Approaches to characterizing and evaluating these materials will be presented. The role of heritage versus new materials will be described.

Johnson, Silvia M.↗
NASA NTRS1973

An analysis of atmospheric entry trajectories for manned and unmanned missions to the planet Venus

A unified atmospheric density model is presented for the planet Venus, and this model is compatible with Russian and American data obtained during the 1967 Venus launch opportunity. Trajectory characteristics involved in atmospheric entry are discussed with reference to roll-control modulation and entry corridor. Subsequent to a trajectory-oriented discussion of potential Venus mission characteristics, a parametric analysis of manned and unmanned vehicle entry trajectories into the Venusian atmosphere is presented. A sensitivity analysis with reference to atmospheric density deviations is included to show the dependence of corridor depth on the atmospheric density profile.

Craig, M. K.↗
NASA NTRSDate not supplied

Enabling Metric-Based Mesh Adaptation for Advanced Compressible Flow Simulations Using US3D

This work presents a metric-based mesh adaptation capability added to the flow solver US3D that is used to improve the accuracy of atmospheric entry simulations. Flow past an entry vehicle in free-flight is usually unsteady and characterized by anisotropic flow features like a strong bow shock and small-scale isotropic flow features like turbulent eddies in the wake. The results presented in this paper demonstrate that we are currently able to iteratively apply metric-based mesh adaptation to improve the solution accuracy by simultaneously targeting isotropic and anisotropic flow features. A simplified workflow of running CFD simulations for entry vehicles is presented where we start off with a coarse initial mesh to compute a first approximation of the flow. This coarse mesh is then iteratively refined using the newly developed metric to improve the resolution of the CFD computation. Furthermore, we demonstrate that we are able to adapt large mesh sizes in a timely fashion which allows us to start thinking about applying this adaptive framework to unsteady atmospheric entry CFD simulations.

Mesh adaptation↗