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Results for “REENTRY CONDITION”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

An approximate method for the calculation of nonequilibrium radiative heat transfer

A simplified method for the calculation of radiative heat transfer in hypersonic reentry flows where local thermal nonequilibrium (LTNE) conditions exist is presented. This method has been incorporated into the computer code RADMC (RADiation/Modified Corrections), which utilizes an approximate 'two-state' model of the electronic levels of atoms and molecules in the determination of the populations of the excited states for both LTNE and local thermal equilibrium (LTE) conditions for each of the relevant chemical species. The population data are used to calculate a correction factor to the radiative cross sections in an eight-step nongray radiative heat-transfer model. Results have been obtained for various points along the proposed trajectory of the Aeroassist Flight Experiment and the Fire II trajectory, and compared with results obtained for the same flowfields from the NEQAIR radiative heat-transfer code.

Greendyke, Robert B.↗
NASA NTRS1960

Some Landing Studies Pertinent to Glider-Reentry Vehicles

Results are presented of some landing studies that may serve as guidelines in the consideration of landing problems of glider-reentry configurations. The effect of the initial conditions of sinking velocity, angle of attack, and pitch rate on impact severity and the effect of locating the rear gear in various positions are discussed. Some information is included regarding the influence of landing-gear location on effective masses. Preliminary experimental results on the slideout phase of landing include sliding and rolling friction coefficients that have been determined from tests of various skids and all-metal wheels.

Houbolt, John C.↗
NASA NTRS2015

Wetlab-2 - Quantitative PCR Tools for Spaceflight Studies of Gene Expression Aboard the International Space Station

Wetlab-2 is a research platform for conducting real-time quantitative gene expression analysis aboard the International Space Station. The system enables spaceflight genomic studies involving a wide variety of biospecimen types in the unique microgravity environment of space. Currently, gene expression analyses of space flown biospecimens must be conducted post flight after living cultures or frozen or chemically fixed samples are returned to Earth from the space station. Post-flight analysis is limited for several reasons. First, changes in gene expression can be transient, changing over a timescale of minutes. The delay between sampling on Earth can range from days to months, and RNA may degrade during this period of time, even in fixed or frozen samples. Second, living organisms that return to Earth may quickly re-adapt to terrestrial conditions. Third, forces exerted on samples during reentry and return to Earth may affect results. Lastly, follow up experiments designed in response to post-flight results must wait for a new flight opportunity to be tested.

ISS research platform↗
NASA NTRS2003

Evaluation of Ceramic Foams and Simulated Reentry Environments

NASA and Ames is conducting ongoing research in lower density reusable TPS material for future reentry vehicles. Ceramic foams from pre ceramic polymer routes have potential for use in both acreage TPS and as tile leading edges for reentry vehicles. One of the key factors to investigate, when developing new materials for reentry applications, is their oxidation behavior in the appropriate reentry environment whrch can be simulated using ground based arc jet (plasma jet) testing. Studies have shown that oxidation rates of materials will differ when exposed to either monatomatic or molecular oxygen and the amount of monoatomic oxygen depends on the conditions particular to a given test situation. Monoatomic oxygen is always present in reentry environment, therefore arc jet testing is required to provide the appropriate conditions (stagnation pressures, heat fluxes, enthalpies, heat loads and atmospheres) encountered during flight. This preliminary work looks at the response of ceramic foams (Si systems) exposed to simulated reentry environments and investigates the influence of microstructure and composition on the materials response.

Stackpoole, Mairead↗
NASA NTRS1996

DSMC simulations of OREX entry conditions

Results of direct simulation Monte Carlo (DSMC) solutions are presented for the Japanese Orbital Reentry Experiment (OREX) vehicle, a 50 deg half-angle spherically blunted cone with a nose radius of 1.35 m and a base diameter of 3.4 m. The flow conditions simulated are those for entry into the Earth's atmosphere at a nominal velocity of about 7.4 km/s and zero incidence. Calculations are made for the higher altitude portion of entry, encompassing the transitional flow regime (altitudes of 200 to 80 km). Comparisons with flight measured values are made for axial acceleration, surface pressure, and stagnation point heating.

Moss, James N.↗
NASA NTRS1986

Direct simulation of hypersonic flows over blunt slender bodies

Results of a numerical study of low-density hypersonic flow about cylindrically blunted wedges and spherically blunted cones with body half angles of 0, 5, and 10 deg are presented. Most of the transitional flow regime encountered during entry between the free molecule and continuum regimes is simulated for a reentry velocity of 7.5 km/s by including freestream conditions of 70 to 100 km. The bodies are at zero angle of incidence and have diffuse and finite catalytic surfaces. Translational, thermodynamic, and chemical nonequilibrium effects are considered in the numerical simulation by utilizing the direct simulation Monte Carlo (DSMC) method. The numerical simulations show that noncontinuum effects such as surface temperature jump, and velocity slip are evident for all cases considered. The onset of chemical dissociation occurs at a simulated altitude of 96 km for the two-dimensional configurations. Comparisons between the DSMC and continuum viscous shock-layer calculations highlight the significant difference in flowfield structure predicted by the two methods.

Moss, J. N.↗
NASA NTRS1992

Low-to-high altitude predictions of three-dimensional ablative reentry flowfields

A new coupled-chemistry PNS scheme has been developed to study 3D hypersonic reentry flows over sphere cones at small angles of attack. A new quasi-steady ablation model for Teflon was used to predict ablative reentry flow fields under laminar, transitional, and turbulent conditions. This solution scheme uses a new two-step solution scheme for solving the species conservation equations under low-altitude conditions. As an example, the scheme is used to study hypersonic flow over a 6-deg sphere-cone configuration at 50 and 125 kft conditions under zero and nonzero angle of attack conditions.

Bhutta, Bilal A.↗
NASA NTRS2005

Implementing Recommendations of the Columbia Accident Investigation Board: Development of On-Orbit IR Thermography

One of NASA's Space Shuttle Return-to-Flight (RTF) efforts has been to develop thermography for the on-orbit inspection of the Reinforced Carbon Carbon (RCC) portion of the Orbiter Wing Leading Edge (WLE). This paper addresses the capability of thermography to detect cracks in RCC by using in-plane thermal gradients that naturally occur on-orbit. Crack damage, which can result from launch debris impact, is a detection challenge for other on-orbit sensors under consideration for RTF, such as the Intensified Television Camera and Laser Dynamic Range Imager. We studied various cracks in RCC, both natural and simulated, along with material characteristics, such as emissivity uniformity, in steady-state thermography. Severity of crack, such as those likely and unlikely to cause burn through were tested, both in-air and in-vacuum, and the goal of this procedure was to assure crew and vehicle safety during reentry by identification and quantification of a damage condition while on-orbit. Expected thermal conditions are presented in typical shuttle orbits, and the expected damage signatures for each scenario are presented. Finally, through statistical signal detection, our results show that even at very low in-plane thermal gradients, we are able to detect damage at or below the threshold for fatality in the most critical sections of the WLE, with a confidence exceeding 1 in 10,000 probability of false negative.

Ottens, Brian P.↗
NASA NTRS2009

The Active Oxidation of Silicon Carbide

The high temperature oxidation of silicon carbide occurs in two very different modes. Passive oxidation forms a protective oxide film which limits further attack of the SiC: SiC(s) + 3/2 O2(g) = SiO2(s) + CO(g) Active oxidation forms a volatile oxide and may lead to extensive attack of the SiC: SiC(s) + O2(g) = SiO(g) + CO(g) Generally passive oxidation occurs at higher oxidant pressures and active oxidation occurs at lower oxidant pressures and elevated temperatures. Active oxidation is a concern for reentry, where the flight trajectory involves the latter conditions. Thus the transition points and rates of active oxidation are a major concern. Passive/active transitions have been studied by a number of investigators. An examination of the literature indicates many questions remain regarding the effect of impurity, the hysteresis of the transition (i.e. the difference between active-to-passive and passive-toactive), and the effect of total pressure. In this study we systematically investigate each of these effects. Experiments were done in both an alumina furnace tube and a quartz furnace tube. It is known that alumina tubes release impurities such as sodium and increase the kinetics in the passive region [1]. We have observed that the active-to-passive transition occurs at a lower oxygen pressure when the experiment is conducted in alumina tubes and the resultant passive silica scale contains sodium. Thus the tests in this study are conducted in quartz tubes. The hysteresis of the transition has been discussed in the detail in the original theoretical treatise of this problem for pure silicon by Wagner [2], yet there is little mention of it in subsequent literature. Essentially Wagner points out that the active-to-passive transition is governed by the criterion for a stable Si/SiO2 equilibria and the passive-to-active transition is governed by the decomposition of the SiO2 film. A series of experiments were conducted for active-to-passive and passive-to-active transitions by increasing and decreasing oxygen pressure, respectively. For pure silicon a dramatic difference was found; whereas for SiC the difference was not as great. This may be due to the oxidation of the carbon in SiC which may break down the scale [3]. The third area is the effect of total pressure. In the literature, low oxygen potentials are achieved via either low total pressure or low oxygen pressure in an O2/Ar mixture. Both types of experiments are done in this study and the differences are discussed with regard to the presence or absence of a boundary layer.

Jacobson, Nathan S.↗
NASA NTRSDate not supplied

Design and Technology Maturation of the Stratospheric Projectile Experiment of Entry Dynamics

The supersonic and transonic dynamic stability of blunt-body reentry vehicles currently poses large risks in all of NASA’s ongoing entry missions (MSR SRL, MSR EES, and Dragonfly). These projects have allocated millions of dollars to testing and modeling efforts to buy down risk by using the current state-of-the-art (SoA) facilities at NASA’s disposal. While these facilities have heritage in supplying dynamics data to reentry missions, their availability is severely limited – particularly with the high number of concur-rent projects requesting simultaneous testing– and are costly when considering the science density per dollar. None of the current SoA facility methodologies allow the test model to have the dynamics fully develop through a flight relevant free-stream profile and as such require extrapolations with resultant high uncertainties in order to relate the test dynamics to flight expectations. SPEED is a NASA Ames Center Innovation Fund (CIF) project that is developing a highly tailorable and cost-effective test methodology to better assess the dynamic stability of blunt-body reentry vehicles via a stratospheric balloon flight. This is accomplished by dropping a suite of instrumented capsules from a stratospheric balloon to gain a statistically relevant dataset of scaled reentry vehicles in mission relevant free-flight conditions. This presentation will walk through how the test methodology is being implemented specifically for the Mars Sample Return (MSR) Earth Entry System (EES) geometry in an awarded Flight Opportunities Program (FOP) test flight in early CY24. SPEED Application to MSR: SPEED consists of three main mechanical systems: the Drop Platform, the Projectile, and the test Capsule. SPEED is being developed as a set of guidelines and recommendations for how to test with the proposed Concept of Operations (Conops) since the specific design parameters will vary depending on the specific project’s reference trajectory and entry vehicle design. As such, this presentation will walk through the development time-line as shown in Fig. 2. This is meant to serve as a blueprint for further missions as desired. Mechanical and Avionics Design. The SPEED test platform designed for the MSR-EES capsule geometry with nominal entry parameters has the ability to carry 10 Capsules to altitude instrumented with: 1. 3-Axis Accelerometer 2. IMU 3. Gyroscope 4. Magnetometer 5. Pressure Transducer cruciform 6. Uplook and Horizon Cameras To package the avionics/instrumentation suite, the capsule is approximately 1’ in diameter with the Outer Mold Line (OML) centroid-scaled from the full EES design. The internal volume is gutted and custom-shaped to fit the desired instrumentation suite, as well as to allow for the positioning of ballast mass such that the Center of Gravity is analogous to the flight vehicle. All structural components in the Capsule and Projectile are 3D printed, which significantly reduces the cost of each flight unit to around $1500 including all instrumentation, avionics, and structural components. Flight Conops. The test Capsule is accelerated to the desired altitude and Mach number while stowed in the Projectile, a missile-like vehicle consisting of steel ballast in the nose, a low-drag OML, and an Ejection Mechanism to reliably release the Capsule into the free-flow supersonic conditions. For the MSR-EES design, the capsule employs ~3kg of ballast mass at the nose to accelerate the 1.25kg test Capsule to ~Mach 1.7 at 23km altitude. This requires an initial release altitude of 40km, the quoted limit of a 80kg payload by the FOP-contracted balloon provider. Once the Ejection Mechanism avionics detect the proper conditions, the spring-loaded Ejection Mechanism will release and – guided by the sabot – expose the test Capsule to the desired test conditions for ~5 seconds of free-flight in the supersonic/transonic regimes. Dynamics in the subsonic regime will also be captured with the instrumentation suite with post-flight recovery operations aimed at recovering the high-G-load capable SD cards after the planned hard impact landings. Testing and Development: In the few months the SPEED project has worked the development of MSR-EES flight test, the team has performed lab and drone based testing which this presentation will overview. After the first design phase, the team fabricated Engineering Demonstration Units (EDUs) of all subsystems to perform validation testing shown in Fig. 5. After validation was completed on the subsystem level, a drone-drop test was performed at the recreational flight ceiling of 400ft altitude to assess the SPEED systems in a flight environment. Parameters such as in-flight stability, hard impact landing performance, and avionics performance were quantified and qualified. The FY23 CIF will culminate in a helicopter drop test aboard an Air National Guard Blackhawk. This will prepare the team for the CY24 FOP stratospheric balloon flight that should provide the final verification to begin offering the test platform for mission support. Focus of Presentation: This presentation will outline the technology maturation path of the SPEED implementation to the MSR-EES capsule baseline as well as the details regarding the mechanical system, avionics and instrumentation, and flight operations. Note that a complementary presentation is being submitted for a methodology overview of the SPEED test platform, introducing the testing technique and benefits as well as the full application space of the technology.

pitch damping coefficient↗
NASA NTRS2006

Orion Aerodynamics for Hypersonic Free Molecular to Continuum Conditions

Numerical simulations are performed for the Orion Crew Module, previously known as the Crew Exploration Vehicle (CEV) Command Module, to characterize its aerodynamics during the high altitude portion of its reentry into the Earth's atmosphere, that is, from free molecular to continuum hypersonic conditions. The focus is on flow conditions similar to those that the Orion Crew Module would experience during a return from the International Space Station. The bulk of the calculations are performed with two direct simulation Monte Carlo (DSMC) codes, and these data are anchored with results from both free molecular and Navier-Stokes calculations. Results for aerodynamic forces and moments are presented that demonstrate their sensitivity to rarefaction, that is, for free molecular to continuum conditions (Knudsen numbers of 111 to 0.0003). Also included are aerodynamic data as a function of angle of attack for different levels of rarefaction and results that demonstrate the aerodynamic sensitivity of the Orion CM to a range of reentry velocities (7.6 to 15 km/s).

Moss, James N.↗
NASA NTRS1987

Direct simulation of stagnation streamline flow for hypersonic reentry

The direct simulation Monte Carlo (DSMC) method is applied to simulate one-dimensional flow along the stagnation streamline. The freestream conditions considered are those encountered by the nose region of the Space Shuttle Orbiter during the hypersonic reentry. The range of altitudes (75 to 92 km) considered in the present calculations covers continuum to the less rarefied portion of the transition flow regime. The calculations account for thermal as well as the chemical nonequilibrium effects. The attention is focused on the flow structure along the stagnation streamline for different specified shock locations at a given altitude. The effect of shock location on the stagnation-point gas composition and heat transfer is analyzed for specific altitude; consequently, these results are appropriate for hemispherical bodies with different nose radii. Finally, comparison is made between the present DSMC results and the viscous shock-layer calculations, which show good agreement at the lowest altitude.

Dogra, Virendra K.↗
NASA NTRS1978

Emittance of TD-NiCr after simulated reentry

The effects of simulated reentry heating on the emittance of TD-NiCr were investigated. Groups of specimens with three different preconditioning treatments were exposed to 6, 24, and 30 half-hour simulated reentry exposure cycles in a supersonic arc tunnel at each of three conditions intended to produce surface temperatures of 1255, 1365, and 1475 K. Emittance was determined at 1300 K on specimens which were preconditioned only and specimens after completion of reentry simulation exposure. Oxide morphology and chemistry were studied by scanning electron microscopy and X-ray diffraction analysis. A consistent relationship was established between oxide morphology and total normal emittance. Specimens with coarser textured oxides tended to have lower emittances than specimens with finer textured oxides.

Clark, R. K.↗
NASA NTRS2013

Flight Performance of the Inflatable Reentry Vehicle Experiment 3

The Inflatable Reentry Vehicle Experiment 3 (IRVE-3) launched July 23, 2012, from NASA Wallops Flight Facility (WFF) on a Black Brant XI suborbital sounding rocket and successfully performed its mission, demonstrating the survivability of a hypersonic inflatable aerodynamic decelerator (HIAD) in the reentry heating environment and also illustrating the effect of an offset center of gravity on the HIAD's lift-to-drag ratio. IRVE-3 was a follow-on to 2009's IRVE-II mission, which demonstrated exo-atmospheric inflation, reentry survivability - without significant heating - and the aerodynamic stability of a HIAD down to subsonic flight conditions. NASA Langley Research Center is leading the development of HIAD technology for use on future interplanetary and Earth reentry missions.

Dillman, Robert↗
NASA NTRS1972

Study of large flexible tunnel for shuttle/payload interface

A theoretical and preliminary design study of a large flexible tunnel for use at the shuttle/payload interface is discussed. The theoretical study consisted of evaluating various design concepts and determining their adaptability to the tunnel requirements. The theoretical study culminated in the selection of one concept. The selected concept was documented with preliminary drawings of a full-scale ground test model. Supporting preliminary structural, thermal, micrometeoroid, material, and weight analyses were conducted. The specified tunnel requirements could be broadly grouped into two categories; environmental and performance. The environmental requirements were those ambient conditions and loads associated with ground, launch, space and reentry of the shuttle vehicle. Materials are presently available which will meet all these environmental requirements and can be designed into the structure to withstand the specified loads.

Source record↗
NASA NTRS2007

Cardiac Repolarization Abnormalities and Potential Evidence for Loss of Cardiac Sodium Currents on ECGs of Patients with Chagas' Heart Disease

Some individuals with Chagas disease develop right precordial lead ST segment elevation in response to an ajmaline challenge test, and the prevalence of right bundle branch block (RBBB) is also high in Chagas disease. Because these same electrocardiographic abnormalities occur in the Brugada syndrome, which involves genetically defective cardiac sodium channels, acquired damage to cardiac sodium channels may also occur in Chagas disease. We studied several conventional and advanced resting 12-lead/derived Frank-lead ECG parameters in 34 patients with Chagas -related heart disease (mean age 39 14 years) and in 34 age-/gender-matched healthy controls. All ECG recordings were of 5-10 min duration, obtained in the supine position using high fidelity hardware/software (CardioSoft, Houston, TX). Even after excluding those Chagas patients who had resting BBBs, tachycardia and/or pathologic arrhythmia (n=8), significant differences remained in multiple conventional and advanced ECG parameters between the Chagas and control groups (n=26/group), especially in their respective QT interval variability indices, maximal spatial QRS-T angles and low frequency HRV powers (p=0.0006, p=0.0015 and p=0.0314 respectively). In relation to the issue of potential damage to cardiac sodium channels, the Chagas patients had: 1) greater than or equal to twice the incidence of resting ST segment elevation in leads V1-V3 (n=10/26 vs. n=5/26) and of both leftward (n=5/26 versus n=0/26) and rightward (n=7/26 versus n=3/26) QRS axis deviation than controls; 2) significantly increased filtered (40-250 Hz) QRS interval durations (92.1 8.5 versus 85.3 plus or minus 9.0 ms, p=0.022) versus controls; and 3) significantly decreased QT and especially JT interval durations versus controls (QT interval: 387.5 plus or minus 26.4 versus 408.9 plus or minus 34.6 ms, p=0.013; JT interval: 290.5 plus or minus 26.3 versus 314.8 plus or minus 31.3 ms; p=0.0029). Heart rates and Bazett-corrected QTc/JTc intervals were not significantly different between groups. Patients with Chagas heart disease have increased cardiac repolarization abnormalities, especially by advanced ECG. Moreover, as a group, they have decreased uncorrected JT and QT interval durations and increased filtered QRS interval durations (versus age/gender-matched controls), all suggesting a potential loss of cardiac sodium channel function that might be mediated, in part, by cardiac autonomic damage. Overall findings support Brugada et al's recent hypothesis that the pathway leading to sudden death may often be similar in Chagas' disease and Brugada syndrome i.e., damage to the sodium channel (infectious/immunologic/autonomic in Chagas' genetic in Brugada) with consequent loss of sodium currents may facilitate a phase II-reentry based arrhythmic substrate for ventricular fibrillation in both conditions. In general, JT interval-related results have been underreported in the Chagas literature.

Schlegel, T. T.↗
NASA NTRS2019

Microscale Analysis of Spacecraft Heat Shields

Imagine entering Earth’s atmosphere after returning from the outer solar system. A heat shield less than 2 inches thick protects you from temperatures up to 2,900° Celsius (5,252° Fahrenheit). Such conditions were experienced by NASA’s Stardust capsule during reentry in 2006. The only materials capable of providing the necessary protection are composites with complex microstructures. Evaluating these materials is difficult, requiring precise knowledge of their properties. To this end, NASA scientists are developing research codes to compute material properties and simulate ablation at the microscale using agency supercomputers. Utilizing these tools, along with experiments, researchers are working to push the limits of spaceflight, allowing for greater flexibility in future space missions.

Thornton, John M.↗