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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Constraints on Mars Aphelion Cloud Belt phase function and ice crystal geometries

This study constrains the lower bound of the scattering phase function of Martian water ice clouds (WICs) throughthe implementation of a new observation aboard the Mars Science Laboratory (MSL). The Phase Function SkySurvey (PFSS) was a multiple pointing all-sky observation taken with the navigation cameras (Navcam) aboardMSL. The PFSS was executed 35 times during the Aphelion Cloud Belt (ACB) season of Mars Year 34 over a solarlongitude range of Ls = 61:4 156:5. Twenty observations occurred in the morning hours between 06:00 and 09:30 LTST, and 15 runs occurred in the evening hours between 14:30 and 18:00 LTST, with an operationallyrequired 2.5 h gap on either side of local noon due the sun being located near zenith. The resultant WIC phasefunction was derived over an observed scattering angle range of 18.3-152.61, normalized, and compared with 9modeled phase functions: seven ice crystal habits and two Martian WIC phase functions currently being implementedin models. Through statistical chi-squared probability tests, the five most probable ice crystal geometriesobserved in the ACB WICs were aggregates, hexagonal solid columns, hollow columns, plates, and bullet rosetteswith p-values greater than or equal to 0.60, 0.57,0.56,0.56, and 0.55, respectively. Droxtals and spheres had pvaluesof 0.35, and 0.2, making them less probable components of Martian WICs, but still statistically possibleones. Having a better understanding of the ice crystal habit and phase function of Martian water ice cloudsdirectly benefits Martian climate models which currently assume spherical and cylindrical particles.

Cooper, Brittney↗
NASA NTRSDate not supplied

SpaceX Dragon Spacecraft Post Flight MMOD Inspection Campaign

The SpaceX Dragon spacecraft performed 20 resupply flights to the International Space Station (ISS) between 2012 and 2020. After each mission, a team led by the NASA Johnson Space Center Hypervelocity Impact Technology (HVIT) Group inspected each Dragon vehicle exterior for hypervelocity impact damage. A general description of the inspected vehicle areas is provided as well as mission details such as exposure duration and launch dates. This paper documents the general inspection procedure for collection of data and the post inspection data analysis process. It also provides details of the observation data collected in addition to the spectroscopic analysis results of intact samples collected to discern the source of the impacting particle. A comparison between observed impacts and the expected number of damage features calculated by Bumper 3 with the latest micrometeoroid and orbital debris (MMOD) environments are also presented. Statistics on the >300 impact features documented in the database will provide insight into the depth to diameter ratios and other relationships. The quality of the comparison between the observations and code predictions are dependent on several factors. The paper provides details of each of these variables.

orbital debris↗
NASA NTRS1988

High-energy particles very near the sun

NASA's long range plans include a Solar Probe (Star Probe) mission in which a spacecraft is placed in an eccentric orbit with perihelion at four solar radii. As part of the study effort for this mission, a Solar Probe Environment Workshop was sponsored by JPL. The report of this committee was issued in September 1978 as JPL Publication 78-64. A brief abstract of this document is given. There are considerable uncertainties in the models of solar energetic particle release and transport. The committee addressed this problem by using different modelling techniques when possible to provide a cross-check on the estimates. These models were used to extrapolate observation at 1 AU to the vicinity of the Sun. Additionally, the occurrence of a flare of a given magnitude must be estimated on a statistical basis. Therefore, it is possible to state a likelihood that the fluxes and fluences will be less than a certain magnitude, but in the event of an extremely large solar flare (occurrence of perhaps once a decade, e.g., August 4, 1972) it is likely that the hazard would be insurmountable. A brief first look indicates that the near-solar particle environment is not a worse hazard than Jupiter.

Goldstein, B. E.↗
NASA NTRS1988

X-ray and radio properties of solar (He-3) rich events

Radio and X-ray properties of solar flares associated with a new sample of individual (He-3) rich solar particle events are examined. Given the association between kilometric type III bursts and (He-3) rich events, the timing of the radio events is used to identify the related X-ray increases. The X-ray events exhibit a rich variety, from the standpoint of both intensity and complexity. Examination of the events shows statistically significant anticorrelations between the He-3/He-4 ratio and the intensity of the event as measured at kilometric wavelengths and in hard and soft X-rays; larger He-3/He-4 ratios occur in smaller flares. The result suggests that a coupling may exist between the preheating phase and the acceleration phase of these events or that mixing occurs between an enriched particle population accelerated within the compact flare and a normal population accelerated by a shock propagating away from an intense flare.

Reames, D. V.↗
NASA NTRS1994

Some properties of millimetric space debris

We describe radar observations at 8510 MHz of 39 small particles in Earth orbit. The altitudes vary between 510 and 1550 km, while the radial velocities lie between -310 and +520 m/s. Regarding all the observations as belonging to one statistical population, we calculate with the principle of least squares a best fitting semimajor axis and eccentricity. The simimajor axis is (7450+98/-92) km, while the eccentricity is (0.039+0.012/-0.016).

Goldstein, S. J., Jr.↗
NASA NTRS2011

Shuttle Hypervelocity Impact Database

With three missions outstanding, the Shuttle Hypervelocity Impact Database has nearly 3000 entries. The data is divided into tables for crew module windows, payload bay door radiators and thermal protection system regions, with window impacts compromising just over half the records. In general, the database provides dimensions of hypervelocity impact damage, a component level location (i.e., window number or radiator panel number) and the orbiter mission when the impact occurred. Additional detail on the type of particle that produced the damage site is provided when sampling data and definitive analysis results are available. Details and insights on the contents of the database including examples of descriptive statistics will be provided. Post flight impact damage inspection and sampling techniques that were employed during the different observation campaigns will also be discussed. Potential enhancements to the database structure and availability of the data for other researchers will be addressed in the Future Work section. A related database of returned surfaces from the International Space Station will also be introduced.

Hyde, James L.↗
NASA NTRS1974

Mariner 4 - A study of the cumulative flux of dust particles over a heliocentric range of 1-1.56 AU 1964-1967

Between December 1964 and December 1967, the Mariner 4 dust particle experiment obtained data concerning the distribution of minute zodiacal dust cloud particles over a heliocentric range of 1-1.56 AU. The first measurement was over the complete heliocentric range, while the two additional measurements were made between 1.1 and 1.25 AU in 1966, and between 1.2 and 1.5 AU in 1967. The initial results of these measurements presented the mean cumulative flux for the respective data periods. The results of a detailed study and comparison of the three measurements are presented, with particular emphasis on the variation of the flux as a function of heliocentric range. A small, but statistically significant, increase in the flux is observed between 1.15 and 1.4 AU. The initial reports showed a lower cumulative flux for the latter two measurements. However, a detailed analysis containing corrections for spacecraft attitude indicate that all three measurements yield similar results, and that the particles detected were in low inclination orbits.

Alexander, W. M.↗
NASA NTRS1977

The radial variation of corotating energetic particle streams in the inner and outer solar system

The radial gradient of long-lived, corotating energetic particle streams was measured using observations of .9-2.2 MeV protons from Helios 1 and 2, IMP 7, Pioneer 10 and Pioneer 11. A positive gradient of approximately 350% per AU is found between .3 AU and 1 AU. Between 1 AU and some 3-5 AU, the gradient is variable with an average value of 100% per AU which is consistent with earlier statistical results. A comparison between measurements at 9 AU and approximately 4 AU shows a negative gradient which is variable from -40 to -100% per AU. Possible solar latitudinal effects on these gradient studies are also discussed. Using solar wind and magnetic field data from Helios 1 between 1 AU and .3 AU, the relation between corotating energetic particle events in the inner solar system and the interplanetary medium is examined. It is found that the energetic particles are contained inside the high speed solar wind stream in a region adjacent to the interaction region between low speed and high speed streams.

Vanhollebeke, M. A. I.↗
NASA NTRS1994

Acceleration of interstellar pickup ions in the disturbed solar wind observed on Ulysses

Acceleration of interstellar pickup H(+) and He(+) as well as of solar wind protons and alpha particles has been observed on Ulysses during the passage of a corotating interaction region (CIR) at approximately 4.5 AU. Injection efficiencies for both the high thermal speed interstellar pickup ions (H(+) and He(+)) and the low thermal speed solar wind ions (H(+) and He(++) are derived using velocity distribution functions of protons, pickup He(+) and alpha particles from less than 1 to 60 keV/e and of ions (principally protons) above approximately 60 keV. The observed spatial variations of the few keV and the few hundred keV accelerated pickup protons across the forward shock of CIR indicate a two stage acceleration mechanism. Thermal ions are first accelerated to speeds of 3 to 4 times the solar wind speed inside the CIR, presumably by some statistical mechanism, before reaching higher energies by a shock acceleration process. Our results also indicate that (1) the injection efficiencies for pickup ions are almost 100 times higher than they are for solar wind ions, (2) pickup H(+) and He(+) are the two most abundant suprathermal ion species and they carry a large fraction of the particle thermal pressure, (3) the injection efficiency is highest for protons, lowest for He(+), and intermediate for alpha particles, (4) both H(+) and He(+) have identical spectral shapes above the cutoff speed for pickup ions, and (5) the solar wind frame velocity distribution function of protons has the form F(w) = F(sub o)w(sup -4) for 1 is less than w is less than approximately 5, where w is the ion speed divided by the solar wind speed. Above w approximately 5-10 the proton spectrum becomes steeper. These results have important implications concerning acceleration of ions by shocks and CIRs, acceleration of anomalous cosmic rays, and particle dynamics in the outer heliosphere.

Gloeckler, G.↗
NASA NTRS2013

The Importance of Earth as a Meteor Detector

In order to understand the complex meteoroid environment that threatens spacecraft in near Earth space, ground based observational techniques provide us with an effective option for evaluating the important parameters of flux, speed, mass, density and directionality. While no observational method (in ]situ or ground based detectors) provides bias free measurements of direct quantities, there are several benefits to using the Earth as a detector for calibrating meteoroid models that extend to the inner Solar System and beyond Earth fs orbit. The Earth constantly interacts with meteoritic particles from comets and asteroids as they evolve from their parent objects through dynamical processes. Modeling these dynamical processes with a physics ]based approach can help reveal the causes of observational features but developing those models involves constraining sequences of poorly defined parameters. These parameters must be tuned to a particular detector that offers direct or indirect measurements of mass, density, flux and speed - the quantities used in evaluating penetration risk. The following topics will be discussed: a) Consistency between ground based and in.situ measurements of flux in Earth orbit. b) Consistency between radar and electro.optical speed determinations and agreement of these with dynamical studies. c) The fact that there are six sporadic sources which cannot be determined by integrated line of sight emissivity: Observations using IRAS or COBE cannot give you all important directionality needed for risk evaluations. d) The large collecting area of the Earth s atmosphere compared to in.situ detectors gives better number statistics in the threat regime. The NASA Meteoroid Environment Office utilizes ground based radar and electro.optical measurements to calibrate the Meteoroid Engineering Model (MEM). As MEM is an engineering design model our main emphasis is on threat size particle, speed, flux and directionality. However, MEM has acknowledged limitations particularly with regard to source strength as a function of mass and work is proceeding with improved distributions that will rectify many of these shortcomings.

Koehler, Heather↗
NASA NTRS2012

Constraining the Statistics of Population III Binaries

We perform a cosmological simulation in order to model the growth and evolution of Population III (Pop III) stellar systems in a range of host minihalo environments. A Pop III multiple system forms in each of the ten minihaloes, and the overall mass function is top-heavy compared to the currently observed initial mass function in the Milky Way. Using a sink particle to represent each growing protostar, we examine the binary characteristics of the multiple systems, resolving orbits on scales as small as 20 AU. We find a binary fraction of approx. 36, with semi-major axes as large as 3000 AU. The distribution of orbital periods is slightly peaked at approx. < 900 yr, while the distribution of mass ratios is relatively flat. Of all sink particles formed within the ten minihaloes, approx. 50 are lost to mergers with larger sinks, and 50 of the remaining sinks are ejected from their star-forming disks. The large binary fraction may have important implications for Pop III evolution and nucleosynthesis, as well as the final fate of the first stars.

Statistics↗
NASA NTRS2017

Mind the Gap: Exploring the Underground of the NASA Space Cancer Risk Model

The REID quantifies the lifetime risk of death from radiation-induced cancer in an exposed astronaut. The NASA Space Cancer Risk (NSCR) 2012 mode incorporates elements from physics, biology, epidemiology, and statistics to generate the REID distribution. The current model quantifies the space radiation environment, radiation quality, and dose-rate effects to estimate a NASA-weighted dose. This weighted dose is mapped to the excess risk of radiation-induced cancer mortality from acute exposures to gamma rays and then transferred to an astronaut population. Finally, the REID is determined by integrating this risk over the individual's lifetime. The calculated upper 95% confidence limit of the REID is used to restrict an astronaut's permissible mission duration (PMD) for a proposed mission. As a statistical quantity characterized by broad, subjective uncertainties, REID estimates for space missions result in wide distributions. Currently, the upper 95% confidence level is over 350% larger than the mean REID value, which can severely limit an astronaut's PMD. The model incorporates inputs from multiple scientific disciplines in the risk estimation process. Physics and particle transport models calculate how radiation moves through space, penetrates spacecraft, and makes its way to the human beings onboard. Epidemiological studies of exposures from atomic bombings, medical treatments, and power plants are used to quantify health risks from acute and chronic low linear energy transfer (LET) ionizing radiation. Biological studies in cellular and animal models using radiation at various LETs and energies inform quality metrics for ions present in space radiation. Statistical methodologies unite these elements, controlling for mathematical and scientific uncertainty and variability. Despite current progress, these research platforms contain knowledge gaps contributing to the large uncertainties still present in the model. The NASA Space Radiation Program Element (SRPE) defines the knowledge gaps that impact our understanding of the cancer risks. These gaps are outlined in NASA's Human Research Roadmap [4], which identifies the research questions and actions recommended for reducing the uncertainty in the current NSCR model and for formulation of future models. The greatest contributors to uncertainty in the current model include radiation quality, dose rate effects, and the transfer of exposure-based risk from other populations to an astronaut population. Future formulations of the risk model may benefit from including other potential sources of uncertainty such as space dosimetry, errors in human epidemiology data, and the impact of microgravity and other spaceflight stressors. Here, we discuss the current capabilities of the NSCR-2012 model and several immediate research needs, highlighting areas expected to have an operational impact on the current model schema. The following subway-style route map outlines the NSCR-2012 model (Green Line), emphasizing the research gaps in the Human Research Roadmap for risk of radiation-induced carcinogenesis (Stops on Dashed Lines). The map diagrams how these research gaps feed specific portions of the model.

Chappell, L. J.↗
NASA NTRS1974

Strongly magnetized classical plasma models

Discrete particle processes in the presence of a strong external magnetic field were investigated. These processes include equations of state and other equilibrium thermodynamic relations, thermal relaxation phenomena, transport properties, and microscopic statistical fluctuations in such quantities as the electric field and the charge density. Results from the equilibrium statistical mechanics of two-dimensional plasmas are discussed, along with nonequilibrium statistical mechanics of the electrostatic guiding-center plasma (a two-dimensional plasma model).

Montgomery, D.↗
NASA NTRS1979

A computer program for thermal radiation from gaseous rocket exhuast plumes (GASRAD)

A computer code is presented for predicting incident thermal radiation from defined plume gas properties in either axisymmetric or cylindrical coordinate systems. The radiation model is a statistical band model for exponential line strength distribution with Lorentz/Doppler line shapes for 5 gaseous species (H2O, CO2, CO, HCl and HF) and an appoximate (non-scattering) treatment of carbon particles. The Curtis-Godson approximation is used for inhomogeneous gases, but a subroutine is available for using Young's intuitive derivative method for H2O with Lorentz line shape and exponentially-tailed-inverse line strength distribution. The geometry model provides integration over a hemisphere with up to 6 individually oriented identical axisymmetric plumes, a single 3-D plume, Shading surfaces may be used in any of 7 shapes, and a conical limit may be defined for the plume to set individual line-of-signt limits. Intermediate coordinate systems may specified to simplify input of plumes and shading surfaces.

Reardon, J. E.↗
NASA NTRS1982

Volcanoes and climate

The evidence that volcanic eruptions affect climate is reviewed. Single explosive volcanic eruptions cool the surface by about 0.3 C and warm the stratosphere by several degrees. Although these changes are of small magnitude, there have been several years in which these hemispheric average temperature changes were accompanied by severely abnormal weather. An example is 1816, the "year without summer" which followed the 1815 eruption of Tambora. In addition to statistical correlations between volcanoes and climate, a good theoretical understanding exists. The magnitude of the climatic changes anticipated following volcanic explosions agrees well with the observations. Volcanoes affect climate because volcanic particles in the atmosphere upset the balance between solar energy absorbed by the Earth and infrared energy emitted by the Earth. These interactions can be observed. The most important ejecta from volcanoes is not volcanic ash but sulfur dioxide which converts into sulfuric acid droplets in the stratosphere. For an eruption with its explosive magnitude, Mount St. Helens injected surprisingly little sulfur into the stratosphere. The amount of sulfuric acid formed is much smaller than that observed following significant eruptions and is too small to create major climatic shifts. However, the Mount St. Helens eruption has provided an opportunity to measure many properties of volcanic debris not previously measured and has therefore been of significant value in improving our knowledge of the relations between volcanic activity and climate.

Toon, O. B.↗
NASA NTRS1991

Dynamics Explorer guest investigator

A data base of satellite particle, electric field, image, and plasma data was used to determine correlations between the fields and the particle auroral boundaries. A data base of 8 days of excellent coverage from all instruments was completed. The geomagnetic conditions associated with each of the selected data periods, the number of UV image passes per study day that were obtained, and the total number of UV images for each day are given in tabular form. For each of the days listed in Table 1, both Vector Electric Field Instrument (VEFI) electric potential data and LAPI integrated particle energy fluxes were obtained. On the average, between 8 and 11 passes of useful data per day were obtained. These data are displayed in a format such that either the statistical electric field model potential or the statistical precipitation energy flux could be superimposed. The Heppner and Maynard (1987) and Hardy et al. (1987) models were used for the electric potential and precipitation, respectively. In addition, the auroral image intensity along the Dynamics Explorer-2 satellite pass could be computed and plotted along with the LAPI precipitation data and Hardy et al. (1987) values.

Sojka, Jan J.↗
NASA NTRS1999

Optical Flow-Field Techniques Used for Measurements in High-Speed Centrifugal Compressors

The overall performance of a centrifugal compressor depends on the performance of the impeller and diffuser as well as on the interactions occurring between these components. Accurate measurements of the flow fields in each component are needed to develop computational models that can be used in compressor design codes. These measurements must be made simultaneously over an area that covers both components so that researchers can understand the interactions occurring between the two components. Optical measurement techniques are being used at the NASA Lewis Research Center to measure the velocity fields present in both the impeller and diffuser of a 4:1 pressure ratio centrifugal compressor operating at several conditions ranging from design flow to surge. Laser Doppler Velocimetry (LDV) was used to measure the intrablade flows present in the impeller, and the results were compared with analyses obtained from two three-dimensional viscous codes. The development of a region of low throughflow velocity fluid within this high-speed impeller was examined and compared with a similar region first observed in a large low-speed centrifugal impeller at Lewis. Particle Image Velocimetry (PIV) is a relatively new technique that has been applied to measuring the diffuser flow fields. PIV can collect data rapidly in the diffuser while avoiding the light-reflection problems that are often encountered when LDV is used. The Particle Image Velocimeter employs a sheet of pulsed laser light that is introduced into the diffuser in a quasi-radial direction through an optical probe inserted near the diffuser discharge. The light sheet is positioned such that its centerline is parallel to the hub and shroud surfaces and such that it is parallel to the diffuser vane, thereby avoiding reflections from the solid surfaces. Seed particles small enough to follow the diffuser flow are introduced into the compressor at an upstream location. A high-speed charge-coupled discharge (CCD) camera is synchronized to the laser pulse rate; this allows it to capture images of seed particle position that are separated by a small increment in time. A crosscorrelation of a particle's position in two consecutive images provides an estimate of flow velocity and direction. Multiple image pairs obtained in rapid succession at a particular flow condition provide enough measurements for statistical significance. PIV provides simultaneous velocity measurements over the entire plane that is illuminated by the light sheet instead of at a single point, as is the case when LDV is used. PIV has a further advantage in that the laser light pulse can be triggered by an external source such as a high-response pressure transducer. This feature will allow PIV to synchronize flow imaging to physical phenomena such as rotating stall or stall precursor waves. We hope that this technique can be used to obtain images of the flow field during and just prior to stall.

Skoch, Gary J.↗
NASA NTRS2004

Software for Analyzing Sequences of Flow-Related Images

Spotlight is a computer program for analysis of sequences of images generated in combustion and fluid physics experiments. Spotlight can perform analysis of a single image in an interactive mode or a sequence of images in an automated fashion. The primary type of analysis is tracking of positions of objects over sequences of frames. Features and objects that are typically tracked include flame fronts, particles, droplets, and fluid interfaces. Spotlight automates the analysis of object parameters, such as centroid position, velocity, acceleration, size, shape, intensity, and color. Images can be processed to enhance them before statistical and measurement operations are performed. An unlimited number of objects can be analyzed simultaneously. Spotlight saves results of analyses in a text file that can be exported to other programs for graphing or further analysis. Spotlight is a graphical-user-interface-based program that at present can be executed on Microsoft Windows and Linux operating systems. A version that runs on Macintosh computers is being considered.

Klimek, Robert↗