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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Global transport of atmospheric smoke following a major nuclear exchange

A fully interactive zonally symmetric general circulation model is used to simulate the transport and evolution of a massive smoke cloud that is likely to form in the atmosphere following a major nuclear war. The presence of such a cloud significantly alters the simulated circulation and the subsequent transport of the smoke particles themselves. While the model indicates a tendency for interhemispheric exchange, the most immediate effect is that the radiatively active particles are carried into the stratosphere by the generation of strong vertical motions and intense convection regardless of their initial injection altitudes.

Haberle, R. M.↗
NASA NTRS2014

Investigation of HZETRN 2010 as a Tool for Single Event Effect Qualification of Avionics Systems

NASA's future missions are focused on long-duration deep space missions for human exploration which offers no options for a quick emergency return to Earth. The combination of long mission duration with no quick emergency return option leads to unprecedented spacecraft system safety and reliability requirements. It is important that spacecraft avionics systems for human deep space missions are not susceptible to Single Event Effect (SEE) failures caused by space radiation (primarily the continuous galactic cosmic ray background and the occasional solar particle event) interactions with electronic components and systems. SEE effects are typically managed during the design, development, and test (DD&T) phase of spacecraft development by using heritage hardware (if possible) and through extensive component level testing, followed by system level failure analysis tasks that are both time consuming and costly. The ultimate product of the SEE DD&T program is a prediction of spacecraft avionics reliability in the flight environment produced using various nuclear reaction and transport codes in combination with the component and subsystem level radiation test data. Previous work by Koontz, et al.1 utilized FLUKA, a Monte Carlo nuclear reaction and transport code, to calculate SEE and single event upset (SEU) rates. This code was then validated against in-flight data for a variety of spacecraft and space flight environments. However, FLUKA has a long run-time (on the order of days). CREME962, an easy to use deterministic code offering short run times, was also compared with FLUKA predictions and in-flight data. CREME96, though fast and easy to use, has not been updated in several years and underestimates secondary particle shower effects in spacecraft structural shielding mass. Thus, this paper will investigate the use of HZETRN 20103, a fast and easy to use deterministic transport code, similar to CREME96, that was developed at NASA Langley Research Center primarily for flight crew ionizing radiation dose assessments. HZETRN 2010 includes updates to address secondary particle shower effects more accurately, and might be used as another tool to verify spacecraft avionics system reliability in space flight SEE environments.

Rojdev, Kristina↗
NASA NTRS2005

Effects of Nuclear Interactions on Accuracy of Space Radiation Transport

Space radiation risk to astronauts and electronic equipments is one major obstacle in long term human space explorations. Space radiation transport codes have been developed to calculate radiation effects behind materials in human missions to the Moon, Mars or beyond. We study how nuclear fragmentation processes affect the accuracy of predictions from such radiation transport. In particular, we investigate the effects of fragmentation cross sections at different energies on fluxes, dose and dose-equivalent from galactic cosmic rays behind typical shielding materials. These results tell us at what energies nuclear cross sections are the most important for radiation risk evaluations, and how uncertainties in our knowledge about nuclear fragmentations relate to uncertainties in space transport predictions.

Lin, Zi-Wei↗
NASA NTRS1994

Nuclear electric propulsion: A better, safer, cheaper transportation system for human exploration of Mars

NASA has completed a preliminary mission and systems study of nuclear electric propulsion (NEP) systems for 'split-sprint' human exploration and related robotic cargo missions to Mars. This paper describes the study, the mission architecture selected, the NEP system and technology development needs, proposed development schedules, and estimated development costs. Since current administration policy makers have delayed funding for key technology development activities that could make Mars exploration missions a reality in the near future, NASA will have time to evaluate various alternate mission options, and it appears prudent to ensure that Mars mission plans focus on astronaut and mission safety, while reducing costs to acceptable levels. The split-sprint nuclear electric propulsion system offers trip times comparable to nuclear thermal propulsion (NTP) systems, while providing mission abort opportunities that are not possible with 'reference' mission architectures. Thus, NEP systems offer short transit times for the astronauts, reducing the exposure of the crew to intergalactic cosmic radiation. The high specific impulse of the NEP system, which leads to very low propellant requirements, results in significantly lower 'initial mass in low earth orbit' (IMLEO). Launch vehicle packaging studies show that the NEP system can be launched, assembled, and deployed, with about one less 240-metric-ton heavy lift launch vehicle (HLLV) per mission opportunity - a very Technology development cost of the nuclear reactor for an NEP system would be shared with the proposed nuclear surface power systems, since nuclear systems will be required to provide substantial electrical power on the surface of Mars. The NEP development project plan proposed includes evolutionary technology development for nuclear electric propulsion systems that expands upon SP-100 (Space Power - 100 kw(e)) technology that has been developed for lunar and Mars surface nuclear power, and small NEP systems for interplanetary probes. System upgrades are expected to evolve that will result in even shorter trip times, improved payload capabilities, and enhanced safety and reliability.

Clark, John S.↗
NASA NTRS1986

Nuclear winter - Three-dimensional simulations including interactive transport, scavenging, and solar heating of smoke

A reexamination is conducted of the 'nuclear winter' hypothesis with a three-dimensional global model modified to allow for localized injection of smoke, its transport by the simulated winds, its absorption of sunlight, and its removal by model-simulated precipitation. Smoke injected into the troposphere is driven upward by solar heating. The tropopause, initially above the smoke, reforms below the heat smoke layer and separates it from precipitation below. Although much smoke is scavenged while the thermal structure is being altered, the residence time of the remaining smoke is greatly increased. Particularly for July conditions, a longer-lasting 'nuclear winter' effect is observed than was found in earlier modeling studies in which normal tropospheric residence times were assumed. In January the smaller solar flux in the northern hemisphere allows faster removal of smoke than in July. Significant cooling of the northern hemisphere continents is predicted; its dependence on season and injected smoke mass is described.

Malone, R. C.↗
NASA NTRS2001

Recent measurements for hadrontherapy and space radiation: nuclear physics

The particles and energies commonly used for hadron therapy overlap the low end of the charge and energy range of greatest interest for space radiation applications, Z=1-26 and approximately 100-1000 MeV/nucleon. It has been known for some time that the nuclear interactions of the incident ions must be taken into account both in treatment planning and in understanding and addressing the effects of galactic cosmic ray ions on humans in space. Until relatively recently, most of the studies of nuclear fragmentation and transport in matter were driven by the interests of the nuclear physics and later, the hadron therapy communities. However, the experimental and theoretical methods and the accelerator facilities developed for use in heavy ion nuclear physics are directly applicable to radiotherapy and space radiation studies. I will briefly review relevant data taken recently at various accelerators, and discuss the implications of the measurements for radiotherapy, radiobiology and space radiation research.

NASA Discipline Radiation Health↗
NASA NTRS1994

Solar modulation and nuclear fragmentation effects in galactic cosmic ray transport through shielding

Crews of manned interplanetary missions may accumulate significant radiation exposures from the Galactic Cosmic Ray (GCR) environment in space. Estimates of how these dose levels are affected by the assumed temporal and spatial variations in the composition of the GCR environment, and by the effects of the spacecraft and body self-shielding on the transported fields are presented. In this work, the physical processes through which shielding alters the transported radiation fields are described. We then present estimates of the effects on model calculations of (1) nuclear fragmentation model uncertainties, (2) solar modulation, (3) variations between solar cycles, and (4) proposed changes to the quality factors which relate dose equivalent to absorbed dose.

Townsend, L. W.↗
NASA NTRSDate not supplied

Ideas For Infusing In-Space Servicing, Assembly and Manufacturing Concepts into Nuclear Electric Propulsion Architectures

NASA is currently investigating nuclear electric propulsion (NEP) for human Mars transport within the space nuclear propulsion portfolio. NEP spacecraft have the following characteristics, they: 1) include very large structures (~100-meter length); 2) are comprised of many components/modules; and 3) have very long lifetimes (e.g., 50 years for fuel rods). Thus, NEP spacecraft can be classified as a “persistent asset,” which is any zero-g or planetary surface system that benefits from in-space assembly (ISA) or multiple visits for servicing, repairs, and upgrades. NEP spacecraft will benefit from taking advantage of, and incorporating, In-space Servicing, Assembly, and Manufacturing (ISAM) capabilities in the spacecraft architecture from the onset, enabling system maintenance, repair, and evolution. ISA has a long history of being proposed for, and studied as, a means for achieving large systems in space. More recently, the benefits of ISA have been recognized by NASA, the Department of Defense (DOD), other government agencies, and commercial space companies, and thus, ISAM is being actively pursued at a national level. Past and current strategies for achieving large structures in space have relied largely on two strategies; the first is to launch monolithic structures (designed to meet launch vehicle requirements for payload size and mass) that are docked or berthed to other monolithic structures on-orbit to form a larger structure (e.g., the International Space Station [ISS]); the second is folding and packaging large structures to fit inside a payload fairing and deploying the full-sized structure (unaided) once on-orbit (e.g., the James Webb Space Telescope [JWST]). To date, conceptual architecture studies performed for NEP spacecraft capable of human-rated Mars transport have only included a combination of the two previously mentioned strategies. This paper will propose ideas for infusing ISAM strategies into NEP vehicle architectures that leverage existing and near future technologies and enable the resulting NEP systems to be realized in a more time- and cost-efficient manner.

in-space assembly↗
NASA NTRSDate not supplied

Ideas for Infusing In-Space Servicing, Assembly, and Manufacturing Concepts into Nuclear Electric Propulsion Architectures

NASA is currently investigating nuclear electric propulsion (NEP) for human Mars transport within the space nuclear propulsion portfolio. NEP spacecraft have the following characteristics, they: 1) include very large structures (~100-meter length); 2) are comprised of many components/modules; and 3) have very long lifetimes (e.g., 50 years for fuel rods). Thus, NEP spacecraft can be classified as a “persistent asset,” which is any zero-g or planetary surface system that benefits from in-space assembly (ISA) or multiple visits for servicing, repairs, and upgrades. NEP spacecraft will benefit from taking advantage of, and incorporating, In-space Servicing, Assembly, and Manufacturing (ISAM) capabilities in the spacecraft architecture from the onset, enabling system maintenance, repair, and evolution. ISA has a long history of being proposed for, and studied as, a means for achieving large systems in space. More recently, the benefits of ISA have been recognized by NASA, the Department of Defense (DOD), other government agencies, and commercial space companies, and thus, ISAM is being actively pursued at a national level. Past and current strategies for achieving large structures in space have relied largely on two strategies; the first is to launch monolithic structures (designed to meet launch vehicle requirements for payload size and mass) that are docked or berthed to other monolithic structures on-orbit to form a larger structure (e.g., the International Space Station [ISS]); the second is folding and packaging large structures to fit inside a payload fairing and deploying the full-sized structure (unaided) once on-orbit (e.g., the James Webb Space Telescope [JWST]). To date, conceptual architecture studies performed for NEP spacecraft capable of human-rated Mars transport have only included a combination of the two previously mentioned strategies. This paper will propose ideas for infusing ISAM strategies into NEP vehicle architectures that leverage existing and near future technologies and enable the resulting NEP systems to be realized in a more time- and cost-efficient manner.

in-space assembly↗
NASA NTRSDate not supplied

Space Exploration Applications for Development of High Capacity Cryocoolers

Long term storage of cryogens is necessary to enable NASAs long duration crewed missions to both the lunar and Martian surfaces. Such missions require in-space transport systems such as Nuclear Thermal Propulsion (NTP), and descent/ascent vehicles for transportation to and from the lunar and Martian surfaces. NTP systems and Lunar/Martian landers utilize cryogenic fluids to minimize architectural volume and mass. To further enhance the capability of these cryogenic systems, the Agency is putting emphasis on reusability, which requires the NTP and ascent/descent elements be replenished on-orbit via tankers or propellant depots, or on the lunar or Martian surface using liquefied in-situ produced propellants. NTP is one of the leading propulsion option for human Mars missions and requires liquid hydrogen to be stored on-orbit for over four years. For such a long duration mission, near “Zero Boil-Off” (ZBO) must be achieved which requires an optimized suite of passive Cryogenic Fluid Management technologies and active cooling (cryocoolers). Tens of Watts of 20K cooling is required to achieve ZBO conditions for NTP, however two-stage cooling using both 20K and 90K systems can lead to a significant reduction in both active cooling mass and power. The use of in-situ resources for lunar and Martian missions will require 150 Watts of 90K cooling for oxygen liquefaction and 300 Watts of 20K cooling for hydrogen liquefaction (lunar only). Descent/Ascent vehicles, propellant depots, and tankers will also require the use of cryocoolers to achieve ZBO conditions. To support these programs, NASA is developing high capacity 20K and 90K reverse turbo-Brayton cycle cryocoolers which offer a scalable, high efficiency, low vibration solution.

cryocooler↗
NASA NTRS1978

An improved thermionic power conversion system for space propulsion

A concept of an out-of-core thermionic nuclear electric power conversion system for 400 Kwe power level is being investigated for space propulsion applications. Two key features distinguish the power system design from previous thermionic power conversion concepts. First, the thermionic converters are located outside a nuclear reactor with a neutron shield inserted to reduce the radiation level on the thermionic converter matrix. Second, multiple liquid-metal heat pipes are used exclusively for both thermal power transport (from the nuclear reactor to the thermionic converters) and waste heat removal (from the thermionic converters to the space radiator); no mechanical or electromagnetic pumps are involved. The system characteristics are are compared to those of the in-core thermionic reactor system concept. In many aspects, the system characteristics, including specific weight, lifetime, dynamics control and safety features are found to be more desirable than those of the in-core system concept.

Hsieh, T. M.↗
NASA NTRS2019

Detection of Nonthermal Hard X-Ray Emission from the “Fermi Bubble” in an External Galaxy

We report new Chandra hard X-ray (>2 keV) and Jansky Very Large Array C-band observations of the nuclear super bubble of NGC 3079, an analog of the “Fermi bubble” in our Milky Way. We detect extended hard X-ray emission on the southwest (SW)side of the galactic nucleus with coherent multiwavelength features in radio, Hα, and soft X-ray. The hard X-ray feature has a cone shape with possibly a weak cap, forming a bubble-like structure with a diameter of∼1.1 kpc. A similar extended feature, however, is not detected on the northeast (NE)side, which is brighter in all other wavelengths such as radio, Hα, and soft X-ray. Scattered photons from the nuclear region or other nearby point-like X-ray bright sources, inverse Compton emission from cosmic-ray(CR)electrons via interaction with the cosmic microwave background, or any individually faint stellar X-ray source populations, cannot explain the extended hard X-ray emission on the SW side and the strongly NE/SW asymmetry. A synchrotron emission model, plus a thermal component accounting for the excess at∼1 keV, can well characterize the broadband radio/hard X-ray spectra. The broadband synchrotron spectra do not show any significant cutoff, and even possibly slightly flatten at higher energy. This rule out a loss-limited scenario in the acceleration of the CR electrons in or around this superbubble. As the first detection of kiloparsec-scale extended hard X-ray emission associated with a galactic nuclear superbubble, the spatial and spectral properties of the multiwavelength emissions indicate that the CR leptons responsible for the broadband synchrotron emission from the SW bubble must be accelerated in situ, instead of transported from the nuclear region of the galaxy.

Jiang-Tao Li↗
NASA NTRS1991

Report of the Nuclear Propulsion Mission Analysis, Figures of Merit Subpanel: Quantifiable figures of merit for nuclear thermal propulsion

The results of an inquiry by the Nuclear Propulsion Mission Analysis, Figures of Merit subpanel are given. The subpanel was tasked to consider the question of what are the appropriate and quantifiable parameters to be used in the definition of an overall figure of merit (FoM) for Mars transportation system (MTS) nuclear thermal rocket engines (NTR). Such a characterization is needed to resolve the NTR engine design trades by a logical and orderly means, and to provide a meaningful method for comparison of the various NTR engine concepts. The subpanel was specifically tasked to identify the quantifiable engine parameters which would be the most significant engine factors affecting an overall FoM for a MTS and was not tasked with determining 'acceptable' or 'recommended' values for the identified parameters. In addition, the subpanel was asked not to define an overall FoM for a MTS. Thus, the selection of a specific approach, applicable weighting factors, to any interrelationships, for establishing an overall numerical FoM were considered beyond the scope of the subpanel inquiry.

Haynes, Davy A.↗
NASA NTRSDate not supplied

DDFRG: Double Differential FRaGmentation Models for Proton and Light Ion Production in High Energy Nuclear Collisions: Closed Form, Analytic Formulas for Transport Codes and other Applications

New models for Double-Differential FRaGmentation (DDFRG) cross sections for proton and light ion production from high energy nucleus-nucleus collisions are developed. The proton model employs thermal production from the projectile, central fireball and target sources, and also quasi-elastic direct knockout production. Light ion production cross sections employ a hybrid coalescence model. The models are able to describe a wide range of experimental data with only a limited set of model parameters. Closed form analytic formulas for double-differential cross sections as well as single-differential energy cross sections are developed. The analytic formulas enable highly efficient computation for space radiation transport codes and other applications.

John W Norbury↗
NASA NTRS1987

High temperature transport properties of air

A general computer code was developed to allow calculation of atom-atom and ion-atom transport collision integrals from accurate potential energy curves described by a set of discrete data points for a broad range of scattering conditions. This code is based upon semiclassical approximations that properly account for quantum mechanical behavior such as tunneling effects near a barrier maximum, resonance charge exchange, and nuclear symmetry effects. Transport collision integrals were determined for N-N, O-O, N(+)-N, and O(+)-O interactions from complete sets of accurate potential functions derived from combined experimental and ab initio structure calculations. For the O-O case, this includes results for excited states. The calculated values of the N(+)-N and O(+)-O resonance charge exchange cross section Q(ex) agree well with measurements from beam experiment that are available at high energies where the diffusion cross section Q(d) satisfies Q(d) approximately equal to 2Q(ex).

Levin, E.↗
NASA NTRS1996

Dose equivalent near the bone-soft tissue interface from nuclear fragments produced by high-energy protons

During manned space missions, high-energy nucleons of cosmic and solar origin collide with atomic nuclei of the human body and produce a broad linear energy transfer spectrum of secondary particles, called target fragments. These nuclear fragments are often more biologically harmful than the direct ionization of the incident nucleon. That these secondary particles increase tissue absorbed dose in regions adjacent to the bone-soft tissue interface was demonstrated in a previous publication. To assess radiological risks to tissue near the bone-soft tissue interface, a computer transport model for nuclear fragments produced by high energy nucleons was used in this study to calculate integral linear energy transfer spectra and dose equivalents resulting from nuclear collisions of 1-GeV protons transversing bone and red bone marrow. In terms of dose equivalent averaged over trabecular bone marrow, target fragments emitted from interactions in both tissues are predicted to be at least as important as the direct ionization of the primary protons-twice as important, if recently recommended radiation weighting factors and "worst-case" geometry are used. The use of conventional dosimetry (absorbed dose weighted by aa linear energy transfer-dependent quality factor) as an appropriate framework for predicting risk from low fluences of high-linear energy transfer target fragments is discussed.

NASA Discipline Number 45-10↗