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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Design of a dynamic test platform for autonomous robot vision systems

The concept and design of a dynamic test platform for development and evluation of a robot vision system is discussed. The platform is to serve as a diagnostic and developmental tool for future work with the RPI Mars Rover's multi laser/multi detector vision system. The platform allows testing of the vision system while its attitude is varied, statically or periodically. The vision system is mounted on the test platform. It can then be subjected to a wide variety of simulated can thus be examined in a controlled, quantitative fashion. Defining and modeling Rover motions and designing the platform to emulate these motions are also discussed. Individual aspects of the design process are treated separately, as structural, driving linkages, and motors and transmissions.

Rich, G. C.↗
NASA NTRS2002

A critical period for functional vestibular development in zebrafish

We have determined a critical period for vestibular development in zebrafish by using a bioreactor designed by NASA to simulate microgravity for cells in culture. A critical period is defined as the briefest period of time during development when stimulus deprivation results in long lasting or permanent sensory deficits. Zebrafish eggs were collected within 3 hours of being laid and fertilized. In experiment 1, eggs were placed in the bioreactor at 3, 24, 30, 36, 48, or 72 hours postfertilization (hPF) and maintained in the bioreactor until 96 hPF. In experiment 2, eggs were placed in the bioreactor immediately after they were collected and maintained in the bioreactor until 24, 36, 48, 60, 66, 72, or 96 hPF. Beginning at 96 hPF, all larvae had their vestibulo-ocular reflexes (VOR) evaluated once each day for 5 days. Only larvae that hatched from eggs that were placed in the bioreactor before 30 hPF in experiment 1 or removed from the bioreactor later than 66 hPF in experiment 2 had VOR deficits that persisted for at least 5 days. These data suggest a critical period for vestibular development in the zebrafish that begins before 30 hPF and ends after 66 hPF. To confirm this, zebrafish eggs were placed in the bioreactor at 24 hPF and removed at 72 hPF. VORs were evaluated in these larvae once each day for 5 days beginning at 96 hPF. These larvae had VOR deficits that persisted for at least 5 days. In addition, larvae that had been maintained in the bioreactor from 24 to 66 hPF or from 30 to 72 hPF, had only temporary VOR deficits. In a final experiment, zebrafish eggs were placed in the bioreactor at 3 hPF and removed at 96 hPF but the bioreactor was turned off from 24 hPF to 72 hPF. These larvae had normal VORs when they were removed from the bioreactor at 96 hPF. Taken as a whole, these data support the idea that there is a critical period for functional maturation of the zebrafish vestibular system. The developmental period identified includes the timeframe during which the vestibular primary afferent neurons are born, innervate their central and peripheral targets, and remodel their central projections. Copyright 2002 Wiley-Liss, Inc.

Non-NASA Center↗
NASA NTRS2016

Molecular Dynamics Modeling of Carbon Nanotube Composite Fracture Using ReaxFF

Carbon nanotube (CNT) fiber reinforced composites with specific tensile strengths and moduli approaching those of aerospace grade carbon fiber composites have recently been reported. This achievement was enabled by the emerging availability of high N/tex yarns in kilometer-scale quantities. While the production of this yarn is an impressive advance, its strength is still much lower than that of the individual CNTs comprising the yarn. Closing this gap requires understanding load transfer between CNTs at the nanometer dimensional scale. This work uses reactive molecular dynamics simulations to gain an understanding at the nanometer scale of the key factors that determine CNT nanocomposite mechanical performance, and to place more realistic upper bounds on the target properties. While molecular dynamics simulations using conventional force fields can predict elastic properties, the ReaxFF reactive forcefield can also model fracture behavior because of its ability to accurately describe bond breaking and formation during a simulation. The upper and lower bounds of CNT composite properties are investigated by comparing systems composed of CNTs continuously connected across the periodic boundary with systems composed of finite length CNTs. These lengths, effectively infinite for the continuous tubes and an aspect ratio of 13 for the finite length case, result from practical limitations on the number of atoms that can be included in a simulation. Experimentally measured aspect ratios are typically on the order of 100,000, so the calculated results should represent upper and lower limits on experimental mechanical properties. Finally, the effect of various degrees of covalent crosslinking between the CNTs and amorphous carbon matrix is considered to identify the amount of CNT-matrix covalent bonding that maximizes overall composite properties.

Jensen, Benjamin D.↗
NASA NTRS1994

Orbital variability in the eclipsing pulsar binary PSR B1957+20

We have conducted timing observations of the eclipsing millisecond binary pulsar PSR B1957+20, extending the span of data on this pulsar to more than five years. During this time the orbital period of the system has varied by roughly Delta P(sub b)/P(sub b) = 1.6 x 10(exp -7), changing quardratically with time and displaying with time and displaying an orbital period second derivative of P(sub b) = (1.43 +/- 0.08) x 10(exp -18)/sec. The previous measurement of a large negative orbital period derivative reflected only the short-term behavior of the system during the early observations; the orbital period derivative is now positive. If, as we suspect, the PSR B1957+20 system is undergoing quasi-cyclic orbital period variations similar to those found in other close binaries such as Algol and RS CVn, then the 0.025 solar mass companion to PSR B1957+20 is most likely non-degenerate, convective, and magnetically active.

Arzoumanian, Z.↗
NASA NTRS1971

Expendable second stage reusable space shuttle booster. Volume 1: Executive summary

The development of an expendable second stage for use with a reusable space shuttle booster is discussed. The configuration of a low-cost, reusable multipurpose space transportation system for the 1980 time period is presented. A system capable of economically placing payloads in earth orbit which are larger and heavier than can be carried in the shuttle orbiter cargo bay is defined. The ESS/reusable shuttle system is complementary to the space shuttle system and provides mission flexibility to permit economical expansion of the overall space program.

Source record↗
NASA NTRS1983

Optical and X-ray observations of 2S 0921-630

The present investigation is concerned with photometric and spectroscopic measurements of 2S 0921-630 covering the years 1975-82. The X-ray source 2S 0921-630 was discovered by Li et al. (1978) and identified with an approximately 17th magnitude star showing He II 4686 A and H-beta in emission. Attention is given to photoelectric photometry, photographic photometry, aspects of periodic behavior, spectroscopy, radial velocity measurements and equivalent widths, and X-ray observations. It is found that the radial velocity data confirm the 9-day period previously suggested for the system and exclude alternative periods of 17.9 and 7.7 days.

Branduardi-Raymont, G.↗
NASA NTRS2020

Seasonality of Biological and Physical Systems as Indicators of Climate Variation and Change

Evidence-based responses to climate change by society require operational and sustained information including biophysical indicator systems that provide up-to-date measures of trends and patterns against historical baselines. Two key components linking anthropogenic climate change to impacts on socio-ecological systems are the periodic inter- and intra-annual variations in physical climate systems (seasonality) and in plant and animal life cycles (phenology). We describe a set of national indicators that reflect sub-seasonal to seasonal drivers and responses of terrestrial physical and biological systems to climate change and variability at the national scale. Proposed indicators and metrics include seasonality of surface climate conditions (e.g., frost and freeze dates and durations), seasonality of freeze/thaw in freshwater systems (e.g., timing of stream runoff and durations of lake/river ice), seasonality in ecosystem disturbances (e.g., wildfire season timing and duration), seasonality in vegetated land surfaces (e.g., green-up and brown-down of landscapes), and seasonality of organismal life-history stages (e.g., timings of bird migration). Recommended indicators have strong linkages to variable and changing climates, include abiotic and biotic responses and feedback mechanisms, and are sufficiently simple to facilitate communication to broad audiences and stakeholders interested in understanding and adapting to climate change.

Seasonality↗
NASA NTRS1999

Superconductor-Magnet Bearings With Inherent Stability and Velocity-Independent Drag Torque

A hybrid superconductor magnet bearing system has been developed based on passive magnetic levitation and the flux pinning effect of high-temperature superconductivity. The rationale lies in the unique capability of a high-temperature superconductor (HTS) to enhance system stability passively without power consumption. Characterization experiments have been conducted to understand its dynamic behavior and to estimate the required motor torque for its driving system design. These experiments show that the hybrid HTS-magnet bearing system has a periodic oscillation of drag torque due mainly to the nonuniform magnetic field density of permanent magnets. Furthermore, such a system also suffers from a small superimposed periodic oscillation introduced by the use of multiple HTS disks rather than a uniform annulus of HTS material. The magnitude of drag torque is velocity independent and very small. These results make this bearing system appealing for high-speed application. Finally, design guidelines for superconducting bearing systems are suggested based on these experimental results.

Lee, Eun-Jeong↗
NASA NTRS2004

New Perspectives on Ancient Mars

Global data sets returned by the Mars Global Surveyor (MGS), Mars Odyssey, and Mars Express spacecraft and recent analyses of Martian meteorites suggest that most of the major geological events of Martian history occurred within the first billion years of solar system formation. This period was a time of heavy impact bombardment of the inner solar system, a process that strongly overprinted much of the Martian geological record from that time. Geophysical signatures nonetheless remain from that period in the Martian crust, and several geochemical tracers of early events are found in Martian meteorites. Collectively, these observations provide insight into the earliest era in Martian history when the conditions favoring life were best satisfied.

Solomon, Sean C.↗
NASA NTRS1991

Automated information retrieval using CLIPS

Expert systems have considerable potential to assist computer users in managing the large volume of information available to them. One possible use of an expert system is to model the information retrieval interests of a human user and then make recommendations to the user as to articles of interest. At Cal Poly, a prototype expert system written in the C Language Integrated Production System (CLIPS) serves as an Automated Information Retrieval System (AIRS). AIRS monitors a user's reading preferences, develops a profile of the user, and then evaluates items returned from the information base. When prompted by the user, AIRS returns a list of items of interest to the user. In order to minimize the impact on system resources, AIRS is designed to run in the background during periods of light system use.

Raines, Rodney Doyle, III↗
NASA NTRS2011

Mars as a Destination in a Capability-Driven Framework

This paper describes NASA s current plans for the exploration of Mars by human crews within NASA s Capability-Driven Framework (CDF). The CDF describes an approach for progressively extending human explorers farther into the Solar System for longer periods of time as allowed by developments in technology and spacecraft systems. Within this framework, Mars defines the most challenging objective currently envisioned for human spaceflight. The paper first describes the CDF and potential destinations being considered within this framework. For destinations relevant to the exploration of Mars, this includes both the Martian surface and the two moons of Mars. This is followed by a brief review of our evolving understanding of Mars to provide the context for the specific objectives set for human exploration crews. This includes results from robotic missions and goals set for future Martian exploration by NASA's community-based forum, the Mars Exploration Program Analysis Group (MEPAG) and the MEPAG-sponsored Human Exploration of Mars - Science Analysis Group (HEM-SAG). The paper then reviews options available for human crews to reach Mars and return to Earth. This includes a discussion of the rationale used to select from among these options for envisioned Mars exploration missions. The paper then concludes with a description of technological and operational challenges that still face NASA in order to be able to achieve the exploration goals for Mars within the CDF.

Hoffman, S. J.↗
NASA NTRS2012

Deep Space Habitat Concept of Operations for Extended Duration Transit Missions

NASA's Capability-Driven Framework (CDF) describes an approach for progressively extending human exploration missions farther into the Solar System for longer periods of time as allowed by developments in technology and spacecraft systems. Within this framework design reference missions (DRMs) targeted for several specific destinations are being used to assess different combinations of vehicles, operations, and advanced technologies to help understand which combination will best support expanded human exploration both efficiently and sustainably. Several of the identified destinations have been found to require missions with a round trip duration exceeding one year. These mission durations exceed the capabilities of current human-rated spacecraft if resupply from Earth is not possible. This makes the design of an efficient and reliable Deep Space Habitat (DSH) critical for reaching these destinations. The paper will describe the current understanding of DSH capabilities and functions that must be exhibited by any future habitat design for these missions. This description of the DSH is presented in the form of a concept of operation, which focuses on the functions that any DSH must provide, as opposed to a specific DSH design concept. Development of a concept of operations, based on DRM features, provides a common basis for assessing the viability of design concepts incorporating differing configurations and technologies. A study team with representation from several NASA Centers and relevant engineering and scientific disciplines collaborated to develop this DSH concept of operations for the transit phases of these missions. The transit phase of a mission is defined as the time after leaving Earth but before arrival at the destination and the time after leaving the destination but before arriving back at Earth. These transit phases were found to have many common features across all of the destinations being assessed for the CDF and thus arguing for a common concept of operations for all of the associated DRMs. The paper first describes the CDF and potential destinations being considered within this framework. DRMs representative of those currently being assessed will then be discussed to illustrate the range of capabilities that the DSH must support. The 18 functions identified by the multi-discipline analysis team are then described at a summary level. Several specific examples of the potential use for this concept of operations are described.

Hoffman, Stephen J.↗