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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Simulation of Unique Pressure Changing Steps and Situations in Psa Processes

A more rigorous cyclic adsorption process simulator is being developed for use in the development and understanding of new and existing PSA processes. Unique features of this new version of the simulator that Ritter and co-workers have been developing for the past decade or so include: multiple absorbent layers in each bed, pressure drop in the column, valves for entering and exiting flows and predicting real-time pressurization and depressurization rates, ability to account for choked flow conditions, ability to pressurize and depressurize simultaneously from both ends of the columns, ability to equalize between multiple pairs of columns, ability to equalize simultaneously from both ends of pairs of columns, and ability to handle very large pressure ratios and hence velocities associated with deep vacuum systems. These changes to the simulator now provide for unique opportunities to study the effects of novel pressure changing steps and extreme process conditions on the performance of virtually any commercial or developmental PSA process. This presentation will provide an overview of the cyclic adsorption process simulator equations and algorithms used in the new adaptation. It will focus primarily on the novel pressure changing steps and their effects on the performance of a PSA system that epitomizes the extremes of PSA process design and operation. This PSA process is a sorbent-based atmosphere revitalization (SBAR) system that NASA is developing for new manned exploration vehicles. This SBAR system consists of a 2-bed 3-step 3-layer system that operates between atmospheric pressure and the vacuum of space, evacuates from both ends of the column simultaneously, experiences choked flow conditions during pressure changing steps, and experiences a continuously changing feed composition, as it removes metabolic CO2 and H20 from a closed and fixed volume, i.e., the spacecraft cabin. Important process performance indicators of this SBAR system are size, and the corresponding CO2 and H20 removal efficiencies, and N2 and O2 loss rates. Results of the fundamental behavior of this PSA process during extreme operating conditions will be presented and discussed.

Ebner, Armin D.↗
NASA NTRS1997

Data Reduction and Analysis from the SOHO Spacecraft

We continue to analyze and interpret data from the MTOF sensor on SoHO, using recently obtained calibration data to improve our understanding of instrument response. We have presented a number of talks demonstrating the excellent instrument resolution and also displaying the temporal behavior of solar wind Fe(sup 54) and Fe(sup 56) isotopes and the element Cr(52). In addition, the isotopic ratios Ne(sup 20)/Ne (sup 22) = (13.8 +/- 0.7) and Ne(sup 20)/Ne(sup 21) = (440 +/- 110) were obtained from MTOF data. These ratios agree with the values obtained from the Apollo foil solar wind experiments and with values which have been derived from measurements on lunar and meteoritic samples.

Ipavich, F. M.↗
NASA NTRS1997

Formation Flying Control of Multiple Spacecraft

The problem of coordination and control of multiple spacecraft (MS) moving in formation is considered. Here, each MS is modeled by a rigid body with fixed center of mass. First, various schemes for generating the desired formation patterns are discussed, Then, explicit control laws for formation-keeping and relative attitude alignment based on nearest neighbor-tracking are derived. The necessary data which must be communicated between the MS to achieve effective control are examined. The time-domain behavior of the feedback-controlled MS formation for typical low-Earth orbits is studied both analytically and via computer simulation. The paper concludes with a discussion of the implementation of the derived control laws, and the integration of the MS formation coordination and control system with a proposed inter-spacecraft communication/computing network.

Hadaegh, F. Y.↗
NASA NTRS2004

Jupiter's Atmospheric Temperatures: From Voyager IRIS to Cassini CIRS

Retrievals run on Cassini Composite Infrared Spectrometer data obtained during the distant Jupiter flyby have been used to generate global temperature maps of the planet in the troposphere and stratosphere. Similar retrievals were performed on Voyager 1 IRIS data and have provided the first detailed IRIS map of the stratosphere. In both data sets, high latitude troposphere temperatures are presented for the first time, and the meridional gradients indicate the presence of circumpolar jets. Thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes. The temperatures retrieved from the two spacecraft were also compared with yearly ground-based data obtained over the intervening two decades. Tropospheric temperatures reveal gradual changes at low latitudes, with little obvious seasonal or short-term variation (Orton et al. 1994). Stratospheric temperatures show much more complicated behavior over short timescales, consistent with quasi-quadrennial oscillations at low latitudes, as suggested in prior analyses of shorter intervals of ground- based data (Orton et al. 1991, Friedson 1999). A scaling analysis indicates that meridional motions, mechanically forced by wave or eddy convergence, play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter time scales. At latitudes away from the equator, the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative. Ground-based observations with improved vertical resolution and/or long-term monitoring from spacecraft are required for this purpose.

Simon-Miller, Amy A.↗
NASA NTRS2004

Engineering Complex Embedded Systems with State Analysis and the Mission Data System

It has become clear that spacecraft system complexity is reaching a threshold where customary methods of control are no longer affordable or sufficiently reliable. At the heart of this problem are the conventional approaches to systems and software engineering based on subsystem-level functional decomposition, which fail to scale in the tangled web of interactions typically encountered in complex spacecraft designs. Furthermore, there is a fundamental gap between the requirements on software specified by systems engineers and the implementation of these requirements by software engineers. Software engineers must perform the translation of requirements into software code, hoping to accurately capture the systems engineer's understanding of the system behavior, which is not always explicitly specified. This gap opens up the possibility for misinterpretation of the systems engineer s intent, potentially leading to software errors. This problem is addressed by a systems engineering methodology called State Analysis, which provides a process for capturing system and software requirements in the form of explicit models. This paper describes how requirements for complex aerospace systems can be developed using State Analysis and how these requirements inform the design of the system software, using representative spacecraft examples.

mission data systems↗
NASA NTRS1984

The Mars Geoscience/Climatology Orbiter 1990 mission

The fundamental objectives of the Mars Geoscience/Climatology Orbiter (MGCO) 1990 mission are related to the determination of the surface composition and topography of the planet Mars, its gravitational and intrinsic magnetic fields, and the seasonal behavior of volatiles, dust, and the atmosphere of Mars. These objectives would be achieved through a global mapping of the planet over a Martian year. For the baseline mission, a single spacecraft would be launched in August 1990, arrive at Mars in August 1991, and map the planet from a Sun-synchronous, near-circular, polar orbit for one Martian year. Attention is given to a science rationale and objectives, a mission description, the flight system, and mission operations.

Low, G. D.↗
NASA NTRS1989

Enhanced element-specific modal formulations for flexible multibody dynamics

The accuracy of current flexible multibody formalisms based on assumed modes is examined in the context of standard spacecraft motions involving structural components undergoing both slow and fast overall translational and rotational motions as well as small deformations. Limitations of current techniques in treating: (1) element-specific coupling behavior of large motion and small deformation, and (2) motion-induced structural stiffness variations, are noted. The roles of nonlinear and linear elastic structural theories in accurately predicting transient large-displacement dynamic behavior of flexible multibody systems are examined in detail. Coupling effects between deformation and overall motion are carefully scrutinized in the context of assumed-mode discretization techniques. Consistently linearized beam, plate, and shell formulations involving in-plane stretch variables are proposed and shown to yield very accurate simulation results and extremely fast modal convergence for most motions involving small strains. In some particular cases, however, in which membrane stiffness dominates bending stiffness, a nonlinear strain formulation is required in order to capture proper coupling between deformation and overall motion.

Ryan, Robert R.↗
NASA NTRS1991

Gravity jitters excited slosh waves in rotating propellant tank under microgravity environment

The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids (cryogenic liquid helium and helium vapor) in a full-scale Gravity Probe-B Spacecraft propellant tank without probe imposed by various frequencies of gravity jitters have been investigated. Results disclose the conditions for the excitation of large amplitude slosh waves which shall be avoided in the design of cryogenic liquid propellant system.

Hung, R. J.↗
NASA NTRS1991

Slosh wave excitation in a partially filled rotating tank due to gravity jitters in a microgravity environment

The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids (cryogenic liquid helium and helium vapor), in a full-scale Gravity Probe-B Spacecraft propellant tank without probe imposed by various frequencies of gravity jitters have been investigated. Twelve case studies of slosh wave excitation due to various frequencies of gravity jitters under different rotating speeds of propellant tank and different levels of background gravity environment have been numerically simulated. Results disclose the conditions for the excitation of large amplitude slosh waves which shall be avoided in the design of cryogenic liquid propellant system.

Hung, R. J.↗
NASA NTRS1991

Gravity jitter excited cryogenic liquid slosh waves in microgravity environment

The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids (cryogenic liquid helium and helium vapor) in a full-scale Gravity Probe-B Spacecraft liquid helium container tank without probe imposed by various frequencies of gravity jitter have been investigated. Results disclose the conditions for the excitation of large amplitude slosh waves which should be avoided in the design of cryogenic liquid propellant system.

Hung, R. J.↗
NASA NTRS1995

The inner magnetosheath of Venus: An analogue for Earth?

The unmagnetized planets provide examples of solar wind interactions that are free from the complications associated with magnetopause reconnection and with sensitive obstacle response to incident solar wind pressure changes. Using the Venus magnetosheath as a testbed, we search for evidence of standing slow mode 'transitions' in the inner subsolar region as reported for Earth by Song et al. Although the system at Venus is much smaller in scale, the Pioneer Venus Orbiter magnetometer data indicate that for perpendicular interplanetary magnetic field conditions the general behavior of the plasma in the magnetosheath is as expected from the simple depletion layer model. In examples of magnetic field measurements chosen for the apparently steady interplanetary conditions during the spacecraft pass, there is no clear evidence for a slow mode structure near the ionopause as might be expected on the basis of the Song et al. study. The implication is that some aspect of the Venus magnetosheath (such as its small size or the presence of local planetary ion production) makes it physically different from Earth's, that the conditions of the magnetosheath during Song's study differed significantly from those in the Venus study, or that the observations of Song et al. do not represent a steady state.

Luhmann, J. G.↗
NASA NTRS2010

Modeling Flight: The Role of Dynamically Scaled Free-Flight Models in Support of NASA's Aerospace Programs

The state of the art in aeronautical engineering has been continually accelerated by the development of advanced analysis and design tools. Used in the early design stages for aircraft and spacecraft, these methods have provided a fundamental understanding of physical phenomena and enabled designers to predict and analyze critical characteristics of new vehicles, including the capability to control or modify unsatisfactory behavior. For example, the relatively recent emergence and routine use of extremely powerful digital computer hardware and software has had a major impact on design capabilities and procedures. Sophisticated new airflow measurement and visualization systems permit the analyst to conduct micro- and macro-studies of properties within flow fields on and off the surfaces of models in advanced wind tunnels. Trade studies of the most efficient geometrical shapes for aircraft can be conducted with blazing speed within a broad scope of integrated technical disciplines, and the use of sophisticated piloted simulators in the vehicle development process permits the most important segment of operations the human pilot to make early assessments of the acceptability of the vehicle for its intended mission. Knowledgeable applications of these tools of the trade dramatically reduce risk and redesign, and increase the marketability and safety of new aerospace vehicles. Arguably, one of the more viable and valuable design tools since the advent of flight has been testing of subscale models. As used herein, the term "model" refers to a physical article used in experimental analyses of a larger full-scale vehicle. The reader is probably aware that many other forms of mathematical and computer-based models are also used in aerospace design; however, such topics are beyond the intended scope of this document. Model aircraft have always been a source of fascination, inspiration, and recreation for humans since the earliest days of flight. Within the scientific community, Leonardo da Vinci, George Cayley, and the Wright brothers are examples of early aviation pioneers who frequently used models during their scientific efforts to understand and develop flying machines. Progress in the technology associated with model testing in worldwide applications has firmly established model aircraft as a key element in new aerospace research and development programs. Models are now routinely used in many applications and roles, including aerodynamic data gathering in wind tunnel investigations for the analysis of full-scale aircraft designs, proof-of-concept demonstrators for radical aeronautical concepts, and problem-solving exercises for vehicles already in production. The most critical contributions of aerospace models are to provide confidence and risk reduction for new designs and to enhance the safety and efficiency of existing configurations.

Chambers, Joseph↗
NASA NTRS2011

Temporal and Spatial Aspects of Gas Release During the 2010 Apparition of Comet 103P/Hartley-2

We report measurements of eight primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, C2H2, H2CO, and NH3) and two product species (OH and NH2) in comet lO3P/Hartley-2 using high dispersion infrared spectroscopy. We quantified the long- and short-term behavior of volatile release over a three-month interval that encompassed the comet's close approach to Earth, its perihelion passage, and flyby of the comet by the Deep Impact spacecraft during the EPOXI mission. We present production rates for individual species, their mixing ratios relative to water, and their spatial distributions in the coma on multiple dates. The production rates for water, ethane, HCN, and methanol vary in a manner consistent with independent measures of nucleus rotation, but mixing ratios for HCN, C2H6, & CH3OH are independent of rotational phase. Our results demonstrate that the ensemble average composition of gas released from the nucleus is well defined, and relatively constant over the three-month interval (September 18 through December 1,7). If individual vents vary in composition, enough diverse vents must be active simultaneously to approximate (in sum) the bulk composition of the nucleus. The released primary volatiles exhibit diverse spatial properties which favor the presence of separate polar and apolar ice phases in the nucleus, establish dust and gas release from icy clumps, and from the nucleus, and provide insights into the driver for the cyanogen (CN) polar jet. The spatial distributions of C2H6 & HCN along the near-polar jet (UT 19.5 October) and nearly orthogonal to it (UT 22.5 October) are discussed relative to the origin of CN. The ortho-para ratio (OPR) of water was 2.85 +/- 0.20; the lower bound (2.65) defines T(sub spin) > 32 K. These values are consistent with results returned from ISO in 1997 .

Mumma, M. J.↗
NASA NTRS2018

Development and Testing of a Vehicle Management System for Autonomous Spacecraft Habitat Operations

As the increased distance between Earth-based mission control and the spacecraft results in increasing communication delays, small crews cannot take on all functions performed by ground today, and so vehicles must be more automated to reduce the crew workload for such missions. In addition, both near-term and future missions will feature significant periods when crew is not present, meaning the vehicles will need to operate themselves autonomously. NASA's Advanced Exploration Systems Program pioneers new approaches for rapidly developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond low-Earth orbit. Under this program, NASA has developed and demonstrated multiple technologies to enable the autonomous operation of a dormant space habitat. These technologies included a fault-tolerant avionics architecture, novel spacecraft power system and power system controller, and autonomy software to control the habitat. The demonstration involved simulation of the habitat and multiple spacecraft sub-systems (power storage and distribution, avionics, and air-side life-support) during a multi-day test at NASA's Johnson Space Center. The foundation of the demonstration was ‘quiescent operations' of a habitat during a 55 minute eclipse period. For this demonstration, the spacecraft power distribution system and air-side life support system were simulated at a high level of fidelity; additional systems were managed, but with lower fidelity operational constraints and system behavior. Operational constraints for real and simulated loads were developed by analyzing on-orbit hardware and evaluating future Exploration capable technology. A total of 13 real and simulated loads were used during the test. Eight scenarios including both nominal and off-nominal conditions were performed. Over the course of the test, every application performed its desired functions successfully during the simulated tests. The results will inform both future tests, as well as provide insight to NASA's domestic and international partners, as they construct the next generation of space habitats to be used on beyond-Earth missions.

Autonomous Systems and Operations↗
NASA NTRS2016

Performance Analysis of Operational Ka-Band Link with Kepler

This paper presents some observations on the signal behavior from an analysis of Kepler Ka-band link. The goal is to characterize the link performance with operational data obtained from the Deep Space Network (DSN) tracking of Kepler spacecraft. Kepler is the first mission supported by the DSN that uses Ka-band as a primary means to return science data. We examine how operational data may differ from the expectation. Operational data often show many surprises where data variations occur without an apparent cause. We try to quantify the signal power fluctuation so that future missions can adequately plan for the link design, especially for missions that operate with lower margin. We also attempt to quantify the effect of rains/heavy clouds and high winds.

performance analysis↗
NASA NTRS1994

Nickel cadmium battery operations and performance

The Earth Radiation Budget Satellite (ERBS), Compton Gamma Ray Observatory (CGRO), Upper Atmosphere Research Satellite (UARS), and Extreme Ultraviolet Explorer (EUVE) spacecraft are operated from NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. On-board power subsystems for each satellite employ NASA Standard 50 Ampere-hour (Ah) nickel-cadmium batteries in a parallel configuration. To date, these batteries have exhibited degradation over periods from several months (anomalous behavior, UARS and CGRO (MPS-1); to little if any, EUVE) to several years (old age, normal behavior, ERBS). Since the onset of degraded performance, each mission's Flight Operations Team (FOT), under the direction of their cognizant GSFC Project Personnel and Space Power Application Branch's Engineers has closely monitored the battery performance and implemented several charge control schemes in an effort to extend battery life. Various software and hardware solutions have been developed to minimize battery overcharge. Each of the four sections of this paper covers a brief overview of each mission's operational battery management and its associated spacecraft battery performance. Also included are new operational procedures developed on-orbit that may be of special interest to future mission definition and development.

Rao, Gopalakrishna↗
NASA NTRS1993

An improved gravity model for Mars: Goddard Mars Model 1

Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, Goddard Mars Model 1 (GMM-1). This model employs nearly all available data, consisting of approximately 1100 days of S band tracking data collected by NASA's Deep Space Network from the Mariner 9 and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM-1 is complete to spherical harmonic degree and order 50, which corresponds to a half-wavelength spatial resolution of 200-300 km where the data permit. GMM-1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM-1 over previous models is a consequence of several factors: improved computational capabilities, the use of otpimum weighting and least squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X band tracking data from the 379-km altitude, nnear-polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM-1, particularly at high latitudes where current data poorly resolve the gravitational signature of the planet.

Smith, D. E.↗
NASA NTRS1976

Experiments on the properties of superfluid helium in zero gravity

The paper describes a research program designed to study the behavior of superfluid liquid helium in low and zero gravity in order to determine the properties which are critically important to its use as a stored cryogen for cooling scientific instruments aboard spacecraft for periods up to several months. The experiment program consists of a series of flights of an experiment package on a free-fall trajectory both on an aircraft and on a rocket. The objectives are to study thickness of thin films of helium as a function of acceleration, heat transfer in thin films, heat transfer across copper-liquid helium interfaces, fluid dynamics of bulk helium in high and low accelerations and under various conditions of rotations, alternate methods of separation of liquid and vapor phases and of efficient venting of the vapor, and undesirable thermomechanical oscillations in the vent pipes. Preliminary results from aircraft tests are discussed.

Mason, P.↗