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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Highly coherent long cavity GaAs/AlGaAs single-quantum-well lasers

The spectral properties of ridge-waveguide graded-index separate-confinement heterostructure single-quantum-well (SQW) GaAs/AlGaAs lasers are measured. Long-cavity lasers (800 microns) exhibit remarkably pure CW single-longitudinal-mode spectra in spite of the short cavity mode spacing. At output power 5 mW, the sidemode suppression exceeds 24 dB and the linewidth is 1.5 MHz. The linewidth-power product (LPP) is 6.4 MHz mW. Measurements of LPP as a function of cavity length L gives a 1/L-squared dependence, in agreement with theory. The results are used to deduce the linewidth enhancement factor alpha at the gain peak wavelength and its dependence on the excitation level. The sublinear gain-carrier density relation in the SQW results in an increase in alpha with increasing carrier density (decreasing cavity length). A decrease in alpha was observed for lasers operating at the second quantized state due to a recovery of the differential gain.

Larsson, Anders↗
NASA NTRS1990

Human factors of the high technology cockpit

The rapid advance of cockpit automation in the last decade has outstripped the ability of the human factors profession to understand the changes in human functions required. High technology cockpits require less physical (observable) workload, but are highly demanding of cognitive functions such as planning, alternative selection, and monitoring. Furthermore, automation creates opportunity for new and more serious forms of human error, and many pilots are concerned about the possibility of complacency affecting their performance. On the positive side, the equipment works as advertized with high reliability, offering highly efficient, computer-based flight. These findings from the cockpit studies probably apply equally to other industries, such as nuclear power production, other modes of transportation, medicine, and manufacturing, all of which traditionally have looked to aviation for technological leadership. The challenge to the human factors profession is to aid designers, operators, and training departments in exploiting the positive side of automation, while seeking solutions to the negative side. Viewgraphs are given.

Wiener, Earl L.↗
NASA NTRS1991

A comparison of chemical propulsion, nuclear thermal propulsion, and multimegawatt electric propulsion for Mars missions

Various propulsion systems are considered for a split-mission piloted exploration of Mars in terms of reducing total initial mass in low earth orbit (IMLEO) as well as trip time. Aerobraked nuclear thermal propulsion (NTP), multimegawatt (MMW) nuclear electric propulsion (NEP), and MMW solar electric propulsion (SEP) are discussed and compared to a baseline aerobraked chemical propulsion system. NTP offers low IMLEO, MMW NEP allows both low IMLEO and a short trip time, and both nuclear systems offer better mission characteristics than the chemical system. The MMW SEP is concluded to be less efficient in spite of a lower IMLEO because of the system's higher specific mass and nonconstant power production. It is recommended that MMW NEP and SEP systems be considered for application to Mars cargo missions. The NEP system is concluded to be the most effective propulsion configuration for piloted Mars missions and lunar base missions.

Frisbee, Robert H.↗
NASA NTRS1992

Renormalization group analysis of the Reynolds stress transport equation

The pressure velocity correlation and return to isotropy term in the Reynolds stress transport equation are analyzed using the Yakhot-Orszag renormalization group. The perturbation series for the relevant correlations, evaluated to lowest order in the epsilon-expansion of the Yakhot-Orszag theory, are infinite series in tensor product powers of the mean velocity gradient and its transpose. Formal lowest order Pade approximations to the sums of these series produce a fast pressure strain model of the form proposed by Launder, Reece, and Rodi, and a return to isotropy model of the form proposed by Rotta. In both cases, the model constant are computed theoretically. The predicted Reynolds stress ratios in simple shear flows are evaluated and compared with experimental data. The possibility is discussed of driving higher order nonlinear models by approximating the sums more accurately.

Rubinstein, R.↗
NASA NTRS1992

The real world and lunar base activation scenarios

A lunar base or a network of lunar bases may have highly desirable support functions in a national or international program to explore and settle Mars. In addition, He-3 exported from the Moon could be the basis for providing much of the energy needs of humankind in the twenty-first century. Both technical and managerial issues must be addressed when considering the establishment of a lunar base that can serve the needs of human civilization in space. Many of the technical issues become evident in the consideration of hypothetical scenarios for the activation of a network of lunar bases. Specific and realistic assumptions must be made about the conduct of various types of activities in addition to the general assumptions given above. These activities include landings, crew consumables, power production, crew selection, risk management, habitation, science station placement, base planning, science, agriculture, resource evaluation, readaptation, plant activation and test, storage module landings, resource transport module landings, integrated operations, maintenance, Base 2 activation, and management. The development of scenarios for the activation of a lunar base or network of bases will require close attention to the 'real world' of space operations. That world is defined by the natural environment, available technology, realistic objectives, and common sense.

Schmitt, Harrison H.↗
NASA NTRS1992

Renormalization group methods for the Reynolds stress transport equations

The Yakhot-Orszag renormalization group is used to analyze the pressure gradient-velocity correlation and return to isotropy terms in the Reynolds stress transport equations. The perturbation series for the relevant correlations, evaluated to lowest order in the epsilon-expansion of the Yakhot-Orszag theory, are infinite series in tensor product powers of the mean velocity gradient and its transpose. Formal lowest order Pade approximations to the sums of these series produce a rapid pressure strain model of the form proposed by Launder, Reece, and Rodi, and a return to isotropy model of the form proposed by Rotta. In both cases, the model constants are computed theoretically. The predicted Reynolds stress ratios in simple shear flows are evaluated and compared with experimental data. The possibility is discussed of deriving higher order nonlinear models by approximating the sums more accurately. The Yakhot-Orszag renormalization group provides a systematic procedure for deriving turbulence models. Typical applications have included theoretical derivation of the universal constants of isotropic turbulence theory, such as the Kolmogorov constant, and derivation of two equation models, again with theoretically computed constants and low Reynolds number forms of the equations. Recent work has applied this formalism to Reynolds stress modeling, previously in the form of a nonlinear eddy viscosity representation of the Reynolds stresses, which can be used to model the simplest normal stress effects. The present work attempts to apply the Yakhot-Orszag formalism to Reynolds stress transport modeling.

Rubinstein, R.↗
NASA NTRS1992

Systems integration of lunar Campsite vehicles

This paper describes the configuration design and subsystems integration resolution for lunar Campsite vehicles and the crew vehicles (CVs) which support them. This concept allows early return to the moon while minimizing hardware development. Once in place, the Campsite can be revisited for extended periods. Configuration and operations issues are addressed, and explanations of the parametric subsystem analysis, as well as descriptions of the hardware concept and performance data, are provided. Within an assumed set of launch and mission constraints, a common vehicle stage design for both the Campsite and the CV landers was the chief design driver. Accommodation of a heat-shielded, ballistic crew transportation/return vehicle, scars for later system growth and upgrades, landing the crew in close proximity to the Campsite, and appropriate kinds of robotic systems were all secondary design drivers. Physical integration of the crew module and airlock, structural system, thermal radiators, power production and storage systems, external life support consumables, and payloads are covered. The vehicle performance data were derived using a Boeing lunar transportation sizing code to optimize vehicle stage sizes and commonality. Configuration trades were conducted and detailed sketches were produced.

Capps, Stephen↗
NASA NTRS1993

Intervention strategies for the management of human error

This report examines the management of human error in the cockpit. The principles probably apply as well to other applications in the aviation realm (e.g. air traffic control, dispatch, weather, etc.) as well as other high-risk systems outside of aviation (e.g. shipping, high-technology medical procedures, military operations, nuclear power production). Management of human error is distinguished from error prevention. It is a more encompassing term, which includes not only the prevention of error, but also a means of disallowing an error, once made, from adversely affecting system output. Such techniques include: traditional human factors engineering, improvement of feedback and feedforward of information from system to crew, 'error-evident' displays which make erroneous input more obvious to the crew, trapping of errors within a system, goal-sharing between humans and machines (also called 'intent-driven' systems), paperwork management, and behaviorally based approaches, including procedures, standardization, checklist design, training, cockpit resource management, etc. Fifteen guidelines for the design and implementation of intervention strategies are included.

Wiener, Earl L.↗
NASA NTRS1994

On the design of flight-deck procedures

In complex human-machine systems, operations, training, and standardization depend on a elaborate set of procedures which are specified and mandated by the operational management of the organization. The intent is to provide guidance to the pilots, to ensure a logical, efficient, safe, and predictable means of carrying out the mission objectives. In this report the authors examine the issue of procedure use and design from a broad viewpoint. The authors recommend a process which we call 'The Four P's:' philosophy, policies, procedures, and practices. We believe that if an organization commits to this process, it can create a set of procedures that are more internally consistent, less confusing, better respected by the flight crews, and that will lead to greater conformity. The 'Four-P' model, and the guidelines for procedural development in appendix 1, resulted from cockpit observations, extensive interviews with airline management and pilots, interviews and discussion at one major airframe manufacturer, and an examination of accident and incident reports. Although this report is based on airline operations, we believe that the principles may be applicable to other complex, high-risk systems, such as nuclear power production, manufacturing process control, space flight, and military operations.

Degani, Asaf↗
NASA NTRS1994

Analysis of phase distribution phenomena in microgravity environments

In the past one of NASA's primary emphasis has been on identifying single and multiphase flow experiments which can produce new discoveries that are not possible except in a microgravity environment. While such experiments are obviously of great scientific interest, they do not necessarily provide NASA with the ability to use multiphase processes for power production and/or utilization in space. The purpose of the research presented in this paper is to demonstrate the ability of multidimensional two-fluid models for bubbly two-phase flow to accurately predict lateral phase distribution phenomena in microgravity environments. If successful, this research should provide NASA with mechanistically-based analytical methods which can be used for multiphase space design and evaluation, and should be the basis for future shuttle experiments for model verification.

Lahey, Richard, Jr.↗
NASA NTRS1996

Design of the Heat Receiver for the U.S./Russia Solar Dynamic Power Joint Flight Demonstration

A joint U.S./Russia program is being conducted to develop, fabricate, launch, and operate a solar dynamic demonstration system on Space Station Mir. The goal of the program is to demonstrate and confirm that solar dynamic power systems are viable for future space applications such as the International Space Station Alpha The major components of the system include a heat receiver, a closed Brayton cycle power conversion unit, a power conditioning and control unit, a concentrator, a radiator, a thermal control system, and a Space Shuttle Carrier. This paper discusses the design of the heat receiver component. The receiver comprises a cylindrical cavity, the walls of which are lined with a series of tubes running the length of the cavity. The engine working fluid, a mixture of xenon and helium, is heated by the concentrated sunlight incident on these tubes. The receiver incorporates integral thermal storage, using a eutectic mixture of lithium fluoride and calcium difluoride as the thermal storage solid-to-liquid phase change materiaL This thermal storage is required to enable power production during eclipse. The phase change material is contained in a series of individual containment canisters.

Strumpf, Hal J.↗
NASA NTRS1999

Pressure Effects on Combustion of Methanol and Methanol-Docecanol Droplets

The objective of this research is to improve understanding of the combustion of binary fuel mixtures in the vicinity of the critical point. Fiber-supported single droplets and two-droplet arrays of methanol and of mixtures of methanol and 1-dodecanol, initially 0.9 mm in diameter, were burned in room-temperature air at pressures from 0.1 MPa to 9.0 MPa in the NASA Lewis 2.2-second drop tower. The work is a continuation of a collaborative Japan-US research effort designed to increase knowledge of high-pressure combustion of fuel sprays, relevant to application in propulsive and power-production devices such as Diesel engines. Some previous publications from this cooperative program may be cited. All of the previous experiments concerned alkanes and alkane mixtures. The new research reported here addresses alcohols and alcohol mixtures, to ascertain the degree to which previous results for alkanes extend to alcohols. There have been many previous experimental studies of methanol droplet combustion and a few of alcohol mixtures, but not at the high pressures of interest here. There is some experimental information on methanol droplet combustion at elevated pressure but none on the alcohol mixtures extending to critical pressures, as in the present study.

Okai, K.↗
NASA NTRS2000

1999 NASA Seal/Secondary Air System Workshop

NASA Glenn hosted the Seals/Secondary Air System Workshop on October 2829, 1999. Each year NASA and our industry and university partners share their respective seal technology development. We use these workshops as a technical forum to exchange recent advancements and "lessons-learned" in advancing seal technology and solving problems of common interest. As in the past we are publishing two volumes. Volume 1 will be publicly available and will be made available on-line through the web page address listed at the end of this chapter. Volume 2 will be restricted under International Traffic and Arms Regulations (I.T.A.R.) In this conference participants gained an appreciation of NASA's new Ultra Efficient Engine Technology (UEET) program and how this program will be partnering with ongoing DOE -industrial power production and DOD- military aircraft engine programs. In addition to gaining a deeper understanding into sealing advancements and challenges that lie ahead, participants gained new working and personal relationships with the attendees. When the seals and secondary fluid management program was initiated, the emphasis was on rocket engines with spinoffs to gas turbines. Today, the opposite is true and we are, again building our involvement in the rocket engine and space vehicle demonstration programs.

Steinetz, Bruce M.↗
NASA NTRS1995

Designing Flight-Deck Procedures

A complex human-machine system consists of more than merely one or more human operators and a collection of hardware components. In order to operate a complex system successfully, the human-machine system must be supported by an organizational infrastructure of operating concepts, rules, guidelines, and documents. The coherency of such operating concepts, in terms of consistency and logic, is vitally important for the efficiency and safety of any complex system. In high-risk endeavors such as aircraft operations, space flight, nuclear power production, manufacturing process control, and military operations, it is essential that such support be flawless, as the price of operational error can be high. When operating rules are not adhered to, or the rules are inadequate for the task at hand, not only will the system's goals be thwarted, but there may also be tragic human and material consequences. To ensure safe and predictable operations, support to the operators, in this case flight crews, often comes in the form of standard operating procedures. These provide the crew with step-by-step guidance for carrying out their operations. Standard procedures do indeed promote uniformity, but they do so at the risk of reducing the role of human operators to a lower level. Management, however, must recognize the danger of over-procedurization, which fails to exploit one of the most valuable assets in the system, the intelligent operator who is "on the scene." The alert system designer and operations manager recognize that there cannot be a procedure for everything, and the time will come in which the operators of a complex system will face a situation for which there is no written procedure. Procedures, whether executed by humans or machines, have their place, but so does human cognition.

Degani, Asaf↗
NASA NTRS2002

Electrical Performance of the International Space Station U.S. Photovoltaic Array During Bifacial Illumination

With the first United States (U.S.) photovoltaic array (PVA) activated on International Space Station (ISS) in December 2000, on-orbit data can now be compared to analytical predictions. Due to ISS operational constraints, it is not always possible to point the front side of the arrays at the Sun. Thus, in many cases, sunlight directly illuminates the backside of the PVA as well as albedo illumination on either the front or the back. During this time, appreciable power is produced since the solar cells are mounted on a thin, solar transparent substrate. It is important to present accurate predictions for both front and backside power generation for mission planning, certification of flight readiness for a given mission, and on-orbit mission support. To provide a more detailed assessment of the ISS power production capability, the authors developed a PVA electrical performance model applicable to generalized bifacial illumination conditions. On-orbit PVA performance data were also collected and analyzed. This paper describes the ISS PVA performance model, and the methods used to reduce orbital performance data. Analyses were performed using SPACE. a NASA-GRC developed computer code for the ISS program office. Results showed a excellent comparison of on-orbit performance data and analytical results.

Delleur, Ann M.↗
NASA NTRS2003

International Space Station Solar Array Bifacial Electrical Performance Model Developed

The first U.S. photovoltaic array (PVA) was activated on the International Space Station (ISS) in December 2000. Though normally Sun-tracking, U.S. ISS arrays are held stationary to minimize plume impingement from the space shuttle during docking and undocking, as well as during ISS assembly operations. Because of these operational constraints, it is not always possible to point the front side of the arrays at the Sun. In these cases, sunlight directly illuminates the backside of the PVA as well as albedo illumination on either the front or the back. Since the solar cells are mounted on a thin, solar transparent substrate, appreciable backside power (about one-third of the front-side power) is produced. To provide a more detailed assessment of the ISS power production capability, researchers at the NASA Glenn Research Center developed a PVA electrical performance model applicable to generalized bifacial illumination conditions. The model validation was done using on-orbit PVA performance.

Delleur, Ann M.↗
NASA NTRS2007

A Minimized Technological Approach towards Human Self Sufficiency off Earth

Since the early 1970's it has been known that it is technically feasible to build large habitats in space where many people could live, more or less, independently off Earth. These large habitats would require decades of Apollo level expenditures to build. The objective of this paper is to begin the study of the minimum technological system that wi11 enable the historic shift from the state where all of humanity is dependent on Earth to the state where an independent human community can exist off Earth. It is suggested that such a system is more on the order of a homestead than a city. A minimum technical system is described that could support one human reproductive unit (family) in free space or on a planetary or lunar surface. The system consists of life support, materials extraction, mobility, and power production. Once the technology is developed for the single unit, many could be deployed. They could reproduce themselves at an exponential rate using space resources and energy. One would imagine cooperation of these units to build any combination of towns, cities and nations in space to extend human life beyond Earth.

Curreri, Peter A.↗