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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Ethynyl-Terminated Ester Oligomers and Polymers

Polyesters of various molecular weights terminated with ethynyl groups. As ethynyl-terminated polyesters are exposed to elevated temperatures, thermally induced reaction of ethynyl groups occurs to provide cross-linking and chain extension. Reaction raises use temperature of polymer and greatly improves resistance to solvents. New materials produced by this process potentially useful as adhesives, composite matrices, solvent-resistant coatings, membranes, and films.

Hergenrother, P. M.↗
NASA NTRS1985

Personal-Computer Video-Terminal Emulator

OWL-1200 video terminal emulator has been written for IBM Personal Computer. The OWL-1200 is a simple user terminal with some intelligent capabilities. These capabilities include screen formatting and block transmission of data. Emulator is written in PASCAL and Assembler for the IBM Personal Computer operating under DOS 1.1.

Buckley, R. H.↗
NASA NTRS1984

Siloxane containing addition polyimides. II - Acetylene terminated polyimides

Acetylene terminated polyimide oligomers having a range of molecular weights have been synthesized by reacting bis (gamma-aminopropyl) tetramethyldisiloxane, aminophenylacetylene and 3, 3', 4, 4' benzophenonetetracarboxylic dianhydride in different molar ratios. The prepolymers were isolated and characterized for melt flow and cure properties. They show promise as adhesives for bonding titanium to titanium and as matrix resins for graphite cloth reinforced composites. The most promising system has been blended in varying proportions with Thermid 600, a commercially available acetylene terminated polyimide oligomer, and the mixtures have been tested for application as composite matrix resins.

Maudgal, S.↗
NASA NTRS1985

Relativistic wind termination - Jets and synchronotron nebulae

An idealized model describing the termination of a relativistic wind owing to its interaction with surrounding nonrelativistic matter, such as the interaction of a pulsar wind with the supernova remnant shell is examined. It is assumed that the large-scale electric and magnetic fields out to the termination distance are controlled by the wind source, in contrast to previous work treating the wind as an isotropic MHD flow. Two effects are found: forced synchrotron radiation from the bulk of the injected particles, and formation of oppositely directed jets of ultrarelativistic particles.

Michel, F. C.↗
NASA NTRS1985

Acetylene terminated matrix resins

The synthesis of resins with terminal acetylene groups has provided a promising technology to yield high performance structural materials. Because these resins cure through an addition reaction, no volatile by-products are produced during the processing. The cured products have high thermal stability and good properties retention after exposure to humidity. Resins with a wide variety of different chemical structures between the terminal acetylene groups are synthesized and their mechanical properties studied. The ability of the acetylene cured polymers to give good mechanical properties is demonstrated by the resins with quinoxaline structures. Processibility of these resins can be manipulated by varying the chain length between the acetylene groups or by blending in different amounts of reactive deluents. Processing conditions similar to the state-of-the-art epoxy can be attained by using backbone structures like ether-sulfone or bis-phenol-A. The wide range of mechanical properties and processing conditions attainable by this class of resins should allow them to be used in a wide variety of applications.

Goldfarb, I. J.↗
NASA NTRS1986

Ethynyl and substituted ethynyl-terminated polysulfones

Ethynyl and substituted ethynyl-terminated polysulfones and their synthesis are disclosed. These polysulfones are thermally cured to induce cross-linking and chain extension, producing a polymer system with improved solvent resistance and use temperatures. Also disclosed are substituted 4-ethynylbenzoyl chlorides as precursors to the substituted ethynyl-terminated polysulfones and a process for preparing the same.

Hergenrother, P. M.↗
NASA NTRS1986

A time-based concept for terminal-area traffic management

An automated air-traffic-management concept that has the potential for significantly increasing the efficiency of traffic flows in high-density terminal areas is discussed. The concept's implementation depends on the techniques for controlling the landing time of all aircraft entering the terminal area, both those that are equipped with on-board four dimensional guidance systems as well as those aircraft types that are conventionally equipped. The two major ground-based elements of the system are a scheduler which assigns conflict-free landing times and a profile descent advisor. Landing times provided by the scheduler are uplinked to equipped aircraft and translated into the appropriate four dimensional trajectory by the on-board flight-management system. The controller issues descent advisories to unequipped aircraft to help them achieve the assigned landing times. Air traffic control simulations have established that the concept provides an efficient method for controlling various mixes of four dimensional-equipped and unequipped, as well as low-and high-performance, aircraft.

Erzberger, H.↗
NASA NTRS1986

Particle acceleration at a termination shock. I - Application to the solar wind and the anomalous component

The results of a numerical study of the diffusive acceleration of charged particles at the termination shock of the solar wind are reported. In the model a realistic magnetic field structure is employed which is similar to that observed in the solar wind. In addition to causing spatial variation of the diffusion tensor, a major effect of the magnetic field is to cause guiding-center drifts of the accelerated particles, both in the solar wind and at the shock. It is demonstrated that the inclusion of the drifts has a large effect on the acceleration. It is concluded, furthermore, that acceleration at the termination shock, in conjunction with drifts, can explain several observed features of the anomalous component.

Jokipii, J. R.↗
NASA NTRS1985

Simulation of time-control procedures for terminal area flow management

Simulations of a terminal area traffic-management system incorporating automated scheduling and time-control (four-dimensional) techniques conducted at NASA Ames Research Center jointly with the Federal Aviation Administration, have shown that efficient procedures can be developed for handling a mix of 4D-equipped and conventionally equipped aircraft. A crucial role in this system is played by an ATC host computer algorithm, referred to as a speed advisory, that allows controllers to maintain accurate time schedules of the conventionally equipped aircraft in the traffic mix. Results are of the most recent simulations in which two important special cases were investigated. First, the effects of a speed advisory on touchdown time scheduling are examined, when unequipped aircraft are constrained to follow fuel-optimized profiles in the near-terminal area, and rescheduling procedures are developed to handle missed approaches of 4D-equipped aircraft. Various performance measures, including controller opinion, are used to evaluate the effectiveness of the procedures.

Alcabin, M.↗
NASA NTRS1986

Use of flight simulation to develop terminal instrument procedures for transport category aircraft

In a collaborative effort between the FAA and NASA, a simulation was conducted to look at the issues involved with flying a large, widebody aircraft in the terminal area using MLS-RNAV procedures. A variety of approach paths, departure paths, and holding patterns were investigated during the course of the study, which included the participation of subject pilots. The simulation made use of paths designed by the FAA Office of Aviation Standards and employed Langley's Visual Motion Simulator (VMS) for their execution. Data obtained from this simulation will be used to support the joint FAA/USAF MLS flight test and demonstration project. This paper describes the flight simulation facility adapted to model terminal area maneuvers for jet transport aircraft using the Microwave Landing System (MLS). A description of the overall project will be presented first, along with a discussion of the guidance schemes used, followed by a description of the simulation hardware and software. A sample of the resulting data will also be presented.

Branstetter, J. R.↗
NASA NTRS1987

Acetylene-Terminated Polyimide Siloxanes

Siloxane-containing addition polyimides yield toughened high-temperature adhesives and matrix resins. Addition polyimide made by reaction of aromatic tetracarboxylic acid dianhydride with aromatic diamine in presence of ethynyl-substituted aromatic monoamine. Acetylene-terminated siloxane imide cured by heating to yield acetylene-terminated polyimide siloxane.

St. Clair, Terry L.↗
NASA NTRS1986

Potential impacts of advanced technologies on the ATC capacity of high-density terminal areas

Advanced technologies for airborne systems (automatic flight control, flight displays, navigation) and for ground ATC systems (digital communications, improved surveillance and tracking, automated decision-making) create the possibility of advanced ATC operations and procedures which can bring increased capacity for runway systems. A systematic analysis is carried out to identify certain such advanced ATC operations, and then to evaluate the potential benefits occurring over time at typical US high-density airports (Denver and Boston). The study is divided into three parts: (1) A Critical Examination of Factors Which Determine Operational Capacity of Runway Systems at Major Airports, is an intensive review of current US separation criteria and terminal area ATC operations. It identifies 11 new methods to increase the capacity of landings and takeoffs for runway systems; (2) Development of Risk Based Separation Criteria is the development of a rational structure for establishing reduced ATC separation criteria which meet a consistent Target Level of Safety using advanced technology and operational procedures; and (3) Estimation of Capacity Benefits from Advanced Terminal Area Operations - Denver and Boston, provides an estimate of the overall annual improvement in runway capacity which might be expected at Denver and Boston from using some of the advanced ATC procedures developed in Part 1. Whereas Boston achieved a substantial 37% increase, Denver only achieved a 4.7% increase in its overall annual capacity.

Simpson, R. W.↗
NASA NTRS1987

Styrene-terminated polysulfone oligomers as matrix material for graphite reinforced composites: An initial study

Styrene terminated polysulfone oligomers are part of an oligomeric class of compounds with end groups capable of thermal polymerization. These materials can be used as matrices for graphite reinforced composites. The initial evaluation of styrene terminated polysulfone oligomer based composites are summarized in terms of fabrication methods, and mechanical and environmental properties. In addition, a description and evaluation is provided of the NASA/Industry Fellowship Program for Technology Transfer.

Garcia, Dana↗
NASA NTRS1986

A time-based concept for terminal-area traffic management

An automated air-traffic-management concept that has the potential for significantly increasing the efficiency of traffic flows in high-density terminal areas is discussed. The concept's implementation depends on techniques for controlling the landing time of all aircraft entering the terminal area, both those that are equipped with on-board four-dimensional (4D) guidance systems as well as those aircraft types that are conventionally equipped. The two major ground-based elements of the system are a scheduler which assigns conflict-free landing times and a profile descent advisor. Landing time provided by the scheduler is uplinked to equipped aircraft and translated into the appropriate 4D trajectory by the-board flight-management system. The controller issues descent advisories to unequipped aircraft to help them achieve the assigned landing times. Air traffic control simulations have established that the concept provides an efficient method for controlling various mixes of 4D-equipped and unequipped, as well as low- and high-performance, aircraft. Piloted simulations of profiles flown with the aid of advisories have verified the ability to meet specified descent times with prescribed accuracy.

Erzberger, Heinz↗
NASA NTRS1987

Digital Autonomous Terminal Access Communication (DATAC) system

In order to accommodate the increasing number of computerized subsystems aboard today's more fuel efficient aircraft, the Boeing Co. has developed the DATAC (Digital Autonomous Terminal Access Control) bus to minimize the need for point-to-point wiring to interconnect these various systems, thereby reducing total aircraft weight and maintaining an economical flight configuration. The DATAC bus is essentially a local area network providing interconnections for any of the flight management and control systems aboard the aircraft. The task of developing a Bus Monitor Unit was broken down into four subtasks: (1) providing a hardware interface between the DATAC bus and the Z8000-based microcomputer system to be used as the bus monitor; (2) establishing a communication link between the Z8000 system and a CP/M-based computer system; (3) generation of data reduction and display software to output data to the console device; and (4) development of a DATAC Terminal Simulator to facilitate testing of the hardware and software which transfer data between the DATAC's bus and the operator's console in a near real time environment. These tasks are briefly discussed.

Novacki, Stanley M., III↗
NASA NTRS1987

Detection of radio-frequency modulated optical signals by two and three terminal microwave devices

An interdigitated photoconductor (two terminal device) on GaAlAs/GaAs heterostructure was fabricated and tested by an electro-optical sampling technique. Further, the photoresponse of GaAlAs/GaAs HEMT (three terminal device) was obtained by illuminating the device with an optical signal modulated up to 8 GHz. Gain-bandwidth product, response time, and noise properties of photoconductor and HEMT devices were obtained. Monolithic integration of these photodetectors with GaAs microwave devices for optically controlled phased array antenna applications is discussed.

Bhasin, K. B.↗
NASA NTRS1986

Morphology and properties of amine terminated poly(arylene ether ketone) and poly(arylene ether sulfone) modified epoxy resin systems

Epoxy resin networks cured with DDS were modified by incorporating tough ductile thermoplastics such as the amine terminated polyether sulfones and amine terminated polyether ketones. Both linear copolymers were able to significantly improve the fracture toughness values at the 15 and 30 weight percent concentrations examined. These improvements in fracture toughness were achieved without any significant change in the flexural modulus.

Cecere, J. A.↗
NASA NTRS1987

Ultra-high-energy cosmic rays in a galactic wind and its termination shock

Results are reported from numerical modeling of the acceleration and transport of ultra-high-energy cosmic rays in a galactic wind and its termination shock. A two-dimensional (azimuthally symmetric) wind and spiral magnetic field, with a spherical termination shock, where the velocity drops suddenly, is assumed. The time-dependent cosmic-ray transport equation, including all major transport effects is solved using an implicit finite-difference scheme. Particles are injected as the shock of low energy, and the subsequent evolution of the distribution function is followed. Iron nuclei are readily accelerated at the shock to energies up to 100 billion GeV, and protons to 10 billion GeV. A major effect aiding the acceleration of these particles is the spiral of the magnetic field carried out by the wind, caused by the rotation of the Galaxy, with the result that the shock is nearly normal over most of its area. Increasing the magnetic field or rotation rate increases the maximum energy attainable. Anisotropies and energy densities of the particles are also discussed. It is concluded that the process is consistent with observations of ultra-high-energy cosmic rays.

Jokipii, J. R.↗