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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

An intelligent tutor for a high performance domain

The use of intelligent tutoring systems based on the apprenticeship approach to training is explored as a possible solution to the problem of training individuals to operate and maintain complex devices, such as those used in the aerospace industry. A general approach to the development of such a system is presented, and a specific intelligent tutoring system designed for training mission control console operators is described as an example.

Fink, Pamela K.↗
NASA NTRS1988

High performance arrays for lightweight spacecraft

JPL is developing the solar arrays for NASA's ultralightweight spacecraft, the Lunar Get-Away Special (L-GAS), which requires 1 kWe after its slow passage through the Van Allen Belts. The solar array design developed for the mission extended recent NASA-developed photovoltain array technology to power levels well below those conventionally considered practical for deployable lightweight array technology. It has become feasible by these means to consider the design of lightweight spacecraft which require up to 3 kWe at the begining of their service life.

Stella, Paul M.↗
NASA NTRS1990

Airdata calibration of a high-performance aircraft for measuring atmospheric wind profiles

The research airdata system of an instrumented F-104 aircraft has been calibrated to measure winds aloft in support of the Space Shuttle wind measurement investigation. The F-104 aircraft was equipped with a research pitot-static noseboom with integral angle-of-attack and flank angle-of-attack vanes and a ring-laser-gyro inertial reference unit. The F-104 aircraft and instrumentation configuration, flight test maneuvers, data corrections, calibration techniques, and resulting calibrations and data repeatability are presented. Recommendations for future airdata systems on aircraft used to measure winds aloft are also given.

Haering, Edward A., Jr.↗
NASA NTRS1990

A vectorized Lanczos eigensolver for high-performance computers

The computational strategies used to implement a Lanczos-based-method eigensolver on the latest generation of supercomputers are described. Several examples of structural vibration and buckling problems are presented that show the effects of using optimization techniques to increase the vectorization of the computational steps. The data storage and access schemes and the tools and strategies that best exploit the computer resources are presented. The method is implemented on the Convex C220, the Cray 2, and the Cray Y-MP computers. Results show that very good computation rates are achieved for the most computationally intensive steps of the Lanczos algorithm and that the Lanczos algorithm is many times faster than other methods extensively used in the past.

Bostic, Susan W.↗
NASA NTRS1990

A parallel-vector algorithm for rapid structural analysis on high-performance computers

A fast, accurate Choleski method for the solution of symmetric systems of linear equations is presented. This direct method is based on a variable-band storage scheme and takes advantage of column heights to reduce the number of operations in the Choleski factorization. The method employs parallel computation in the outermost DO-loop and vector computation via the 'loop unrolling' technique in the innermost DO-loop. The method avoids computations with zeros outside the column heights, and as an option, zeros inside the band. The close relationship between Choleski and Gauss elimination methods is examined. The minor changes required to convert the Choleski code to a Gauss code to solve non-positive-definite symmetric systems of equations are identified. The results for two large-scale structural analyses performed on supercomputers, demonstrate the accuracy and speed of the method.

Storaasli, Olaf O.↗
NASA NTRS1990

High-performance fault-tolerant VLSI systems using micro rollback

A technique called micro rollback, which allows most of the performance penalty for concurrent error detection to be eliminated, is presented. Detection is performed in parallel with the transmission of information between modules, thus removing the delay for detection from the critical path. Erroneous information may thus reach its destination module several clock cycles before an error indication. Operations performed on this erroneous information are undone using a hardware mechanism for fast rollback of a few cycles. The implementation of a VLSI processor capable of micro rollback is discussed, as well as several critical issues related to its use in a complete system.

Tamir, Yuval↗
NASA NTRS1991

High performance, accelerometer-based control of the Mini-MAST structure at Langley Research Center

Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line of sight pointing accuracy and constraints on rms surface roughness. In order for these concepts to become operational, it is imperative that the benefits of active vibration control be shown to be practical in ground based experiments. The results of an experiment shows the successful application of the Maximum Entropy/Optimal Projection control design methodology to active vibration control for a flexible structure. The testbed is the Mini-Mast structure at NASA-Langley and has features dynamically traceable to future space systems. To maximize traceability to real flight systems, the controllers were designed and implemented using sensors (four accelerometers and one rate gyro) that are actually mounted to the structure. Ground mounted displacement sensors that could greatly ease the control design task were available but were used only for performance evaluation. The use of the accelerometers increased the potential of destabilizing the system due to spillover effects and motivated the use of precompensation strategy to achieve sufficient compensator roll-off.

Collins, Emmanuel G., Jr.↗
NASA NTRS1990

High performance VLSI telemetry data systems

NASA-Goddard has over the last five years developed generic ground telemetry data system elements addressing the budget limitations-driven demand for greater modularity, flexibility, and interchangeability. These design solutions, which may be characterized as a 'functional components approach', encompasses both hardware and software components; the former involve telemetry application-specific ICs for data rate requirements of up to 300 Mbps, while the latter extend to embedded local software intelligence. Attention is given to the consequences of the functional components approach for VLSI components.

Chesney, J.↗
NASA NTRS1990

LaRC-I-TPI - A status report on a new high performance, thermoplastic polyimide

A new thermoplastic polyimide designated LaRC-I-TPI has been prepared from 4,4'-isophthaloyldiphthalic anhydride (IDPA) and 1,3-phenylenediamine (m-PDA), phthalic anhydride endcapped or unendcapped. It is closely related to the well-known commercial LaRC-TPI. A survey of the synthesis and some thermal, film, adhesive, fracture toughness, and composite properties of this new polyimide is presented. While both materials have similar properties at comparable stages of development, LaRC-I-TPI should be less expensive to manufacture as a result of the use of lower cost readily available monomers.

Pratt, J. Richard↗
NASA NTRS1991

A new generation of high performance engines for spacecraft propulsion

Experimental data validating advanced engine designs at three thrust levels (5, 15, and 100 lbF) is presented. All of the three engine designs considered employ a Moog bipropellant torque motor valve, platelet injector design, and iridium-lined rhenium combustion chamber. Attention is focused on the performance, robustness, duration, and flexibility characteristics of the engines. It is noted that the 5- and 15-lbF thrust engines can deliver a steady state specific impulse in excess of 310 lbF-sec/lbm at an area ratio of 150:1, while the 150-lbF thrust engines deliver a steady state specific impulse of 320 lbF-sec/lbm at an area ratio of 250:1. The hot-fire test results reveal specific impulse improvements of 15 to 25 sec over conventional fuel film cooled columbium chamber designs while operating at maximum chamber temperatures.

Rosenberg, Sanders D.↗
NASA NTRS1991

High performance computing system for flight simulation at NASA Langley

The computer architecture and components used in the NASA Langley Advanced Real-Time Simulation System (ARTSS) are briefly described and illustrated with diagrams and graphs. Particular attention is given to the advanced Convex C220 processing units, the UNIX-based operating system, the software interface to the fiber-optic-linked Computer Automated Measurement and Control system, configuration-management and real-time supervisor software, ARTSS hardware modifications, and the current implementation status. Simulation applications considered include the Transport Systems Research Vehicle, the Differential Maneuvering Simulator, the General Aviation Simulator, and the Visual Motion Simulator.

Cleveland, Jeff I., II↗
NASA NTRS1990

Film properties of high performance semi-interpenetrating polyimide networks

Consideration is given to an approach to provide a semi-IPN in which two constituent materials have nearly the same chemical structure and polymer chain length. A reactive endcapped LARC-TPI polyamic acid having a formulated molecular weight of 20,000 is prepared and then combined with various quantities of a commercial LARC-TPI polyamic acid solution. The polyimide films of semi-IPNs are tested along with two constituent materials. The physical and mechanical properties of the polyimide films are presented. The applicability of using this approach to minimize phase separation and to maximize long-term phase stability is discussed. The concept of controlling morphology by chemistry is proven for providing LARC-TPI based semi-2-IPNs. A very long chain LARC-TPI endcapped with a nadic group exhibits physical properties almost identical to unendcapped LARC-TPI.

Gerber, M. K.↗
NASA NTRS1991

A two-time-scale autopilot for high-performance aircraft

A two-time-scale autopilot is proposed for the Aircraft Controls Design Challenge problem. This control law uses a nonlinear aircraft model constructed from the given vehicle simulation. The vehicle model is partitioned into slow translational dynamics and fast rotational dynamics. Feedback linearization is then employed to synthesize control laws for these two-time scales. Due to the nature of the synthesis, the control law is suitable for automatic trajectory following, and also for pilot control.

Menon, P. K. A.↗
NASA NTRS1991

Strategies for large scale structural problems on high-performance computers

Novel computational strategies are presented for the analysis of large and complex structures. The strategies are based on generating the response of the complex structure using large perturbations from that of a simpler model, associated with a simpler structure (or a simpler mathematical/discrete model of the original structure). Numerical examples are presented to demonstrate the effectiveness of the strategies developed.

Noor, Ahmed K.↗
NASA NTRS1991

Rotordynamic Instability Problems in High-Performance Turbomachinery, 1990

The present workshop continues to report field experience and experimental results, and it expands the use of computational and control techniques with the integration of damper, bearing, and eccentric seal operation results. The intent of the workshop was to provide a continuing impetus for an understanding and resolution of these problems.

Source record↗
NASA NTRS1990

A parallel-vector algorithm for rapid structural analysis on high-performance computers

A fast, accurate Choleski method for the solution of symmetric systems of linear equations is presented. This direct method is based on a variable-band storage scheme and takes advantage of column heights to reduce the number of operations in the Choleski factorization. The method employs parallel computation in the outermost DO-loop and vector computation via the loop unrolling technique in the innermost DO-loop. The method avoids computations with zeros outside the column heights, and as an option, zeros inside the band. The close relationship between Choleski and Gauss elimination methods is examined. The minor changes required to convert the Choleski code to a Gauss code to solve non-positive-definite symmetric systems of equations are identified. The results for two large scale structural analyses performed on supercomputers, demonstrate the accuracy and speed of the method.

Storaasli, Olaf O.↗