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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 685 records · Page 38

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NASA NTRS1982

Implementation of the DAST ARW II control laws using an 8086 microprocessor and an 8087 floating-point coprocessor

A 5 MHZ single-board microprocessor system which incorporates an 8086 CPU and an 8087 Numeric Data Processor is used to implement the control laws for the NASA Drones for Aerodynamic and Structural Testing, Aeroelastic Research Wing II. The control laws program was executed in 7.02 msec, with initialization consuming 2.65 msec and the control law loop 4.38 msec. The software emulator execution times for these two tasks were 36.67 and 61.18, respectively, for a total of 97.68 msec. The space, weight and cost reductions achieved in the present, aircraft control application of this combination of a 16-bit microprocessor with an 80-bit floating point coprocessor may be obtainable in other real time control applications.

Kelly, G. L.↗

NASA NTRS1982

Portable design rules for bulk CMOS

It is pointed out that for the past several years, one school of IC designers has used a simplified set of nMOS geometric design rules (GDR) which is 'portable', in that it can be used by many different nMOS manufacturers. The present investigation is concerned with a preliminary set of design rules for bulk CMOS which has been verified for simple test structures. The GDR are defined in terms of Caltech Intermediate Form (CIF), which is a geometry-description language that defines simple geometrical objects in layers. The layers are abstractions of physical mask layers. The design rules do not presume the existence of any particular design methodology. Attention is given to p-well and n-well CMOS processes, bulk CMOS and CMOS-SOS, CMOS geometric rules, and a description of the advantages of CMOS technology.

Griswold, T. W.↗

NASA NTRS1983

Determination of Elevator and Rudder Hinge Forces on the Learjet Model 55 Aircraft

The empennage structure on the Learjet 55 aircraft was quite similar to the empennage structure on earlier Learjet models. However, due to an important structural change in the vertical fin along with the new loads environment on the 50 series aircraft, a structural test was required on the vertical fin, but the horizontal tail was substantiated by a comparative analysis with previous tests. NASTRAN analysis was used to investigate empennage deflections, stress levels, and control surface hinge forces. The hinge force calculations were made with the control surfaces in the deflected as well as undeflected configurations. A skin panel buckling analysis was also performed, and the non-linear effects of buckling were simulated in the NASTRAN model to more accurately define internal loads and stress levels. Comparisons were then made between the Model 55 and the Model 35/36 stresses and internal forces to determine which components were qualified by previous tests. Some of the methods and techniques used in this analysis are described.

Boroughs, R. R.↗

NASA NTRS1983

30/20 GHz spacecraft GaAs FET solid state transmitter for trunking and customer-premise-service application

Sixteen 30 dB 0.5 W amplifier modules were combined to satisfy the requirement for a graceful degradation. If one module fails, the output power drops by only 0.43 dB. Also, by incorporating all the gain stages within the combiner the overall combining efficiency is maximized. A 16 way waveguide divider combiner was developed to minimize the insertion loss associated with such a large corporate feed structure. Tests showed that the 16 way insertion loss was less than 0.5 dB. To minimize loss, a direct transition from waveguide to microstrip, using a finline on duroid substrate, was developed. The FETs fabricated on MBE grown material, demonstrated superior performances. For example, a 600 micrometer device was capable of 320 mW output power with 5 dB gain and 26.6% efficiency at 21 GHz. The 16 module amplifier gave 8.95 W saturated output power with 30 dB gain. The overall efficiency was 9%. The 3 dB bandwidth was 2.5 GHz. At 17.7 GHz the amplifier had 5 W output power and at 20.2 GHz it still had 4.4 W.

Saunier, P.↗

NASA NTRS1985

Space shuttle flight readiness firing dress rehearsal for STS-1

The static firing of the Space Shuttle Main Engine in preparation for the launch of the Enterprise Orbiter is discussed. The following were also tested: structures and mechanics; thermal design integration; propulsion and power; avionics and software; guidance, navigation, and control; mechanical systems; communications and tracking; and integrated ground systems.

Riles, W. L.↗

NASA NTRS1982

Capillary Pump Loop (CPL) heat pipe development status report

The capillary pump loop (CPL) was re-introduced as a potential candidate for the management of large heat loads. It is currently being evaluated for application in the thermal management of large space structures. Test efforts were conducted to establish the feasibility of the CPL heat pipe design.

Source record↗

NASA NTRS1985

Application of homomorphic signal processing to stress wave factor analysis

The stress wave factor (SWF) signal, which is the output of an ultrasonic testing system where the transmitting and receiving transducers are coupled to the same face of the test structure, is analyzed in the frequency domain. The SWF signal generated in an isotropic elastic plate is modelled as the superposition of successive reflections. The reflection which is generated by the stress waves which travel p times as a longitudinal (P) wave and s times as a shear (S) wave through the plate while reflecting back and forth between the bottom and top faces of the plate is designated as the reflection with p, s. Short-time portions of the SWF signal are considered for obtaining spectral information on individual reflections. If the significant reflections are not overlapped, the short-time Fourier analysis is used. A summary of the elevant points of homomorphic signal processing, which is also called cepstrum analysis, is given. Homomorphic signal processing is applied to short-time SWF signals to obtain estimates of the log spectra of individual reflections for cases in which the reflections are overlapped. Two typical SWF signals generated in aluminum plates (overlapping and non-overlapping reflections) are analyzed.

Karagulle, H.↗

NASA NTRS1985

Processing technology for high efficiency silicon solar cells

Recent advances in silicon solar cell processing have led to attainment of conversion efficiency approaching 20%. The basic cell design is investigated and features of greatest importance to achievement of 20% efficiency are indicated. Experiments to separately optimize high efficiency design features in test structures are discussed. The integration of these features in a high efficiency cell is examined. Ion implantation has been used to achieve optimal concentrations of emitter dopant and junction depth. The optimization reflects the trade-off between high sheet conductivity, necessary for high fill factor, and heavy doping effects, which must be minimized for high open circuit voltage. A second important aspect of the design experiments is the development of a passivation process to minimize front surface recombination velocity. The manner in which a thin SiO2 layer may be used for this purpose is indicated without increasing reflection losses, if the antireflection coating is properly designed. Details are presented of processing intended to reduce recombination at the contact/Si interface. Data on cell performance (including CZ and ribbon) and analysis of loss mechanisms are also presented.

Spitzer, M. B.↗

NASA NTRS1984

Neutral buoyancy evaluation of technologies for space station external operations

In order to perform a complete systems analysis for almost any large space program, it is vital to have a thorough understanding of human capabilities in extravehicular activity (EVA). The present investigation is concerned with the most significant results from the MIT Space Systems Lab's neutral buoyancy tests. An evaluation of neutral buoyancy is considered along with the tested structures, aspects of learning, productivity, time and motion analysis, and assembly loads. Attention is given to EVA assembly with a manned maneuvering unit, teleoperated structural assembly, an integrated control station, a beam assembly teleoperator, and space station proximity operations.

Akin, D. L.↗

NASA NTRS1985

Experimental study of the minority-carrier transport at the polysilicon-monosilicon interface

This paper presents the results of an experimental study designed to explore both qualitatively and quantitatively the mechanism of the improved current gain in bipolar transistors with polysilicon emitter contacts. Polysilicon contacts were deposited and heat treated at different conditions. The electrical properties were measured using p-n junction test structures that are much more sensitive to the contact properties than are bipolar transistors. A simple phenomenological model was used to correlate the structural properties with electrical measurements. Possible transport mechanisms are examined and estimates are made about upper bounds on transport parameters in the principal regions of the devices. The main conclusion of this study is that the minority-carrier transport in the polycrystalline silicon is dominated by a highly disordered layer at the polysilicon-monosilicon interface characterized by very low minority-carrier mobility. The effective recombination velocity at the n(+) polysilicon-n(+) monosilicon interface was found to be a strong function of fabrication conditions. The results indicate that the recombination velocity can be much smaller than 10,000 cm/s.

Neugroschel, A.↗

NASA NTRS1983

Evaluation of laminar flow control systems concepts for subsonic commercial transport aircraft

An evaluation was made of laminar flow control (LFC) system concepts for subsonic commercial transport aircraft. Configuration design studies, performance analyses, fabrication development, structural testing, wind tunnel testing, and contamination-avoidance techniques were included. As a result of trade studies, a configuration with LFC on the upper wing surface only, utilizing an electron beam-perforated suction surface, and employing a retractable high-lift shield for contamination avoidance, was selected as the most practical LFC system. The LFC aircraft was then compared with an advanced turbulent aircraft designed for the same mission. This comparison indicated significant fuel savings and reduced direct operating cost benefits would result from using LFC.

Pearce, W. E.↗

NASA NTRS1985

Fault models

A major problem in the qualification of integrated circuit cells and in the development of adequate tests for the circuits is to lack of information on the nature and density of fault models. Some of this information is being obtained from the test structures. In particular, the Pinhole Array Capacitor is providing values for the resistance of gate oxide shorts, and the Addressable Inverter Matrix is providing values for parameter distributions such as noise margins. Another CMOS fault mode, that of the open-gated transistor, is examined and the state of the transistors assessed. Preliminary results are described for a number of open-gated structures such as transistors, inverters, and NAND gates. Resistor faults are applied to various CMOS gates and the time responses are noted. The critical value for the resistive short to upset the gate response was determined.

Sayah, H. R.↗

NASA NTRS1985

High-efficiency silicon solar cells

Fabrication and characterization of high-efficiency metal insulator, n-p (MINP) cells is described. Particular attention was paid to development of measurement methods for surface recombination and density of surface states. A modified Rosier test structure was used successfully for density of surface states. Silicon oxide and silicon nitride passivants were studied. Heat treatment after plasma enhanced chemical vapor deposition (CVD) of silicon nitride was shown to be beneficial. A more optimum emitter concentration profile was modeled.

Olsen, L. C.↗

NASA NTRS1985

Application of homomorphic signal processing to stress wave factor analysis

The stress wave factor (SWF) signal, which is the output of an ultrasonic testing system where the transmitting and receiving transducers are coupled to the same face of the test structure, is analyzed in the frequency domain. The SWF signal generated in an isotropic elastic plate is modelled as the superposition of successive reflections. The reflection which is generated by the stress waves which travel P times as a longitudinal (P) wave and s times as a shear (S) wave through the plate while reflecting back and forth between the bottom and top faces of the plate is designated as the reflection with P, s. Short-time portions of the SWF signal are considered for obtaining spectral information on individual reflections. If the significant reflections are not overlapped, the short-time Fourier analysis is used. A summary of the elevant points of homomorphic signal processing, which is also called cepstrum analysis, is given. Homomorphic signal processing is applied to short-time SWF signals to obtain estimates of the log spectra of individual reflections for cases in which the reflections are overlapped. Two typical SWF signals generated in aluminum plates (overlapping and non-overlapping reflections) are analyzed.

Williams, J. H., Jr.↗

NASA NTRS1986

Direct experimental determination of voltage across high-low junctions

High-low (HL) junctions form a part of many semiconductor devices, including back surface field solar cells. A first experimental determination and interpretation of the voltage across the HL junction under low- and high-injection conditions is presented as a function of the voltage across a nearby p/n junction. Theoretical analysis from first principles is shown to bear well on the experimental results. In addition, a test structure is proposed for measurement of the effective surface recombination velocity at the HL junctions.

Daud, T.↗

NASA NTRS1987

Measuring Conductor Widths and Spacings Electrically

Widths and spacings of conductor lines on integrated circuits measured electrically by split cross-bridge resistor technique. Speeds evaluation of integrated-circuit fabrication processes. When measurement of probe currents and voltages and reduction of measurement data automated, test structure probed and characterized in less than one second.

Buehler, Martin G.↗

NASA NTRS1986

The split-cross-bridge resistor for measuring the sheet resistance, linewidth, and line spacing of conducting layers

A new test structure was developed for evaluating the line spacing between conductors on the same layer using an electrical measurement technique. This compact structure can also be used to measure the sheet resistance, linewidth, and line pitch of the conducting layer. Using an integrated-circuit fabrication process, this structure was fabricated in diffused polycrystalline silicon and metal layers and measured optically and electrically. For the techniques used, the optical measurements were typically one-quarter micron greater than the electrical measurements. Most electrically measured line pitch values were within 2 percent of the designed value. A small difference between the measured and designed line pitch is used to validate sheet resistance, linewidth, and line spacing values.

Buehler, M. G.↗

NASA NTRS1986

Application of multiple objective optimization techniques to finite element model tuning

This report examines tuning a finite element model using vector optimization techniques. Structural models using finite element theory often need to be adjusted so they can accurately simulate the real structure. The goal is to tune the model such that it will reproduce data derived from structural tests. First, the performance indices are extremized using multiple objective optimization theory, producing a set of possible solutions. Next, the solutions are rank ordered according to a decision maker's preferences to select the best answer. The tuning process was applied to a T-38 horizontal stabilizer. Numerous weighted solutions contained a best static deformation model, a best frequency model and three intermediate combinations of these two models. This automated procedure proved to be a versatile method capable of producing solutions for many types of tuning problems.

Devore, Charles R.↗