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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Materials experiment carrier concepts definition study. Volume 3: Programmatics, part 2

Project logic, schedule and funding information was derived to enable decisions to be made regarding implementation of MEC system development. A master schedule and cost and price estimates (ROM) were developed for a project that consists of development of an all-up MEC, its integration with payloads and its flight on one 90 day mission. In Part 2 of the study a simple initial MEC was defined to accommodate three MPS baseline payloads. The design of this initial MEC is illustrated. The project logic, detailed schedules, and ROM cost estimate relate to a project in which this initial MEC is developed, integrated with payloads and flown once for 180 days.

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NASA NTRS1983

Flight evaluation of modifications to a digital electronic engine control system in an F-15 airplane

The third phase of a flight evaluation of a digital electronic engine control system in an F-15 has recently been completed. It was found that digital electronic engine control software logic changes and augmentor hardware improvements resulted in significant improvements in engine operation. For intermediate to maximum power throttle transients, an increase in altitude capability of up to 8000 ft was found, and for idle to maximum transients, an increase of up to 4000 ft was found. A nozzle instability noted in earlier flight testing was investigated on a test engine at NASA Lewis Research Center, a digital electronic engine control software logic change was developed and evaluated, and no instability occurred in the Phase 3 flight evaluation. The backup control airstart modification was evaluated, and gave an improvement of airstart capability by reducing the minimum airspeed for successful airstarts by 50 to 75 knots.

Burcham, F. W., Jr.↗
NASA NTRS1983

Active stabilization of a flexible antenna feed tower

Active stabilization logic is synthesized to hold a feed at the focus of a spacecraft antenna dish. The feed support structure is modeled as a tetrahedron made up of flexible bars and connected to the dish by six short legs containing force actuators. Using the symmetry of the structure, the model can be decomposed into four uncoupled subsystems: pitch/forward motions with four degrees of freedom (DOF) and two controls; roll/lateral motions with four DOF and two controls; vertical motions with three DOF and one control; and yaw motion with one DOF and one control. This greatly simplifies the synthesis of control logic.

Bryson, A. E., Jr.↗
NASA NTRS1982

Evolutionary space platform concept study. Volume 3: Programmatics for manned space platform concepts

The programmatic data for the reference concept of the Manned Space Platform is presented. Details regarding work breakdown structure (WBS) and dictionary, the facilities and equipment required to produce the modules, the project schedule and logic diagram, a preliminary assessment of environmental impacts and details regarding the estimated costs for the reference concept are included. The proposed WBS which was developed to provide summary and system level segregation of the nonrecurring and recurring portions of the Manned Space Platform project is also included. The accompanying dictionary outlines the function and activities contained within each WBS element. The facility and equipment required to produce the various modules is discussed. Generally, required equipment is within the existing state of the art although the size of some of the items to be manufactured is a consideration. A preliminary manufacturing flow was also provided. The project schedules presented consist of the Master Project Summary Schedule, the Master Project Phasing Chart and the Logic Network.

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NASA NTRS1982

Single event upset sensitivity of low power Schottky devices

Data taken from tests involving heavy ions in the Berkeley 88 in. cyclotron being directed at low power Schottky barrier devices are reported. The tests also included trials in the Harvard cyclotron with 130 MeV protons, and at the U.C. Davis cyclotron using 56 MeV protons. The experiments were performed to study the single event upsets in MSI logic devices containing flip-flops. Results are presented of single-event upsets (SEU) causing functional degradation observed in post-exposure tests of six different devices. The effectiveness of the particles in producing SEUs in logic device functioning was found to be directly proportional to the proton energy. Shielding was determined to offer negligible protection from the particle bombardment. The results are considered significant for the design and fabrication of LS devices for space applications.

Price, W. E.↗
NASA NTRS1983

Flight evaluation of modifications to a digital electronic engine control system in an F-15 airplane

The third phase of a flight evaluation of a digital electronic engine control system in an F-15 has recently been completed. It was found that digital electronic engine control software logic changes and augmentor hardware improvements resulted in significant improvements in engine operation. For intermediate to maximum power throttle transients, an increase in altitude capability of up to 8000 ft was found, and for idle to maximum transients, an increase of up to 4000 ft was found. A nozzle instability noted in earlier flight testing was investigated on a test engine at NASA Lewis Research Center, a digital electronic engine control software logic change was developed and evaluated, and no instability occurred in the Phase 3 flight evaluation. The backup control airstart modification was evaluated, and gave an improvement of airstart capability by reducing the minimum airspeed for successful airstarts by 50 to 75 knots.

Burcham, F. W., Jr.↗
NASA NTRS1984

Research in the design of high-performance reconfigurable systems

An initial design for the Bit Processor (BP) referred to in prior reports as the Processing Element or PE has been completed. Eight BP's, together with their supporting random-access memory, a 64 k x 9 ROM to perform addition, routing logic, and some additional logic, constitute the components of a single stage. An initial stage design is given. Stages may be combined to perform high-speed fixed or floating point arithmetic. Stages can be configured into a range of arithmetic modules that includes bit-serial one or two-dimensional arrays; one or two dimensional arrays fixed or floating point processors; and specialized uniprocessors, such as long-word arithmetic units. One to eight BP's represent a likely initial chip level. The Stage would then correspond to a first-level pluggable module. As both this project and VLSI CAD/CAM progress, however, it is expected that the chip level would migrate upward to the stage and, perhaps, ultimately the box level. The BP RAM, consisting of two banks, holds only operands and indices. Programs are at the box (high-level function) and system level. At the system level initial effort has been concentrated on specifying the tools needed to evaluate design alternatives.

Slotnick, D. L.↗
NASA NTRS1985

Segmented Detector for Cosmic Gamma Rays

Segmented structure distinguishes gamma rays of cosmic origin from internal radioactivity. Preamplifier and discriminator channel connects each electrically independent segment of gamma-ray detector to logic circuitry. Logic compares and analyzes events in segments to determine sources. According to Monte Carlo calculations, sensitivity of detector two to three times better than conventional detectors because background interactions discerned and eliminated.

Varnell, L. S.↗
NASA NTRS1986

Interface Circuits for Self-Checking Microprocessors

Fault-tolerant-microcomputer concept based on enhancing "simple" computer with redundancy and self-checking logic circuits detect hardware faults. Interface and checking logic and redundant processors confer on 16-bit microcomputer ability to check itself for hardware faults. Checking circuitry also checks itself. Concept of self-checking complementary pairs (SCCP's) employed throughout ICL unit.

Rennels, D. A.↗
NASA NTRS1984

Periodic binary sequence generators: VLSI circuits considerations

Feedback shift registers are efficient periodic binary sequence generators. Polynomials of degree r over a Galois field characteristic 2(GF(2)) characterize the behavior of shift registers with linear logic feedback. The algorithmic determination of the trinomial of lowest degree, when it exists, that contains a given irreducible polynomial over GF(2) as a factor is presented. This corresponds to embedding the behavior of an r-stage shift register with linear logic feedback into that of an n-stage shift register with a single two-input modulo 2 summer (i.e., Exclusive-OR gate) in its feedback. This leads to Very Large Scale Integrated (VLSI) circuit architecture of maximal regularity (i.e., identical cells) with intercell communications serialized to a maximal degree.

Perlman, M.↗
NASA NTRS1985

Fault detection and accommodation testing on an F100 engine in an F-15 airplane

The fault detection and accommodation (FDA) methodology for digital engine-control systems may range from simple comparisons of redundant parameters to the more complex and sophisticated observer models of the entire engine system. Evaluations of the various FDA schemes are done using analytical methods, simulation, and limited-altitude-facility testing. Flight testing of the FDA logic has been minimal because of the difficulty of inducing realistic faults in flight. A flight program was conducted to evaluate the fault detection and accommodation capability of a digital electronic engine control in an F-15 aircraft. The objective of the flight program was to induce selected faults and evaluate the resulting actions of the digital engine controller. Comparisons were made between the flight results and predictions. Several anomalies were found in flight and during the ground test. Simulation results showed that the inducement of dual pressure failures was not feasible since the FDA logic was not designed to accommodate these types of failures.

Myers, L. P.↗
NASA NTRS1982

Electron lithography STAR design guidelines. Part 1: The STAR user design manual

The STAR system developed by NASA enables any user with a logic diagram to design a semicustom digital MOS integrated circuit. The system is comprised of a library of standard logic cells and computer programs to place, route, and display designs implemented with cells from the library. Library cells of the CMOS metal gate and CMOS silicon gate technologies were simulated using SPICE, and the results are shown and compared.

Trotter, J. D.↗
NASA NTRS1982

Electron lithography STAR design guidelines. Part 2: The design of a STAR for space applications

The STAR design system developed by NASA enables any user with a logic diagram to design a semicustom digital MOS integrated circuit. The system is comprised of a library of standard logic cells and computr programs to place, route, and display designs implemented with cells from the library. Also described is the development of a radiation-hard array designed for the STAR system. The design is based on the CMOS silicon gate technology developed by SANDIA National Laboratories. The design rules used are given as well as the model parameters developed for the basic array element. Library cells of the CMOS metal gate and CMOS silicon gate technologies were simulated using SPICE, and the results are shown and compared.

Trotter, J. D.↗
NASA NTRS1984

Space platform expendables resupply concept definition study. Volume 3: Work breakdown structure and work breakdown structure dictionary

The work breakdown structure (WBS) for the Space Platform Expendables Resupply Concept Definition Study is described. The WBS consists of a list of WBS elements, a dictionary of element definitions, and an element logic diagram. The list and logic diagram identify the interrelationships of the elements. The dictionary defines the types of work that may be represented by or be classified under each specific element. The Space Platform Expendable Resupply WBS was selected mainly to support the program planning, scheduling, and costing performed in the programmatics task (task 3). The WBS is neither a statement-of-work nor a work authorization document. Rather, it is a framework around which to define requirements, plan effort, assign responsibilities, allocate and control resources, and report progress, expenditures, technical performance, and schedule performance. The WBS element definitions are independent of make-or-buy decisions, organizational structure, and activity locations unless exceptions are specifically stated.

Source record↗
NASA NTRS1984

F-15 digital electronic engine control system description

A digital electronic engine control (DEEC) was developed for use on the F100-PW-100 turbofan engine. This control system has full authority control, capable of moving all the controlled variables over their full ranges. The digital computational electronics and fault detection and accomodation logic maintains safe engine operation. A hydromechanical backup control (BUC) is an integral part of the fuel metering unit and provides gas generator control at a reduced performance level in the event of an electronics failure. The DEEC's features, hardware, and major logic diagrams are described.

Myers, L. P.↗
NASA NTRS1984

NASA Lewis F100 engine testing

Two builds of an F100 engine model derivative (EMD) engine were evaluated for improvements in engine components and digital electronic engine control (DEEC) logic. Two DEEC flight logics were verified throughout the flight envelope in support of flight clearance for the F100 engine model derivative program (EMPD). A nozzle instability and a faster augmentor transient capability was investigated in support of the F-15 DEEC flight program. Off schedule coupled system mode fan flutter, DEEC nose-boom pressure correlation, DEEC station six pressure comparison, and a new fan inlet variable vane (CIVV) schedule are identified.

Werner, R. A.↗
NASA NTRS1984

Airstart performance of a digital electronic engine control system on an F100 engine

The digital electronic engine control (DEEC) system installed on an F100 engine in an F-15 aircraft was tested. The DEEC system incorporates a closed-loop air start feature in which the fuel flow is modulated to achieve the desired rate of compressor acceleration. With this logic the DEEC equipped F100 engine can achieve air starts over a larger envelope. The DEEC air start logic, the test program conducted on the F-15, and its results are described.

Burcham, F. W., Jr.↗