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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Experimental study of shock wave interference heating on a cylindrical leading edge at Mach 6 and 8

This paper presents the details of an experimental study of shock wave interference heating on a cylindrical leading edge representative of the cowl of a rectangular hypersonic engine inlet. The study was conducted at Mach numbers of 6.3, 6.5 and 8.0. This study has provided the first (1) detailed pressure and heat transfer rate distributions for a two-dimensional shock wave interference on a cylinder and (2) insight into the effects of temperature dependent specific heats on the phenomena. The peak pressure and heat transfer rates were 10 times the undisturbed flow stagnation point levels. The peak levels and their gradients increased with Mach number. Variation in specific heats and hence the ratio of specific heats with temperature manifest in slightly lower loads and amplification factors than for corresponding perfect gas conditions.

Wieting, Allan R.↗
NASA NTRS1988

Linear and nonlinear interpretation of CV-580 lightning data

Numerical models developed for the study of lightning strike data acquired by in-flight aircraft are applied to the data measured on the CV-580. The basic technique used is the three dimensional time domain finite difference solution of Maxwell's equations. Both linear and nonlinear models are used in the analysis. In the linear model, the lightning channel and the aircraft are assumed to form a linear time invariant system. A transfer function technique can then be used to study the response of the aircraft to a given lightning strike current. Conversely, the lightning current can be inferred from the measured response. In the nonlinear model, the conductivity of air in the vicinity of the aircraft is calculated and incorporated into the solution of the Maxwell's equations. The nonlinear model thus simulates corona formation and air breakdown. Results obtained from the models are in reasonable agreement with the measured data. This study provides another validation of the models and increases confidence that the models may be used to predict aircraft response to any general lightning strike.

Ng, Poh H.↗
NASA NTRS1989

The ultraviolet radiation environment of Antarctica - McMurdo Station during September-October 1987

Daily data from the Nimbus-7 TOMS were combined with a model of atmospheric radiative transfer to compute the time evolution of ultraviolet irradiance, at wavelengths from 290 to 350 nm, incident on McMurdo Station during September-October 1987. Large changes in column ozone occur as the polar vortex moves over the site. This is accompanied by correspondingly large variations in UV radiation at the earth's surface. At a wavelength near 305 nm, the irradiance in early October exceeds values appropriate to an unperturbed ozone layer by a factor of 5-6. As December 21 approaches, the noontime UV irradiance increases, irrespective of changes in ozone.

Lubin, Dan↗
NASA NTRS1987

Nacelle aerodynamic performance

The boundary layer transition location was measured on a nacelle shape using the sublimating chemical flow visualization technique. This technique involves coating the surface with a thin film of volatile chemical solid, which, during exposure to a free stream airflow, rapidly sublimates in the turbulent boundary layer as a result of high shear stress and high mass transfer near the surface. Transition is indicated because the chemical coating remains relatively unaffected in the laminar region due to lower shear and low mass transfer. The slow response time of the chemical in a laminar boundary allowed for two test conditions during the same flight. The aircraft was first flown at the desired airspeed and altitude with the noise source off. Once a pattern had developed, the noise source was turned on to the desired setting and a new chemical pattern was sought. In this fashion a direct comparison of the effect of the noise could be determined.

Obara, Clifford J.↗
NASA NTRS1990

Applications of ISES for meteorology

The results are summarized from an initial assessment of the potential real-time meteorological requirements for the data from Eos systems. Eos research scientists associated with facility instruments, investigator instruments, and interdisciplinary groups with data related to meteorological support were contacted, along with those from the normal operational user and technique development groups. Two types of activities indicated the greatest need for real-time Eos data: technology transfer groups (e.g., NOAA's Forecasting System Laboratory and the DOD development laboratories), and field testing groups with airborne operations. A special concern was expressed by several non-U.S. participants who desire a direct downlink to be sure of rapid receipt of the data for their area of interest. Several potential experiments or demonstrations are recommended for ISES which include support for hurricane/typhoon forecasting, space shuttle reentry, severe weather forecasting (using microphysical cloud classification techniques), field testing, and quick reaction of instrumented aircraft to measure such events as polar stratospheric clouds and volcanic eruptions.

Try, Paul D.↗
NASA NTRS1991

The role of the Remotely Augmented Vehicle (RAV) laboratory in flight research

An overview is presented of the unique capabilities and historical significance of the Remotely Augmented Vehicle (RAV) Lab at NASA-Dryden. The role is reviewed of the RAV Lab in enhancing flight test programs and efficient testing of new aircraft control laws. The history of the RAV Lab is discussed with a sample of its application using the X-29 aircraft. The RAV Lab allows for closed or open loop augmentation of the research aircraft while in flight using ground based, high performance real time computers. Telemetry systems transfer sensor and control data between the ground and the aircraft. The RAV capability provides for enhanced computational power, improved flight data quality, and alternate methods for the testing of control system concepts. The Lab is easily reconfigured to reflect changes within a flight program and can be adapted to new flight programs.

Cohen, Dorothea↗
NASA NTRS1991

Multiple shock-shock interference on a cylindrical leading edge

The details of an experimental study of shock wave interference heating on a cylindrical leading edge representative of the cowl of a rectangular hypersonic engine inlet are presented. This Mach 8 study has provided the first detailed pressure and heat transfer rate distributions on a cylinder resulting from a two-dimensional shockwave interference pattern created by two incident oblique shock waves intersecting the cylinder bow shock wave. The peak heat transfer rate was 38 times the undisturbed flow stagnation point level and occurred when the two oblique shock waves coalesced prior to intersecting the cylinder bow shock wave. Development of pressure deflection diagrams identified a new interference pattern consisting of concomitant supersonic jets separated from each other by a shear layer and submerged in the subsonic region between the bow shock wave and body.

Wieting, Allan R.↗
NASA NTRS1991

The role of the remotely augmented vehicle (RAV) laboratory in flight research

This paper presents on overview of the unique capabilities and historical significance of the Remotely Augmented Vehicle (RAV) Laboratory at the NASA Dryden Flight Research Facility. The report reviews the role of the RAV Laboratory in enhancing flight test programs and efficient testing of new aircraft control laws. The history of the RAV Laboratory is discussed with a sample of its application using the X-29 aircraft. The RAV Laboratory allows for closed- or open-loop augmentation of the research aircraft while in flight using ground-based, high performance real-time computers. Telemetry systems transfer sensor and control data between the ground and the aircraft. The RAV capability provides for enhanced computational power, improved flight data quality, and alternate methods for the testing of control system concepts. The Laboratory is easily reconfigured to reflect changes within a flight program and can be adapted to new flight programs.

Cohen, Dorothea↗
NASA NTRS1991

Formation of the protosolar nebula

Theoretical models are discussed of the collapse of a dense molecular cloud core to form the protosolar nebula that produce the sun and the planet. The theoretical models use the equations of hydrodynamics, gravitation, and radiative transfer to follow the time evolution of a cloud collapsing under its own self-gravity. Both semi-analytical and fully numerical solutions (in two and three spatial dimensions) were calculated by several workers, One challenge is to find a set of initial conditions that will lead to the formation of a suitable protosolar nebula. Detailed results are shown for 2-D models, both with and without turbulent viscosity for redistributing angular momentum, and for 3-D models investigating the strength of gravitational torques associated with nonaxisymmetry produced during the collapse phase.

Tscharnuter, Werner M.↗
NASA NTRS1992

Convergence characteristics of the multiple input, multiple output LMS algorithm

The convergence characteristics of the multiple input, multiple output LMS algorithm, as applied to active noise and vibration control systems, are examined. The mean square error during the convergence process, as well as the final converged value, are examined analytically and in computer simulation. It is shown that the ratio of number of error sensors to number of control sources has a significant influence upon both the converging and converged value of the mean square error. Other active control system variables, such as the inherent time delays and structural/acoustic transfer functions, are also shown to have a significant influence upon the convergence process.

Snyder, Scott D.↗
NASA NTRS1992

Radiation exposure predictions for short-duration stay Mars missions

The human radiation environment for several short-duration stay manned Mars missions is predicted using the Mission Radiation Calculation program, which was developed at NASA Langley Research Center. This program provides dose estimates for Galactic cosmic rays (GCR) and large and ordinary solar proton flare events for various amounts of effective spacecraft shielding and a given time history of the spacecraft's heliocentric position. The results of this study show that most of the missions can survive the most recent large flares if a 25 g/sq cm storm shelter is assumed. The dose predictions show that missions during solar minima are not necessarily the minimum dose cases, due to increased GCR contribution during this time period. The direct transfer mission studied has slightly lower doses than the outbound Venus swingby mission, with the greatest dose differences for the assumed worst case scenario. The GCR dose for a mission can be reduced by having the crew spend some fraction of its day nominally in the storm shelter.

Striepe, Scott A.↗
NASA NTRS1993

Life: Origin and evolution on Earth--How can we escape?

Exploitation of gene regulation rather than the creation of new genes has been predominantly responsible for the evolutionary advances in animals and plants that are widely recognized today. Until very recently it was not possible to examine life in the absence of gravity. We can now imagine forms of life in the universe adapting to circumstances different from those found on Earth. Our own life forms would surely become different in time if they were transferred to other planets with different conditions, including much lower or higher gravity.

Markert, Clement L.↗
NASA NTRS1995

A numerical model for dynamic wave rotor analysis

A numerical model has been developed which can predict the dynamic (and steady state) performance of a wave rotor, given the geometry and time dependent boundary conditions. The one-dimensional, perfect gas, CFD based code tracks the gasdynamics in each of the wave rotor passages as they rotate past the various ducts. The model can operate both on and off-design, allowing dynamic behavior to be studied throughout the operating range of the wave rotor. The model accounts for several major loss mechanisms including finite passage opening time, fluid friction, heat transfer to and from the passage walls, and leakage to and from the passage ends. In addition, it can calculate the amount of work transferred to and from the fluid when the flow in the ducts is not aligned with the passages such as occurs in off-design operation. Since it is one-dimensional, the model runs reasonably fast on a typical workstation. This paper will describe the model and present the results of some transient calculations for a conceptual four port wave rotor designed as a topping cycle for a small gas turbine engine.

Paxson, D. E.↗
NASA NTRS1996

STS-76 Flight Day 5

On this fifth day of the STS-76 mission, the flight crew, Cmdr. Kevin P. Chilton, Pilot Richard A. Searfoss, and Mission Specialists Shannon W. Lucid, Linda M. Godwin, Michael R. Clifford, and Ronald M. Sega, pay tribute to the late astronaut Bob Overmeyer with views from the Atlantis/Mir configuration with the Earth in the background. Atlantis astronauts, interviewed by reporters from NASA Centers and Russia during an in-orbit press conference, describe their observations of Comet Hyakutake as it continues its close pass by Earth, remarking on the comet's brilliance and visibility. The astronauts and cosmonauts also took time out from their transfer and resupply activities to talk with Charlie Gibson of 'Good Morning America'.

Source record↗
NASA NTRS1994

Toward Real Time Neural Net Flight Controllers

NASA Ames Research Center has an ongoing program in neural network control technology targeted toward real time flight demonstrations using a modified F-15 which permits direct inner loop control of actuators, rapid switching between alternative control designs, and substitutable processors. An important part of this program is the ACTIVE flight project which is examining the feasibility of using neural networks in the design, control, and system identification of new aircraft prototypes. This paper discusses two research applications initiated with this objective in mind: utilization of neural networks for wind tunnel aircraft model identification and rapid learning algorithms for on line reconfiguration and control. The first application involves the identification of aerodynamic flight characteristics from analysis of wind tunnel test data. This identification is important in the early stages of aircraft design because complete specification of control architecture's may not be possible even though concept models at varying scales are available for aerodynamic wind tunnel testing. Testing of this type is often a long and expensive process involving measurement of aircraft lift, drag, and moment of inertia at varying angles of attack and control surface configurations. This information in turn can be used in the design of the flight control systems by applying the derived lookup tables to generate piece wise linearized controllers. Thus, reduced costs in tunnel test times and the rapid transfer of wind tunnel insights into prototype controllers becomes an important factor in more efficient generation and testing of new flight systems. NASA Ames Research Center is successfully applying modular neural networks as one way of anticipating small scale aircraft model performances prior to testing, thus reducing the number of in tunnel test hours and potentially, the number of intermediate scaled models required for estimation of surface flow effects.

Jorgensen, C. C.↗
NASA NTRS2001

The Colocation, or Lack Thereof, of Deep Convection and Cold Tropopause Temperatures in the Tropical Winter Western Pacific

Recent work has suggested that dehydration near the tropical tropopause during the northern hemisphere winter is separate in place and time from the actual transfer of mass from the troposphere to the stratosphere. In fact, some work suggests that dehydration takes place in an environment where the motion is downward, with such downward motion induced either by radiative cooling over cold cloud tops or turbulent heat flux divergence due to convection. Radiative heating and cooling rates at the tropical tropopause are quite small and very sensitive to the temperature profile and underlying cloudiness. Given this, the idea of downward motion in the region of coldest temperatures and dehydration implies that coldest temperatures and underlying cloudiness are colocated. This may not necessarily be the case. This paper attempts to explore, on a preliminary basis: (1) The sensitivity of radiative heating rates at the tropical tropopause to details of the temperature profile and underlying cloudiness and (2) the relative positions of high cold clouds and cold tropopause temperatures.

Pfister, Leonhard↗
NASA NTRS2003

Exploration of Advanced Probabilistic and Stochastic Design Methods

The primary objective of the three year research effort was to explore advanced, non-deterministic aerospace system design methods that may have relevance to designers and analysts. The research pursued emerging areas in design methodology and leverage current fundamental research in the area of design decision-making, probabilistic modeling, and optimization. The specific focus of the three year investigation was oriented toward methods to identify and analyze emerging aircraft technologies in a consistent and complete manner, and to explore means to make optimal decisions based on this knowledge in a probabilistic environment. The research efforts were classified into two main areas. First, Task A of the grant has had the objective of conducting research into the relative merits of possible approaches that account for both multiple criteria and uncertainty in design decision-making. In particular, in the final year of research, the focus was on the comparison and contrasting between three methods researched. Specifically, these three are the Joint Probabilistic Decision-Making (JPDM) technique, Physical Programming, and Dempster-Shafer (D-S) theory. The next element of the research, as contained in Task B, was focused upon exploration of the Technology Identification, Evaluation, and Selection (TIES) methodology developed at ASDL, especially with regards to identification of research needs in the baseline method through implementation exercises. The end result of Task B was the documentation of the evolution of the method with time and a technology transfer to the sponsor regarding the method, such that an initial capability for execution could be obtained by the sponsor. Specifically, the results of year 3 efforts were the creation of a detailed tutorial for implementing the TIES method. Within the tutorial package, templates and detailed examples were created for learning and understanding the details of each step. For both research tasks, sample files and tutorials are attached in electronic form with the enclosed CD.

Marvis, Dimitri N.↗
NASA NTRS2003

Exploration of Advanced Probabilistic and Stochastic Design Methods

The primary objective of the three year research effort was to explore advanced, non-deterministic aerospace system design methods that may have relevance to designers and analysts. The research pursued emerging areas in design methodology and leverage current fundamental research in the area of design decision-making, probabilistic modeling, and optimization. The specific focus of the three year investigation was oriented toward methods to identify and analyze emerging aircraft technologies in a consistent and complete manner, and to explore means to make optimal decisions based on this knowledge in a probabilistic environment. The research efforts were classified into two main areas. First, Task A of the grant has had the objective of conducting research into the relative merits of possible approaches that account for both multiple criteria and uncertainty in design decision-making. In particular, in the final year of research, the focus was on the comparison and contrasting between three methods researched. Specifically, these three are the Joint Probabilistic Decision-Making (JPDM) technique, Physical Programming, and Dempster-Shafer (D-S) theory. The next element of the research, as contained in Task B, was focused upon exploration of the Technology Identification, Evaluation, and Selection (TIES) methodology developed at ASDL, especially with regards to identification of research needs in the baseline method through implementation exercises. The end result of Task B was the documentation of the evolution of the method with time and a technology transfer to the sponsor regarding the method, such that an initial capability for execution could be obtained by the sponsor. Specifically, the results of year 3 efforts were the creation of a detailed tutorial for implementing the TIES method. Within the tutorial package, templates and detailed examples were created for learning and understanding the details of each step. For both research tasks, sample files and tutorials are attached in electronic form with the enclosed CD.

Mavris, Dimitri N.↗