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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Conflict Prevention and Separation Assurance Method in the Small Aircraft Transportation System

A multilayer approach to the prevention of conflicts due to the loss of aircraft-to-aircraft separation which relies on procedures and on-board automation was implemented as part of the SATS HVO Concept of Operations. The multilayer system gives pilots support and guidance during the execution of normal operations and advance warning for procedure deviations or off-nominal operations. This paper describes the major concept elements of this multilayer approach to separation assurance and conflict prevention and provides the rationale for its design. All the algorithms and functionality described in this paper have been implemented in an aircraft simulation in the NASA Langley Research Center s Air Traffic Operation Lab and on the NASA Cirrus SR22 research aircraft.

Consiglio, Maria C.↗
NASA NTRS1972

A Flying Ejection Seat

To increase aircrewmen's chances for safe rescue in combat zones, the armed forces are investigating advanced escape and rescue concepts that will provide independent flight after ejection and thus reduce the risk of capture. One of the candidate concepts is discussed; namely, a stowable autogyro that serves as the crewman's seat during normal operations and automatically converts to a flight vehicle after ejection. Discussed are (1) the mechanism subsystems that the concept embodies to meet the weight and cockpit-packaging constraints and (2) tests that demonstrated the technical feasibility of the stowage, deployment, and flight operation of the rotor lift system.

Hollrock, R. H.↗
NASA NTRS1994

Robotic vehicle mobility and task performance: A flexible control modality for manned systems

In the early 1980's, a number of concepts were developed for applying robotics to ground systems. The majority of these early application concepts envisioned robotics technology embedded in dedicated unmanned systems; i.e., unmanned systems with no provision for direct manned control of the platform. Although these concepts offered advantages peculiar to platforms designed from the outset exclusively for unmanned operation--i.e., no crew compartment--their findings would require costs and support for a new class of unmanned systems. The current era of reduced budgets and increasing focus on rapid force projection has created new opportunities to examine the value of an alternative concept: the use of existing manned platforms with an ability to quickly shift from normal manned operation to unmanned should a particularly harzardous situation arise. The author of this paper addresses the evolution of robotic vehicle concepts and technology testbeds from exclusively unmanned systems to a variety of 'optionally manned' systems which have been designed with minimum intrusion actuator and control equipment to minimize degradation of vehicle performance in manned modes of operation.

Eldredge, Frederick↗
NASA NTRS2024

Conceptual Design and Validation of a Bent-Perforation-Path Acoustic Liner

An acoustic liner concept is developed that increases the effective thickness of perforate sheet holes by bending the perforation paths within the facesheet. This significantly increases both the viscous-loss resistance and mass reactance properties of the acoustic liner, creating low-frequency absorption utilizing a small amount of liner volume. An initial concept is designed, 3D-printed, and tested in a normal-incidence impedance tube to verify the acoustic properties. Comparisons to an impedance model are shown with good agreement to test data, although further work needs to be done to more accurately capture the losses associated with bends within the hole. Follow-on concepts are also discussed that attempt to address the current shortcomings of the initial design.

acoustic liner perforate impedance↗
NASA NTRS1978

The effect of technology advancements on the comparative advantages of electric versus chemical propulsion for a large cargo orbit transfer vehicle

Techniques for sizing electrically or chemically propelled orbit transfer vehicles and analyzing fleet requirements are used in a comparative analysis of the two concepts for various levels of traffic to geosynchronous orbit. The vehicle masses, fuel requirements, and fleet sizes are determined and translated into launch vehicle payload requirements. Technology projections beyond normal growth are made and their effect on the comparative advantages of the concepts is determined. A preliminary cost analysis indicates that although electric propulsion greatly reduces launch vehicle requirements substantial improvements in the cost and reusability of power systems must occur to make an electrically propelled vehicle competitive.

Rehder, J. J.↗
NASA NTRS1977

Scaling a discrete structural model to match measured modal frequencies

The structure modification problem, where the computer model of a structure is to be upgraded on the basis of experimental measurements of normal mode frequencies, is approached by the modal energy concept. The modes for correlation with test data are selected on the basis of relative strain energy participation. The resulting procedure can be viewed as an extension of White's (1972) method. Its advantage lies in that both the number and choice of structural parameters to be varied in the modification are arbitrary.

Taylor, J. E.↗
NASA NTRS1984

Dual clearance squeeze film damper for high load conditions

Squeeze film dampers are widely used to control vibrations in aircraft turbine engines and other rotating machinery. However, if shaft unbalance rises appreciably above the design value (e.g., due to a turbine blade loss), a conventional squeeze film becomes overloaded, and is no longer effective in controlling vibration amplitudes and bearing forces. A damper concept characterized by two oil films is described. Under normal conditions, only one low-clearance film is active, allowing precise location of the shaft centerline. Under high unbalance conditions, both films are active, controlling shaft vibration in a near-optimum manner, and allowing continued operation until a safe shutdown can be made.

Fleming, D. P.↗
NASA NTRS1984

Stray light analysis of the Diffuse Infrared Background Experiment (DIRBE)

The straylight analysis of the diffuse infrared background experiment (DIRBE) on the cosmic background explorer (COBE) mission is discussed. From the statement of work (SOW), the purpose of DIRBE is to measure, or set upper limits on, the spectral and spatial character of the diffuse extra galactic infrared radiation. Diffuse infrared sources within our own galaxy are measured. The required reduction of the unwanted radiation imposes severe design and operating restrictions on the DIRBE instrument. To accomplish its missions, it will operate at a multitude of wavelengths ranging from 1.25 um out to 200 to 300 microns. The operating bands and the required point source normalized irradiance transmittance (PSNIT) are shown. The important straylight concepts in the DIRBE design are reviewed. The model and assumptions used in APART analysis are explained. The limitations due to the scalar theory used in the analysis are outlined.

Breault, R. P.↗
NASA NTRS1985

Dual clearance squeeze film damper for high load conditions

Squeeze film dampers are widely used to control vibrations in aircraft turbine engines and other rotating machinery. However, if shaft unbalance rises appreciably above the design value (e.g., due to a turbine blade loss), a conventional squeeze film becomes overloaded, and is no longer effective in controlling vibration amplitudes and bearing forces. A damper concept characterized by two oil films is described. Under normal conditions, only one low-clearance film is active, allowing precise location of the shaft centerline. Under high unbalance conditions, both films are active, controlling shaft vibration in a near-optimum manner, and allowing continued operation until a safe shutdown can be made.

Fleming, D. P.↗
NASA NTRS2003

Laminar Soot Processes (LSP) Experiment: Findings From Space Flight Measurements

The present experimental study of soot processes in hydrocarbon-fueled laminar nonbuoyant and nonpremixed (diffusion) flames at microgravity within a spacecraft was motivated by the relevance of soot to the performance of power and propulsion systems, to the hazards of unwanted fires, and to the emission of combustion-generated pollutants. Soot processes in turbulent flames are of greatest practical interest, however, direct study of turbulent flames is not tractable because the unsteadiness and distortion of turbulent flames limit available residence times and spatial resolution within regions where soot processes are important. Thus, laminar diffusion flames are generally used to provide more tractable model flame systems to study processes relevant to turbulent diffusion flames, justified by the known similarities of gas-phase processes in laminar and turbulent diffusion flames, based on the widely-accepted laminar flamelet concept of turbulent flames. Unfortunately, laminar diffusion flames at normal gravity are affected by buoyancy due to their relatively small flow velocities and, as discussed next, they do not have the same utility for simulating the soot processes as they do for simulating the gas phase processes of turbulent flames.

Sunderland, P. B.↗
NASA NTRS2005

The Small Aircraft Transportation System (SATS), Higher Volume Operations (HVO) Off-Nominal Operations

The ability to conduct concurrent, multiple aircraft operations in poor weather, at virtually any airport, offers an important opportunity for a significant increase in the rate of flight operations, a major improvement in passenger convenience, and the potential to foster growth of charter operations at small airports. The Small Aircraft Transportation System, (SATS) Higher Volume Operations (HVO) concept is designed to increase traffic flow at any of the 3400 nonradar, non-towered airports in the United States where operations are currently restricted to one-in/one-out procedural separation during Instrument Meteorological Conditions (IMC). The concept's key feature is pilots maintain their own separation from other aircraft using procedures, aircraft flight data sent via air-to-air datalink, cockpit displays, and on-board software. This is done within the Self-Controlled Area (SCA), an area of flight operations established during poor visibility or low ceilings around an airport without Air Traffic Control (ATC) services. The research described in this paper expands the HVO concept to include most off-nominal situations that could be expected to occur in a future SATS environment. The situations were categorized into routine off-nominal operations, procedural deviations, equipment malfunctions, and aircraft emergencies. The combination of normal and off-nominal HVO procedures provides evidence for an operational concept that is safe, requires little ground infrastructure, and enables concurrent flight operations in poor weather.

Baxley, B.↗
NASA NTRS1983

High-speed digital signal normalization for feature identification

A design approach for high speed normalization of digital signals was developed. A reciprocal look up table technique is employed, where a digital value is mapped to its reciprocal via a high speed memory. This reciprocal is then multiplied with an input signal to obtain the normalized result. Normalization improves considerably the accuracy of certain feature identification algorithms. By using the concept of pipelining the multispectral sensor data processing rate is limited only by the speed of the multiplier. The breadboard system was found to operate at an execution rate of five million normalizations per second. This design features high precision, a reduced hardware complexity, high flexibility, and expandability which are very important considerations for spaceborne applications. It also accomplishes a high speed normalization rate essential for real time data processing.

Ortiz, J. A.↗
NASA NTRS1978

Modeling and parameter uncertainties for aircraft flight control system design

As aircraft designs trend toward further applications of control-configured vehicle concepts, aircraft control systems increasingly rely on stability augmentation to obtain normal flying qualities and reasonable structural margins. Although the control system designer would choose to have a perfect dynamic description of the vehicle, he knows that a level of uncertainty of plant dynamics will exist. This paper gives typical values of plant uncertainties for some recent aircraft design and development programs. Histories of pertinent aerodynamic, inertial, and structural parameters from program initiation to aircraft certification are given. These data can be used as typical of future vehicles so that control system design concepts can be evaluated with due consideration to their sensitivity to uncertainties in plant dynamics.

Rickard, W. W.↗
NASA NTRS2001

Ceiling Fires Studied to Simulate Low-Gravity Fires

A unique new way to study low-gravity flames in normal gravity has been developed. To study flame structure and extinction characteristics in low-stretch environments, a normal gravity low-stretch diffusion flame was generated using a cylindrical PMMA sample of varying large radii, as shown in the photograph. These experiments have demonstrated that low-gravity flame characteristics can be generated in normal gravity through the proper use of scaling. On the basis of this work, it is feasible to apply this concept toward the development of an Earth-bound method of evaluating material flammability in various gravitational environments from normal gravity to microgravity, including the effects of partial gravity low-stretch rates such as those found on the Moon (1/6g) or Mars (1/3g). During these experiments, the surface regression rates for PMMA were measured for the first time over the full range of flammability in air, from blowoff at high stretch, to quenching at low stretch, as plotted in the graph. The solid line drawn through the central portion of the data (3<a<100 sec-1) has a slope of unity, which indicates regression is proportional to stretch. The figure coordinates assume that the values of stretch are equivalent, whether derived from forced stretch or from buoyant stretch. The excellent correlation of the regression-rate data over the two-order-of-magnitude variation of stretch shows the reasonableness of this assumption.

Olson, Sandra L.↗
NASA NTRS1998

Static Performance of a Wing-Mounted Thrust Reverser Concept

An experimental investigation was conducted in the Jet-Exit Test Facility at NASA Langley Research Center to study the static aerodynamic performance of a wing-mounted thrust reverser concept applicable to subsonic transport aircraft. This innovative engine powered thrust reverser system is designed to utilize wing-mounted flow deflectors to produce aircraft deceleration forces. Testing was conducted using a 7.9%-scale exhaust system model with a fan-to-core bypass ratio of approximately 9.0, a supercritical left-hand wing section attached via a pylon, and wing-mounted flow deflectors attached to the wing section. Geometric variations of key design parameters investigated for the wing-mounted thrust reverser concept included flow deflector angle and chord length, deflector edge fences, and the yaw mount angle of the deflector system (normal to the engine centerline or parallel to the wing trailing edge). All tests were conducted with no external flow and high pressure air was used to simulate core and fan engine exhaust flows. Test results indicate that the wing-mounted thrust reverser concept can achieve overall thrust reverser effectiveness levels competitive with (parallel mount), or better than (normal mount) a conventional cascade thrust reverser system. By removing the thrust reverser system from the nacelle, the wing-mounted concept offers the nacelle designer more options for improving nacelle aero dynamics and propulsion-airframe integration, simplifying nacelle structural designs, reducing nacelle weight, and improving engine maintenance access.

Asbury, Scott C.↗
NASA NTRS1975

Experiments on solar photovoltaic power generation using concentrator and liquid cooling

Calculations and experimental data are presented leading to the development of a practical, economical solar photovoltaic power supply. The concept involves concentration of sunlight up to about 100 times normal solar intensity in a solar tracking collector and directing this to an array of solar cells. The cells are immersed in water circulated from a thermal reservoir which limits cell temperature rise to about 20 C above ambient during the day and which cools to ambient temperature during the night. Experiments were conducted on solar cells using a Fresnel lens for magnification, a telescope equatorial mount with clock drive, and tap water circulated through the solar cell holder cavity. Test results show that cells operate satisfactorily under these conditions. Power outputs achieved experimentally with cell optimized for 25 suns were linear with concentration to about 15 suns. Cells optimized for 100 suns were not available, but a corresponding linear relation of power output with concentration is anticipated. Test results have been used in a design analysis of the cost of systems utilizing this technique.

Beam, B. H.↗