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At least 1,027 records · Page 57

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NASA NTRS1983

Effects of nacelle position and shape on performance of subsonic cruise aircraft

The reduction of installed-propulsion-system drag by installing circular and D-shaped-cross-section nacelles in an underwing-aft position is investigated experimentally in the NASA-Langley 16-foot transonic wind tunnel. Measurements were made at Mach 0.70 to 0.85, -2.5 to 4.1-deg angle of attack, and 3.4 to 4.0 million/ft Reynolds numbers using the NASA USB full-span transonic transport model; and results were compared with those for the wing-body and underwing-forward/pylon-mounted-nacelle (UTW) configurations. While all nacelle configurations are found to have interference drag, which can probably be reduced by eliminating supersonic flows, both aft configurations are shown to reduce drag relative to UTW and increase lift coefficients. The aft D-nacelle had the lowest drag, 6.8 percent of airplane drag lower than UTW at Mach 8.0 and lift coefficient 0.45. Wing pressure distributions and the effects of deflectors are discussed.

Bangert, L. H.↗

NASA NTRS1985

High-Pressure Coupling for Open-Ended Tubes

Temporary fitting easily installed and removed without damage to tubes. Tube-end pressure coupling consists of few parts easy to install and remove. Couplings useful mainly for repeated temporary connections necessary for high pressure testing or prestressing of tubes with finished ends.

Anderson, A. N.↗

NASA NTRS1983

Flight service evaluation of advanced composite ailerons on the L-1011 transport aircraft

Flight service evaluation of composite inboard ailerons on the L-1011 are covered. Four shipsets of graphite/epoxy composite inboard ailerons were installed on L-1011 aircraft for this maintenance evaluation program. These include two Delta aircraft and two TWA aircraft. A fifth shipset of composite ailerons were installed in 1980 on Lockheed's flight test L-1011. A visual inspection was also conducted on these components. No visible damage was observed on any of the composite ailerons, and no maintenance action has occurred on any of the parts except for repainting of areas with paint loss. Flight hours on the airline components at the time of inspection ranged from 2886 to 4190 hours, after approximately 1 year of service.

Stone, R. H.↗

NASA NTRS1983

Upgrading and performance of the SAO laser ranging system in Matera

The performance of the SAO lasers was improved considerably in terms of accuracy, range noise, data yield, and reliability. With the narrower laser pulse (2.5-3.0 nsec) and a new analog pulse processing system, the systematic range errors were reduced to 3-5 cm and range noise has been reduced to 5-15 cm on low satellites and 10-18 cm on Lageos. Pulse repetition rate was increased to 30 ppm and considerable improvement has been made in signal-to-noise ratio by using a 3 Angstrom interference filter and by reducing the range gate window down to 200-400 nsec. The first upgraded system was installed in Arequipa, Peru in the spring of 1982. The second upgraded system is now in operation in Matera, Italy. The third system is expected to be installed in Israel during 1984.

Maddox, J.↗

NASA NTRS1983

Remarks on the layout of the subsonic free jet wind tunnels

By means of a recently installed wind tunnel with a circular free jet, it is shown that requirements concerning the flow parameters (e.g., uniform velocity profile and uniform and low turbulence level in the nozzle exit) can be easily and at moderate expenses fulfilled without changing the settling chamber and the nozzle itself. The installations in the settling chamber are adjustable. The structure is not limited to settling chambers with a circular cross section.

Vagt, J. D.↗

NASA NTRS1984

V/STOL wind-tunnel testing

Factors influencing effective program planning for V/STOL wind-tunnel testing are discussed. The planning sequence itself, which includes a short checklist of considerations that could enhance the value of the tests, is also described. Each of the considerations, choice of wind tunnel, type of model installation, model development and test operations, is discussed, and examples of appropriate past and current V/STOL test programs are provided. A short survey of the moderate to large subsonic wind tunnels is followed by a review of several model installations, from two-dimensional to large-scale models of complete aircraft configurations. Model sizing, power simulation, and planning are treated, including three areas is test operations: data-acquisition systems, acoustic measurements in wind tunnels, and flow surveying.

Koenig, D. G.↗

NASA NTRS1983

AC propulsion system for an electric vehicle, phase 2

A second-generation prototype ac propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the Contractor's site. The system consisted of a Phase 2, 18.7 kw rated ac induction traction motor, a 192-volt, battery powered, pulse-width-modulated, transistorized inverter packaged for under rear seat installation, a 2-axis, 2-speed, automatically-shifted mechanical transaxle and a microprocessor-based powertrain/vehicle controller. A diagnostics computer to assist tuning and fault finding was fabricated. Dc-to-mechanical-system efficiency varied from 78% to 82% as axle speed/torque ranged from 159 rpm/788 nm to 65 rpm/328 nm. Track test efficiency results suggest that the ac system will be equal or superior to dc systems when driving urban cycles. Additional short-term work is being performed under a third contract phase (AC-3) to raise transaxle efficiency to predicted levels, and to improve starting and shifting characteristics. However, the long-term challenge to the system's viability remains inverter cost. A final report on the Phase 2 system, describing Phase 3 modifications, will be issued at the conclusion of AC-3.

Slicker, J. M.↗

NASA NTRS1984

An experimental investigation of the effect of boundary layer refraction on the noise from a high-speed propeller

Models of supersonic propellers were previously tested for acoustics in the Lewis 8- by 6-Foot Wind Tunnel using pressure transducers mounted in the tunnel ceiling. The boundary layer on the tunnel ceiling is believed to refract some of the propeller noise away from the measurement transducers. Measurements were made on a plate installed in the wind tunnel which had a thinner boundary layer than the ceiling boundary layer. The plate was installed in two locations for comparison with tunnel ceiling noise data and with fuselage data taken on the NASA Dryden Jetstar airplane. Analysis of the data indicates that the refraction increases with: increasing boundary layer thickness; increasing free stream Mach number; increasing frequency; and decreasing sound radiation angle (toward the inlet axis). At aft radiation angles greater than about 100 deg there was little or no refraction. Comparisons with the airplane data indicated that not only is the boundary layer thickness important but also the shape of the velocity profile. Comparisons with an existing two-dimensional theory, using an idealized shear layer to approximate the boundary layer, showed that the theory and data had the same trends. Analysis of the data taken in the tunnel at two different distances from the propeller indicates a decay with distance in the wind tunnel at high Mach numbers but the decay at low Mach numbers is not as clear.

Dittmar, J. H.↗

NASA NTRS1982

The design and development of a rectangular, shingle-type photovoltaic module

A shingle-type photovoltaic module has been designed and developed to meet the requirements of specifications for residential applications. The module is ideally suited for installation directly to the sheathing of a sloping, south-facing roof of a residential, industrial, or commercial building. The design requirements are examined, taking into account also module safety requirements. Aspects of module design and analysis are discussed, giving attention to installation details, solar cells and electrical circuit design, the encapsulation system, substrate lamination, and the module-to-module interconnecting cable. Details of module assembly experience and test and outdoor exposure experience are also considered.

Shepard, N. F., Jr.↗

NASA NTRS1983

Application of laser anemometry to cryogenic wind tunnels

The installation and tests conducted with the laser Doppler and transit anemometer in the 0.3-Meter Transonic Cryogenic Tunnel are described. Using residual particulates in the flow field, a series of free stream velocity measurements were conducted which agreed to within 1-percent of predicted values for a range of Mach numbers, 0.2 to 0.85, and temperatures, 100 to 250 K. Measurements about a shock wave provided an estimate of scattering particulate size of 4 microns or less. The particle concentration is approximately 3 x 10 to the 5th to 1.6 x 10 to the 6th/cu m. Necessary isolation of the plenum wall windows from ambient air with slightly positive pressure of dry nitrogen gas to prevent condensation on the window surface was achieved. This was accomplished through the use of large enclosures fixed to the tunnel wall. A second method used an additional sheet of thin plate glass to create the dry gas pocket next to the plenum window. The installation of a laser anemometer in the National Transonic Facility is examined. The laser transit anemometer has been tentatively selected for the initial entry because of its compact laser-optics package.

Hunter, W. W., Jr.↗

NASA NTRS1982

Cost estimates for flat plate and concentrator collector arrays

The current module and installation costs for the U.S. National Photovoltaic Program's grid-connected systems are significantly higher than required for economic viability of this alternative. Attention is accordingly given to the prospects for installed module cost reductions in flat plate, linear focus Fresnel concentrator, and point focus Fresnel concentrator candidate systems. Cost projections indicate that all three systems would meet near-term and midterm goals, provided that module costs of $2.80/W(p) and $0.70/W(p), respectively, are met. The point focus Fresnel system emerges as the most viable for the near term.

Shimada, K.↗

NASA NTRS1985

Improved Highway Pads for Tracked Vehicles

New pads attach faster and hold more securely than conventional pads. Rubber pad held on tread by bent locking tab and by lip that engages recess in tread. Tab hammered in during installation and pried out during removal. New designs ease installation of rubber pads on treads of tracked vehicles to prevent damage to highways. Designs apply to bulldozers, cranes, and excavating machines.

Collins, Earl R., Jr.↗

NASA NTRS1986

Smoothed Two-Dimensional Edges for Laminar Flow

New concept allows passive method for installing flaps, slats, iceprotection equipment, and other leading-edge devices on natural-laminar-flow (NLF) wings without causing loss of laminar flow. Two-dimensional roughness elements in laminar boundary layers strategically shaped to increase critical (allowable) height of roughness. Facilitates installation of leading-edge devices by practical manufacturing methods.

Holmes, B. J.↗

NASA NTRS1982

Combustion system for radiation investigations

An inlet interface flange, inlet diffuser, fuel struts and nozzles, combustor liner, liner housing and exhaust flange comprise a system to be installed in an existing test facility. The system was designed for operation at 40 atmospheres inlet pressure, 900 K inlet temperature, and air flow to 80 kg/sec. Six penetrations are provided in the outer pressure housing. Adapters at the penetrations, permit use of various types of radiation instrumentation. Five total radiation radiometers and two heat flux gases were installed. Rotating exhaust instrumentation can also be used to determine combustor performance. Data are presented showing total radiation at three axial positions of the combustor, and comparison of total radiation with data from a heat flux gage.

Wear, J. D.↗

NASA NTRS1982

Development and flight evaluation of an augmented stability active controls concept: Executive summary

A pitch active control system (PACS) was developed and flight tested on a wide body jet transport (L-1011) with a flying horizontal stabilizer. Two dual channel digital computers and the associated software provide command signals to a dual channel series servo which controls the stabilizer power actuators. Input sensor signals to the computer are pitch rate, column trim position, and dynamic pressure. Control laws are given for the PACS and the system architecture is defined. Discussions are given regarding piloted flight simulation and vehicle system simulation and vehicle system simulation tests that are performed to verify control laws and system operation prior to installation on the aircraft. Modifications to the basic aircraft included installation of the PACS, addition of a c.g. management system to provide a c.g. range from 25 to 39% mac, and downrigging of the geared elevator to provide the required nose down control authority for aft c.g. flight test conditions. Three pilots used the Cooper-Harper Rating Scale to judge flying qualities of the aircraft with PACS on and off. The handling qualities with the c.g. at 39% mac (41% stability margin) and PACS operating were judged to be as good as the handling qualities with the c.g. at 25% mac (+15% stability margin) and PACS off.

Guinn, W. A.↗

NASA NTRS1984

Second Sailplane Project: The RP-2

Progress has been made on the design fabrication and installation of a tension carry-through linkage between the aft parts of the port and starboard wings to resist forward bending deflection on the RP-2 sailplane. In addition, towhook/release mechanisms, landing gear and wheel brake assembly, compound curved sandwich composite fuselage shells and an enclosed trailer to house and transport the complete disassembled aircraft, have all undergone various stages of design, fabrication, installation and testing.

Source record↗

NASA NTRS1984

Orbital transfer vehicle propulsion issues

The development of a reusable and space-based orbital transfer vehicle (OTV) necessitates an integral approach toward structural and propulsion subsystems design. A single engine installation necessitates moving the engine further aft and/or relocation of the engine gimbal point to accommodate vehicle control requirements. Penalties associated with gimbal point relocation without increasing stage length or modifying typical advanced engine concepts, as well as a method for minimizing such penalties, are presented for a single engine toroidal tank OTV configuration. Alternative integrated vehicle structure/engine concepts are also presented for multi-engine configurations. Features of these potential concepts are given which indicate the need for substantial additional study of feedline gimbal alternatives before firmly establishing advanced engine design. The issue of vehicle/engine integration is addressed in three areas: interfaces (physical and functional), installation requirements, and reliability apportionment (i.e., number of engines required to assure mission completion).

Bergeron, R. P.↗

NASA NTRS1984

Flight service evaluation of advanced composite ailerons on the L-1011 transport aircraft

A flight service evaluation of composite inboard ailerons on the L-1011 is discussed. This is the second annual report of the maintenance evaluation program, and covers the period from July 1983 when the first yearly inspections were completed, through July 1984. Four shipsets of graphite/epoxy composite ailerons were installed on L-1011 aircraft for this maintenance evaluation program. These include two Delta aircraft and two TWA aircraft. A fifth shipset of composite ailerons were installed in 1980 on Lockheed's flight test L-1011. A visual inspection was also conducted on these components. No visible damage was observed on any of the composite ailerons, and no maintenance action has occurred on any of the composite parts except for repainting of areas with paint loss. Flight hours on the airline components at the time of inspection ranged from 6318 to 6989 hours, after approximately 2 years of service.

Stone, R. H.↗