SEARCH · Search NASA

Results for “tandems”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29

All sources NASA NTRS DOE OSTI

NASA NTRS1992

High-speed civil transport - Advanced flight deck challenges

This paper presents the results of a nine month study of the HSCT flight deck challenges and assessment of its benefits. Operational requirements are discussed and the most significant findings for specified advanced concepts are highlighted. These concepts are a no nose-droop configuration, a far forward cockpit location and advanced crew monitoring and control of complex systems. Results indicate that the no nose-droop configuration is critically dependent on the design and development of a safe, reliable and certifiable synthetic vision system (SVS). This configuration would cause significant weight, performance and cost penalties. A far forward cockpit configuration with a tandem seating arrangement allows either an increase in additional payload or potential downsizing of the vehicle leading to increased performance efficiency and reductions in emissions. The technologies enabling such capabilities, which provide for Category III all-weather opreations on every flight represent a benefit multiplier in a 20005 ATM network in terms of enhanced economic viability and environmental acceptability.

Swink, Jay R.↗

NASA NTRS1991

Display format and highlight validity effects on search performance using complex visual displays

Display format and highlight validity were shown to affect visual display search performance; however, these studies were conducted on small, artificial displays of alphanumeric stimuli. A study manipulating these variables was conducted using realistic, complex Space Shuttle information displays. A 2x2x3 within-subjects analysis of variance found that search times were faster for items in reformatted displays than for current displays. The significant format by highlight validity interaction showed that there was little difference in response time to both current and reformatted displays when the highlight validity was applied; however, under the non or invalid highlight conditions, search times were faster with reformatted displays. Benefits of highlighting and reformatting displays to enhance search and the necessity to consider highlight validity and format characteristics in tandem for predicting search performance are discussed.

Donner, Kimberly A.↗

NASA NTRS1993

The Stickney impact of Phobos - A dynamical model

The hypervelocity impact that excavated the Stickney crater on Phobos is numerically modeled in order to understand the effects this collision had on the interior and surface of Phobos. The model assumes homogeneity prior to impact based on Fujiwara's (1991) results. Constitutive relations for water ice and basalt are applied in tandem models. Fracture energetics is used to show that the impact itself is sufficient to cause the cracks observed on Phobos. It is further shown that the Stickney impact itself could not have created large voids; thus, the low density of Phobos must either be compositional in nature or else the result of porosity at a scale sufficiently small to avoid scattering the impact energy substantially.

Asphaug, E.↗

NASA NTRS1991

High-dynamic-range MCP structures

We report on the development of a new high-dynamic-range two-stage Multi-Anode Microchannel Array (MAMA) imaging tube designed for improved high count rate performance at FUV and EUV wavelengths. The new two-stage MAMA tube employs two 25-mm-diameter format MCPs placed in tandem with a small gap between the plates. The front (input) MCP is designed to be a low-gain converter plate that supports an opaque photocathode and converts the detected photons to electrons, while the second (output) MCP is of higher conductivity and thus maintains the overall gain of the multiplier at high count rates. The second MCP is mounted in proximity focus with a (224 x 960)-pixel fine-fine coincidence MAMA array for high-spatial-resolution imaging studies. The applied voltage across each MCP can be controlled independently. We report on the gain and dynamic range performance characteristics of the two-stage MAMA tube in two different configurations: first, with the output MCP having moderate conductivity (about 100 MOhm); and second, with the output MCP having very high conductivity (about 2 MOhm). These results are compared and contrasted with those of the more conventional MAMA tube configuration which employs a single high-gain curved-channel MCP.

Slater, David C.↗

NASA NTRS1991

High-reflective multilayers as narrowband VUV filters

A novel coating has been developed for the 120-230 nm wavelength VUV region which yields significantly higher reflectivity over selectable bandwidths and can be used to fabricate high-performance narrowband reflection filters; the spectral properties of such filters are greatly enhanced through their use in tandem. The coating uses a combination of high and low refractive index dielectric pairs. The proper choice of high-low ratio reduces the effects of VUV absorption for high refractive index films whose extinction coefficient is much higher than for a low-index material.

Zukic, Muamer↗

NASA NTRS1993

An initial comparison of CFD with experiment for a geometrically simplified STOVL model

The transition flight performance of a representative Short Take-Off or Vertical Landing (STOVL) model is investigated using side-by-side experimental and numerical simulations. The model consists of a 60 deg cropped delta wing planform; a simple fuselage shape blended to the wing; and tandem, circular, high-pressure-air lift jets that exit perpendicular to the flat lower surface. The configuration was chosen to minimize the geometric modeling complexity while retaining the important flow physics of the lift-jet/aerodynamic surface interaction. Three-dimensional, turbulent Navier-Stokes computations are made using a multiple, overset grid scheme. Results are presented and compared with the measured forces and pressures for the model at a freestream Mach number of 0.14 and a 10 deg angle-of-attack without lift jets operating. Computed surface flow patterns and particle traces show that the simulation predicts primary and secondary wing leading edge vortices for these conditions.

Roth, Karlin R.↗

NASA NTRS1993

Applying design principles to fusion reactor configurations for propulsion in space

We applied three design principles (DPs) to adapt and optimize three candidate-terrestrial-fusion-reactor configurations for propulsion in space. The three design principles are: (1) provide maximum direct access to space for waste radiation, (2) operate components as passive radiators to minimize cooling-system mass, and (3) optimize the plasma fuel, fuel mix, and temperature for best specific Jet power. The three candidate-terrestrial-fusion-reactor configurations are: (1) the thermal-barrier-tandem-mirror (TBTM), (2) field-reversed-mirror (FRM), and (3) levitated-dipole-field (LDF). The resulting three candidate-space-fusion-propulsion systems have their initial-mass-to-LEO minimized and their specific jet power and reusability maximized. We performed a preliminary rating of these configurations and concluded that the leading engineering-design solution to space fusion propulsion is a modified TBTM that we call the Mirror Fusion Propulsion System.

Carpenter, Scott A.↗

NASA NTRS1993

Tomographic decoding algorithm for a nonoverlapping redundant array

A tomographic reconstruction algorithm is developed for the nonoverlapping redundant array X-ray imaging system whereby the background contributions from out-of-focus planes can be eliminated. The algorithm makes use of two constraints derived from the physical characteristics of the nonoverlapping redundant array system in tandem with the correlation decoding process. It is simple, direct, and noniterative. Tomographic images of computer-generated planar and three-dimensional objects are provided to illustrate the effectiveness of the algorithm.

Yin, Lo I.↗

NASA NTRS1993

Ozone absorption cross section measurements in the Wulf bands

A tandem dual-beam spectrometer has been developed to determine ozone absorption cross sections for 13 selected wavelengths between 750 and 975 nm at room temperature. The increasingly pronounced structure in this region may interfere with atmospheric trace gas transitions that are useful for remote sensing and complicate the measurement of aerosols. Ozone concentrations were determined by absorption at the common HeNe laser transition near 632.8 nm using the absolute cross section reported previously. The overall accuracy of these room temperature measurements is generally better than 2 percent. A synoptic near-IR spectrum scaled to these measurements is employed for comparison with results of previous studies.

Anderson, Stuart M.↗

NASA NTRS1993

A two-stage virtual impactor for continuous concentration of particles in an aerosol

A two-stage virtual impactor has been designed and fabricated to concentrate aerosol particles. In this impactor, the minor flow from the first stage of the impactor is introduced into the second stage as the primary flow. The cut-point of the impactor is designed to be about 0.3 micron. The sample aerosol is introduced into the impactor at a flow rate of 8.0 atm-l/min and after the two stages of separation, particles are collected into the minor flow of 0.06 atm-l/min with 84 percent efficiency. The tandem arrangement of the two stages increases the concentration of larger particles by a factor of greater than 100. The small size and the low flow rates make the impactor compatible with the sampling requirements of instruments used for the chemical and physical characterization of particles from low-particle number density aerosols. In particular, the high particle concentration factor of the impactor will make it possible to analyze individual particles in real time from aerosols containing less than 10 particles per cft by the mass spectrometric methods developed in our laboratory.

Sinha, M. P.↗

NASA NTRS1921

The Caproni Seaplane

The Caproni Company recently built a seaplane of unusual design. The main supporting surfaces consisted of three triplanes in tandem, the lower wings being attached to the hull, which was described as providing accommodation for a hundred passengers. On one of the first flights, the seaplane fell into a lake, nose down, and was destroyed. The authors wish to show that this failure could have been predicted. The failure could have been predicted by applying some fundamental principles of aeronautics, especially those relating to longitudinal stability, the lack of which caused the loss of the seaplane.

Munk, Max↗

NASA NTRS1923

Reduction in efficiency of propellers due to slipstream

In the slipstream behind a propeller there is a considerable amount of kinetic energy which has been imparted to it by the engine without producing any corresponding propeller thrust. The increased absorption of power reduces the propeller efficiency. Attention has been previously directed to this question by Bendemann and Madelung and other writers. Their contribution serves to verify a simple method of calculating the reduction in the propeller efficiency due to the slip stream. That method of calculation is given here. Explanations and examples are given for as single propeller and for two propellers mounted in tandem.

Munk, Max M↗

NASA NTRS1953

Accelerations and Passenger Harness Loads Measured in Full-Scale Light-Airplane Crashes

Full-scale light-airplane crashes simulating stall-spin accidents were conducted to determine the decelerations to which occupants are exposed and the resulting harness forces encountered in this type of accident. Crashes at impact speeds from 42 to 60 miles per hour were studied. The airplanes used were of the familiar steel-tube, fabric-covered, tandem, two-seat type. In crashes up to an impact speed of 60 miles per hour, crumpling of the forward fuselage structure prevented the maximum deceleration at the rear-seat location from exceeding 26 to 33g. This maximum g value appeared independent of the impact speed. Restraining forces in the seatbelt - shoulder-harness combination reached 5800 pounds. The rear-seat occupant can survive crashes of the type studied at impact speeds up to 60 miles per hour, if body movement is restrained by an adequate seatbelt-shoulder-harness combination so as to prevent injurious contact with obstacles normally present in the cabin. Inwardly collapsing cabin structure, however, is a potential hazard in the higher-speed crashes.

Eiband, A. Martin↗

NASA NTRS1954

Wind-tunnel Studies of the Performance of Multirotor Configurations

The power requirements measured in static thrust and in level forward flight are presented for two helicopter rotor configurations. One is a coaxial rotor arrangement having the rotors spaced approximately 19 percent of the rotor radius; the other is a tandem configuration in which the rotor-shaft spacing is 3 percent greater than the rotor diameter and in which the rotors lie in the same plane. The experimental measurements are compared with the results of calculations based on existing NACA single-rotor theory.

Richard C Dingeldein↗

NASA NTRS1954

The normal component of the induced velocity in the vicinity of a lifting rotor and some examples of its application

Paper presents a practical method for computing the approximate values of the normal component of the induced velocity at points in the flow field of a lifting rotor. Tables and graphs of the relative magnitudes of the normal component of the induced velocity are given for selected points in the longitudinal plane of symmetry of the rotor and on the lateral rotor axis. A method is also presented for utilizing the tables and graphs to determine the interference induced velocities arising from the second rotor of a tandem or side-by-side-rotor helicopter and the induced flow angle at a horizontal tail plane. (author)

Castles, Walter, R↗

NASA NTRS1954

Method for Studying Helicopter Longitudinal Maneuver Stability

A theoretical analysis of helicopter maneuver stability is made and the results are compared with experimental results for both a single and a tandem rotor helicopter. Techniques are described for measuring in flight the significant stability derivatives for use with the theory to aid in design studies of means for achieving marginal maneuver stability for a prototype helicopter.

Amer, Kenneth B↗

NASA NTRS1942

The resistance coefficient of commercial round wire grids

The resistance coefficients of commercial types of round wire grids were examined for the purpose of obtaining the necessary data on supercharger test stands for throttling the inducted air to a pressure corresponding to a desired air density. The measurements of the coefficients ranged up to Reynolds numbers of 1000. In the arrangement of two grids in tandem, which was necessary in order to obtain high resistance coefficients with the solidity, that is, mesh density of grid, was found to be accompanied by a further relationship with the mutual spacing of the individual grids.

Eckert, B↗

NASA NTRS1989

High altitude reconnaissance aircraft design

A Universities Space Research Association (USRA) sponsored (undergraduate) study is presented on the feasibility and design of a high altitude reconnaissance/research aircraft. The aircraft mission was to carry 1,000-3,000 lb of atmospheric pollutant monitoring equipment for 1-5 hr at an altitude of 100,000-130,000 ft. Three configurations subject to the same mission requirements were studied in detail. The three designs analyzed were the tandem-wing-twin-boom, joined wing, and conventional twin-boom configurations. The performance of the three proposed configurations is presented and shows that high altitude flight is possible with current technology. Different possible propulsion systems were investigated and suggestions are made for further investigation and better optimization of the designs.

Poladian, D.↗