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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Design study of technology requirements for high performance single-propeller-driven business airplanes

Developments in aerodyamic, structural and propulsion technologies which influence the potential for significant improvements in performance and fuel efficiency of general aviation business airplanes are discussed. The advancements include such technolgies as natural laminar flow, composite materials, and advanced intermittent combustion engines. The design goal for this parameter design study is a range of 1300 nm at 300 knots true airspeed with a payload of 1200lbs at 35,000 ft cruise altitude. The individual and synergistic effects of various advanced technologies on the optimization of this class of high performance, single engine, propeller driven business airplanes are identified.

Kohlman, D. L.↗
NASA NTRS1983

Speed benefits of tilt-rotor designs for LHX

The merits of an advanced helicopter and a tilt rotor aircraft for light utility, scout, and attack roles in combat missions envisioned for the year 2000 and beyond were compared. It is demonstrated that speed has increasing value for 11 different mission classes broadly encompassing the intended LHX roles. Helicopter speeds beyond 250 knots are judged to have lower military worth. Since the tilt rotor concept offers a different cost speed relationship than that of helicopters, assessment of a tilt rotor LHX variant was warranted. The technical parameters of an advanced tilt rotor are stablished. Parameters of representative missions are identified, computed relative value of the tilt rotor LHX are compared to the baseline helicopter, a first-order life cycle estimate for the tilt rotor LHX is established, military worth of the alternative design is computed and the results are evaluated. It is suggested that the tilt rotor is the solution with the greatest capability for meeting the uncertainties of future needs.

Mcdaniel, R. L.↗
NASA NTRS1984

The 157 Micron (C II) Luminosity of the Galaxy

The diffuse far infrared (C II) emission of several regions of the Galactic plane were sampled. Mechanisms for the excitation of carbon ions are discussed in reference to the role of carbon ion transitions in cooling diffuse atomic hydrogen. Observations indicate that the C II emission probably arises at the edges of giant molecular clouds and appears to have localized knot-like features. The total C II luminosity of the Galaxy is approximately 6 to 10 to the 7th power L(solar).

Stacey, G. J.↗
NASA NTRS1985

Shape Preserving Spline Interpolation

A rational spline solution to the problem of shape preserving interpolation is discussed. The rational spline is represented in terms of first derivative values at the knots and provides an alternative to the spline-under-tension. The idea of making the shape control parameters dependent on the first derivative unknowns is then explored. The monotonic or convex shape of the interpolation data can then be preserved automatically through the solution of the resulting non-linear consistency equations of the spline.

Gregory, J. A.↗
NASA NTRS1985

Multivariate Spline Algorithms for CAGD

Two special polyhedra present themselves for the definition of B-splines: a simplex S and a box or parallelepiped B, where the edges of S project into an irregular grid, while the edges of B project into the edges of a regular grid. More general splines may be found by forming linear combinations of these B-splines, where the three-dimensional coefficients are called the spline control points. Univariate splines are simplex splines, where s = 1, whereas splines over a regular triangular grid are box splines, where s = 2. Two simple facts render the development of the construction of B-splines: (1) any face of a simplex or a box is again a simplex or box but of lower dimension; and (2) any simplex or box can be easily subdivided into smaller simplices or boxes. The first fact gives a geometric approach to Mansfield-like recursion formulas that express a B-spline in B-splines of lower order, where the coefficients depend on x. By repeated recursion, the B-spline will be expressed as B-splines of order 1; i.e., piecewise constants. In the case of a simplex spline, the second fact gives a so-called insertion algorithm that constructs the new control points if an additional knot is inserted.

Boehm, W.↗
NASA NTRS1985

Development of an energy-absorbing passenger seat for a transport aircraft

Commercial air transport passenger safety and survivability, in the event of an impact-survivable crash, are subjects receiving increased technical focus/study by the aviation community. A B-720 aircraft, highly instrumented, and remotely controlled from the ground by a pilot in a simulated cockpit, was crashed on a specially prepared gravel covered impact site. The aircraft was impacted under controlled conditions in an air-to-ground gear-up mode, at a nominal speed of 150 knots and 4-1/2 deg glide slope. Data from a number of on board, crash worthiness experiments provided valuable information related to structural loads/failure modes, antimisting kerosene fuel, passenger and attendant restraint systems and energy absorbing seats. The development of an energy absorbing (EA) seat accomplished through innovative modification of a typical modern standard commercial aviation transport, three passenger seat is described.

Eichelberger, C. P.↗
NASA NTRS1985

Icing tunnel tests of Electro-Impulse De-Icing of an engine inlet and high-speed wings

A brief review is given of four earlier tests in the NASA Lewis Icing Research Tunnel and of flight tests in NASA's Icing Research Aircraft and in a Cessna 206 airplane. Details are given of recent icing tunnel tests of thicker-skinned wings, a Gates Learjet, a composite leading edge, and a Boeing 767, and of a Falcon Fanjet engine inlet. These were tested at speeds from 87 to 220 knots, air temperatures from -2 to -15 C, LWC values of 0.6 to 2.4 grams/cu meter, and median droplet diameters from 12 to 20 microns. Energy requirements are reported, as well as conclusions from comparisons of several Electro-Impulse De-Icing coil system designs. Fundamental studies of the structural dynamics and ice shedding of a 12.7 cm (5 inch) diameter semicylinder are described. Some potential problem areas are discussed: fatigue of skin and coil mountings, system weight and cost, electro-magnetic interference and noise.

Zumwalt, G. W.↗
NASA NTRS1985

Force-free equilibria of magnetized jets

Force-free equilibrium configurations of magnetic-pressure-dominated magnetized supersonic jets confined by slowly varying external pressure are investigated analytically. For the case where internal dissipation mechanisms are active, the lowest-energy field configuration is found to be the superposition of an axisymmetric mode and a helical mode with a wavelength equal to 5 times the jet radius, and the pressure below which the nonaxisymmetric mode becomes energetically favorable is given as 2700 times the product of the 4th power of the magnetic helicity per unit length and the -6th power of the magnetic flux. A model of the total and polarized emission of such a configuration is developed and applied to the extended well-collimated astronomically resolved jet NGC 6251. The model is shown to reproduce significant features such as transverse oscillations of the ridge line, width oscillations and emission knots, the projected magnetic-field configuration, oscillations of the degree of polarization, and the distribution of the Faraday rotation measure.

Koenigl, A.↗
NASA NTRS1984

Energy release in solar flares

On the basis of observations of energy release in solar flares, it is proposed that different processes may operate on four different time scales; (1) the subsecond scale of subbursts that prominently figure in mm-wave records; (2) the few-seconds scale of elementary bursts featured in hard X-ray records; (3) the few-minutes scale of the impulsive phase; and (4) the longer than tens-of-minutes scale of the gradual phase. It is proposed that the magnetic field concentration into 'magnetic knots' at the photosphere is of consequence to coronal magnetic field structure, so that magnetic fields in this region may be seen as an array of elementary flux tubes. It is further proposed that the gradual phase of energy release involves a steady process of reconnection, while the impulsive phase involves a more stochastic process of reconnection due to mode interaction.

Sturrock, P. A.↗
NASA NTRS1985

The 157-micron forbidden C II luminosity of the Galaxy. II - The presence of knotlike features in the forbidden C II emission

The measurement by Stacey et al. (1983) of the diffuse 157-micron emission of singly ionized carbon from the Galactic plane is augmented by measurements at two additional galactic longitudes. The results indicate that the total forbidden C II flux from the Galaxy is about 6 x 10 to the 7th solar luminosity - a factor of 8 lower than the previous estimate. It is likely that the measurement at l(II) = 8.0 deg was due to a knot in the forbidden C II emission. The results indicate that the forbidden C II flux has a half width of roughly 0.34 deg, in agreement with the (C-12)O (J = 1-0) half widths. The forbidden C II emission probably arises in at the edges of molecular clouds.

Stacey, G. J.↗
NASA NTRS1984

Twin tilt nacelle V/STOL aircraft

This paper describes the second government-conducted, piloted flight simulation of the Grumman Design 698 V/STOL (vertical and short takeoff and landing) aircraft. Emphasis is on the aircraft's handling qualities as rated by various NASA, Navy, and GAC pilots with flight experience ranging from CTOL (conventional take-off and landing) to V/STOL aircraft. The Design 698 had been modified to resolve the flight problems that were of most concern to the pilots in the first investigation (Phase I). Those problems included an adverse nonminimum phase (NMP) acceleration response in both the longitudinal and lateral axes, a large thrust-response lag, and adverse ground effects. The adverse NMP acceleration is an attribute of the vertical vanes (a Grumman patent) positioned in the fan exhaust flow. The primary modifications included using the vertical-vane deflection as a thrust spoiling method, the addition of the cross-shafted propulsion system, and the implementation of two velocity and attitude control modes (standard and precision) for speeds below 50 knots.

Eskey, M. A.↗
NASA NTRS1985

Does orientation affect the smoothness of parsec-scale radio jets?

The compact, nonthermal radio sources which are studied with very-long-baseline interferometry (VLBI) are often found to have a linear structure with a bright, nearly unresolved component at one end. This asymmetric structure is usually referred to as a 'core-jet' morphology. In some sources there are bright bumps or knots - regions of enhanced radio emission - along the 'jets', while other sources have relatively smooth, featureless jets. This paper reports the result of a study of the differences between compact radio sources with bumpy and smooth jets. It is concluded that most, if not all, of the difference in jet smoothness can be attributed to the orientation of the radio axis with respect to the line of sight. Thus, the VLBI observations do not necessarily imply that there are intrinsic differences in the smoothness of parsec-scale radio jets.

Jones, D. L.↗
NASA NTRS1986

The flare kernel in the impulsive phase

The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area.

Dejager, C.↗
NASA NTRS1984

Backup control airstart performance on a digital electronic engine control-equipped F100-engine

The air start capability of a backup control (BUC) was tested for a digital electronic engine control (DEEC) equipped F100 engine, which was installed in an F-15 aircraft. Two air start schedules were tested. Using the group 1 start schedule, based on a 40 sec timer, an air speed of 300 knots was required to ensure successful 40 and 25% BUC mode spooldown airstarts. If core rotor speed (N2) was less than 40% a stall would occur when the start bleed closed, 40 sec after initiation of the air start. All jet fuel starter (JFS) assisted air starts were successful with the group 1 start schedule. For the group 2 schedule, the time between pressurization and start bleed closure ranged between 50 sec and 72 sec. Idle rps was lower than the desired 65% for air starts at higher altitudes and lower air speeds.

Johnson, J. B.↗
NASA NTRS1986

Implementation and flight tests for the Digital Integrated Automatic Landing System (DIALS). Part 1: Flight software equations, flight test description and selected flight test data

Five flight tests of the Digital Automated Landing System (DIALS) were conducted on the Advanced Transport Operating Systems (ATOPS) Transportation Research Vehicle (TSRV) -- a modified Boeing 737 aircraft for advanced controls and displays research. These flight tests were conducted at NASA's Wallops Flight Center using the microwave landing system (MLS) installation on runway 22. This report describes the flight software equations of the DIALS which was designed using modern control theory direct-digital design methods and employed a constant gain Kalman filter. Selected flight test performance data is presented for localizer (runway centerline) capture and track at various intercept angles, for glideslope capture and track of 3, 4.5, and 5 degree glideslopes, for the decrab maneuver, and for the flare maneuver. Data is also presented to illustrate the system performance in the presence of cross, gust, and shear winds. The mean and standard deviation of the peak position errors for localizer capture were, respectively, 24 feet and 26 feet. For mild wind conditions, glideslope and localizer tracking position errors did not exceed, respectively, 5 and 20 feet. For gusty wind conditions (8 to 10 knots), these errors were, respectively, 10 and 30 feet. Ten hands off automatic lands were performed. The standard deviation of the touchdown position and velocity errors from the mean values were, respectively, 244 feet and 0.7 feet/sec.

Hueschen, R. M.↗
NASA NTRS1985

Coronal X-ray activity preceding solar flares

The characteristics of coronal emplacements preceding solar flares were investigated based on a comprehensive survey of Skylab soft X-ray images. A search interval of 30 min before flare was used in the X-ray observations. X-ray images with preflare enhancements were compared with high resolution H-alpha images and photospheric magnetograms and preflare enhancements were found in a statistically significant number of the observed preflare intervals. The enhancement events consisted of loops, kernels, and sinuous features with one to three separate preflare structures appearing in each interval. Typical gas pressures in the preflare X-ray features were estimated on the order of a few dyne per sq cm and densities were 4-10 x 10 to the -9th per cu cm for assumed average temperatures. H-alpha brightenings in the form of knots and patches were found in conjunction with the X-ray preflare features in nearly all of the intervals. It is concluded that H-alpha emission is characteristic of preflare emission processes. The observational data are interpreted within the framework of existing loop preheating models, and the results are discussed in detail.

Webb, D. F.↗
NASA NTRS1985

The W3 molecular cloud

Extensive J = 1 to 0 (C-12)(O-16) and (C-13)(O-16) observations of the W3 molecular cloud and the surrounding region are presented and discussed. The velocity structure in the region is strongly suggestive of a model of large-scale, externally induced star formation. It is shown that star formation occurred in W3 and the nearby star-forming region W3(OH) after the gas within which they lie was swept up by the expanding W4 ionization front. Two condensations dominate the mass structure of the core of W3, one associated with IRS 4 and the other with IRS 5 and 1. A velocity difference between the two condensations is interpreted as indicating the two sources actually are discrete knots.

Thronson, H. A., Jr.↗
NASA NTRS1986

IC 3475 - A stripped dwarf galaxy in the Virgo cluster

B and R CCD and H I observations of the Virgo dwarf galaxy IC 3475 were obtained. The galaxy is very large, having a diameter of about 10 kpc; its hydrogen content is at least 60 times smaller than that of a normal dwarf irregular galaxy; and the galaxy shows a central bar structure with knots and inclusions scattered throughout its body but with the majority in the bar region. The results support the hypothesis that IC 3475 is a dwarf irregular galaxy that has been stripped of its neutral gas.

Vigroux, L.↗