SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The architecture of programmable processors is described, with particular reference to the design of a programmable delta-modulation decoder capable of receiving DM encoders employing different schemes. A switching receiver implementation, allowing communication between different DM algorithms, is designed and shown.
A nonsteady vortex-lattice method is introduced for predicting the dynamic stability derivatives of a delta wing undergoing an oscillatory motion. The analysis is applied to several types of small oscillations in pitch. The angle of attack varied between + or - 1 deg, with the mean held at 0 deg when the flow was assumed to be attached and between + or - 1 deg and the mean held at 15 deg when both leading-edge separation and wake roll-up were included. The computed results for damping in pitch are compared with several other methods and with experiments, and are found to be consistent and in good agreement.
Unconnected phase narrowband Delta VLBI data strategies are evaluated for enhancing deep space cruise navigation and for rapidly redetermining the spacecraft trajectory after a midcourse correction maneuver. Results of a covariance analysis study are presented for a Jupiter bound spacecraft based on a simulated data strategy consisting of daily 10 minute narrowband scans from two baselines augmented with conventional two way range and Doppler passes. For post-maneuver recovery, the narrowband strategy achieves a factor of two improvement in orbit determination performance. Cruise OD performance is also significantly enhanced due to the ability of the narrowband data to accurately sense the orientation of the orbital plane.
A new type of global operator to be used in evaluating matrix elements of two-particle delta functions is introduced. It is based, like the Trivedi one-particle operator, on the Poisson equation and is easier to apply than the method of Hiller, Sucher and Feinberg. After a test in the helium isoelectronic sequence, the new method is applied successfully to the interesting problem of hyperfine structure in muonic helium.
A tip section of a delta wing having an NACA 0004-65 airfoil section and a 600 leading-edge sweepback was equipped with a porous leading-edge section through which hot gas was 'bled for anti-icing. Heating rates for anti-icing were determined for a wide range of icing conditions. The effects of gas flow through the porous leading-edge section on airfoil pressure distribution and drag in dry air were investigated. The drag increase caused by an ice formation on the unheated airfoil was measured for several icing conditions. Experimental porous surface- to free-stream convective heat-transfer coefficients were obtained in dry air and compared with theory. Adequate icing protection was obtained at all icing conditions investigated. Savings in total gas-flow rate up to 42 percent may be obtained with no loss in anti-icing effectiveness by sealing half the upper-surface porous area. Gas flow through the leading-edge section had no appreciable effect on airfoil pressure distribution. The airfoil section drag increased slightly (5-percent average) with gas flow through the porous surface. A heavy glaze-ice formation produced after 10 minutes of icing caused an increase in section drag coefficient of 240 percent. Experimental convective heat-transfer coefficients obtained with hot-gas flow through the porous area in dry air and turbulent flow were 20 to 30 percent lower than the theoretical values for a solid surface under similar conditions. The transition region from laminar to turbulent flow moved forward as the ratio of gas velocity through the porous surface to air-stream velocity was increased.
A LOFT program was developed as part of the DC-9 training program which serves as a prototype for much of Delta's other aircraft training programs. The LOFT used differs little from the ideology presented in the Advisory Circular. Difficulty and experienced concerns regarding the effectiveness of LOFT as a complete training vehicle are explored.
The drag reduction potential of leading edge devices on a 60 degree delta wing at high lift was examined. Geometric variations of fences, chordwise slots, pylon type vortex generators, leading edge vortex flaps, and sharp leading edge extensions were tested individually and in specific combinations to improve high-alpha drag performance with a minimum of low-alpha drag penalty. The force, moment, and surface static pressure data for angles of attack up to 23 degrees, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter are documented.
The drag reduction devices selected for evaluation were the fence, slot, pylon-type vortex generator, and sharp leading-edge extension. These devices were tested on a 60 degree flatplate delta (with blunt leading edges) in the Langley Research Center 7- by 10-foot high-speed tunnel at low speed and to angles of attack of 28 degrees. Balance and static pressure measurements were taken. The results indicate that all the devices had significant drag reduction capability and improved longitudinal stability while a slight loss of lift and increased cruise drag occurred.
The INSAT-1A, the first in a series of 12 transponder communications satellites developed for India, is described as well as the launch plans. The launch vehicle will be the Delta 3910 configuration which incorporates an extended long tank Thor booster, nine Castor IV strap-on motors, a TR-201 second stage, and an 8 foot fairing. The satellite will be placed in a suborbital trajectory. A DAM-D stage will then thrust it into a synchronous transfer orbit. An apogee kick motor will be fired to circularize its orbit at a geosynchronous altitude of 19,300 nautical miles.
Observations are presented of a semiforbidden transition of C II at lambda 2325 toward Delta Scorpii. This line is intrinsically so weak that saturation and blending problems are completely absent, allowing the C II column density to be determined unambiguously. Furthermore, since C II is the dominant ionization state of carbon in H I regions, the total carbon abundance follows directly. While the detection of weak, semiforbidden interstellar lines requires high resolution and high photometric accuracy, observations of these lines promise substantial improvements concerning the knowledge of gas-phase abundances and, consequently, of the composition and structure of grains. The reported results represent the first direct evidence from absorption measurements that carbon is depleted from the interstellar gas by amounts sufficient to provide a substantial fraction of the mass of interstellar grains.
A 'pylon vortex generator' concept has been proposed for alleviating the subsonic pitch-up instability of highly swept supersonic-cruise wings. Fixed at a part-span location, this leading-edge device utilizes the lateral velocity component in the flow approaching the swept leading edge to generate a streamwise vortex, opposite in sense to the tip vortex. The vortex-induced downwash outboard of the device serves to control the leading-edge stall development in the wing-tip regions. Wind-tunnel results on 60-deg and 74-deg flat-plate delta wings are presented to illustrate the operation of the pylon vortex generator in modifying the spanwise leading-edge separation characteristics resulting in effective alleviation of the pitch-up.
Landsat multispectral scanner data and color and color infrared photographs acquired from a U-2 aircraft are combined with surface measurements for salinity mapping of the San Fransisco Bay Delta. A regression model is developed between the surface truth data and Landsat digital data for 29 sample sites, and is then extended over the entire study area. Results are in general agreement with reported salinity distribution values. It appears to be impossible to establish any quantitative judgement regarding the salinity values by visual interpretation of the imagery within the test site.
The variation of the electronic transition moment with internuclear separation has been calculated for the beta and delta systems of NO. Theoretical band intensities for the fundamental and first two overtones have also been calculated for the ground state. The results are based on the self-consistent-field plus configuration-interaction technique, and they are compared with the existing experimental data. Theoretical potential-energy curves and the spectroscopic constants for the X-squared Pi, B-squared Pi, and C-squared Pi electronic states of NO are also reported.
Static and unsteady pressures were measured on a 50.45 degree clipped delta wing in the Langley Transonic Dynamics Tunnel with Freon as the test medium. Data taken at M = 0.9 is presented for static and oscillatory deflections of the trailing edge control surface and for the wing in pitch. Comparisons of the static measured data are made with results computed using the Bailey-Ballhaus small disturbance code.
The aerodynamic forces acting on a delta wing, mounted on a free-to-roll sting-balance apparatus, were measured. Two wing planforms having leading edge sweeps of 76 and 80 deg were tested, but only the wing with the 80 deg sweep would undergo periodic self-induced roll oscillation. The time dependent forces and roll angles for this wing were then recorded for various test conditions. In these tests a considerable drop in the average normal force of the free-to-roll wing was measured, relative to the normal force obtained in the static tests. Also, the helium-bubble flow visualization technique was used to gain some insight into the periodic motion of the separated leading edge vortices.
An unsteady vortex lattice method is presented for the calculation of the aerodynamic forces acting on lifting surfaces undergoing complex three dimensional motion. For the present case the nonsymmetric motion of a slender delta wing was considered and the resulting lateral characteristics were calculated. The flow separation line was specified along the wing leading edge and the emanating vortex sheet shape and rollup was then calculated. Numerical results are presented for the combined high angle of attack and side slip condition and for the wing constant roll and coning motions.
This paper highlights some current results from ongoing analytical studies of vortex flaps on highly swept delta wings. A brief discussion of the vortex flow analysis tools is given along with comparisons of the theories to vortex flap force and pressure data. Theoretical trends in surface pressure distribution for both angle-of-attack variation and flap deflection are correctly predicted by Free Vortex Sheet theory. Also shown are some interesting calculations for attached-flow and vortex-flow flap hinge moments that indicate flaps utilizing vortex flow may generate less hinge moment than attached flow flaps. Finally, trailing-edge flap effects on leading-edge flap thrust potential are investigated and theory-experiment comparisons made.
An investigation has been made to determine the effects of external stores on the stability and control characteristics of a delta wing fighter airplane model at Mach numbers from 0.60 to 2.01 for a Reynolds number of 3.0 X 1 million per foot. The angle-of-attack range was from about -4 degrees to 20 degrees at a sideslip angle of 0 degrees for the transonic tests, and from about -4 degrees to 10 degrees at sideslip angles of 0 degrees and 3 degrees for the supersonic tests. In general, the results of the tests indicated no seriously detrimental effects of the stores on the stability and control characteristics of the model but did show an increase in the minimum drag level throughout the Mach number range. However, the drag-due-to-lift was such that for subsonic/transonic speeds, the drag at higher lifts was essentially unaffected and the indications are that the maneuvering capability may not be impaired by the stores.