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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 253 records · Page 14
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NASA NTRS1978

Delta launch Canadian communications satellite Telesat-D (Anik-B)

Telesat-D (Anik-B) is the first of a series of three (Telesat-D, -E, -F) second generation satellites developed for Telesat/Canada. These second generation satellites will replace three first generation HS-333 satellites (Telesat-A, -B, -C) developed for Telesat/CNADA AND LAUNCHED BY Delta 2914 vehicles in 1972, 1973, and 1975 and successfully placed in orbit as Anik-A1, -A2, -A3. The Telesat-D(Anik-B) satellite will be place in sync-transfer orbit by a Delta 3914 launch vehicle, currently scheduled for launch on December 15, 1978. The Telesat-E and -F(Anik-C1 and -C2) missions are scheduled for launch on the Space Shuttle in 1981 to replace the function of the Anik-A2 and -A3 (Telesat-B, and -C) satellites. The Anik-B will provide point-to-point voice, TV, and data communications traffic to Canada's ten provinces.

Source record↗
NASA NTRS1978

The Space Shuttle Ground Terminal Delta Modulation System

Shuttle voice processing uses a Variable Slope Delta Modulation scheme which is a variant of the ABATE algorithm. This paper summarizes the ground terminal subsystem which processes the multiplexed voice and telemetry data digital sequence in the downlink processing and digitizes the voice signal in the uplink processing. The Delta Modulation System (DMS) performance characteristics are given in terms of an intelligibility test score and in terms of time and frequency responses measured on a production system developed for NASA Goddard Space Flight Center. Implementation details of the encoder and decoder algorithms are given in terms of the circuit logic used to implement them.

Auger, R. L.↗
NASA NTRS1979

The ratio of deuterium to hydrogen in interstellar space. IV - The lines of sight to Delta, Epsilon, and Iota Orionis

Deuterium absorption features in spectra of Delta, Epsilon, and Iota Ori obtained with Copernicus are analyzed. The Iota Ori line-of-sight analysis, which is quite detailed because of the high-velocity H I components superposed on the deuterium features, gives a D/H ratio (which is uncertain because of a complex profile) of 0.000014. A D/H ratio of the order of 7 millionths is determined for Delta and Epsilon Ori. For the complex line profiles involved, one may regard this as a formal lower limit. Several attempts were made to increase the ratio N(D I)/N(H I) in the context of reasonable models for the line of sight, but with no success; the derived values are therefore regarded as actual values, not lower limits. Since the derived value is an average on the line of sight, the possibility cannot be ruled out that the true ratios N(D I)/N(H I) in individual nearby components differ from the mean values. The mean value for these two directions is lower by a factor of 4 than the best value for the Zeta Pup line of sight (the highest yet derived for path lengths greater than 50 pc).

Laurent, C.↗
NASA NTRS1980

A vortex-lattice method for the calculation of the nonsteady separated flow over delta wings

An analysis is made of the wake structure and the forces on a delta wing as it undergoes nonsteady motion, wherein the flow separates at the leading edge. Comparisons of these predictions with existing experimental and theoretical data for the nonsteady linear and nonlinear motions indicate good agreement. It was found that the time-dependent, wake-shedding numerical procedure applied here for the wake rollup and the lift force calculation resulted in considerable saving of computer time over methods using the iterative wake rollup procedure. Calculated results for various motions of the delta wing, including the plunging motion, are presented for both the separated and the attached flow cases.

Levin, D.↗
NASA NTRS1980

Delta V errors due to attitude correction maneuvers of a spinning spacecraft

A statistical error analysis has been performed to evaluate the change in velocity of a spin stabilized spacecraft due to thruster induced attitude correction maneuvers. Analytical expressions were developed to determine the mean and variance of the velocity in terms of the nominal values and uncertainties of key spacecraft parameters. These parameters include thrust, thruster timing, thruster alignment, plume impingement force and estimated spacecraft mass. Typical values of these parameters and their uncertainties for NASA's Galileo spacecraft were used to evaluate these expressions. The results of the analysis allow the effect of attitude correction maneuvers to be evaluated with respect to the functional requirements on nongravitational acceleration. Other results include the identification of major sources of delta V error and studies of the sensitivity of delta V to variations in the error sources.

Zipursky, H. J.↗
NASA NTRS1980

Atmospheric quenching of vibrationally excited O2/1 Delta/

The paper presents photolysis absorption spectroscopy experimental results which show rapid vibrational quenching of O2(1 Delta, v not less than 1) molecular oxygen fragments in an atmospheric environment. The reactions of this species were determined by flash photolysis of ozone in the Hartley band combined with absorption spectroscopic detection of O2(1 Delta v equals 0) fragments and resonance fluorescence detection of O(3P). It was shown that rapid vibrational deactivation occurs under atmospheric conditions; in addition, an upper limit was determined for the photolytic channel of the O(1D) + O3 yields O2(1 Sigma) reaction.

Klais, O.↗
NASA NTRS1980

Differential Very Long Baseline Interferometry (delta VLBI) spacecraft tracking system demonstration. Part 2: Data acquisition and processing

A set of experiments in the use of Differential Very Long Baseline Interferometry (delta VLBI) for spacecraft navigation were completed. Data using both Voyager spacecraft and a single quasar were acquired during the Jupiter encounter time period. The data were processed and analyzed to assess the navigation accuracy of delta VLBI. The data reduction and techniques for assessing data quality and consistency are discussed.

Christensen, C. S.↗
NASA NTRS1981

Experimental and theoretical study of three interacting, closely-spaced, sharp-edged 60 deg delta wings at low speeds

Wind tunnel tests were conducted to determine the subsonic longitudinal aerodynamic characteristics of lifting configuration consisting of a 60 deg delta main wing with two smaller 60 deg delta wings (called sub-wings) attached underneath. The test was designed to determine the effects on lift, drag, and pitching moment due to various placement of the subwings in relation to the main wing. Test results indicate the increasing vertical separation between the main wing and the sub-wings produced the most significant results; a 23.1% increase in maximum lift coefficient, a reduction in drag coefficient at high lift coefficients, and an increase in longitudinal stability. Lateral separation of the sub-wings produced no significant changes. Placement of the sub-wings rearward increases the initial lift curve slope and maximum lift coefficient and also increase the longitudinal stability. Results of a computer study using a vortex lattice code supported the experimental conclusions.

Faery, H. F., Jr.↗
NASA NTRS1981

Self-induced wing rock of slender delta wings

As part of a research program aimed at exploring basic mechanisms that cause wing rock in combat aircraft, an investigation was conducted to study the aerodynamic factors which cause the low-speed wing rock exhibited by slender delta wings. A flat-plate delta wing with 80 deg leading-edge sweep was subjected to conventional static-force tests and dynamic wind-tunnel experiments which included forced-oscillation, rotary, and free-to-roll tests. In addition, visualization of the flow phenomena involved was obtained by observing tuft patterns and using a helium-bubble technique. This paper summarizes the results of this study. Fundamental information is presented on the aerodynamic mechanisms that cause the wing rock and the problem of mathematically modeling the aerodynamics and motions is discussed.

Nguyen, L. T.↗
NASA NTRS1982

The effect of delta 3 on a yawing HAWT blade and on yaw dynamics

A single degree of freedom aeroelastic computer model, WMSTAB3, was employed to perform a parametric analysis of HAWT blade behavior during yaw maneuvers. Over 1,000 different combinations of delta sub 3 and normal frequency were analyzed. The effect of delta sub 3 and flapping stiffness on flapping frequency, phase, and magnitude are discussed. The moments transmitted to the fixed system during yaw maneuvers were calculated and reduced to time constants of response to step changes in wind direction. The significance of the time constants for the configurations considered relative to yaw response rate and lag angle is discussed, along with their possible significance for large HAWT.

Perkins, F. W.↗
NASA NTRS1981

Nitric oxide delta band emission in the earth's atmosphere - Comparison of a measurement and a theory

Attention is given to the altitude dependent emission rate in the delta-bands of nitric oxide as measured in the earth's atmosphere at night by a scanning ultraviolet spectrometer. It is noted that the reaction responsible is the two-body association of nitrogen and oxygen atoms. The measurements show a vertical intensity beneath the layer for the delta-band system of 19 R. The horizontal emission rate is found to increase from 70 R at 117 km to 140 R at 150 km. The data are analyzed with a one-dimensional, time-dependent, vertical-transport model of odd nitrogen photochemistry. The calculated and measured intensities agree so long as the quenching of N(2D) by atomic oxygen is near 5 x 10 to the -13 cu cm/sec.

Rusch, D. W.↗
NASA NTRS1981

A modified adaptive delta modulator

This paper presents the results of a study in data compression of adaptive delta modulated video signals. The Song mode ADM is first investigated at a sampling rate of 16 Mbits/s and shown not to produce enough redundancy to warrant entropy encoding. A modified adaptive delta modulator algorithm is presented that operates at a sampling rate of 16 Mbits/s and does produce sufficient redundancy to yield a 40-50 percent data compression by using a simple code on 4 bit data blocks. Other techniques such as field interpolation and direct substitution are shown to increase the possible data compression further without noticeable degradation in the two input images used in this investigation. The effects of channel errors in the transmission of packet video over a computer network are considered. A leaky integrator is used to reduce the effects of channel errors in the data bits. It is shown that the effects of channel errors can be reduced by field interpolating those packets that can be shown to contain errors.

Barba, J.↗
NASA NTRS1982

Delta mission planning in the Shuttle transition era

Delta mission planning is aimed at providing Shuttle transition era user support which is flexible, dependable, and reliable. The flexibility of support is being enhanced by the development of a new Delta vehicle model, the 3920, capable of providing backup compatible performance for Shuttle SSUS-D (solid spinning upper stage) users. Reliable interfaces, flexible scheduling policies, and new launch facilities will help satisfy increased user demand.

Grimes, D. W.↗
NASA NTRS1982

Measurement and visualization of skin friction on the leeside of delta wings in supersonic flow

The reported investigation was conducted with the aid of the NASA Ames High Reynolds Number Wind Tunnel. The flow conditions considered involved free stream Mach numbers of 2 and 3, and a Reynolds number of approximately 10,000,000 p. m. The employed model was a delta wing with an angle of 70 deg. A method reported by Tanner (1977) was used for the measurement of the skin friction. This method involves the use of a laser interferometer to determine the change in the thickness of an oil film. The procedure can also be employed for a visualization of skin friction in the form of interferograms. The investigation shows that skin friction measurements can provide a significant contribution to a physical understanding of the flow processes at the delta wing.

Szodruch, J.↗
NASA NTRS1982

The Galileo Delta-VEGA mission to Jupiter

Project Galileo is to perform a more comprehensive investigation of the Jupiter system than was possible with Voyager. The Galileo spacecraft consists of both a planetary Orbiter and an atmospheric entry Probe. In connection with budgetary considerations and schedule problems, plans concerning the implementation of the project were changed a number of times. For the first seven months of 1982, the project Galileo was baselined as a Delta-VEGA transfer to be launched in 1985 by the Space Shuttle using the U.S. Air Force two-stage IUS as the upper stage augmented by a spacecraft Injection Module. The new mission and systems aspects of this 1985 Galileo Delta-VEGA baseline are compared to the prior 1985 Centaur direct transfer baseline. The techniques developed to virtually restore all the mission science in spite of greatly reduced launch vehicle performance are discussed. In July 1982, the U.S. Government reinstated the Centaur development and stipulated that Galileo be launched by Shuttle/Centaur in 1986.

Oneil, W. J.↗
NASA NTRS1982

The Delta improved second stage - First flight results

On July 16, 1982 the successful launch of the Landsat-D spacecraft marked a significant step in the evolutionary growth of the Delta launch vehicle. This growth is related to the development of the Improved Second Stage (ISS). The second utilization of the ISS occurred August 26, 1982 with the successful launch of the Canadian Telesat-F communications satellite. Used in conjunction with the PAM third stage, this spacecraft was placed in a geosynchronous transfer orbit with extremely high accuracy. The various steps in the 22-year history of the Delta launch vehicle are briefly examined. In mid-1979 it became apparent that the expendable-to-Shuttle transition time would increase over that previously planned. In connection with this development, it was decided to design the ISS. Attention is given to design details, a system description, the development schedule, aspects of performance capability, first flight results, and future performance improvements.

Grimes, D. W.↗
NASA NTRS1982

Error estimation for delta VLBI angle and angle rate measurements over baselines between a ground station and a geosynchronous orbiter

Baselines between a ground station and a geosynchronous orbiter provide high resolution Delta VLBI data which is beyond the capability of ground-based interferometry. The effects of possible error sources on such Delta VLBI data for the determination of spacecraft angle and angle rate are investigated. For comparison, the effects on spacecraft-only VLBI are also studied.

Wu, S. C.↗
NASA NTRS1983

The application of near-nadir Delta-k radar techniques to geodetic altimetry and oceanographic remote sensing

This paper first examines the extension of two-frequency, or Delta-k near-nadir remote sensing techniques to off-nadir radar altimetry. A different approach to sea state sensing is investigated which appears to offer much higher accuracy. The second section examines the Delta-k method of sensing rough surface area correlation or ocean wavenumber spectrum. The technique shows promise of directly sensing this parameter, in contrast with synthetic-aperture radar methods which are based on complex wave interaction mechanisms and mathematical transformations requiring the acquisition of voluminous data.

Miller, L. S.↗