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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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NASA NTRS1991

Project ARES 2: High-altitude battery-powered aircraft

A high-altitude, battery-powered, propeller-driven aircraft was designed and is being built by undergraduate students at California State University, Northridge. The aircraft will fly at an altitude of 104,000 ft at Mach 0.2 (190 ft/sec) and will be instrumented to record flight performance data, including low Reynolds number propeller and airfoil information. This project will demonstrate the feasibility of electric-powered flight in a low-density, low-temperature Earth environment that models the atmosphere of Mars. Data collected will be used to design a Mars aircraft to investigate the surface of Mars prior to manned missions. The instrumented payload and the mission profile for the high-altitude Earth flight were determined. Detailed aerodynamic and structural analyses were performed. Control, tracking, and data recording subsystems were developed. Materials were obtained and fabrication begun. The aircraft has a 32-ft wing span, a wing area of 105 sq ft, is 17.5 ft long, has a 12-in payload bay, and weighs 42 lb. It is composed primarily of lightweight materials, including Mylar, and composite materials, including graphite/epoxy and aramid core honeycomb sandwich. Low-altitude flight testing to check guidance and control systems and to calibrate data-gathering instruments will take place this summer, followed shortly by the 104,000-ft flight.

Source record↗
NASA NTRS1992

The statistical cusp - A flux transfer event model

In this paper, we predict the precipitation signatures which are associated with transient magnetopause reconnection, following recent observations of the dependence of dayside ionospheric convection on the orientation of the IMF. We then employ a simple model of the longitudinal motion of flux-transfer-event signatures to show how such events can easily reproduce the local time distribution of cusp occurrence probabilities, as observed by low-altitude satellites. This is true even in the limit where the cusp is a series of discrete events. Furthermore, we investigate the existence of double cusp patches predicted by the simple model and show how these events may be identified in the data.

Smith, M. F.↗
NASA NTRS1992

Upflowing ionospheric ions in the auroral region

Observations of upflowing ionospheric ions are obtained nearly simultaneously by DE 1 and DE 2 over the nightside auroral regions. At low altitudes, the mean value of the net upward ion number flux is of the order of 10 exp 9/sq cm per sec. The ionosphere is predominantly O(+), and the flux of ions with energy greater than 5 eV is a very small fraction (less than 1 percent) of the total ion flux. At high altitudes, the upflowing ions are accelerated by a parallel electric field and heated (with characteristic energies of hundreds of electron volts). Comparing upflowing fluxes at high and low altitudes yields an estimated height of the bottom of the auroral acceleration region of 1400-1700 km for the region of peak potential drop. This low-altitude acceleration could either be from a parallel electric field or from perpendicular acceleration. The fluxes at the edges of the arc are mostly H(+) thus implying a higher-altitude base of the acceleration region at the edges where the potential drop is lower.

Lu, G.↗
NASA NTRS1992

Vision-based range estimation using helicopter flight data

Pilot aiding during low-altitude flight depends on the ability to detect and locate obstacles near the helicopter's intended flightpath. Computer-vision-based methods provide one general approach for obstacle detection and range estimation. Several algorithms have been developed for this purpose, but have not been tested with actual flight data. This paper presents results obtained using helicopter flight data with a feature-based range estimation algorithm. A method for recursively estimating range using a Kalman filter with a monocular sequence of images and knowledge of the camera's motion is described. The helicopter flight experiment and one of four resulting datasets is briefly discussed. Finally the performance of the range estimation algorithm is explored based on comparison of the range estimates with true range measurements collected during the flight experiment.

Smith, Phillip N.↗
NASA NTRS1991

Architecting a mission plan for Lunar Observer

The present status of NASA's Lunar Observer study effort at JPL is discussed in the context of an ongoing 20-year series of studies focused on defining a robotic, low-altitude, polar-orbiting mission to the moon. The primary emphasis of the discussion is a review of the various systems-level factors that drive the overall architecture of the mission plan. Selected top-level project and science requirements are summarized and the current mission and science objectives are presented. A brief description of the candidate science instrument complement is included. Several significant orbital effects caused by the lunar gravity field are explained and the variety of trajectory and maneuver options considered for both getting to the moon and orbiting there are described. Several candidate mission architectures are outlined and the mission plans chosen for future study are described. Two mission options result: a single-spacecraft, single-launch scenario, and a multiple-spacecraft, multiple-launch concept.

Ridenoure, Rex W.↗
NASA NTRS1992

Active and passive microwave measurements of soil moisture in FIFE

During the intensive field campaigns of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) in May-October of 1987, several nearly simultaneous measurements were made with low-altitude flights of the L-band radiometer and C- and X-band scatterometers over two transects in the Konza Prairie Natural Research Area, some 8 km south of Manhattan, Kansas. These measurements showed that although the scatterometers were sensitive to soil moisture variations in most regions under the flight path, the L-band radiometer lost most of its sensitivity in regions unburned for many years. The correlation coefficient derived from the regression between the radar backscattering coefficient and the soil moisture was found to improve with the increase in antenna incidence angle. This is attributed to a steeper falloff of the backscattering coefficient as a function of local incidence at angles near nadir than at angles greater than 30 deg.

Wang, J. R.↗
NASA NTRS1992

Vision-based range estimation using helicopter flight data

Pilot aiding during low-altitude flight depends on the ability to detect and locate obstacles near the helicopter's intended flightpath. Computer-vision-based methods provide one general approach for obstacle detection and range estimation. Several algorithms have been developed for this purpose, but have not been tested with actual flight data. This paper presents results obtained using helicopter flight data with a feature-based range estimation algorithm. A method for recursively estimating range using a Kalman filter with a monocular sequence of images and knowledge of the camera's motion is described. The helicopter flight experiment and four resulting datasets are discussed. Finally the performance of the range estimation algorithm is explored in detail based on comparison of the range estimates with true range measurements collected during the flight experiment.

Smith, Phillip N.↗
NASA NTRS1992

ERS-1 and Almaz ocean wave monitoring experiments

Preliminary results from two ocean wave monitoring experiments conducted in 1991 using the high-altitude ERS-1 synthetic aperture radar (SAR) and the low-altitude ex-USSR Almaz 1 SAR are presented. ERS-1 imagery of the Gulf Stream supports the idea that a future wide-swath scansar will be a valuable tool for monitoring large-scale ocean dynamics at high resolution. A direct comparison of ERS-1 and Almaz 1 ocean wave spectra shows major deficiencies in the ERS-1 high range-to-velocity ratio R/V sensor that are partially resolved with the lower-altitude Almaz platform. Optimum wave imaging from space will require both a low R/V and low off-nadir angle.

Beal, R. C.↗
NASA NTRS1992

Diminished effects of El Chichon on stratospheric aerosols, early 1984 to late 1986

Stratospheric aerosol collections by wire impactors, taken mainly over the western U.S. from early 1984 to late 1986, show the diminishing effects of El Chichon's 1982 eruption, and provide a set of data for judging subsequent volcanic effects. Decrease in sulfate burden during the study time is due to preferential gravitational settling-out of large (above 0.5-micron diameter) sulfate aerosol droplets. As a result of settling from higher levels, lower altitude (12.2-15.2 km) air early in 1984 tends to contain more sulfate than higher level (19.8-21.3 km) air. As of late 1986, however, high- and low-altitude sulfate contents have decreased and are similar, suggesting large-particle settling has been completed. The later sulfate collection size distributions resemble unimodal background spectra, whereas earlier ones are bimodal. Average sulfate load for all altitudes decreases during the period of study from 0.4 to 0.08 microgram/cu m. The latter value is somewhat higher than a volcanically unenriched pre-El Chichon level, suggesting that even as of 1987, stratospheric background had not been obtained.

Snetsinger, K. G.↗
NASA NTRS1992

Clustering methods for removing outliers from vision-based range estimates

The present approach to the automation of helicopter low-altitude flight uses one or more passive imaging sensors to extract environmental obstacle information; this is then processed via computer-vision techniques to yield a time-varying map of range to obstacles in the sensor's field of view along the vehicle's flight path. Attention is given to two related techniques which can eliminate outliers from a sparse range map, clustering sparse range-map information into different spatial classes that rely on a segmented and labeled image to aid in spatial classification within the image plane.

Hussien, B.↗
NASA NTRS1992

Dynamics Explorer measurements of particles, fields, and plasma drifts over a horse-collar auroral pattern

As shown from ground-based measurements and satellite-borne imagers, one type of global auroral pattern characteristic of quiet (usually northward IMF) intervals is that of a contracted but thickened emission region of a pattern referred to as 'horse-collar' aurora (Hones et al., 1989). In this report we use the Dynamics Explorer data set to examine a case in which this horse-collar pattern was observed by the DE-1 auroral imager, while at the same time DE-2, at lower altitude, measured precipitating particles, electric and magnetic fields, and plasma drifts. Our analysis shows that, in general, there is close agreement between the optical signatures and the particle precipitation patterns. In many instances, over scales ranging from tens to a few hundred kilometers, electron precipitation features and upward field-aligned currents are observed at locations where the plasma flow gradients indicate negative V-average x E. The particle, plasma, and field measurements made along the satellite track and the 2D perspective of the imager provide a means of determining the configuration of convective flows in the high-latitude ionosphere during this interval of northward IMF. Recent mapping studies are used to relate the low-altitude observations to possible magnetospheric source regions.

Sharber, J. R.↗
NASA NTRS1985

Severe wind flow of small spatial and temporal scales: The microburst and related phenomena

Low-altitude winds on the meso- and microscale are the primary focus of study for the Research Applications Program (RAP) of NCAR. Local weather features such as microbursts, microburst lines, gust fronts, and convergent wind boundaries have been observed and documented extensively. A microburst is a strong, small-scale convective storm outflow which diverges horizontally in all directions upon impact with the ground (Fujita, 1981). A microburst line is composed of two or more microbursts which occur either simultaneously or consecutively, and subsequently form a diverging line of outflow. The temporal and spatial scales of these phenomena are shown. Microbursts and microburst lines generally occur on both the meso- and microscale, while gust fronts and convergent wind boundaries overlap into the mesoscale. Microbursts, in particular, not only are small spatially but are also a short-lived phenomenon. Clearly, some of these features are on a much smaller spatial and temporal scale than can be resolved by a global wind measurement. During the past three years, three experiments were held in the Denver, CO, area to observe boundary-layer winds. Their main objectives were observation and documentation of those weather features discussed above. The Joint Airport Weather Studies (JAWS) Project, which ran in the summer of 1982, was set up to study microbursts. The Convective Initiation Project (1984) was designed to document clear-air convergent wind boundaries, including gust fronts, and their role in convective storm initiation. This project was immediately followed by the Classify, Locate, and Avoid Wind Shear experiment that expanded upon the work done in JAWS. Details on the scales of these weather features are presented. The wind sensors used to detect these phenomena are also discussed. Concluding comments address the usefulness of a global wind measurement system as it pertains to our local scale of interest.

Roberts, Rita D.↗
NASA NTRS1955

Performance of Four Experimental High-btu-per-gallon Fuels in a Single Turbojet Combustor

Performance characteristics of four hydrocarbon fuels having high Btu per gallon were determined in a single turbojet combustor. At simulated low-altitude operating conditions, the fuels with high Btu per gallon generally produced more carbon than did JP-4 and JP-5 fuels. The deposits were reduced appreciably with a fuel-oil additive. At high-altitude conditions, the high Btu-per-gallon fuels gave lower efficiencies than did JP-4 or JP-5 fuels. No attempts were made to improve performance by combustor design modification.

Jonash, Edmund R↗
NASA NTRS1928

Preliminary Flight Tests of the N.A.C.A. Roots Type Aircraft Engine Supercharger

An investigation of the suitability of the N.A.C.A. Roots type aircraft engine supercharger to flight-operating conditions, as determined the effects of the use of the supercharger upon engine operation and airplane performance, is described in this report. Attention was concentrated on the operation of the engine-supercharger unit and on the improvement of climbing ability; some information concerning high speeds at altitude was obtained. The supercharger was found to be satisfactory under flight-operating conditions. Although two failures occurred during the tests, the causes of both were minor and have been eliminated. Careful examination of the engines revealed no detrimental effects which could be attributed to supercharging. Marked improvements in climbing ability and high speeds at altitude were effected. It was also found that the load which could be carried to a given moderate or high altitude in a fixed time was considerably augmented. A slight sacrifice of low-altitude performance was necessitated, however, by the use of a fixed-pitch propeller. From a consideration of the very satisfactory flight performance of the Roots supercharger and of its inherent advantages, it is concluded that this type is particularly attractive for use in certain classes of commercial airplanes and in a number of military types.

Gardiner, Arthur W↗
NASA NTRS1957

Satellite and space propulsion system

Previous papers of this conference have described rocket systems capable of launching sizable payloads into satellite orbits. Propulsion systems that might be suitable for the next steps are discussed in this paper. Some of the uses for propulsion systems once satellites have been established are as follows: (1) increasing lifetime of low-altitude satellite, (2) controlling and altering satellite orbits, (3) lunar and interplanetary exploration and (4) auxiliary electric power. (author)

Moeckel, W E↗
NASA NTRS1976

Beach Erosion

Two miles of beach at Cape Canaveral eroded by construction of a port and jetties was recently restored. Such work in harbors of many cities often disrupts normal flow of sand for many miles along coasts. Brevard County, FL residents now enjoy a 400 ft. wide public beach in an area in imminent danger of destructive erosion just a year previously. Before and after aerial photos show how more than two miles of beach were rebuilt with 2.7 million cubic yards of sand helping abate the erosion problem caused by construction of jetties. NASA volunteered its remote-sensing technology and instrumented aircraft to provide low-altitude color infrared photography about every three months since 1972.

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NASA NTRS1955

Investigation in the Langley Free-Flight Tunnel of the Low-Speed Stability and Control Characteristics of a 1/10-Scale Model Simulating the Convair F-102A Airplane

An investigation of the low-speed, power-off stability and control characteristics of a 1/10-scale model simulating the Convair F-102A airplane has been made in the Langley free-flight tunnel. The model in its basic configuration and with two modifications involving leading- edge slats and an increase in vertical-tail size was flown through a lift-coefficient range from 0.7 to the stall. Only relatively low-altitude conditions were simulated. The longitudinal stability characteristics of the model were considered satisfactory for all conditions investigated. The lateral stability characteristics were considered satisfactory for the basic configuration over the lift-coefficient range investigated, except near the stall, where large values of static directional instability caused the model to be directionally divergent. An 80-percent increase in vertical-tail area increased the angle of attack at which the model became directionally divergent. The longitudinal and lateral control characteristics were generally satisfactory. Although the adverse sideslip characteristics for the model were considered acceptable over the angle-of-attack range, analysis indicates that the adverse sideslip characteristics of the airplane may be objectionable at high angles of attack.

Boisseau, Peter C.↗
NASA NTRS1953

Investigation of the Low-Speed Stability and Control Characteristics of a 1/10-Scale Model of the Convair YF-102 Airplane in the Langley Free-Flight Tunnel

An investigation of the low-speed, power-off stability and control characteristics of a 1/10-scale model of the Convair YF-102 airplane has been made in the Langley free-flight tunnel. The model was flown over a lift-coefficient range from 0.5 to the stall in its basic configuration and with several modifications involving leading-edge slats and increases in vertical-tail size. Only relatively low-altitude conditions were simulated and no attempt was made to determine the effect of freeing the controls. The longitudinal stability characteristics of the model were considered satisfactory for all conditions investigated. The lateral stability characteristics were considered satisfactory for the basic configuration over the speed range investigated except near the stall, where large values of static directional instability caused the model to be directionally divergent. The addition of leading-edge slats or an 8-percent increase in vertical-tail area increased the angle of attack at which the model became directionally divergent. The use of leading-edge slats in combination with a 40-percent increase in vertical-tail size eliminated the directional divergence and produced satisfactory stability characteristics through the stall. The longitudinal and lateral control characteristics were generally satisfactory. Although the adverse sideslip characteristics for the model were considered satisfactory over the angle-of-attack range, analysis indicates that the adverse sideslip characteristics of the airplane may be objectionable at high angles of attack.

Johnson, Joseph L., Jr.↗