Engineering topics

Keller, V. W.

Publications and source records attributed to Keller, V. W..

At least 19 records

NASA NTRS2008

Sea State and Weather Capability for NASA's Constellation Program

Marine weather and related parameters such as wind, ocean wave height and period, air temperature, sea surface temperature, visibility, and potential for icing are critical to the design, operation, and safety of crewed space vehicles. The National Aeronautics and Space Administration's (NASA's) Constellation Program requires detailed assessment of marine weather related parameters that may be encountered during launch, abort, landing, and crew rescue operations for the crewed Axes/Orion space vehicles. This information is required for both space vehicle design and operational purposes. The space vehicles must be designed such that they cam withstand the environment they are likely to encounter. The crewed Axes/Orion space vehicles will launch from NASA's Kennedy Space Center (KSC), Florida for both International Space Station (ISS) missions with 51.6deg inclination orbits and lunar missions with approximately 280 inclination orbits. Since both missions will fly ever the Atlantic Ocean on ascent to orbit and will fly over the Pacific Ocean on descent from orbit, an unlikely but possible emergency abort could require parachuting the Orion capsule and crew into the ocean. This situation could potentially put the crew in an isolated and hazardous environment for severn hours while they await rescue. Therefore, abort, landing, and crew rescue elements of the Constellation Program must address weather related parameters on a global scale. This paper describes buoy measurement data, sea surface temperature satellite data, and sea state computer model data that are being utilized by the Constellation Program to address these design and operational issues.

Barbre, R. E.↗

NASA NTRS2008

Sea State and Weather Assessment Capability for NASA's Constellation Program

Marine weather and related parameters such as wind, ocean wave height and period, air temperature, sea surface temperature, visibility, and potential for icing are critical to the design, operation, and safety of crewed space vehicles. The National Aeronautics and Space Administration's (NASA's) Constellation Program requires detailed assessment of marine weather related parameters that may be encountered during launch, abort, landing, and crew rescue operations for the crewed Ares/Orion space vehicles. This information is required for both space vehicle design and operational purposes. The space vehicles must be designed such that they can withstand the environment they are likely to encounter. The crewed Ares/Orion space vehicles will launch from NASA's Kennedy Space Center (KSC), Florida for both International Space Station (ISS) missions with 51.6 o inclination orbits and lunar missions with approximately 28 inclination orbits. Since both missions will fly over the Atlantic Ocean on ascent to orbit and will fly over the Pacific Ocean on descent from orbit, an unlikely but possible emergency abort could require parachuting the Orion capsule and crew into the ocean. This situation could potentially put the crew in an isolated and hazardous environment for several hours while they await rescue. Therefore, abort, landing, and crew rescue elements of the Constellation Program must address weather related parameters on a global scale. This paper describes buoy measurement data, sea surface temperature satellite data, and sea state computer model data that are being utilized by the Constellation Program to address these design and operational issues.

Barbre, B. J.↗

NASA NTRS1992

Geostationary earth observatory remote sensing instruments

The results of conceptual studies conducted of several remote sensing instruments for the development of the geostationary earth observatory element of NASA's Mission to Planet Earth program are presented. Remote sensing instruments provisionally identified to provide the required measurements include imagers, sounders, radiometers, and other passive instruments suited for geostationary orbit. A number of the instruments defined purposely parallel the wavelength or channel specifications to ensure direct intercomparisons of the differing but complementary temporal and spatial measurements.

Keller, V. W.↗

NASA NTRS1989

Laser atmospheric wind sounder (LAWS)

The principle of operation of a space based Doppler lidar wind measuring system is discussed along with laser wavelength selection considerations. Differences in accommodating the Laser Atmospheric Wind Sounder (LAWS) on the Earth Observing System (EOS) polar platform and the Manned Space Station are presented. The impact of the LAWS instrument support subsystems are specifically discussed.

Beranek, R. G.↗

NASA NTRS1986

Double window viewing chamber assembly

A viewing chamber which permits observation of a sample retained therein includes a pair of double window assemblies mounted in opposed openings in the walls thereof so that a light beam can directly enter and exit from the chamber. A flexible mounting arrangement for the outer windows of the window assemblies enables the windows to be brought into proper alignment. An electrical heating arrangement prevents fogging of the outer windows whereas desiccated air in the volume between the outer and inner windows prevents fogging of the latter.

Keller, V. W.↗

NASA NTRS1986

Ice nucleus activity measurements of solid rocket motor exhaust particles

The ice Nucleus activity of exhaust particles generated from combustion of Space Shuttle propellant in small rocket motors has been measured. The activity at -20 C was substantially lower than that of aerosols generated by unpressurized combustion of propellant samples in previous studies. The activity decays rapidly with time and is decreased further in the presence of moist air. These tests corroborate the low effectivity ice nucleus measurement results obtained in the exhaust ground cloud of the Space Shuttle. Such low ice nucleus activity implies that Space Shuttle induced inadvertent weather modification via an ice phase process is extremely unlikely.

Keller, V. W.↗

NASA NTRS1986

Development testing of large volume water sprays for warm fog dispersal

A new brute-force method of warm fog dispersal is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray induced air flow. Fog droplets are removed by coalescence/rainout. The efficiency of the technique depends upon the drop size spectra in the spray, the height to which the spray can be projected, the efficiency with which fog laden air is processed through the curtain of spray, and the rate at which new fog may be formed due to temperature differences between the air and spray water. Results of a field test program, implemented to develop the data base necessary to assess the proposed method, are presented. Analytical calculations based upon the field test results indicate that this proposed method of warm fog dispersal is feasible. Even more convincingly, the technique was successfully demonstrated in the one natural fog event which occurred during the test program. Energy requirements for this technique are an order of magnitude less than those to operate a thermokinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway.

Keller, V. W.↗

NASA NTRS1986

Large volume water sprays for dispersing warm fogs

A new method for dispersing of warm fogs which impede visibility and alter schedules is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray-induced air flow; the fog droplets are removed by coalescence/rainout. The efficiency of this fog droplet removal process depends on the size spectra of the spray drops and optimum spray drop size is calculated as between 0.3-1.0 mm in diameter. Water spray tests were conducted in order to determine the drop size spectra and temperature response of sprays produced by commercially available fire-fighting nozzles, and nozzle array tests were utilized to study air flow patterns and the thermal properties of the overall system. The initial test data reveal that the fog-dispersal procedure is effective.

Keller, V. W.↗

NASA NTRS1985

Status of warm fog dispersal research

A new concept for dispersing warm fog is presented. This brute force technique uses large volume recycled water sprays. Energy requirements for this technique are an order of magnitude less than those to operate a thermo-kinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway. Tests conducted to provide drop spectra measurements and temperature response measurements of suitable water sprays are described. Three mobile firefighting modules capable of spraying up to 630 l/s (10,000 gpm) to a height in excess of 50 m were utilized. Periodic operation of two parallel rows of nozzles in a heavy fog resulted in downwind-correlated increases in the visual range measured with a forward scatter visibility meter.

Keller, V. W.↗

NASA NTRS1985

Demonstration of a new method for dispersing warm fogs

Low visibility due to warm fog has caused costly disruptions in the case of aircraft schedules, and fog-related difficulties can arise in connection with Space Shuttle flights. As current methods of fog elimination are not entirely satisfactory, Kelley (1983) has proposed a new brute force procedure for warm fog dispersal. This procedure makes use of recycled water sprays. Fog droplets are removed by coalescence/rainout. Details regarding the involved approaches are described, and a demonstration of the method is discussed. Attention is given to tests conducted in October 1984, visual range improvement in response of water spray fog dispersal, a systematic investigation concerning a selection of firefighting nozzles, and histograms of fog droplet number concentration measured in the spray curtain outflow with a forward scattering spectrometer probe.

Keller, V. W.↗

NASA NTRS1983

Space shuttle exhaust cloud properties

A data base describing the properties of the exhaust cloud produced by the launch of the Space Transportation System and the acidic fallout observed after each of the first four launches was assembled from a series of ground and aircraft based measurements made during the launches of STS 2, 3, and 4. Additional data were obtained from ground-based measurements during firings of the 6.4 percent model of the Solid Rocket Booster at the Marshall Center. Analysis indicates that the acidic fallout is produced by atomization of the deluge water spray by the rocket exhaust on the pad followed by rapid scavening of hydrogen chloride gas aluminum oxide particles from the Solid Rocket Boosters. The atomized spray is carried aloft by updrafts created by the hot exhaust and deposited down wind. Aircraft measurements in the STS-3 ground cloud showed an insignificant number of ice nuclei. Although no measurements were made in the column cloud, the possibility of inadvertent weather modification caused by the interaction of ice nuclei with natural clouds appears remote.

Anderson, B. J.↗

NASA NTRS1983

An application of model testing for the study of rocket exhaust cloud properties

The application of the 6.4-percent Shuttle Model Test Facility to the study of the Shuttle exhaust cloud properties is discussed with emphasis on the properties related to the production of the deposition (submillimeter drops composed of an acidic liquid and alumina solids) which occurs with each launch. An analysis of test data suggests that the major fraction of the liquid in the deposition is produced directly through the interaction between the exhaust and the deluge water spray and then modified by rapid scavenging of wet acidic aluminum oxide particles. Based on this conclusion, the possibility arises that the acid in the deposition can be neutralized by addition of a base to the deluge water. Current work with the 6.4-percent model is directed toward verification of this hypothesis.

Anderson, B. J.↗

NASA NTRS1983

Microphysical properties of the Shuttle exhaust cloud

A data base describing the properties of the exhaust cloud produced by the launch of the STS has been developed based on data from a series of ground and aircraft based measurements made during the launches of STS 2, 3, and 4. Aircraft observations were performed during the STS-3 launch with a NOAA WP-3D Orion hurricane research aircraft which contained instrumentation for cloud condensation nucleus and ice nucleus counting, Aitken particle counting, and pH determination. Ground observations were conducted at 50 different sites, as well as in the direct exhaust from the solid rocket booster flame trench at all three launches. The data is analyzed in order to determine any possible adverse impacts of the exhaust products on human health and/or the environment. Analyses of the exhaust cloud measurements indicate that in the case of the ground cloud where plenty of large water drops are present and considerable scavenging and fallout of aerosol takes place, possible adverse impacts of the remaining aerosols (CCN and IN) on natural precipitation processes which may occur in the launch area hours after the launch are remote. However, it is determined that under certain atmospheric conditions there could be short term adverse effects on visibility.

Keller, V. W.↗

NASA NTRS1982

Influence of air velocity on the habit of ice crystal growth from the vapor

The effect of air velocity on the growth behavior of ice crystals growing from water vapor was investigated at temperatures between 0 and -35 C and at supersaturation levels ranging from 2 to 40 percent, using a laboratory chamber in which it was possible to make these variations. It was found that crystal growth was most sensitive to changes in the air velocity at temperatures near -4 C and -15 C where, near water saturation, the introduction of only a 5 cm/s air velocity induced skeletal transitions (columns to needles near -4 C and plates to dendrites near -15 C). The experiments provide conditions which simulate growth of ice crystals in the atmosphere, where crystal growth takes place at or somewhat below water saturation.

Keller, V. W.↗

NASA NTRS1981

Microphysical development of a pulsating cumulus tower - A case study

In-cloud microphysical data collected within a 22-minute period during seven consecutive passes at the -13 C sampling level of a deep (base +22 C) convective cloud provide observational evidence for a secondary ice production mechanism at work in the Florida environment. The observed microphysical characteristics of the convective tower, particularly the spatial distribution and habit of the ice phase relative to the updraft, are consistent with a rime-splintering hypothesis for secondary ice production. It is shown that the cloud's updraft structure is critically important in governing the timing of the ice production by controlling the flux of graupel particles through the critical temperature zone (-3 C to -8 C). The importance of the cloud's pulsation growth dynamics on the microphysics is emphasized, particularly as it relates to rapidly glaciating cumuli.

Keller, V. W.↗

NASA NTRS1980

Ice crystal growth in a dynamic thermal diffusion chamber

Ice crystals were grown in a supersaturated environment produced by a dynamic thermal diffusion chamber, which employed two horizontal plates separated by a distance of 2.5 cm. Air was circulated between and along the 1.2 m length of the plates past ice crystals which nucleated and grew from a fiber suspended vertically between the two plates. A zoom stereo microscope with a magnification which ranged from 3X to 80X and both 35 mm still photographs and 16 mm time lapse cine films taken through the microscope were used to study the variation of the shape and linear growth rate of ice crystals as a function of the ambient temperature, the ambient supersaturation, and the forced ventilation velocity. The ambient growth conditions were varied over the range of temperature 0 to -40 C, over the range of supersaturation 4% to 50% with respect to ice, and over the range of forced ventilation velocities 0 cm/s to 20 cm/s.

Keller, V. W.↗

NASA NTRS1980

Water-ice and water-updraft relationships near -10 C within populations of Florida cumuli

Evidence is presented for a sequential development of cloud water, rainwater, graupel, and crystalline ice with the aging of the cloud. This evidence is based on in-cloud microphysical data set collected in Florida convective towers that were penetrated close to their tops near -10 C; the very rapid onset of graupel that appears on repeat penetrations of some towers is of particular interest. A separate data set shows a large scatter in the relationship between the maximum value of cloud water and vertical velocity which indicates that measurements of cloud water can be misleading as an indication of growth activity. The sequential pass data showing the evolution of ice and water are consistent with a rime-splintering, secondary ice production hypothesis.

Sax, R. I.↗

NASA NTRS1980

Growth of ice discs from the vapor and the mechanism of habit change of ice crystals

Ice crystals nucleated on a liquid nitrogen cooled glass fiber grow first as thin disks which subsequently transform to plates and columns as they thicken and extend to regions of higher supersaturation. Crystals are often found to be dislocation-free, which suggests that growth results from surface nucleation, the habit depending on preferential nucleation in an adsorbed multilayer on basal or prism face.

Keller, V. W.↗