Engineering topics

Brinker, David

Publications and source records attributed to Brinker, David.

12 records

NASA NTRS2010

Results and Conclusions from the NASA Isokinetic Total Water Content Probe 2009 IRT Test

The NASA Glenn Research Center has developed and tested a Total Water Content Isokinetic Sampling Probe. Since, by its nature, it is not sensitive to cloud water particle phase nor size, it is particularly attractive to support super-cooled large droplet and high ice water content aircraft icing studies. The instrument comprises the Sampling Probe, Sample Flow Control, and Water Vapor Measurement subsystems. Results and conclusions are presented from probe tests in the NASA Glenn Icing Research Tunnel (IRT) during January and February 2009. The use of reference probe heat and the control of air pressure in the water vapor measurement subsystem are discussed. Several run-time error sources were found to produce identifiable signatures that are presented and discussed. Some of the differences between measured Isokinetic Total Water Content Probe and IRT calibration seems to be caused by tunnel humidification and moisture/ice crystal blow around. Droplet size, airspeed, and liquid water content effects also appear to be present in the IRT calibration. Based upon test results, the authors provide recommendations for future Isokinetic Total Water Content Probe development.

Reehorst, Andrew↗

NASA NTRS2009

Progress Towards the Remote Sensing of Aircraft Icing Hazards

NASA has teamed with the FAA, DoD, industry, and academia for research into the remote detection and measurement of atmospheric conditions leading to aircraft icing hazards. The ultimate goal of this effort is to provide pilots, controllers, and dispatchers sufficient information to allow aircraft to avoid or minimize their exposure to the hazards of in-flight icing. Since the hazard of in-flight icing is the outcome of aircraft flight through clouds containing supercooled liquid water and strongly influenced by the aircraft s speed and configuration and by the length of exposure, the hazard cannot be directly detected, but must be inferred based upon the measurement of conducive atmospheric conditions. Therefore, icing hazard detection is accomplished through the detection and measurement of liquid water in regions of measured sub-freezing air temperatures. The icing environment is currently remotely measured from the ground with a system fusing radar, lidar, and multifrequency microwave radiometer sensors. Based upon expected ice accretion severity for the measured environment, a resultant aircraft hazard is then calculated. Because of the power, size, weight, and view angle constraints of airborne platforms, the current ground-based solution is not applicable for flight. Two current airborne concepts are based upon the use of either multifrequency radiometers or multifrequency radar. Both ground-based and airborne solutions are required for the future since groundbased systems can provide hazard detection for all aircraft in airport terminal regions while airborne systems will be needed to provide equipped aircraft with flight path coverage between terminal regions.

Reehorst, Andrew↗

NASA NTRS2004

Exploring PV on the Red Planet: Mars Array Technology Experiment and Dust Accumulation and Removal Technology

The environment on the surface of Mars is different in several critical ways from the orbital environment in which space solar arrays normally operate. Some important differences are: 1) Low intensity, low temperature operation; 2) Spectrum modified by atmospheric dust, varies with time; 3) Indirect sunlight; 4) Possibility of dust atoms at some times of year; 5) Deposited dust; 6) Wind; 7) Peroxide-rich reactive soil. We are developing two experiments to test operation of solar arrays on the surface of Mars, to be flown on the 2001 Surveyor Lander mission. The Mars Array Technology Experiment (MATE) will test the operation of several types of solar cells under Mars conditions, and determine the direct and scattered solar spectrum at the surface. The Dust Accumulation and Removal Technology (DART) experiment will monitor the amount of dust deposition on a target solar cell, measure the characteristics of the dust, and test the feasibility of dust removal.

Landis, Geoffrey A.↗

NASA NTRS2002

Overview of Photovoltaic Calibration and Measurement Standards at GRC

Photovoltaic (PV) systems (cells and arrays) for spacecraft power have become an international market. This market demands accurate prediction of the solar array power output in space throughout the mission life of the spacecraft. Since the beginning of space flight, space-faring nations have independently developed methods to calibrate solar cells for power output in low Earth orbit (LEO). These methods rely on terrestrial, laboratory, or extraterrestrial light sources to simulate or approximate the air mass zero (AM0) solar intensity and spectrum.

Baraona, Cosmo↗

NASA NTRS2002

A Summary of The 2000-2001 NASA Glenn Lear Jet AM0 Solar Cell Calibration Program

Calibration of solar cells for space is extremely important for satellite power system design. Accurate prediction of solar cell performance is critical to solar array sizing, often required to be within 1%. The NASA Glenn Research Center solar cell calibration airplane facility has been in operation since 1963 with 531 flights to date. The calibration includes real data to Air Mass (AM) 0.2 and uses the Langley plot method plus an ozone correction factor to extrapolate to AM0. Comparison of the AM0 calibration data indicates that there is good correlation with Balloon and Shuttle flown solar cells. This paper will present a history of the airplane calibration procedure, flying considerations, and a brief summary of the previous flying season with some measurement results. This past flying season had a record 35 flights. It will also discuss efforts to more clearly define the ozone correction factor.

Scheiman, David↗

NASA NTRS2001

MIR Solar Array Return Experiment: Power Performance Measurements and Molecular Contamination Analysis Results

A solar array segment was recently removed from the Mir core module and returned for ground-based analysis. The segment, which is similar to the ones the Russians have provided for the FGB and Service Modules, was microscopically examined and disassembled by US and Russian science teams. Laboratory analyses have shown the segment to he heavily contaminated by an organic silicone coating, which was converted to an organic silicate film by reactions with atomic oxygen within the. orbital flight environment. The source of the contaminant was a silicone polymer used by the Russians as an adhesive and bonding agent during segment construction. During its life cycle, the array experienced a reduction in power performance from approx. 12%, when it was new and first deployed, to approx. 5%, when it was taken out of service. However, current-voltage measurements of three contaminated cells and three pristine, Russian standard cells have shown that very little degradation in solar array performance was due to the silicate contaminants on the solar cell surfaces. The primary sources of performance degradation is attributed to "thermal hot-spotting" or electrical arcing; orbital debris and micrometeoroid impacts; and possibly to the degradation of the solar cells and interconnects caused by radiation damage from high energy protons and electrons.

Visentine, James↗

NASA NTRS2001

Status of Photovoltaic Calibration and Measurement Standards

The 7th International Workshop on Space Solar Cell Calibration and Measurement was held on September 25-27, 2000 in Girdwood, Alaska. Representatives from eight countries discussed international standards for single and multijunction solar cell measurement and calibration methods, round robin intercomparisons, and irradiation test methods for space solar cells. Progress toward adoption of an ISO standard on single junction cells was made. Agreement was reached to begin work on new standards for multijunction cells and irradiation testing. Progress on present single junction round robin measurements was discussed and future multijunction round robins were planned. The next workshop will be held in Germany in October 2001.

Baraona, Cosmo↗

NASA NTRS2000

Issues and Effects of Atomic Oxygen Interactions With Silicone Contamination on Spacecraft in Low Earth Orbit

The continued presence and use of silicones on spacecraft in low Earth orbit (LEO) has been found to cause the deposition of contaminant films on surfaces which are also exposed to atomic oxygen. The composition and optical properties of the resulting SiO(x)- based (where x is near 2) contaminant films may be dependent upon the relative rates of arrival of atomic oxygen, silicone contaminant and hydrocarbons. This paper presents results of in-space silicone contamination tests, ground laboratory simulation tests and analytical modeling to identify controlling processes that affect contaminant characteristics.

Banks, Bruce↗

NASA NTRS1991

High performance etchant for thinning p(+)-InP and its application to p(+)n InP solar cell fabrication

An etchant, namely (o-H3PO4)u: (HNO3)v: (H2O2)t: (H2O)1-(u+v+t) is developed for thinning, after contacting, the p(+) emitter layer of p(+)n InP structures made by thermal diffusion. Varying u, v, and t, reproducible etch rates of 5 to 110 nm/min are obtained. After thinning the 0.6- to 2.5-micron thick p(+) InP layer down to 60-250 nm, specular surfaces are obtained at up to 80 nm/min etch rate. Due to its intrinsic qualities the resisual P-rich oxide after thinning the emitter layer provides surface passivation of p(+) InP surfaces and can also serve as a first-layer AR coating.

Faur, Maria↗

NASA NTRS1987

Design considerations for a GaAs nipi doping superlattice solar cell

A new GaAs nipi doping superlattice solar cell structure is presented, which holds promise for high efficiency coupled with very high radiation tolerance. The structure has all contacts on the unilluminated side. Design constraints are presented which this structure must satisfy in order to exhibit high efficiency and high radiation tolerance. The results of self-consistent quantum mechanical calculations are presented which show that a viable design of this cell would include relatively thick n and p layers which are fairly heavily doped.

Clark, Ralph↗

NASA NTRS1987

Self-consistent calculations and design considerations for a GaAs nipi doping superlattice solar cell

The authors present design constraints which show that a previously proposed GaAs nipi doping superlattice solar cell structure would not work as an efficient space solar cell. A structure based on the CLEFT process, which shows promise of being an efficient cell with very high radiation tolerance, is proposed. In order to test theoretically its viability and to optimize its design, self-consistent quantum mechanical calculations were made for a number of thicknesses of the n, i, and p layers and the dopings in the n and p layers. These results show that: 1) an i layer is not necessary; in fact, its presence makes it difficult to satisfy one of the key constraints; 2) a near-optimum design with 750-A thick n and p layers with dopings of 2.5E18/cu cm and a selective contact separation of 20 microns would yield both high efficiency and very high radiation tolerance.

Clark, Ralph O.↗

NASA NTRS1985

A proposed GaAs-based superlattice solar cell structure with high efficiency and high radiation tolerance

A solar cell structure is proposed which uses a GaAs nipi doping superlattice. An important feature of this structure is that photogenerated minority carriers are very quickly collected in a time shorter than bulk lifetime in the fairly heavily doped n and p layers and these carriers are then transported parallel to the superlattice layers to selective ohmic contacts. Assuming that these already-separated carriers have very long recombination lifetimes, due to their being across an indirect bandgap in real space, it is argued that the proposed structure may exhibit superior radiation tolerance along with reasonably high beginning-of-life efficiency.

Goradia, Chandra↗