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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

LEDs for Extraterrestrial Agriculture: Tradeoffs between Color Perception and Photon Efficacy

Growing food on extraterrestrial surfaces requires the development of efficient lighting technologies to provide photons for photosynthesis. Here we discuss the development and demonstration of LED panels with a high color fidelity index that can achieve a photon efficacy of 3.6 µmol of photons per joule of input electrical energy. As of June 2021, this is higher than commercial LED fixtures on Earth. This high efficacy makes LED technology a preferred option to solar fiber optics for extraterrestrial applications. Increasing the fraction of red LEDs and photons increases the efficacy but decreases the perception of color.

Bioregenerative↗
NASA NTRS1987

Development of an LED display system for cross-track distance and velocity for Loran-C flight

The methodology for estimating cross-track velocity by combining rate-gyro and Loran-C data is illustrated in block diagrams. At present, preliminary analysis has established values for K sub 1, K sub 2, the parameters of the digital control loops. A computer program was written to implement a digital simulation of the system as illustrated. Given a model for the noise in the rate-gyro and Loran-C receiver, and their dynamic response, the simulation provides a working model to establish good control loop parameters. The layout of the LED display for flight testing of Loran-C approach flying, which was constructed during a visit to Langley Research Center, is shown. Four bar-graph LED displays are paired to provide cross-track distance and velocity from a Loran-C defined runway centerline. Two seven-segment LED displays are used to provide alphanumeric readout of range to touchdown and desired height. A metal case was built, a circuit board designed, and manufactured with the assistance of NASA Langley personnel.

Dogan, Norry↗
NASA NTRS2005

GOES Satellite Data Validation Via Hand-held 4 LED Sun Photometer at Norfolk State University

Sun photometry is a passive means of measuring a quantity of light radiation. The GIFTS- IOMI/GLOBE Water Vapor/Haze Sun photometer contains four light emitting diodes (LEDs), which are used to convert photocurrent to voltage. The intensity of the incoming and outgoing radiation as detected on the Earth s surface can be affected by aerosols and gases in the atmosphere. The focus of this research is primarily on aerosol and water vapor particles that absorb and reemit energy. Two LEDs in the photometer correspond to light scattered at 530 nm (green spectrum) and 620 nm (red spectrum). They collect data pertaining to aerosols that scatter light. The other two LEDs detect the light scattered by water vapor at wavelengths of 820 nm and 920 nm. The water vapor measurements will be compared to data collected by the Geostationary Observation Environmental Satellite (GOES). Before a comparison can be made, the extraterrestrial constant (ET), which is intrinsic to each sun photometer, must be measured. This paper will present determination of the ET constant, from which the aerosol optical thickness (AOT) can be computed for comparison to the GOES satellite to ascertain the reliability of the sun photometer.

Reynolds, Arthur, Jr.↗
NASA NTRS2016

Comparative Study of Lettuce and Radish Grown Under Red and Blue LEDs and White Fluorescent Lamps

Growing vegetable crops in space will be an essential part of sustaining astronauts during long-range missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop yield, there is also recent interest in analyzing the subtle effects of additional wavelengths on plant growth. For instance, since plants often look purplish gray under red and blue LEDs, the addition of green light allows easy recognition of disease and the assessment of plant health status. However, it is important to know if wavelengths outside the traditional red and blue wavebands have a direct effect on enhancing or hindering the mechanisms involved in plant growth. In this experiment, a comparative study was performed on two short cycle crops of red romaine lettuce (Lactuca sativa cv. "Outredgeous") and radish (Raphanus sativa cv. 'Cherry Bomb'), which were grown under two light treatments. The first treatment being red (630 nm) and blue (450 nm) LEDs alone, while the second treatment consisted of daylight tri-phosphor fluorescent lamps (CCT approximately 5000 K) at equal photosynthetic photon flux (PPF). The treatment effects were evaluated by measuring the fresh biomass produced, plant morphology and leaf dimensions, leaf chlorophyll content, and adenosine triphosphate (ATP) within plant leaf/storage root tissues.

Food Production↗
NASA NTRS1977

Diodes stabilize LED output

Small-signal diodes are placed in series with light-emitting diodes (LED's) to stabilize LED output against temperature fluctuations. Simple inexpensive method compensates for thermal fluctuations over a broad temperature range. Requiring few components, technique is particularly useful where circuit-board space is limited.

Deters, R. A.↗
NASA NTRS1980

Germanium-on-InP heterojunction-structure LED

Ge-on-InP heterojunction structure LED has been developed where in Ge film is evaporated onto commercially available InP substrate. Forward bias of device is approximately 1 volt, and it emits light in 9.800 angstrom region. Technique permits easy and inexpensive fabrication of LED for application at this wavelength.

Hawrylo, F. Z.↗
NASA NTRS1979

LED instrument approach instruction display

A display employing light emitting diodes (LED's) was developed to demonstrate the feasibility of such displays for presenting landing and navigation information to reduce the workload of general aviation pilots during IFR flight. The display consists of a paper tape reader, digital memory, control electronics, digital latches, and LED alphanumeric displays. A presentable digital countdown clock-timer is included as part of the system to provide a convenient means of monitoring time intervals for precise flight navigation. The system is a limited capability prototype assembled to test pilot reaction to such a device under simulated IFR operation. Pilot opinion indicates that the display is helpful in reducing the IFR pilots workload when used with a runway approach plate. However, the development of a compact, low power second generation display was recommended which could present several instructions simultaneously and provide information update capability. A microprocessor-based display could fulfill these requirements.

Meredith, B. D.↗
NASA NTRS1991

Nonintrusive Measurement Of Temperature Of LED Junction

Temperature inferred from spectrum of emitted light. Method of determining temperature of junction based on two relevant characteristics of LED. Gap between valence and conduction electron-energy bands in LED material decreases with increasing temperature, causing wavelength of emitted photon to increase with temperature. Other, as temperature increases, non-radiative processes dissipate more of input electrical energy as heat and less as photons in band-gap wavelenth region; optical and quantum efficiencies decrease with increasing temperature. In principal, either characteristic alone used to determine temperature. However, desirable to use both to obtain indication of uncertainty.

Leidecker, Henning↗
NASA NTRS1992

Investigation of the bandwidth of multimode optical fibers used with 1550-nm LED and laser sources

Multimode optical fibers are not intended to be used with 1550-nm sources; however, it is desirable to utilize 1300/1550-nm wavelength division multiplexing (WDM) on some multimode fibers at Kennedy Space Center (KSC). No information from fiber vendors nor from the literature is available to support this use. Preliminary studies at KSC have suggested that these fibers might be usable at 1550-nm if the fibers possessed enough bandwidth when sourced by LEDs. Detailed bandwidth studies were made on 12 multimode fibers using 1300- and 1550-nm lasers and LEDs. The results showed that the modal bandwidth at 1550-nm was about 50 percent of the 1300-nm value and that the chromatic dispersion could be predicted by extrapolating the vendor's specifications for wavelengths outside the 1550-nm region. Utilizing these data, predictions of the fiber's optical bandwidth were accurately made. Problems with launch conditions and possible differential attenuation at connectors was noted at 1300-nm but was less significant at 1550-nm. It appears that the multimode fibers studied will offer adequate performance in the 1550-nm region for a number of current KSC needs. Studies of additional fibers are encouraged to gain more confidence and better understanding of the 1550-nm bandwidth of KSC's multimode optical fibers before committing to 1300/1550-nm WDM.

White, Preston A., III↗
NASA NTRS2005

Satellite Calibration With LED Detectors at Mud Lake

Earth-monitoring instruments in orbit must be routinely calibrated in order to accurately analyze the data obtained. By comparing radiometric measurements taken on the ground in conjunction with a satellite overpass, calibration curves are derived for an orbiting instrument. A permanent, automated facility is planned for Mud Lake, Nevada (a large, homogeneous, dry lakebed) for this purpose. Because some orbiting instruments have low resolution (250 meters per pixel), inexpensive radiometers using LEDs as sensors are being developed to array widely over the lakebed. LEDs are ideal because they are inexpensive, reliable, and sense over a narrow bandwidth. By obtaining and averaging widespread data, errors are reduced and long-term surface changes can be more accurately observed.

Hiller, Jonathan D.↗
NASA NTRS2011

Expedition Earth and Beyond: Engaging Classrooms in Student-Led Research Using NASA Data, Access to Scientists, and Integrated Educational Strategies

Classroom teachers are challenged with engaging and preparing today s students for the future. Activities are driven by state required skills, education standards, and high-stakes testing. Providing educators with standards-aligned, inquiry-based activities that will help them engage their students in student-led research in the classroom will help them teach required standards, essential skills, and help inspire their students to become motivated learners. The Astromaterials Research and Exploration Science (ARES) Education Program, classroom educators, and ARES scientists at the NASA Johnson Space Center created the Expedition Earth and Beyond education program to help teachers promote student-led research in their classrooms (grades 5-14) by using NASA data, providing access to scientists, and using integrated educational strategies.

Graff, P. V.↗
NASA NTRS2012

Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps

Growing vegetable crops in space will be an essential part of sustaining astronauts during long-term missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop production, there have also been recent interests in analyzing the subtle effects of green light on plant growth, and to determine if it serves as a source of growth enhancement or suppression. A comparative study was performed on two short cycle crops of lettuce (Outredgeous) and radish (Cherry Bomb) grown under two light treatments. The first treatment being red and blue LEDs, and the second treatment consisting of white fluorescent lamps which contain a portion of green light. In addition to comparing biomass production, physiological characterizations were conducted on how the light treatments influence morphology, water use, chlorophyll content, and the production of A TP within plant tissues.

Mickens, Matthew A.↗
NASA NTRS2014

Microorganisms in the Stratosphere (MIST): In-flight Sterilization with UVC Leds

The stratosphere (10 km to 50 km above sea level) is a unique place on Earth for astrobiological studies of microbes in extreme environments due to the combination of harsh conditions (high ultraviolet radiation, low pressure, desiccation, and low temperatures). Microorganisms in the Stratosphere (MIST) will attempt to characterize the diversity of microbes at these altitudes using a balloon collection device on a meteorological weather balloon. A major challenge of such an aerobiology study is the potential for ground contamination that makes it difficult to distinguish between collected microbes and contaminants. One solution is to use germicidal ultraviolet light emitting diodes (UV LEDs) to sterilize the collection strip. To use this solution, an optimal spatial arrangement of the lights had to be determined to ensure the greatest chance of complete sterilization within the 30 to 60 minute time of balloon ascent. A novel, 3D-printed test stand was developed to experimentally determine viable Bacillus pumilus SAFR-032 spore reduction after exposure to ultraviolet radiation at various times, angles, and distances. Taken together, the experimental simulations suggested that the UV LEDs on the MIST flight hardware should be active for at least 15 minutes and mounted within 4 cm of the illuminated surface at any angle to achieve optimal sterilization. These findings will aid in the production of the balloon collection device to ensure pristine stratospheric microbial samples are collected. Flight hardware capable of in-flight self-sterilization will enable future life detection missions to minimize both forward contamination and false positives.

Exobiology↗
NASA NTRS2015

LEDs Illuminate Bulbs for Better Sleep, Wake Cycles

Life on the International Space Station (ISS) wreaks havoc on an astronaut’s biological rhythms, and one way NASA mitigates the problem is through the use of LED lighting to alternately stimulate energy and focus and induce relaxation. Satellite Beach, Florida-based Lighting Science partnered with Kennedy Space Center to commercialize an LED system designed for the ISS, resulting in its DefinityDigital product line of light bulbs now used in numerous homes, hotel chains, and resorts.

Source record↗
NASA NTRS2016

Biological Research in Canisters (BRIC) - Light Emitting Diode (LED)

The Biological Research in Canisters - LED (BRIC-LED) is a biological research system that is being designed to complement the capabilities of the existing BRIC-Petri Dish Fixation Unit (PDFU) for the Space Life and Physical Sciences (SLPS) Program. A diverse range of organisms can be supported, including plant seedlings, callus cultures, Caenorhabditis elegans, microbes, and others. In the event of a launch scrub, the entire assembly can be replaced with an identical back-up unit containing freshly loaded specimens.

Biological↗
NASA NTRS2014

UV-LED

UV-LED is part of a small satellite technology demonstration mission that will demonstrate non-contacting charge control of an isolated or floating mass using new solid-state ultra-violet light emitting diodes (UV-LEDs). Integrated to the Saudisat-4 spacecraft and launched onboard the Dnepr in June 19, 2014, the project is a collaboration between the NASA Ames Research Center (ARC), Stanford University, and King Abdulaziz City for Science and Technology (KACST). This technology demonstration will validate a novel method of charge control that will improve the performance of drag-free spacecraft allowing for concurrent science collection during charge management operations as well as reduce the mass, power and volume required while increasing lifetime and reliability of a charge management subsystem. These improvements are crucial to the success of ground breaking missions such as LISA and BBO, and demonstrate the ability of low cost small satellite missions to provide technological advances that far exceed mission cost.

Faied, Dohy↗
NASA NTRS2014

UV-LED Project

UV-LED is part of a small satellite technologydemonstration mission that willdemonstrate non-contacting charge controlof an isolated or floating mass usingnew solid-state ultra-violet light emittingdiodes (UV-LEDs). Integrated tothe Saudisat-4 spacecraft and launchedonboard the Dnepr in June 19, 2014,the project is a collaboration betweenthe NASA Ames Research Center (ARC),Stanford University, and King AbdulazizCity for Science and Technology(KACST). This technology demonstrationwill validate a novel method of chargecontrol that will improve the performanceof drag-free spacecraft allowingfor concurrent science collection duringcharge management operations as wellas reduce the mass, power and volumerequired while increasing lifetime and reliabilityof a charge management subsystem.These improvements are crucial tothe success of ground breaking missionssuch as LISA and BBO, and demonstratethe ability of low cost small satellite missionsto provide technological advancesthat far exceed mission cost.

Soulage, Michael↗
NASA NTRS2004

Proton damage in LEDs with wavelengths above the silicon wavelength cutoff

This paper has examined the effects of proton damage on two types of LEDs in the wavelength region above the silicon bandgap limit. Unlike AlGaAs LEDs, the optical power linearity in both types of devices changes significantly after irradiation. This may be caused by the lower heterojunction barriers associated with these materials.

Johnston, Allan H.↗