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Gaddy, Edward

Publications and source records attributed to Gaddy, Edward.

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Transformational Solar Array Final Report

We have made outstanding progress in the Base Phase towards achieving the final NASA Research Announcement (NRA) goals. Progress is better than anticipated due to the lighter than predicted mass of the IMM solar cells. We look forward to further improvements in the IMM cell performance during Option I and Option II; so, we have confidence that the first four items listed in the table will improve to better than the NRA goals. The computation of the end of life blanket efficiency is uncertain because we have extrapolated the radiation damage from room temperature measurements. The last three items listed in the Table were not intended to be accomplished during the Base Phase; they will be achieved during Option I and Option II.

Gaddy, Edward↗
NASA NTRS2017

Transformational Solar Array Option I Final Report

This report summarizes the work performed under NASA contract NNC16CA19C from May 2, 2017 through April 2, 2018. This work is directed toward meeting the goals of the associated NASA NRA and, of course, the requirements of the contract. In brief, the goals are: (1) Over 47% beginning of life cell efficiency at 5 AU and -125 °C (2) Over 32% end of life efficiency at the blanket level at 50 W m-2, -125 °C and 4E15 1 MeV e cm-2 (3) Over 8 W kg-1 at EOL for the entire array including structure, deployment, and pointing mechanisms using beginning of life performance. (4) A stowed packaging density of greater than 66 kW m-3 (5) An ability to survive launch and numerous deploy retract cycles without degradation (6) An output higher than 300 V (7) An ability to operate in a plasma generated by xenon thrusters, typically 1E8 cm-3 ions with an average energy of 2 eV (8) A design compatible with electrostatic and magnetic cleanliness (9) Record breaking inverted metamorphic (IMM) 6 junction solar cells (10) IMM solar cells that have no anomalous flat spot behavior at low irradiance and low temperature (11) A mock-up production line for the low-cost manufacture of spacecraft blanket arrays. The Option I phase of the project continued efforts, started in the base-phase, to eliminate or reduce to very low levels the flat spots that reduce power to an unacceptable value in a significant percentage of cells and to reduce outgassing contamination of the concentrators to acceptable levels. Option I adds tasks to increase the efficiency of IMM cells from those produced in the Base Phase, to eliminate delamination of the coatings that were present in previous versions of the concentrator mirrors, to evaluate pressure sensitive adhesive as a method of fixing solar cell assemblies to blankets, to design a magnetically clean brake for ROSA, to test the robustness of a sample blanket in deploy and retract, to test for the adequate performance of a blanket in vibration and thermal environments, and to define the capital equipment needed to optimize production of the Transformational Array. 5 Work for this Final Report showed that the greatest likely improvement in the solar cells would be by emphasizing the effort for the IMM4 solar cells and stopping work on other IMM cells. For this phase, the solar cell work was primarily on the IMM4 cells with little work on IMM5 and none on IMM6 cells.

Gaddy, Edward↗
NASA NTRS2002

The Performance of Advanced III-V Solar Cells

Test results show triple junction solar cells with efficiencies as high as 27% at 28C and 136.7 mw/sq cm. Triple junction cells also achieve up to 27.5% at -120 C and 5 mw/sq cm, conditions applicable to missions to Jupiter. Some triple junction cells show practically no degradation as a result of Low Intensity Low Temperature (LILT) effects, while others show some; this degradation can be overcome with minor changes to the cell design.

Mueller, Robert L.↗
NASA NTRS2000

Development of an Electrostatically Clean Solar Array Panel

The results of design, analysis, and qualification of an Electrostatically Clean Solar Array (ECSA) panel are described. The objective of the ECSA design is to provide an electrostatic environment that does not interfere with sensitive instruments on scientific spacecraft. The ECSA design uses large, ITO-coated coverglasses that cover multiple solar cells, an aperture grid that covers the intercell areas, stress-relieved interconnects for connecting the aperture grid to the coverglasses, and edge clips to provides an electromagnetically shielded enclosure for the solar array active circuitry. Qualification coupons were fabricated and tested for photovoltaic response, conductivity, and survivability to launch acoustic and thermal cycling environments simulating LEO and GEO missions. The benefits of reducing solar panel interaction with the space environment are also discussed.

Stern, Theodore G.↗
NASA NTRS2000

Terra Flexible Blanket Solar Array Deployment, On-Orbit Performance and Future Applications

The Terra spacecraft (formerly identified as EOS AM1) is the flagship in a planned series of NASA/GSFC (Goddard Space Flight Center) Earth observing system satellites designed to provide information on the health of the Earth's land, oceans, air, ice, and life as a total ecological global system. It has been successfully performing its mission since a late-December 1999 launch into a 705 km polar orbit. The spacecraft is powered by a single wing, flexible blanket array using single junction (SJ) gallium arsenide/germanium (GaAs/Ge) solar cells sized to provide five year end-of-life (EOL) power of greater than 5000 watts at 127 volts. It is currently the highest voltage and power operational flexible blanket array with GaAs/Ge cells. This paper briefly describes the wing design as a basis for discussing the operation of the electronics and mechanisms used to achieve successful on-orbit deployment. Its orbital electrical performance to date will be presented and compared to analytical predictions based on ground qualification testing. The paper concludes with a brief section on future applications and performance trends using advanced multi-junction cells and weight-efficient mechanical components.

Kurland, Richard↗
NASA NTRS2000

Terra Flexible Blanket Solar Array Deployment, On-Orbit Performance and Future Applications

The Terra spacecraft (formerly identified as EOS AM1) is the flagship in a planned series of NASA/GSFC (Goddard Space Flight Center) Earth observing system satellites designed to provide information on the health of the Earth's land, oceans, air, ice, and life as a total ecological global system. It has been successfully performing its mission since a late-December 1999 launch into a 705 km polar orbit. The spacecraft is powered by a single wing, flexible blanket array using single junction (SJ) gallium arsenide/germanium (GaAs/Ge) solar cells sized to provide five year end-of-life (EOL) power of greater than 5000 watts at 127 volts. It is currently the highest voltage and power operational flexible blanket array with GaAs/Ge cells. This paper briefly describes the wing design as a basis for discussing the operation of the electronics and mechanisms used to achieve successful on-orbit deployment. Its orbital electrical performance to date will be presented and compared to analytical predictions based on ground qualification testing. The paper concludes with a brief section on future applications and performance trends using advanced multi-junction cells and weight-efficient mechanical components. A viewgraph presentation is attached that outlines the same information as the paper and includes more images of the Terra Spacecraft and its components.

Kurland, Richard↗
NASA NTRS1994

Goddard Space Flight Center solar array missions, requirements and directions

The Goddard Space Flight Center (GSFC) develops and operates a wide variety of spacecraft for conducting NASA's communications, space science, and earth science missions. Some are 'in house' spacecraft for which the GSFC builds the spacecraft and performs all solar array design, analysis, integration, and test. Others are 'out of house' spacecraft for which an aerospace contractor builds the spacecraft and develops the solar array under direction from GSFC. The experience of developing flight solar arrays for numerous GSFC 'in house' and 'out of house' spacecraft has resulted in an understanding of solar array requirements for many different applications. This presentation will review those solar array requirements that are common to most GSFC spacecraft. Solar array technologies will be discussed that are currently under development and that could be useful to future GSFC spacecraft.

Gaddy, Edward↗
NASA NTRS1994

Goddard Space Flight Center Solar Array Missions, Requirements and Directions

The Goddard Space Flight Center (GSFC) develops and operates a wide variety of spacecraft for conducting NASA's communications, space science, and earth science missions. Some are "in house" spacecraft for which the GSFC builds the spacecraft and performs all solar array design, analysis, integration, and test. Others are "out of house" spacecraft for which an aerospace contractor builds the spacecraft and develops the solar array under direction from GSFC. The experience of developing flight solar arrays for numerous GSFC "in house" and "out of house" spacecraft has resulted in an understanding of solar array requirements for many different applications. This presentation will review those solar array requirements that are common to most GSFC spacecraft. Solar array technologies will be discussed that are currently under development and that could be useful to future GSFC spacecraft.

Gaddy, Edward↗