Electrical/Electronics

Integrated Solar Array Power Management System

Marshall Space Flight Center, Alabama When solar cells are electrically connected to form solar arrays, they are organized into strings. Each string represents a specific number of cells connected in series to produce a specific voltage. The strings are then connected in parallel to add their currents to meet the array power requirement. This requires that the strings have the same voltage. Blocking diodes are used to take out strings with voltage that is too low, resulting in loss of power. When the arrays are mounted to a non-coplanar surface such as a spacecraft body or inflatable structure, many strings will have voltages lower than the rated voltage. This regulator manages the voltage of each string individually so that its power may be used, regardless of its voltage. It does this by converting each string’s energy into a series of high-voltage pulses that charges a reservoir capacitor to one of a set of common voltages used by the spacecraft bus. This allows for use of all of the illuminated strings in producing well-regulated power at pre-programmed voltages.

Posted in: Briefs, Power Management

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High-Energy-Density Solid-State Li-Ion Battery with Enhanced Safety

John H. Glenn Research Center, Cleveland, Ohio High-energy-density and safe rechargeable batteries are required for NASA’s future exploration missions. Lithium-ion (Li-ion) batteries are attractive energy storage systems due to their relatively high energy and power densities. However, the unfavorable side reactions between the electrodes and the liquid electrolyte adversely impact performance. These interfacial reactions are in the form of either anodic oxidation of the electrolyte, or dissolution of the cathode into the electrolyte. As a result, the practical capacity and cycle life of the battery are limited. More importantly, the reactions at the cathode-electrolyte interface pose a serious threat to safety due to the electrolyte decomposition and formation of gaseous products within the cell. In addition, growth of lithium dendrite on the anode can cause cell short circuit and lead to fire or even explosion in the presence of liquid electrolyte.

Posted in: Briefs, Thermal Management

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CMOS-Compatible Ohmic Contact RF MEMS Switch

Lyndon B. Johnson Space Center, Houston, Texas Radio frequency (RF) microelectromechanical system (MEMS) switches have advantages over their solid-state counterparts. However, ohmic contact MEMS devices face several significant limitations, preventing entry into the mass market. These limitations are cost, reliability, packaging, and integration.

Posted in: Briefs, Electronics

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Miller-Jogging for Synthesizer Lock Algorithm Extension

NASA’s Jet Propulsion Laboratory, Pasadena, California The University of California Los Angeles (UCLA) has developed a wide range of CMOS (complementary metal–oxide–semiconductor) phase lock loop (PLL) chips with self-healing/self-calibration capabilities, allowing them to adapt, on the fly, to changes in temperature and other environment parameters. All CMOS PLLs typically have three major settings that self-healing and calibration can adjust: VCO (voltage controlled oscillator) coarse tuning, divider tuning, and CML (current mode logic) tuning. Previous work done at UCLA uses these “knobs” or settings exclusively to self-lock a PLL. Locking criteria is established by monitoring the control voltage with an analog-to-digital converter (ADC) to see if the PLL loop is settled in the middle of the range (locked), or sitting at the ground or supply (unlocked).

Posted in: Briefs, Electronics

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Deployable Antenna Circuit Board Material Design and Fabrication Process

This technology has applications in solar arrays for small satellites. NASA’s Jet Propulsion Laboratory, Pasadena, California The Integrated Solar Array and Reflectarray (ISARA) antenna requires a rugged circuit board material that will meet the following requirements: (1) remains sufficiently flat over the required operating temperature range with solar cells mounted, and under full solar illumination, including heat dissipation due to ≈30% efficiency solar cells; (2) provides a sufficiently high-quality RF-grade circuit board material needed to print the reflectarray antenna; (3) is sufficiently thin (<2.5 mm) to fit within the available stowage volume; and (4) has low mass density (≈5 kg/m2).

Posted in: Briefs, TSP, Electronics

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Rigorous Antenna Noise Temperature Calculation Method for International Space Station Visiting Spacecraft

Lyndon B. Johnson Space Center, Houston, Texas The temperature of the orbiting space station’s Sun-facing side could be up to 250 °F (≈120 °C) and will be a significant antenna noise temperature contributor for visiting spacecraft communication and tracking systems during rendezvous. The conventional antenna noise temperature calculation does not take into account the space station reflection effects, and results in an underestimated antenna and system noise temperature. Thus, the visiting spacecraft communication and tracking system performance could be overestimated during rendezvous.

Posted in: Briefs, Electronics & Computers

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Recurring Anomaly Detection System (ReADS)

Ames Research Center, Moffett Field, California NASA Engineering & Safety Center (NESC) subject matter experts analyze records in various International Space Station and shuttle databases to identify recurring anomalies. The key problems these experts face in analyzing such database records are:

Posted in: Briefs, Electronics & Computers

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