Physical Sciences

Deployable Shell Structures With Shape-Control Actuators

Hierarchical distributed control systems would effect both deployment and fine shape control. Advanced control systems that include built-in smart-material elastic-deformation structural actuators have been proposed for deployable thin-shell structures that are required to be maintained in precise shapes once deployed. This approach to structural shape control was conceived to enable the development of lightweight telescope mirrors, radar reflectors, and the like that could be stowed compactly for launching and transport, then deployed in outer space to required precise shapes at much larger dimensions (of the order of 10 m). The concept may also be applicable to similar, but probably smaller structures for terrestrial use.

Posted in: Briefs, TSP, Physical Sciences

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Software for Simulating Two-Phase Systems

Møtran (signifying "multi-phase transient") is a package of software for simulating flows in two-phase (gas/liquid) fluid systems like networks of such components as pipes, T junctions, pumps, evaporators, and condensers. The software is based on a two-fluid formulation that can accommodate unequal velocities and temperatures for the two phases. Møtran provides for single-phase, bubbly, slug, stratified, and annular flow regimes. Mechanistic models are used for establishing the boundaries between flow regimes and for constitutive relations that represent wall shear, interfacial shear, wall heat transfer, interfacial heat transfer, and phase change. Constitutive models are provided for each of the flow regimes, and all are selected and calculated dynamically during solution for each grid point in the network. The software is applicable at all levels of gravitation, whether steady or time varying. Møtran includes a state-of-the-art graphical user interface (GUI) and an integrated fluid-property database. The user assembles the representation of the fluid system (which can be of arbitrary topology) through drag-and-drop operations on the GUI. The software predicts pressures, volume fractions, temperatures, and velocities of the phases throughout the system.

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Software for Improved Processing of DRWP Signals

The Automated Adaptive Signal Processing (AASP) computer program extracts wind data from the outputs of Doppler-radar wind profilers (DRWPs). Unlike prior software used for this purpose, AASP does not rely on manual intervention to prevent a DRWP system from locking onto and tracking interfering signals (e.g., signals from side lobes of radar beams). AASP identifies interference signals in the range-gated spectra produced by a DRWP, then tracks the height- and time-continuous atmospheric signal in each radar beam. AASP then combines the radial velocity components from three or five beams and computes the horizontal and vertical wind components. AASP produces high-quality wind profiles within a single radar cycle, without need for averaging for quality control. It also calculates an indication of the level of confidence with each wind estimate. The single-cycle capability enables users to detect temporal shifts in wind earlier and with greater confidence than was possible by use of prior software. AASP comprises two coupled software subsystems: (1) a subsystem that implements signal-processing algorithms and (2) a subsystem that provides a quality-control capability and that generates displays of spectra, of wind estimates, and of the performances of the DRWP hardware.

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Large-Aperture Telescope Synthesized From Small Mirrors

A report proposes a design concept for synthesizing a reflecting telescope with a large-aperture (diameter ≈100 m) primary mirror from a sparse arrangement of four smaller (diameter ≈10 m) primary mirrors. The telescope would be placed in orbit for viewing Earth with high resolution. The primary and secondary mirrors would be mounted on a lightweight structure that would be deployed in orbit.

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Uplink/Downlink Spacecraft Radio Occultation Measurements

A report proposes a method to increase the accuracy of Doppler measurements made at the beginnings and endings of Earth/spacecraft radio occultations. Such measurements can reveal structural details of occulting objects in outer space. Heretofore, one-way measurements have been used, and have been subject to degradation of accuracy by frequency fluctuations of an onboard oscillator.

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Integrated Environmental Monitoring Instrument

This is a semiautonomous reference instrument with radio-communication and networking capability. A miniature, battery-powered, semiautonomous environmental monitoring instrument contains advanced meteorological sensors, a Global Positioning System (GPS) receiver for determining its position, radio-communication circuitry, and a controller that performs measurement, control, and data-communication interface functions. The instrument could serve as a high-accuracy radiosonde, though its intended use is in providing reference measurements for calibration and comparison of ordinary radiosondes.

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Molten-Carbonate Electrolyzers for Making CO and O2

Molten-carbonate fuel cells would be operated in reverse. Electrochemical cells in which molten carbonates would serve as electrolytes have been proposed for use in electrolyzing CO2. The proposal was made in an effort to implement a concept of in situ resource utilization (ISRU) for the exploration of Mars; the basic idea is to generate CO (if needed as a fuel) and O2 (for oxidizing fuel and/or for breathing) by electrolysis of CO2 from the Martian atmosphere. On Earth, molten-carbonate electrolyzers could be used to make breathable O2 for medical use, pure O2 for oxidizing surfaces of semiconductor chips, and CO as a feedstock for synthesis of alcohols and hydrocarbons. In both terrestrial and spacecraft life-support systems, the electrolyzers could be used to regenerate breathable O2 from CO2.

Posted in: Briefs, TSP, Physical Sciences

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