Physical Sciences

Passive Radiative Cooler for Use in Outer Space

High-temperature superconductors are cooled radiatively to operating temperatures. The figure depicts a passive radiative cooler designed for use in outer space. The design of this device conjoins radiative and conductive thermal-isolation features, which, in further conjunction with a favorable spacecraft attitude and on-orbit thermal environment, can be utilized to cool specimens of high-temperature superconducting materials to operating temperatures. Once installed on a spacecraft or even on the lunar surface, the passive radiative cooler will perform the cooling function that would otherwise be performed by a more expendables-hungry cryogenic system. This device, which has the added advantage of no moving parts, can operate in low orbit around the Earth in the space-shuttle cargo bay. Small and adaptable to many spacecraft and mounting configurations, this device can be used to demonstrate applications that involve superconductivity. Commercially, this device can advance the art by providing a simplified alternative for satellites equipped with infrared (IR) detectors or apparatuses that exploit superconductivity.

Posted in: Briefs

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Magnetically Enhanced Propellant Isolator for Ion Sources

A magnetic field inhibits the diffusion of electrons. A magnetically enhanced, high-voltage propellant isolator has been conceived for incorporation into materials-processing or space-based ion systems. The high-voltage isolator is needed to provide electrical isolation between the ion source, typically at high voltage, and the gas-feed system.

Posted in: Briefs, TSP

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Buoy Instrumented for Spectral Measurement of Water Quality

An instrumented buoy measures selected aspects of the spectrum of upwelling light for assessment of "water quality." The buoy carries a previously patented optical-backscatter probe that contains a hyperspectral sensor. The output of the probe is processed by a small onboard computer. Cellular-telephone circuitry on the buoy transmits spectral-signature data to a computer system that, in turn, makes the data available immediately over the World Wide Web. Power is supplied by gel batteries charged by a solar photovoltaic panel on top of the buoy. The scalable optical-backscatter probe is a scalable module fabricated separately from the buoy and the other equipment described above; the buoy and the other equipment are designed to accommodate and mate with the optical probe. Optionally, the instrumentation on the buoy can be augmented by incorporation of additional sensors (e.g., a pH sensor current meter). The current version of the buoy is not intended to function in the presence of high wind and waves; it is designed primarily for operation under relatively calm-sea conditions in shallow, semienclosed natural bodies of water (ponds, lakes, lagoons).

Posted in: Briefs

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Magnetostrictive Heat Switches Actuated by Flux Tubes

A switch would remain "open" or "closed" until actuated to change its state. In a proposed improvement on the basic concept of a magnetostrictive heat switch for cryogenic applications, the magnetic field needed for actuation would be generated by a superconducting flux tube (SFT). A closely related concept for a magnetostrictive heat switch was presented in "Magnetostrictive Heat Switch for Cryogenic Use" (NPO-20274), NASA Tech Briefs, Vol. 23, No. 8, (August, 1999), p.48. To recapitulate: The main thermal contact in the heat switch would be made or broken by making or breaking, respectively, the mechanical contact between (1) the moving end of a rod of magnetostrictive material and (2) a fixed contact pad. The magnetic field needed for actuation would be generated by use of a superconducting solenoid.

Posted in: Briefs, TSP

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Liquid Shell Insulation

At high temperatures and pressures, probes would last just long enough to take readings. A new concept called "liquid shell insulation" has been proposed as a means of temporary thermal protection for scientific instrument probes that are required to operate for short times in hot, high-pressure environments. Liquid shell insulation was conceived to protect probes that would be dropped from spacecraft to great depths in the atmospheres of the outer planets. For example, at a depth of 1,000 km on Jupiter, a probe would have to withstand a pressure of about 4,000 Earth atmospheres (≈0.4 GPa) and a temperature of about 1,800 K. On Earth, liquid shell insulation might be useful for protecting probes that would be inserted in undersea volcanic vents or deep oil wells.

Posted in: Briefs, TSP

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Magnetostrictive Valves Actuated by Flux Tubes

Power would be applied during toggling only. Magnetostrictive valves for cryogenic applications would be actuated by superconducting flux tubes (SFTs), according to a proposal. The reasoning behind this proposal closely tracks that of the proposal to use SFTs in magnetostrictive heat switches, as reported in the preceding article.

Posted in: Briefs, TSP

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Fluorometer for Analysis of Photosynthesis in Phytoplankton

Measurements could be made in situ and in vivo. An instrument that measures the characteristic lifetime of fluorescence of chlorophyll has been invented for in situ, real-time oceanographic studies of photosynthesis in phytoplankton. The basic design and principle of operation lend themselves to development of the instrument as a relatively inexpensive, sensitive, compact, rugged, portable, low-power-consumption, hand-held, shipboard unit. Similar units with designs adapted to agricultural applications (e.g., assessment of physiological statuses of crops) are also envisioned.

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