Physical Sciences

Hand-Held Instrument for Imaging Hydrogen Fires

Hydrogen fires can be seen even in full daylight. A hand-held instrument that contains two silicon-based charge-coupled-device (CCD) video cameras (see figure) has been developed for imaging hydrogen fires. This or a similar instrument is needed because the visible light emitted by a hydrogen fire is so dim that the fire cannot be seen by the unaided human eye — at least, not in bright daylight. Like some other CCD-camera-based instruments developed previously for the same purpose, this instrument is designed to operate at infrared wavelengths where hydrogen fires appear bright, relative to solar background light. One CCD camera is called the "cloudy" camera, while the other is called the "sunny" camera, to indicate the different lighting conditions under which the cameras are designed to operate. In front of the "cloudy" camera is a long-wavelength-pass filter with a cutoff wavelength of 800 nm; during overcast, this filter blocks enough background light to make a hydrogen flame appear bright against the background. In front of the "sunny" camera there is a long-wavelength-pass filter with a cutoff wavelength of 1,100 nm; this filter blocks the solar background in the presence of full sunshine, such that a hydrogen flame is brighter than the solar background. The infrared images in the cameras are converted electronically and displayed to the instrument operator as visible images on miniature cathode-ray tubes in electronic viewfinders. A switch enables the operator to select the camera depending on the current light conditions. Optionally, both cameras and their viewfinders can be used simultaneously for binocular viewing.

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Improvements in Computed-Tomography Imaging Spectrometry

CGHs are used for dispersion, and a modified calibration procedure saves time. Two major improvements, described below, have been made in the construction and operation of a computed-tomography imaging spectrometer (CTIS). These plus future improvements can be expected to enhance the practicality and commercial viability of CTISs, which, in principle, offer unprecedented capabilities for imaging with spatial, spectral, and temporal resolution. For example, the CTIS in its present form could be used in medical and pharmaceutical applications to perform spectral imaging of transient scenes that contain fluorescent dyes. With increases in spectral accuracy and spatial resolution, it could be used for remote sensing.

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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.

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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.

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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).

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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.

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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.

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