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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2004

The Millimeter-Wave Bolometric Interferometer

The Millimeter-wave Bolometric Interferometer (MBI) is a proposed ground-based instrument designed for a wide range of cosmological and astrophysical observations including studies of the polarization of the cosmic microwave background (CMB). MBI combines the advantages of two well-developed technologies - interferometers and bolometric detectors. Interferometers have many advantages over .filled-aperture telescopes and are particularly suitable for high resolution imaging. Cooled bolometers are the highest sensitivity detectors at millimeter and sub-millimeter wavelengths. The combination of these two technologies results in an instrument with both high sensitivity and high angular resolution.

Ali, S.↗
NASA NTRS2004

BLAST: The Balloon-Borne Large Aperture Submillimeter Telescope

BLAST is the Balloon-borne Large-Aperture Sub-millimeter Telescope. It will fly from a Long Duration Balloon (LDB) platform from Antarctica. The telescope design incorporates a 2 m primary mirror with large-format bolometer arrays operating at 250, 350 and 500 microns. By providing the first sensitive large-area (10 sq. deg.) sub-mm surveys at these wavelengths, BLAST will address some of the most important galactic and cosmological questions regarding the formation and evolution of stars, galaxies and clusters. Galactic and extragalactic BLAST surveys will: (1) identify large numbers of high-redshift galaxies; (2) measure photometric redshifts, rest-frame FIR luminosities and star formation rates thereby constraining the evolutionary history of the galaxies that produce the FIR and sub-mm background; (3) measure cold pre-stellar sources associated with the earliest stages of star and planet formation; (4) make high-resolution maps of diffuse galactic emission over a wide range of galactic latitudes. In addition to achieving the above scientific goals, the exciting legacy of the BLAST LDB experiment will be a catalogue of 3000-5000 extragalactic sub-mm sources and a 100 sq. deg. sub-mm galactic plane survey. Multi-frequency follow-up observations from SIRTF, ASTRO-F, and Herschel, together with spectroscopic observations and sub-arcsecond imaging from ALMA are essential to understand the physical nature of the BLAST sources.

Devlin, Mark↗
NASA NTRS2003

Continuous Magnetic Refrigerators for Cooling in the 0.05 to 10 K Range: Progress and Future Development

Low temperature refrigeration is an increasingly vital technology for NASA s Space Science program since most detectors being developed for x-ray, IR and sub-millimeter missions must be cooled to below 100 mK in order to meet the requirements for energy and spatial resolution. For space applications, magnetic refrigeration has an inherent advantage over alternative techniques because it does not depend on gravity. Adiabatic demagnetization refrigerators, or ADRs, are relatively simple, solid state devices. The basic elements are a magnetocaloric refrigerant (usually an encapsulated paramagnetic salt) located in the bore of a superconducting magne$, and a heat switch linking the salt to a heat sink. The alignment of magnetic spins with the magnetic field causes the refrigerant to warm as the magnetic field increases and cool as the field decreases. Thus the simple process of magnetizing the refrigerant to high field with the heat switch closed, then demagnetizing it with the heat switch open allows one to obtain temperatures well below 100 mK using a heat sink as warm as 4.2 K. The refrigerant can maintain a low temperature for a length of time depending on the applied and parasitic heat loads, its mass, and the initial magnetic field strength. Typically ADRs are designed for 12-24 hours of hold time, after which they must be warmed up and recycled. The drawback to single-shot ADRs is that the cooling power per unit mass is relatively low. Refrigerants that are suitable for low temperature operation necessarily have low magnetic ion density, and therefore low entropy density. Since ADRs store entropy, systems with even modest cooling powers (a few microwatts) at temperatures below 100 mK tend to be massive, averaging 10-15 kg.

Shirron, Peter↗
NASA NTRS2004

Mirror Requirements for SAFIR

Large-aperture lightweight low-cost cryogenic mirrors are an enabling technology for planned NASA far-infrared and sub-millimeter missions such as CMB-Pol, SAFIR and SPECS. This paper examines d e mirror requirements necessary to design, build and characterize mirror segments for large space telescopes operating at temperatures of less than 1OK. Such mirrors should be diffraction limited in the far-IR with an areal density of less than 10 kg/sq m, aperture of 1 to 2 meters and cost of less than $500,000 per square meter.

Stahl, H. Philip↗
NASA NTRS2004

Dynamics and Stability of Capillary Surfaces: Liquid Switches at Small Scales

The dynamics and stability of systems of interfaces is central to a range of technologies related to the Human Exploration and Development of Space (HEDS). Our premise is that dramatic shape changes can be manipulated to advantage with minimal input, if the system is near instability. The primary objective is to develop the science base to allow novel approaches to liquid management in low-gravity based on this premise. HEDS requires efficient, reliable and lightweight technologies. Our poster will highlight our progress toward this goal using the capillary switch as an example. A capillary surface is a liquid/liquid or liquid/gas interface whose shape is determined by surface tension. For typical liquids (e.g., water) against gas on earth, capillary surfaces occur on the millimeterscale and smaller where shape deformation due to gravity is unimportant. In low gravity, they can occur on the centimeter scale. Capillary surfaces can be combined to make a switch a system with multiple stable states. A capillary switch can generate motion or effect force. To be practical, the energy barriers of such a switch must be tunable, its switching time (kinetics) short and its triggering mechanism reliable. We illustrate these features with a capillary switch that consists of two droplets, coupled by common pressure. As long as contact lines remained pinned, motions are inviscid, even at sub-millimeter scales, with consequent promise of low-power consumption at the device level. Predictions of theory are compared to experiment on i) a soap-film prototype at centimeter scale and ii) a liquid droplet switch at millimeter-scale.

Steen, Paul H.↗
NASA NTRS2004

Chemical Constraints on the Early Solar System

Chemical abundances of comets and star-forming regions provide p o w d clues to the conditions which prevailed in the outer solar nebula. Hence comparative spectroscopic studies of cometary and molecular cloud gases provide vital insights into conditions in the solar protoplanetary disk at heliocentric distances beyond 5 AU 4.6 Gyr ago. We proposed a research program which combined optical and sub-millimeter techniques with laboratory spectroscopy, and sought to determine key diagnostic constraints on single-star protoplanetary disk models.

Wyckoff, Susan↗
NASA NTRS1999

Multi-Bandwidth Frequency Selective Surfaces for Near Infrared Filtering: Design and Optimization

Frequency selective surfaces are widely used in the microwave and millimeter wave regions of the spectrum for filtering signals. They are used in telecommunication systems for multi-frequency operation or in instrument detectors for spectroscopy. The frequency selective surface operation depends on a periodic array of elements resonating at prescribed wavelengths producing a filter response. The size of the elements is on the order of half the electrical wavelength, and the array period is typically less than a wavelength for efficient operation. When operating in the optical region, diffraction gratings are used for filtering. In this regime the period of the grating may be several wavelengths producing multiple orders of light in reflection or transmission. In regions between these bands (specifically in the infrared band) frequency selective filters consisting of patterned metal layers fabricated using electron beam lithography are beginning to be developed. The operation is completely analogous to surfaces made in the microwave and millimeter wave region except for the choice of materials used and the fabrication process. In addition, the lithography process allows an arbitrary distribution of patterns corresponding to resonances at various wavelengths to be produced. The design of sub-millimeter filters follows the design methods used in the microwave region. Exacting modal matching, integral equation or finite element methods can be used for design. A major difference though is the introduction of material parameters and thicknesses tha_ may not be important in longer wavelength designs. This paper describes the design of multi-bandwidth filters operating in the I-5 micrometer wavelength range. This work follows on previous design [1,2]. In this paper extensions based on further optimization and an examination of the specific shape of the element in the periodic cell will be reported. Results from the design, manufacture and test of linear wedge filters built using micro-lithographic techniques and used ir spectral imaging applications will be presented.

Cwik, Tom↗
NASA NTRS2000

Monolithic Power Amplifiers Covering 70-115 GHz

A number of monolithic W-band power amplifiers have been developed for local oscillators of the Far Infrared and Sub-millimeter Telescope.

power amplifiers monolithic microwave integrated c↗
NASA NTRS2001

In-Situ Detections of a Satellite Breakup by the SPADUS Experiment

For the first time, a particle detector in Earth orbit has provided evidence to directly link sub-millimeter orbital debris to a specific satellite breakup. The University of Chicago's Space Dust instrument (SPADUS), on the U.S. Air Force's Advanced Research and Global Observation Satellite (ARGOS), has been operating in a nearly polar orbit at an altitude of about 830 km since soon after its launch on 23 February 1999. The experiment was designed primarily to detect small natural and man-made particles less than 100 microns in diameter. Using a dual-plane Polyvinylidene Fluoride (PVDF)-based detection system, SPADUS can measure dust particle flux, mass distribution, velocity, and trajectory. During its first year in orbit, SPADUS recorded 195 impacts, about one impact every two days. In late March 2000 the instrument detection rate soared by approximately an order of magnitude, suggesting a potential encounter with a cloud or stream of debris. A review of the impact times and ARGOS orbital characteristics indicated that most of the detections occurred at multiples of half-revolution intervals deep in the northern and southern hemispheres, with a clear majority of impacts found in the latter. Orbital analyses linked these impact events to the orbital plane intersections of ARGOS and the debris cloud of a Chinese orbital stage (International Designator 1999-057C, US Satellite Number 25942) which had undergone a severe fragmentation on 11 March 2000 at an altitude 100 km below that of ARGOS. Approximately 40 of the SPADUS detections during the period 25 March 1 April could be associated with the postulated Chinese debris cloud. Other periods of high impact flux on SPADUS may be related to debris clouds from different sources.

Tuzzolino, A. J.↗