Tech Briefs

On-the-Fly Mapping for Calibrating Directional Antennas

Source-size corrections are not necessary in this method.  An improved method of calibrating a large directional radio antenna of the type used in deep-space communication and radio astronomy has been developed. This method involves a raster-scanning-and-measurement technique denoted on-the-fly (OTF) mapping, applied in consideration of the results of a systematic analysis of the entire measurement procedure. Phenomena to which particular attention was paid in the analysis include (1) the noise characteristics of a total-power radiometer (TPR) that is used in the measurements and (2) tropospherically induced radiometer fluctuations. The method also involves the use of recently developed techniques for acquisition and reduction of data. In comparison with prior methods used to calibrate such antennas, this method yields an order-of-magnitude improvement in the precision of determinations of antenna aperture efficiency, and improvement by a factor of five or more in the precision of determination of pointing error and beam width. Prerequisite to a meaningful description of the present method is some background information concerning three aspects of the problem of calibrating an antenna of the type in question:

Posted in: Briefs, TSP

Read More >>

Coronagraphic Notch Filter for Raman Spectroscopy

Design could be optimized for attenuating pump light and transmitting Raman-scattered light. A modified coronagraph has been proposed as a prototype of improved notch filters in Raman spectrometers. Corona-graphic notch filters could offer alternatives to both (1) the large and expensive double or triple monochromators in older Raman spectrometers and (2) holographic notch filters, which are less expensive but are subject to environmental degradation as well as to limitations of geometry and spectral range.

Posted in: Briefs, TSP

Read More >>

Preparing and Analyzing Iced Airfoils

SmaggIce version 1.2 is a computer program for preparing and analyzing iced airfoils.It includes interactive tools for (1)measuring ice-shape characteris- tics,(2)controlled smoothing of ice shapes,(3)curve discretization,(4)gen- eration of artificial ice shapes,and (5)de- tection and correction of input errors. Measurements of ice shapes are essential for establishing relationships between characteristics of ice and effects of ice on airfoil performance.The shape-smoothing tool helps prepare ice shapes for use with already available grid-generation and computational-fluid-dynamics soft- ware for studying the aerodynamic effects of smoothed ice on airfoils.The artificial ice-shape generation tool supports para- metric studies since ice-shape parameters can easily be controlled with the artificial ice.In such studies,artificial shapes gen- erated by this program can supplement simulated ice obtained from icing re- search tunnels and real ice obtained from flight test under icing weather condition. SmaggIce also automatically detects geometry errors such as tangles or dupli- cate points in the boundary which may be introduced by digitization and provides tools to correct these.By use of interactive tools included in SmaggIce version 1.2,one can easily characterize ice shapes and prepare iced airfoils for grid genera- tion and flow simulations.

Posted in: Briefs

Read More >>

Rapid Chemometric Filtering of Spectral Data

Target species would be identified in real time.   A method of rapid, programmable filtering of spectral transmittance, reflectance, or fluorescence data to measure the concentrations of chemical species has been proposed. By "programmable" is meant that a variety of spectral analyses can readily be performed and modified in software, firmware, and/or electronic hardware, without need to change optical filters or other optical hardware of the associated spectrometers. The method is intended to enable real-time identification of single or multiple target chemical species in applications that involve high-throughput screening of multiple samples. Examples of such applications include (but are not limited to) combinatorial chemistry, flow cytometry, bead assays, testing drugs, remote sensing, and identification of targets.

Posted in: Briefs, TSP

Read More >>

Centrifugal Adsorption System

Notable features include efficient collection of bioproducts and removal of bubbles. The centrifugal adsorption cartridge system (CACS) is an apparatus that recovers one or more bioproduct(s) from a dilute aqueous solution or suspension flowing from a bioreactor. The CACS can be used both on Earth in unit gravity and in space in low gravity. The CACS can be connected downstream from the bioreactor; alternatively, it can be connected into a flow loop that includes the bioreactor so that the liquid can be recycled. A centrifugal adsorption cartridge in the CACS (see figure) includes two concentric cylinders with a spiral ramp between them. The volume between the inner and outer cylinders, and between the turns of the spiral ramp is packed with an adsorbent material. The inner cylinder is a sieve tube covered with a gas- permeable, hydrophobic membrane.

Posted in: Machinery & Automation, Briefs

Read More >>

Ultrasonic Apparatus for Pulverizing Brittle Material

Characteristics include light weight, low preload, and low power demand. The figure depicts an apparatus that pulverizes brittle material by means of a combination of ultrasonic and sonic vibration, hammering, and abrasion. The basic design of the apparatus could be specialized to be a portable version for use by a geologist in collecting powdered rock samples for analysis in the field or in a laboratory. Alternatively, a larger benchtop version could be designed for milling and mixing of precursor powders for such purposes as synthesis of ceramic and other polycrystalline materials or preparing powder samples for x-ray diffraction or x-ray fluorescence measurements to determine crystalline structures and compositions. Among the most attractive characteristics of this apparatus are its light weight and the ability to function without need for a large preload or a large power supply: It has been estimated that a portable version could have a mass <0.5 kg, would consume less than 1 W·h of energy in milling a 1-cm 3 volume of rock, and could operate at a preload <10 N.

Posted in: Briefs, TSP

Read More >>

Liquid-Metal-Fed Pulsed Plasma Thrusters

A short document proposes liquid- metal- fed pulsed plasma thrusters for small spacecraft. The propellant liquid for such a thruster would be a low- melting- temperature metal that would be stored molten in an unpressurized, heated reservoir and would be pumped to the thruster by a magneto- hydrodynamic coupler. The liquid would enter the thruster via a metal tube inside an electrically insulating ceramic tube. A capacitor would be connected between the outlet of the metal tube and the outer electrode of the thruster. The pumping would cause a drop of liquid to form at the outlet, eventually growing large enough to make contact with the outer electrode. Contact would close the circuit through the capacitor, causing the capacitor to discharge through the drop. The capacitor would have been charged with enough energy that the discharge would vaporize, ionize, and electromagnetically accelerate the contents of the metal drop. The resulting plasma would be ejected at a speed of about 50 km/s. The vaporization of the drop would reopen the circuit through the capacitor, enabling recharging of the capacitor. As pumping continued, a new drop would grow and the process would repeat.

Posted in: Briefs, TSP

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.