Miniature Birefringence-Measuring System

A miniature birefringence-measuring system has been developed for use in investigating extensional flows of non-Newtonian polymers in microgravity. The system could also be used on Earth to perform general optical-retardation and dichroism measurements, to measure stresses with high sensitivity, to characterize polymers, and to measure orientation angles of molecular chains. The system includes a dual-crystal transverse electro-optical phase modulator that makes it possible to measure small (of the order of 10 -9) changes in the birefringence of a material under test as the material is subjected to extensional deformation or shear stress.

Posted in: Briefs, TSP, Test & Measurement, Measurements, Polymers

Thrust Stand Measures Thrusts of

The development of miniature, cold- gas thrusters for on-orbit propulsion of such small devices as remotely piloted cameras and for inclusion in astronaut propulsion backpacks gave rise to a need to measure thrusts ranging from 0.04 to 0.8 lb (0.2 to 3.6 N). In addition, there was a need to measure thrust in a vacuum environment as well as in air at a pressure of 1 atmosphere (0.1 MPa), and over a wide range of propellant inlet pressures. The primary obstacle to be overcome for such measurements was to solve the problem of delivering the cold-gas propellant (compressed nitrogen gas) to the thruster without affecting thrust measurements, particularly those below 1/4 lb (1 N).

Posted in: Briefs, TSP, Test & Measurement, Attitude control, Attitude control, Propellants, Gases, Spacesuits, Spacecraft

Software for Designing Model Rockets for Base-Heating Tests

The Impulse Combustion Excel (ICE) computer program was developed to facilitate and accelerate the design and analysis of subscale rocket engines for use in base-heating tests. Such tests are performed on the ground to obtain data for estimating the heating effects of hot exhaust plumes on the aft regions of full-scale rockets during ascent. The computer program is so named because typically, a base-heating test involves impulse combustion — short-duration (of the order of 100 ms long) hot firing using flight propellants. Heretofore, the design of the subscale engines and base-heating tests has been a difficult, time-consuming, iterative process. ICE can be expected to reduce the testing times and costs and to yield improved designs. ICE can be used to design models to be tested in both wind tunnels and vacuum tanks.

Posted in: Briefs, Test & Measurement, CAD / CAM / CAE, CAD, CAM, and CAE, Scale models, Rocket engines, Thermal testing

Measuring NO and OH Concentrations at High Pressure

An apparatus based on line-of-sight resonant absorption of ultraviolet light yields measurement data from which one can calculate the concentrations of nitric oxide (NO) and of hydroxyl radicals (OH) in a laboratory flat flame at a pressure up to 30 atm ≈3 MPa). The basic measurement principle is distinct from the principles of laser-induced fluorescence and other laser diagnostic techniques; hence, the data generated by this apparatus could provide independent verification of data from laser-based instruments.

Posted in: Briefs, TSP, Test & Measurement, Measurements, Optics, Optics, Nitrogen oxides, Test equipment and instrumentation

Automated Apparatus for Testing Gyroscopes

The Gyroscope Automated Testbed is a computer-controlled apparatus designed primarily for automated testing of vibratory gyroscopes. It can also be used to test other devices: By changing testing-system/tested-device interface circuitry that is part of the apparatus, one can set up the apparatus to test nonvibratory gyroscopes. The apparatus can also be used as a general-purpose noise-analysis system for characterizing a variety of devices in addition to gyroscopes.

Posted in: Briefs, TSP, Test & Measurement, Automation, Test equipment and instrumentation

Electromechanical Testing of Microelectromechanical Devices

A method of electromechanical testing has been proposed for general diagnosis, evaluation of performance, and burn-in (accelerated life testing) of microelectromechanical devices. The tests would ordinarily be performed at the wafer level; that is, after the devices have been fabricated on wafers but before the wafers have been diced and the dies packaged. Alternatively or in addition, the tests could be performed at other stages of the fabrication process.

Posted in: Briefs, TSP, Test & Measurement, Microelectricmechanical device, Microelectromechanical devices, Microelectricmechanical device, Microelectromechanical devices, Test procedures

Mechanism for Adjusting and Measuring Tension in a Cable

The figure illustrates a simple mechanism designed for anchoring one end of a cable on a structure and for adjusting the tension in the cable. Unlike turnbuckles and other conventional cable-tensioning mechanisms, this mechanism also facilitates direct measurement of the tension in the cable. Several of these mechanisms are used in concert in order to suspend a structure for thermal isolation.

Posted in: Briefs, TSP, Test & Measurement, Measurements, Fittings, Mountings, Parts

Power Supply for Miniature Quadrupole Mass Spectrometer

A lightweight, low-power-consumption power supply has been developed to generate a combination of radio-frequency (RF) and dc voltages needed for the operation of a miniature quadrupole mass spectrometer that could operate unattended in the field for a long time, possibly using a battery as an energy source. More specifically, the circuit is designed to supply large, variable, frequency- and amplitude-stable RF voltages, variously floating or superimposed on positive or negative dc voltages, for application to primarily capacitive mass-spectrometer loads with capacitances of the order of 50 pF.

Posted in: Briefs, Test & Measurement, Integrated circuits, Integrated circuits, Electric power, Energy consumption, Test equipment and instrumentation

Instrument Measures Fluorescence From Chlorophyll in Plants

An optoelectronic instrument, known as a plant fluorescence sensor, is being developed for use as a working tool in agricultural settings. This instrument is a remote, passive monitor that provides a means of discerning plant stress at very early stages. With sufficient warning, the user could provide timely applications of fertilizer, water, and/or pesticide to achieve maximum crop yield at minimum cost. Figure 1 presents two views of the plant fluorescence sensor. The instrument is the subject of U. S. Patent 5,567,947.

Posted in: Briefs, Test & Measurement, Imaging, Imaging and visualization, Sensors and actuators, Imaging, Imaging and visualization, Sensors and actuators, Test equipment and instrumentation, Agricultural vehicles and equipment

Laser Heating for Testing Rocket-Engine Insulating Phenolic

A continuous-wave CO2 laser has been selected as a source of heat for testing the thermal response of carbon-cloth phenolic like that used as insulating material in a reusable solid-fuel rocket motor (RSRM). The particular thermal response of interest, observed during operation of an RSRM, is pocketing. By suitable adjustment of the size and power of the laser beam, the rate of heating can be made nearly identical to that in the RSRM nozzle during operation.

Posted in: Briefs, Test & Measurement, Lasers, Lasers, Solid propellants, Insulation, Rocket engines, Test equipment and instrumentation, Thermal testing

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