Tech Briefs

Plumbing Fixture for a Microfluidic Cartridge

A fixture has been devised for making the plumbing connections between a microfluidic device in a replaceable cartridge and an external fluidic system. The fixture includes a 0.25-in. (6.35-mm) thick steel plate, to which the cartridge is fastened by two 10-32 thumb screws. The plate holds one plumbing fitting for the inlet and one for the outlet of the microfluidic device. Each fitting includes a fused-silica tube of 0.006-in. (≈0.15-mm) inside diameter within a fluorinated ethylene-propylene (FEP) tube of 0.0155-in. (≈0.39-mm) inside diameter and 0.062-in. (≈1.57-mm) outside diameter. The FEP tube is press-fit through the steel plate so that its exposed end is flush with the surface of the plate, and the silica tube protrudes 0.03 in. (≈0.76 mm) from the plate/FEPtube- end surface. The cartridge includes a glass cover plate that contains 0.06-mm-wide access ports. When the cartridge is fastened to the steel plate, the silica tubes become inserted through the access ports and into the body of the cartridge, while the ends of the FEP tubes become butted against the glass cover plate. An extremely tight seal is thereby made.

Posted in: Briefs, Mechanical Components, Mechanics, Seals and gaskets, Hydraulic equipment

Camera Mount for a Head-Up Display

A mounting mechanism was designed and built to satisfy requirements specific to a developmental head-up display (HUD) to be used by pilots in a Boeing 757 airplane. This development was necessitated by the fact that although such mounting mechanisms were commercially available for other airplanes, there were none for the 757. The mounting mechanism supports a miniature electronic camera that provides a forward view. The mechanism was designed to be integrated with the other HUD instrumentation and to position the camera so that what is presented to the pilot is the image acquired by the camera, overlaid with alphanumeric and/or graphical symbols, from a close approximation of the pilot’s natural forward perspective. The mounting mechanism includes an L-shaped mounting arm that can be adjusted easily to the pilot’s perspective, without prior experience. The mounting mechanism is lightweight and flexible and presents little hazard to the pilot.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Imaging and visualization, Head-up displays, Commercial aircraft

Core-Cutoff Tool

Damage and waste are reduced.

A tool makes a cut perpendicular to the cylindrical axis of a core hole at a predetermined depth to free the core at that depth. The tool does not damage the surrounding material from which the core was cut, and it operates within the core-hole kerf.

Posted in: Briefs, Manufacturing & Prototyping, Tools and equipment, Milling, Waste materials

Single-Point Access to Data Distributed on Many Processors

A description of the functions and data structures is defined that would be necessary to implement the Chapel concept of distributions, domains, allocation, access, and interfaces to the compiler for transformations from Chapel source to their run-time implementation for these concepts. A complete set of object-oriented operators is defined that enables one to access elements of a distributed array through regular arithmetic index sets, giving the programmer the illusion that all the elements are collocated on a single processor. This means that arbitrary regions of the arrays can be fragmented and distributed across multiple processors with a single point of access. This is important because it can significantly improve programmer productivity by allowing the programmers to concentrate on the high-level details of the algorithm without worrying about the efficiency and communication details of the underlying representation.

Posted in: Briefs, TSP, Information Sciences, Computer software and hardware, Data acquisition and handling, Data management, Productivity

Computing a Stability Spectrum by Use of the HHT

Unlike in the predecessor method, the mathematical sign of the damping is retained.

The Hilbert-Huang transform (HHT) is part of the mathematical basis of a method of calculating a stability spectrum. This method can be regarded as an extended and improved version of a prior HHT-based method of calculating a damping spectrum. In the prior method, information on positive damping (which leads to stability) and negative damping (which leads to instability) becomes mixed into a single squared damping loss factor. Hence, there is no way to distinguish between stability and instability by examining a damping spectrum. In contrast, in the present stability-spectrum method, information on the mathematical sign of the damping is retained, making it possible to identify regions of instability in a spectrum. This method is expected to be especially useful for analyzing vibration- test data for the purpose of predicting vibrational instabilities in structures (e.g., flutter in airplane wings).

Posted in: Briefs, TSP, Information Sciences, Mathematical analysis, Vibration

Estimating Dust and Water Ice Content of the Martian Atmosphere From THEMIS Data

Researchers at JPL and Arizona State University conducted a comparative study of three candidate algorithms for estimating components of the Martian atmosphere, using raw (uncalibrated) data collected by the Thermal Emission Imaging System (THEMIS). THEMIS is an instrument onboard the Mars Odyssey spacecraft that acquires image data in five visible and nine infrared (IR) wavelength bands. The algorithms under study used data collected from eight of the nine IR bands to estimate the dust and water ice content of the atmosphere. Such an algorithm could be used in onboard data processing to trigger other algorithms that search for features of scientific interest and to reduce the volume of data transmitted to Earth.

Posted in: Briefs, TSP, Information Sciences, Mathematical models, Data acquisition and handling, Imaging and visualization, Soils, Water, Spacecraft

Theoretical Studies of Routes to Synthesis of Tetrahedral N4

A paper [Chem. Phys. Lett. 345, 295 (2001)] describes theoretical studies of excited electronic states of nitrogen molecules, with a view toward utilizing those states in synthesizing tetrahedral N4, or Td N4 — a metastable substance under consideration as a high-energy-density rocket fuel. Several ab initio theoretical approaches were followed in these studies, including complete active space selfconsistent field (CASSCF), state-averaged CASSCF (SA-CASSCF), singles configuration interaction (CIS), CIS with secondorder and third-order correlation corrections [CIS(D) and CIS(3)], and linear response singles and doubles coupledcluster (LRCCSD). Standard double zeta polarized and triple zeta double polarized one-particle basis sets were used.

Posted in: Briefs, Physical Sciences, Spacecraft fuel, Research and development

Estimation Filter for Alignment of the Spitzer Space Telescope

A document presents a summary of an onboard estimation algorithm now being used to calibrate the alignment of the Spitzer Space Telescope (formerly known as the Space Infrared Telescope Facility). The algorithm, denoted the S2P calibration filter, recursively generates estimates of the alignment angles between a telescope reference frame and a star-tracker reference frame. At several discrete times during the day, the filter accepts, as input, attitude estimates from the star tracker and observations taken by the Pointing Control Reference Sensor (a sensor in the field of view of the telescope). The output of the filter is a calibrated quaternion that represents the best current mean-square estimate of the alignment angles between the telescope and the star tracker. The S2P calibration filter incorporates a Kalman filter that tracks six states — two for each of three orthogonal coordinate axes. Although, in principle, one state per axis is sufficient, the use of two states per axis makes it possible to model both short- and long-term behaviors. Specifically, the filter properly models transient learning, characteristic times and bounds of thermomechanical drift, and long-term steady-state statistics, whether calibration measurements are taken frequently or infrequently. These properties ensure that the S2P filter performance is optimal over a broad range of flight conditions, and can be confidently run autonomously over several years of in-flight operation without human intervention.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Calibration, Mathematical models, Imaging and visualization, Spacecraft

Antenna for Measuring Electric Fields Within the Inner Heliosphere

A document discusses concepts for the design of an antenna to be deployed from a spacecraft for measuring the ambient electric field associated with plasma waves at a location within 3 solar radii from the solar photosphere. The antenna must be long enough to extend beyond the photoelectron and plasma sheaths of the spacecraft (expected to be of the order of meters thick) and to enable measurements at frequencies from 20 Hz to 10 MHz without contamination by spacecraft electric-field noise. The antenna must, therefore, extend beyond the thermal protection system (TPS) of the main body of the spacecraft and must withstand solar heating to a temperature as high as 2,000 °C while not conducting excessive heat to the interior of the spacecraft.

Posted in: Briefs, TSP, Physical Sciences, Measurements, Antennas, Test equipment and instrumentation, Spacecraft

Improved High-Voltage Gas Isolator for Ion Thruster

A report describes an improved highvoltage isolator for preventing electrical discharge along the flow path of a propellant gas being fed from a supply at a spacecraft chassis electrical potential to an ion thruster at a potential as high as multiple kilovolts. The isolator must survive launch vibration and must remain electrically nonconductive for thousands of hours under conditions that, in the absence of proper design, would cause formation of electrically conductive sputtered metal, carbon, and/or decomposed hydrocarbons on its surfaces.

Posted in: Briefs, TSP, Physical Sciences, High voltage systems, Propellants, Gases, Insulation, Fuel injection, Spacecraft

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