Tech Briefs

Graded-Index “Whispering-Gallery” Optical Microresonators

Improvements would include equidistant resonances and reduced evanescent field. Graded-index-of- refraction dielectric optical microresonators have been proposed as a superior alternative to prior dielectric optical microresonators, which include microspheres (described in several prior NASA Tech Briefs articles) and microtori wherein electromagnetic waves propagate along circumferential paths in “whispering-gallery” modes. The design and method of fabrication of the proposed microresonators would afford improved performance by exploiting a combination of the propagation characteristics of the whisperinggallery modes and the effect of a graded index of refraction on the modes.

Posted in: Briefs, TSP, Physical Sciences

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Thermally Stable Piezoelectric and Pyroelectric Polymers

Neither mechanical nor solvent treatment is necessary for orientation of polymer molecules. A class of thermally stable piezoelectric and pyroelectric polymers, and an improved method of making them, have been invented. These polymers can be used as substrates for a wide variety of electro- mechanical transducers, sensors, and actuators.

Posted in: Briefs, Materials

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Combustion Synthesis of Ca3(PO4)2 Net-Shape Surgical Implants

More-biocompatible materials are produced in fewer processing steps. ASelf-propagating high-temperature combustion synthesis (SHS) is the basis of a method of making components of porous tricalcium phosphate [Ca3(PO4)2] and related compounds in net sizes and shapes for use as surgical implants that are compatible with bone. Ca3(PO4)2-based materials are among those preferred for use in orthopedic, restorative, and reconstructive surgery. As explained below, the SHS method offers advantages over prior methods of manufacturing Ca3(PO4)2-based surgical implants.

Posted in: Briefs, TSP, Materials

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Robust Control for the Mercury Laser Altimeter

Mercury Laser Altimeter Science Algorithms is a software system for controlling the laser altimeter aboard the Messenger spacecraft, which is to enter into orbit about Mercury in 2011. The software will control the altimeter by dynamically modifying hardware inputs for gain, threshold, channel- disable flags, range- window start location, and range- window width, by using ranging information provided by the spacecraft and noise counts from instrument hardware. In addition, because of severe bandwidth restrictions, the software also selects returns for downlink. To reduce mission risk, the software incorporates three different modes of operation. The three modes are denoted as fixed, range-driven, and closedloop (or adaptive). The fixed mode provides fixed hardware inputs for all but the threshold. The range-driven mode receives and utilizes ranging information from the spacecraft regarding its slant range to the planet or asteroid. The adaptive mode is capable of improving upon the ranging information provided by the spacecraft by use of a closed-loop range-estimation algorithm. The software is sufficiently robust that it could be used on other missions, and in fact, this has already been proposed.

Posted in: Briefs, TSP, Software

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DAVE-ML Utility Programs

DAVEtools is a set of Java archives (*.jar files) that embodies tools for manipulating flight-dynamics models that have been encoded in dynamic aerospace vehicle exchange markup language (DAVE-ML). [DAVE-ML is an application program, written in Extensible Markup Language (XML), for encoding complete computational models of the dynamics of aircraft and spacecraft. The goal in the continuing development of DAVE-ML is to expedite the exchange and validation of dynamical models, via the Internet, in a manner that is consistent and is independent of computational-simulation facilities, computing languages, and simulation software.] At present, DAVEtools includes two tools: dave (a basic DAVE-ML parser), which generates a Java-based version of a model encoded in DAVE-ML and dave2sl, which builds on dave to create Simulink® representations of models encoded in DAVE-ML.

Posted in: Briefs, Software

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Software for Alignment of Segments of a Telescope Mirror

The Segment Alignment Maintenance System (SAMS) software is designed to maintain the overall focus and figure of the large segmented primary mirror of the Hobby-Eberly Telescope. This software reads measurements made by sensors attached to the segments of the primary mirror and from these measurements computes optimal control values to send to actuators that move the mirror segments. The software also acts as a logger for the collected data, a server from which the hardware of the control computer can acquire control information and other computers can collect data, and a monitoring and diagnostic system. The software provides a graphical user interface through which human operators can exert control. The software supports four modes of operation: Operate — The server acquires the sensory data and processes them into commands for the actuators. Calibrate — Calibration tests are performed on the edge sensors and the relationships between actuator commands and sensor responses are quantified. Standby — The server is initialized in standby mode, from which it can make the transition to any of the other three modes. Diagnostic — This mode provides access to all sensory data in real time and is intended for use in diagnosis of sensor anomalies.

Posted in: Briefs, Software

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Simulation of Dropping of Cargo With Parachutes

Decelerator System Simulation (DSS) is a computer program for predicting and analyzing the dynamics of a load of cargo dropped with parachutes from an aircraft. A DSS simulation runs from the first motion in the aircraft until the payload reaches the ground. Intended for use in support of airdrop tests for the X- 38 program, DSS was developed by modifying and augmenting an older program, denoted UD233A, used for simulating the dynamics of a space-shuttle solid rocket booster falling with a parachute. The main effort in converting UD233A into DSS involved development of computational models for simulating the inflation of one or more parachute( s), the dynamics of the payload and the slings connecting the parachute( s) with the payload, and the extraction of the payload and parachutes from the aircraft.

Posted in: Briefs, Software

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