Apparatus Characterizes Transient Voltages in Real Time

The figure shows a prototype of a relatively inexpensive electronic monitoring apparatus that measures and records selected parameters of lightning-induced transient voltages on communication and power cables. The selected parameters, listed below, are those most relevant to the ability of lightning-induced transients to damage electronic equipment. This apparatus bridges a gap between some traditional transient-voltage recorders that record complete waveforms and other traditional transient-voltage recorders that record only peak values: By recording the most relevant parameters and only those parameters this apparatus yields more useful information than does a traditional peak-value (only) recorder while imposing much smaller data-storage and data-transmission burdens than does a traditional complete-waveform recorder. Also, relative to a complete-waveform recorder, this apparatus is more reliable and can be built at lower cost because it contains fewer electronic components. The transients generated by sources other than lightning tend to have frequency components well below 1 MHz. Most commercial transient recorders can detect and record such transients, but cannot respond rapidly enough for recording lightning-induced transient voltage peaks, which can rise from 10 to 90 percent of maximum amplitude in a fraction of a microsecond. Moreover, commercial transient recorders cannot rearm themselves rapidly enough to respond to the multiple transients that occur within milliseconds of each other on some lightning strikes. One transient recorder, designed for Kennedy Space Center earlier [ Fast Transient-Voltage Recorder (KSC- 11991), NASA Tech Briefs, Vol. 23, No. 10, page 6a (October 1999)], is capable of sampling transient voltages at peak values up to 50 V in four channels at a rate of 20 MHz. That recorder contains a trigger circuit that continuously compares the amplitudes of the signals on four channels to a preset triggering threshold. When a trigger signal is received, a volatile memory is filled with data for a total time of 200 ms. After the data are transferred to nonvolatile memory, the recorder rearms itself within 400 ms to enable recording of subsequent transients. Unfortunately, the recorded data must be retrieved through a serial communication link. Depending on the amount of data recorded, the memory can be filled before retrieval is completed. Although large amounts of data are recorded and retrieved, only a small part of the information (the selected parameters) is usually required. The present transient-voltage recorder provides the required information, without incurring the overhead associated with the recording, storage, and retrieval of complete transient-waveform data. In operation, this apparatus processes transient voltage waveforms in real time to extract and record the selected parameters. An analog-to-digital converter that operates at a speed of as much as 100 mega-samples per second is used to sample a transient waveform. A real-time comparator and peak detector are implemented by use of fast field-programmable gate arrays

Development of Sensors for Aerospace Applications

Advances in technology have led to the availability of smaller and more accurate sensors. Computer power to process large amounts of data is no longer the prevailing issue; thus multiple and redundant sensors can be used to obtain more accurate and comprehensive measurements in a space vehicle. The successful integration and commercialization of micro- and nanotechnology for aerospace applications require that a close and interactive relationship be developed between the technology provider and the end user early in the project. Close coordination between the developers and the end users is critical since qualification for flight is time-consuming and expensive. The successful integration of micro- and nanotechnology into space vehicles requires a coordinated effort throughout the design, development, installation, and integration processe

Paper Session I-C - Commercial Use of KSC\u27s Cable Inspection Technologies and Potential Opportunities in the Near Future

NASA\u27s requirements for reliable cable inspection technologies for the complex wiring systems of the Space Shuttle led to the development of new technology that was successfully licensed and commercialized. Similar requirements in the aging aircraft community have led to the feasibility testing of this technology in commercial aircraft. Rapidly emerging advances in the field of electronics presents the opportunity to apply wiring inspection technologies to various problems in a cost-effective manner. This presentation will describe the pathway from technology development to commercialization taken with NASA\u27s cable inspection technology as well as offer a glimpse of future commercial opportunities. ASRC scientists and engineers, working in conjunction with with NASA engineers, are in the process of developing an advanced cable tester capable of detecting subtle defects in cables. The objective is to be able to proactively repair a cable before a short or an open condition develops. Early detection of an impending fault is critical to ensure safe flying conditions for the Space ShuttJe and for commercial and military aircraft

Paper Session II-C - Low Cost Self-calibrating, Field Serviceable Signal Conditioning Amplifier

Multiple sensors are used to conduct measurements during every Space Shuttle flow. Often, these measurements have to be installed at locations where available space is minimal. Signal conditioners have a frequent need to be removed from service for calibration, typically, on an annual basis. The calibration must be performed in a shop with traceable test equipment, and can require several hours of manpower. A low cost miniaturized Signal Conditioning Amplifier (SCA), based on the use of Application-Specific Integrated Circuits (ASIC) and IEEE 1451-compliant, will reduce the manpower required to set up new measurements and to replace or calibrate existing ones. The SCA is connected to a transducer attached to a Transducer Electronic Data Sheet (TEDS), which is read by the amplifier upon power up. The TEDS contains information required by the amplifier to configure itself to operate with a particular transducer. The signal conditioner is capable of performing continuous health checks and auto-calibration and significantly reduces operating and maintenance costs of a data acquisition system. The use of ASICs will also allow for the implementation of multichannel devices for additional reduction in space and power requirements

Nano Sensors for Gas Detection in Space and Ground Support Applications

Personnel living in a space environment as well as technicians and engineers preparing spacecraft for launch can potentially be exposed to small amounts of hazardous gases. It is therefore important to be able to detect, identify and quantify the presence of a gas especially when its presence could lead to a fatal situation. The use of small and sensitive sensors can allow for the placement of these devices over a large area, thus allowing for a more precise and timely determination of a gas leak. ASRC Aerospace and its research partners are developing nano sensors for detection of various gases, including but not limited to: H2, NH3, N2O4, hydrazine and others. Initial laboratory testing has demonstrated the capability to detect the gases in concentrations lower than parts per million. Testing and development is continuing to improve the response and recovery times, to increase the sensitivity of the devices. Different coatings and electrodes are currently being evaluated to determine the optimum configuration of a variety of gases. The small footprint of the Nano sensors allows for several devices, each responsive in a different way to different gases, to be placed into a single substrate. Multiple devices embedded into a single substrate results in increased reliability and in a decrease for periodic calibrations. The use of different coatings will result in a small electronic nose capable of distinguishing between different gases. A multi-channel signal conditioner amplifier built on a small multi chip module is used to process the output of the sensors and to deliver a signal that can be remotely monitored. All the data is digitized and transmitted over the same cable pair used to power the amplifier. Multiple outputs can be connected to a single cable pair in order to minimize the added weight and expense associated with cabling in a spacecraft. The sensors will be run through a qualification process to evaluate their suitability for space applications we are expecting to have fully functional sensors available for initial field deployment and testing by the end of the year 2006

Online Cable Tester and Rerouter

Hardware and algorithms have been developed to transfer electrical power and data connectivity safely, efficiently, and automatically from an identified damaged/defective wire in a cable to an alternate wire path. The combination of online cable testing capabilities, along with intelligent signal rerouting algorithms, allows the user to overcome the inherent difficulty of maintaining system integrity and configuration control, while autonomously rerouting signals and functions without introducing new failure modes. The incorporation of this capability will increase the reliability of systems by ensuring system availability during operations

Next Generation Vehicle Sensors

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Orbiter Lessons Learned

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Efficient Processing of Data for Locating Lightning Strikes

Two algorithms have been devised to increase the efficiency of processing of data in lightning detection and ranging (LDAR) systems so as to enable the accurate location of lightning strikes in real time. In LDAR, the location of a lightning strike is calculated by solving equations for the differences among the times of arrival (DTOAs) of the lightning signals at multiple antennas as functions of the locations of the antennas and the speed of light. The most difficult part of the problem is computing the DTOAs from digitized versions of the signals received by the various antennas. One way (a time-domain approach) to determine the DTOAs is to compute cross-correlations among variously differentially delayed replicas of the digitized signals and to select, as the DTOAs, those differential delays that yield the maximum correlations. Another way (a frequency-domain approach) to determine the DTOAs involves the computation of cross-correlations among Fourier transforms of variously differentially phased replicas of the digitized signals, along with utilization of the relationship among phase difference, time delay, and frequency

Monte Carlo Simulation to Estimate Likelihood of Direct Lightning Strikes

A software tool has been designed to quantify the lightning exposure at launch sites of the stack at the pads under different configurations. In order to predict lightning strikes to generic structures, this model uses leaders whose origins (in the x-y plane) are obtained from a 2D random, normal distribution