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Scalable SCPPM Decoder

A decoder was developed that decodes a serial concatenated pulse position modulation (SCPPM) encoded information sequence. The decoder takes as input a sequence of four bit loglikelihood ratios (LLR) for each PPM slot in a codeword via a XAUI 10-Gb/s quad optical fiber interface. If the decoder is unavailable, it passes the LLRs on to the next decoder via a XAUI 10-Gb/s quad optical fiber interface. Otherwise, it decodes the sequence and outputs information bits through a 1- GB/s Ethernet UDP/IP (User Datagram Protocol/Internet Protocol) interface.

Posted in: Information Sciences, Briefs

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Rugged, Portable, Real-Time Optical Gaseous Analyzer for Hydrogen Fluoride

Applications include trace gas sensor applications where rapid sampling is required, particularly in human-occupied closed volumes. Hydrogen fluoride (HF) is a primary evolved combustion product of fluorinated and perfluorinated hydrocarbons. HF is produced during combustion by the presence of impurities and hydrogen-containing polymers including polyimides. This effect is especially dangerous in closed occupied volumes like spacecraft and submarines. In these systems, combinations of perfluorinated hydrocarbons and polyimides are used for insulating wiring. HF is both highly toxic and short-lived in closed environments due to its reactivity. The high reactivity also makes HF sampling problematic.

Posted in: Physical Sciences, Information Sciences, Briefs, TSP

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Onboard Sensor Data Qualification in Human-Rated Launch Vehicles

Applications include sensor data qualification and equipment condition monitoring in commercial power plants. The avionics system software for human-rated launch vehicles requires an implementation approach that is robust to failures, especially the failure of sensors used to monitor vehicle conditions that might result in an abort determination. Sensor measurements provide the basis for operational decisions on human-rated launch vehicles. This data is often used to assess the health of system or subsystem components, to identify failures, and to take corrective action. An incorrect conclusion and/or response may result if the sensor itself provides faulty data, or if the data provided by the sensor has been corrupted. Operational decisions based on faulty sensor data have the potential to be catastrophic, resulting in loss of mission or loss of crew. To prevent these later situations from occurring, a Modular Architecture and Generalized Methodology for Sensor Data Qualification in Human-rated Launch Vehicles has been developed.

Posted in: Information Sciences, Briefs, TSP

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Monitoring of International Space Station Telemetry Using Shewhart Control Charts

This technique can be applied to monitoring critical systems such as electrical power generation and manufacturing equipment. Shewhart control charts have been established as an expedient method for analyzing dynamic, trending data in order to identify anomalous subsystem performance as soon as such performance would exceed a statistically established baseline. Additionally, this leading indicator tool integrates a selection methodology that reduces false positive indications, optimizes true leading indicator events, minimizes computer processor unit duty cycles, and addresses human factor concerns (i.e., the potential for flight-controller data overload). This innovation leverages statistical process control, and provides a relatively simple way to allow flight controllers to focus their attention on subtle system changes that could lead to dramatic off-nominal system performance. Finally, this capability improves response time to potential hardware damage and/or crew injury, thereby improving space flight safety.

Posted in: Information Sciences, Briefs, TSP

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Time Manager Software for a Flight Processor

Data analysis is a process of inspecting, cleaning, transforming, and modeling data to highlight useful information and suggest conclusions. Accurate timestamps and a timeline of vehicle events are needed to analyze flight data. When data is gathered onboard a rocket, precise time stamping is even more important due to the rocket’s high speeds and the requirement to integrate data over time for inertial navigation calculations.

Posted in: Information Sciences, Briefs

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Simulation of Oxygen Disintegration and Mixing With Hydrogen or Helium at Supercritical Pressure

These models can be used in simulations of gas turbine engines. The simulation of high-pressure turbulent flows, where the pressure, p, is larger than the critical value, pc, for the species under consideration, is relevant to a wide array of propulsion systems, e.g. gas turbine, diesel, and liquid rocket engines. Most turbulence models, however, have been developed for atmospheric-p turbulent flows. The difference between atmospheric-p and supercritical-p turbulence is that, in the former situation, the coupling between dynamics and thermodynamics is moderate to negligible, but for the latter it is very significant, and can dominate the flow characteristics. The reason for this stems from the mathematical form of the equation of state (EOS), which is the perfect-gas EOS in the former case, and the real-gas EOS in the latter case.

Posted in: Information Sciences, Briefs

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Theory of a Traveling Wave Feed for a Planar Slot Array Antenna

A design procedure was developed for the coupling slots between the feed waveguide and the radiating waveguides. Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the element spacing in the feed waveguide is chosen to produce a beam squinted from the broadside.

Posted in: Information Sciences, Briefs

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