Physical Sciences

ISS Ammonia Leak Detection Through X-Ray Fluorescence

An astrophysics instrument can be used to detect and localize ISS ammonia leaks.

Ammonia leaks are a significant concern for the International Space Station (ISS). The ISS has external transport lines that direct liquid ammonia to radiator panels where the ammonia is cooled and then brought back to thermal control units. These transport lines and radiator panels are subject to stress from micrometeorites and temperature variations, and have developed small leaks. The ISS can accommodate these leaks at their present rate, but if the rate increased by a factor of ten, it could potentially deplete the ammonia supply and impact the proper functioning of the ISS thermal control system, causing a serious safety risk.

Posted in: Briefs, TSP, Physical Sciences, Test & Measurement, Hoses, Radiators, Hazardous materials, Risk assessments, Spacecraft

Hydrometeor Size Distribution Measurements by Imaging the Attenuation of a Laser Spot

Measurement of the DSD’s second moment is made by way of the Beer-Lambert law.

The optical extinction of a laser due to scattering of particles is a well-known phenomenon. In a laboratory environment, this physical principle is known as the Beer-Lambert law, and is often used to measure the concentration of scattering particles in a fluid or gas. This method has been experimentally shown to be a usable means to measure the dust density from a rocket plume interaction with the lunar surface. Using the same principles and experimental arrangement, this technique can be applied to hydrometeor size distributions, and for launch-pad operations, specifically as a passive hail detection and measurement system.

Posted in: Briefs, TSP, Physical Sciences, Test & Measurement, Measurements, Lasers, Lasers, Particulate matter (PM), Refractory materials, Test equipment and instrumentation

Victim Simulator for Victim Detection Radar

This simulator can be placed for long periods of time in environments that would be unsafe for a human subject.

Testing of victim detection radars has traditionally used human subjects who volunteer to be buried in, or climb into a space within, a rubble pile. This is not only uncomfortable, but can be hazardous or impractical when typical disaster scenarios are considered, including fire, mud, or liquid waste. Human subjects are also inconsistent from day to day (i.e., they do not have the same radar properties), so quantitative performance testing is difficult. Finally, testing a multiple-victim scenario is difficult and expensive because of the need for multiple human subjects who must all be coordinated.

Posted in: Briefs, TSP, Physical Sciences, Test & Measurement, Computer simulation, Radar, Radar, Disaster and emergency management, Emergency management, Anthropometric test devices, Test equipment and instrumentation

Complementary Barrier Infrared Detector (CBIRD) Contact Methods

The performance of the CBIRD detector is enhanced by using new device contacting methods that have been developed. The detector structure features a narrow gap adsorber sandwiched between a pair of complementary, unipolar barriers that are, in turn, surrounded by contact layers. In this innovation, the contact adjacent to the hole barrier is doped n-type, while the contact adjacent to the electron barrier is doped p-type.

Posted in: Briefs, Physical Sciences, Sensors and actuators, Sensors and actuators, Radiation, Test equipment and instrumentation

Multimode Directional Coupler for Utilization of Harmonic Frequencies From TWTAs

The design is easily scaled to higher frequency TWTAs.

A novel waveguide multimode directional coupler (MDC) intended for the measurement and potential utilization of the second and higher order harmonic frequencies from high-power traveling wave tube amplifiers (TWTAs) has been successfully designed, fabricated, and tested. The design is based on the characteristic multiple propagation modes of the electrical and magnetic field components of electromagnetic waves in a rectangular waveguide.

Posted in: Briefs, TSP, Physical Sciences, Waveguides, Waveguides, Product development

High-Power, High-Speed Electro-Optic Pockels Cell Modulator

Electro-optic modulators rely on a change in the index of refraction for the optical wave as a function of an applied voltage. The corresponding change in index acts to delay the wavefront in the waveguide. The goal of this work was to develop a high-speed, highpower waveguide-based modulator (phase and amplitude) and investigate its use as a pulse slicer. The key innovation in this effort is the use of potassium titanyl phosphate (KTP) waveguides, making the high-power, polarization- based waveguide amplitude modulator possible. Furthermore, because it is fabricated in KTP, the waveguide component will withstand high optical power and have a significantly higher RF modulation figure of merit (FOM) relative to lithium niobate. KTP waveguides support highpower TE and TM modes — a necessary requirement for polarization-based modulation as with a Pockels cell.

Posted in: Briefs, TSP, Physical Sciences, Optics, Waveguides, Optics, Waveguides, Refractory materials

Autonomous Control of Space Nuclear Reactors

Autonomous operation and safety are addressed simultaneously.

Nuclear reactors to support future robotic and manned missions impose new and innovative technological requirements for their control and protection instrumentation. Long-duration surface missions necessitate reliable autonomous operation, and manned missions impose added requirements for failsafe reactor protection. There is a need for an advanced instrumentation and control system for spacenuclear reactors that addresses both aspects of autonomous operation and safety.

Posted in: Briefs, Physical Sciences, Electronic control systems, Electronic control systems, Nuclear energy, Robotics, Reliability, Reliability

Dual-Polarization, Multi-Frequency Antenna Array for use with Hurricane Imaging Radiometer

New approach promises to be more cost effective and can reduce on-station aircraft time.

Advancements in common aperture antenna technology were employed to utilize its proprietary genetic algorithm-based modeling tools in an effort to develop, build, and test a dual-polarization array for Hurricane Imaging Radiometer (HIRAD) applications. Final program results demonstrate the ability to achieve a lightweight, thin, higher-gain aperture that covers the desired spectral band.

Posted in: Briefs, Physical Sciences, Antennas, Imaging, Imaging and visualization, Antennas, Imaging, Imaging and visualization, Weather and climate

Conjugate Thermal Analysis of a Generic LED Light Bulb

Thermal and fluid modeling is used to understand temperature fields and airflow around the bulb.

The design and application of LED (Light Emitting Diode) lighting solutions provides new opportunities for thermofluid- mechanical modeling enabled by multiphysics analysis. A coupled thermal and fluid modeling effort was used to understand the temperature fields and airflow around a generic LED light bulb.

Posted in: Briefs, Physical Sciences, Software, CAD / CAM / CAE, CAD, CAM, and CAE, Computational fluid dynamics, Light emitting diodes (LEDs), Light emitting diodes (LEDs), Thermal testing

Analysis of Spiral Resonator Filters

Improved performance coupled with reduced size requires the development of novel filter designs for use in advanced wireless systems.

Increasing demand for more advanced wireless systems necessitates the introduction of novel designs that are capable of simultaneously fulfilling multiple operating and performance criteria. The implementation of high-datarate transmission systems has required the development of innovative designs for microwave filters that must fit within a reduced volume to allow integration of multiple filters in more compact wireless systems. Additionally, the filter’s specific passband frequencies and quality factors must be achieved within the system’s geometrical and topological constraints.

Posted in: Briefs, Physical Sciences, Software, Wireless communication systems, Wireless communication systems

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