Physical Sciences

Through-the-Wall Small Weapon Detection Based on Polarimetric Radar Techniques

Detecting concealed small weapons carried by people has received significant interest from law enforcement agencies as well as the military, most frequently for application in controlling checkpoints (in airports, border crossings, public spaces, etc.). Imaging systems for concealed weapons based on radar or other sensor technologies have been recently developed and tested. Most of the existing electromagnetic (EM) sensors suitable for this application operate at very high frequencies, usually in the millimeter or terahertz frequency bands and produce high-resolution images. Although these EM waves can penetrate through clothing (textile materials), they have very poor penetration properties through many common construction materials (such as brick or concrete). Most through-the-wall radars must operate at much lower frequencies, usually below 4 GHz, in order to “see” targets behind walls. However, at those low frequencies, the image resolution is degraded, so small weapons carried by humans may be difficult to detect directly in the image domain.

Posted in: Briefs, Physical Sciences, Imaging, Radar, Security systems, Sensors and actuators

Fiber-Optic Seismic Sensor for Unattended Ground Sensing

Seismic military sensors are required to be robust, reliable, compact, and easy to install and operate to be effective in the battlefield environment. Three types of sensor technologies were addressed that provide improved design and novel signal processing techniques: (a) a wavelength scanning, pulsed-laser-based demodulation system; (b) digital lock-in amplifier and field-programmable gate array (techniques) for weak signal detection and processing; and (c) improved seismic sensitivity based on carbon fiber optic composite cantilever and fiber-Bragg-grating (FBG).

Posted in: Briefs, Physical Sciences, Fiber optics, Sensors and actuators, Defense industry

Performance and Operability of a Dual-Cavity Flame Holder in a Supersonic Combustor

Supersonic combustion has been of interest for many years in order to support future Air Force hypersonic missions. The current generation of hydrocarbon-fueled scramjet combustors typically requires a flame-holding device to facilitate flame ignition and stable combustion. The amount of time available for fuel injection, fuel-air mixing, and combustion is very short — on the order of 1 millisecond. This short dwell time, along with the relatively long ignition delay times of hydrocarbon fuels, makes the flow path and flame holder design extremely important. This study investigates the perormance and operability of using a symmetric dual-cavity flame holder flow path to stabilize and enhance supersonic combustion.

Posted in: Briefs, Physical Sciences, Hydrocarbons, Scramjet engines, Performance tests, Hypersonic and supersonic aircraft, Military aircraft

Gesture-Directed Sensor-Information Fusion Gloves

Current chemical-protection gear for warfighters on the ground inhibits electronic communication via keyboards, cell phones, and remote-control devices. To improve communications capabilities for the warfighter wearing protective gear in hazardous environments, a series of eGloves has been developed with a view toward freeing the warfighter of the need to type on a keyboard while wearing a Mission-Oriented Protective Posture (MOPP) suit. The eGloves can help the warfighter transmit gestures with the hands and fingers from within the protective gear, or they can be used to transmit encoded ASCII characters.

Posted in: Briefs, Physical Sciences, Communication protocols, Human machine interface (HMI), Product development, Protective clothing, Military vehicles and equipment

GigE Advanced Imaging Sensor

The Wide-Field Dynamic Range (WFDR) camera is a high-sensitivity, wide-field-of-regard sensor of importance to future military surveillance and survivability systems. It is intended to be used in harsh, noisy military platforms with multiple camera streams simultaneously gathered. By developing a Gigabit Ethernet (GigE) video transport solution for multiple cameras with low latency and high data reliability, a flexible processing architecture will be developed that allows optimization of processor throughput for real-time imaging in defense applications.

Posted in: Briefs, Physical Sciences, Architecture, Optics, Sensors and actuators, Surveillance, Military vehicles and equipment

Liquid-Crystal-Based Optical Phased Array for Steering Lasers

A paper describes the basic design and concepts of tunable liquid-crystal polarization gratings with a nematic liquid crystal (LC) optical phase plate, with a large, continuous in- plane gradient that is variable, and its application to a beam steering device with high efficiency.

Posted in: Briefs, Physical Sciences, Calibration, Lasers, Waveguides

Power for Micro Autonomous Systems

The Micro Autonomous Systems and Technology (MAST) Collaborative Technology Alliance (CTA) has been initiated to spur basic research in small autonomous robots, particularly in four main areas: Microsystem Mechanics, Autonomous Processing, Micro electronics, and Integration. In order to focus its efforts, the Army proposed multiple scenario missions of increasing difficulty to work towards: small unit building search (flat, straight walls, no wind, etc.), a small unit cave search (potential for wind gusts, no regular surfaces to use as reference points), and perimeter defense (longer required mission time, and range and potentially harsh environments). The size ranges considered were defined as “palm-size” and below, where no lower limit was specified.

Posted in: Briefs, Physical Sciences, Microelectricmechanical device, Robotics

Indoor Navigation for Unmanned Aerial Vehicles

This research proposed the use of inexpensive, lightweight range sensors for indoor unmanned aerial vehicle (UAV) navigation. Two potential range sensors were tested for suitability and error characteristics. The SHARP infrared range sensors provide a narrow beam and a higher resolution distance measurement, at the expense of de creased range (approximately 150–180 cm maximum). The MaxBotix® EX1™ ultrasonic range sensors had a longer range (up to 6.45 m) and a wider beam.

Posted in: Briefs, Physical Sciences, Navigation and guidance systems, Sensors and actuators, Flight tests, Unmanned aerial vehicles

Modular, Portable, and Reconfigurable Wireless Sensing System

A modular, portable, reconfigurable wireless sensor system monitors and records environmental conditions in an aircraft cabin. By designing a sensor system that can be easily configured for different needs (with the ability and flexibility to accommodate different/ extra sensors), the system can be used to measure parameters that meet multiple research requirements. Through design considerations such as generalized signal interface, and hierarchical code structure that can be easily reworked for new sensors, this system can be used to measure parameters that meet multiple research requirements. This sensor system, the ASCENT 1000, is configured with temperature, humidity, sound level, carbon di-oxide, and pressure sensors. The system has been calibrated in the laboratory without the use of a pressure chamber.

Posted in: Briefs, Physical Sciences, Sensors and actuators, Wireless communication systems, Passenger compartments

Characterizing Turbulent Wind Flow Near a Wind Barrier Using Sonic Anemometers

The Holloman High Speed Test Track (HHSTT) facility at Holloman Air Force Base (HAFB), NM, has a test section of 1.8 km that contains an artificial rain field generation capability over the track. The raindrops produced can be excessively deflected when the cross-track wind speed is greater than 1 m/s. To extend testing times to days when moderate wind conditions (1 to 5 m/s) are present, the HHSTT plans to construct a wind barrier for cross-track wind reduction. Before the construction of a complete wind barrier, an observational study was carried out to characterize the mean and turbulent wind fields using a small prototype section of the wind barrier.

Posted in: Briefs, Physical Sciences, Water, Test equipment and instrumentation, Test facilities, Turbulence