Tech Briefs

Molecularly Imprinted Polymer (MIP)-Coated Microbeam MEMS Sensor for Chemical Detection

Monitoring trace gases is of great importance in a wide range of applications. Detecting a diverse range of chemical agents requires an adaptable sensor platform capable of identifying threats before they cause harm. Research and development in hazardous-materials detection technology focuses on increasing speed, sensitivity, and selectivity while reducing size and cost. Although the current state-of-the-art vapor detector (Joint Chemical Agent Detector) is lightweight, handheld, and easily attaches to a belt, it still provides added bulk to a soldier on foot. Recently, microcantilever-based technology has emerged as a viable platform due to its many advantages such as small size, high sensitivity, and low cost. However, microcantilevers lack the inherent ability to selectively identify chemicals of interest. The key to overcoming this challenge is to functionalize the top surface of the microcantilever with a sorbent layer (i.e., polymer) that allows for selective binding between the microbeam and analyte(s) of interest.

Posted in: Briefs, Sensors, Sensors and actuators, Chemicals, Coatings Colorants and Finishes, Gases, Polymers, Hazardous materials

SIRE: A MIMO Radar for Landmine and IED Detection

Low-frequency ultra-wideband (UWB) radar has garnered attention for the detection of landmines and improvised explosive devices (IEDs) in recent years. The low frequencies used by these radars provide the necessary ground penetration capabilities for detection, and the wide bandwidth signals used are necessary for range resolution. Cross-range resolution that depends on the size of the antenna aperture can be improved by generating a synthetic aperture. Typical airborne synthetic aperture radars (SAR) that can provide high resolution in cross range are not practical for this problem due to cost limitations.

Posted in: Briefs, Aerospace, Defense, Radar, Hazards and emergency management, Protective equipment, Military vehicles and equipment

Multi-Temporal Analysis of Underbody IED Theater Events on Ground Vehicles

Modeling and simulation were used to analyze the effects of underbody blasts on moving vehicles.

Recently, modeling and simulation (M&S) engineers have made impressive strides in improving ground vehicle reliability and soldier safety. This work involved live-fire testing and evaluation (LFT&E) of the effects of underbody improvised explosive device (IED) blasts on moving ground vehicles. A multi-fidelity, multi-temporal M&S methodology was developed and successfully applied towards reconstruction of theater IED events.

Posted in: Briefs, Aerospace, Defense, Information Technology, Failure analysis, Crashworthiness, Impact tests, Military vehicles and equipment

Blast Mitigation Seat Testing

Blast energy-attenuation (EA) seats, although not new to the market, have not been fully tested with respect to energy attenuation capability and the resulting effects on occupant protection. The Ground Systems Survivability (GSS) Interiors Seat Team tested and evaluated EA seats over a one-year period using a drop tower test method.

Posted in: Briefs, Aerospace, Defense, Seats and seating, Protective equipment, Safety testing and procedures, Test equipment and instrumentation

Blast-Induced Acceleration in a Shock Tube

High-fidelity simulation of blast flow conditions can aid in developing strategies to mitigate blast-induced brain injury.

The prevalence of blast-induced traumatic brain injury (bTBI) has prompted an urgent need to develop improved mitigation strategies and advance medical care targeting casualties with bTBI. Despite considerable effort, the basic mechanisms of blast-induced brain injury are still undefined. Based largely upon computational modeling, several candidate mechanisms of nonimpact bTBI have been identified and include head acceleration. This work hypothesizes that explosion flow conditions can cause head acceleration sufficient to injure the brain, and that these inertial forces combine with other injury mechanisms to yield bTBI.

Posted in: Briefs, Aerospace, Defense, Medical, Computer simulation, Diagnosis, Medical equipment and supplies, Head injuries, Occupant protection

Structural Composites with Tuned EM Chirality

Several metamaterials show promise in providing advanced radio frequency control.

Work on structural composites with tunable chiral elements has produced electronically tunable overall chiral composites, mechanically tunable chiral composites, flat lenses with soft hyperbolic focusing due to indefinite overall permittivity, a tunable flat lens based on chiral elements with adjustable focal spot based on applied mechanical deformation, and a three-phase periodic composite that demon strates positive and negative refraction, depending on the input frequency and angle of incidence. A MATLAB code directly computes the group velocity and pass bands for a given set of wave vectors, and generates an intuitive plot for quick, but thorough analysis.

Posted in: Briefs, Aerospace, Defense, Materials, Analysis methodologies, Composite materials

Advanced, Single-Polymer, Nanofiber-Reinforced Composite

Continuous nanofibers provide unique advantages for future structural nanocomposites.

A strategic goal of the U.S. Air Force is to be able to deliver munitions to targets anywhere around the globe in less than an hour. This will require very high speeds and novel lightweight and temperature-resistant materials. Nanocomposites are promising emerging materials for structural and functional applications due to unique properties of their nanoscale constituents. However, the currently available nanocomposites based mostly on nanoparticles lack the high strength and stiffness required for structural applications.

Posted in: Briefs, Aerospace, Defense, Materials, Composite materials, Fibers, Nanomaterials, Polymers

Quantitative Diagnostics of Multilayered Composite Structures with Ultrasonic Guided Waves

This nondestructive methodology inspects a sound-absorbing composite structural system consisting of polymeric and metallic materials.

Aging infrastructure has a major impact on safety, increasing the need to assess damage severity. Machinery, systems, and components such as airplanes, cars, pumps, and pipes in the oil and chemical industry are subject to varying cyclic service loading and environmental influences. Sometimes multilayered coatings are used, requiring a high-resolution inspection to confirm the presence of a defect such as a delamination, and accurately locate and quantify its size. Highly attenuating materials may significantly increase the inspection time while limiting defect observability. Guided waves have been recognized as having excellent potential for nondestructive inspection. However, the presence of viscoelastic coatings used for corrosion protection is one of the major obstacles for guided wave inspection.

Posted in: Briefs, Aerospace, Defense, Manufacturing & Prototyping, Materials, Diagnostics, Composite materials, Inspections, Non-destructive tests

Reactive, Multifunctional, Micellar, Composite Nanoparticles for Destruction of Bio-Agents

Multifunctional composites have been investigated for destruction of bio-agents. These materials’ unique properties at the nano scale, including their abrasive character and high surface area leading to very close contact with cells, and their unusual surface morphology leading to high surface reactivity, make them promising biocides. Nanoparticles can also be prepared in a variety of forms such as powders, slurries, pellets, and membranes, making them more convenient and widely applicable for bio-agent destruction. Additionally, nanoparticles can generally be easily stored, which increases their flexibility.

Posted in: Briefs, Aerospace, Defense, Materials, Composite materials, Nanomaterials

Ontology for Insider Threat Indicators

The study of insider threat presents some of the most complex challenges in information security. Even defining the insider threat has proven difficult, with interpretations and scope varying depending on the problem space. Organizations have begun to acknowledge the importance of detecting and preventing insider threats, but there is a surprising lack of standards within the insider threat domain to assist in the development, description, testing, and sharing of these techniques. For many organizations, establishing an insider threat program and beginning to look for potentially malicious insider activity is a new business activity.

Posted in: Briefs, Aerospace, Defense, Information Technology, Security systems, Data management

Data Mining in Cyber Operations

Data mining models describe dynamic behavior of attacks and failures, enabling defenders to detect and differentiate simultaneous attacks on a target network.

Defending cyberspace is a complex and largely scoped challenge that considers emerging threats to security in space, land, and sea. The global cyber infrastructure presents many challenges because of the complexity and massive amounts of information transferred across the global network daily. The cyber infrastructure is made up of the data resources, network protocols, computing platforms, and computational services that bring people, information, and computational tools together.

Posted in: Briefs, Aerospace, Defense, Information Technology, Communication protocols, Cyber security, Data acquisition

Framework for Resilient Remote Monitoring

This method provides continuous monitoring across network-attached devices to identify and mitigate targeted cyber attacks.

System administrators and cyber defenders continue to face challenges in securing systems as attacks keep increasing in the level of sophistication, and the number of connected systems keeps increasing. To support and automate manual activities associated with obtaining information about systems and taking corrective action in response to suspicious activities, an increasing number of technologies for remote monitoring are becoming available with the premise of increasing resiliency by decreasing the time-to-detect and time-to-mitigate targeted attacks.

Posted in: Briefs, Aerospace, Defense, Information Technology, Cyber security

Communication Protocol for CyAMS and the Cyber Fighter Associate Interface

This program evaluates agility maneuvers that may be employed within networks to mitigate the effect of cyber attacks.

As the military adopts more networked equipment, the opportunity for cyber attacks to occur has also risen. To mitigate the effect these attacks have, network administrators and security experts must be able to decide on the best course of action based on many factors. The Cyber Fighter Associate (CyFiA) will help decide the best course of action given a set of cyber agility maneuvers by measuring the cost and utility of potential maneuvers, along with node and network facts, to select the maneuvers that will lead to mission success.

Posted in: Briefs, Aerospace, Defense, Information Technology, Communication protocols, Cyber security

Testing Multijunction Solar Cell Efficiency

The photovoltaic community is closer than ever to achieving ultra-high multijunction solar cell efficiencies (>50%). Subcells from III–V compound semiconductors are approaching ideal Shockley–Queisser behavior and emit significant radiation of photons with energies equal to or above the optical bandgap because non-radiative recombination has been minimized with advanced growth processes. The optical environment of a solar cell controls where the radiated photons from a subcell are directed, and this greatly affects its efficiency. Thus the optical design of multijunction architectures is crucial for maximizing performance. To date, light trapping and radiative coupling have been investigated as promising optical design strategies. Light trapping inhibits the radiative emission of a subcell in order to reduce the dark current and increase voltage.

Posted in: Briefs, Aerospace, Defense, Architecture, Optics, Solar energy, Semiconductors

Thermal Response of Ultra-High Molecular Weight Polyethylene (UHMWPE) Materials in a Flash Flame Test

Testing was performed on Ultra-High Molecular Weight Polyethylene (UHMWPE) fabric and composite material in a flash flame environment when protected by a flame-resistant (FR) fabric outer layer. UHMWPE material has excellent ballistic protection properties, but has generally not been considered for ballistic protection garments due to its low melting point. This research was conducted to determine if UHMWPE materials could be considered for use in the recently developed protective undergarment (PUG) if worn beneath an FR uniform.

Posted in: Briefs, Aerospace, Defense, Materials, Composite materials, Fabrics, Polymers, Thermal testing

Thermal Conductivity Measurement Setup for Low-Temperature Characterization of Laser Materials

Operating lasers at cryogenic temperatures gained maturity only in the mid-90s due mostly to the progress in transparent, laser-grade ceramics and semiconductor pump sources. The main limiting factors for power scaling of room-temperature solid-state lasers are thermal effects such as thermal lensing, induced polarization losses, and fracture.

Posted in: Briefs, Aerospace, Defense, Conductivity

Non-Destructive Damping Measurement for MEMS Acceleration Switches

Microelectromechanical systems (MEMS) three-axis acceleration threshold sensors have been developed to measure acceleration threshold levels using voltage switching when the threshold is reached. Switches with different damping coefficients result in different mechanical impedances and response times. Analytical and numerical methods to model damping coefficient values based on empirical data are needed to characterize three-axis acceleration sensors; traditional methods use the displacement of an underdamped system to calculate the damping ratio.

Posted in: Briefs, Aerospace, Defense, Mechanical Components, Simulation and modeling, Sensors and actuators, Switches

Fabricating Transparent and Stretchable Supercapacitors Based on Wrinkled Graphene Electrodes

Stretchable electronic devices, including solar cells, light-emitting diodes, batteries, and textile supercapacitors, have been developed to retain their functions even when under large strains (up to 40%). Some transparent solar cells, batteries, and supercapacitors have also been developed. However, most of the currently developed electrodes and the associated supercapacitor cells cannot be both transparent and stretchable.

Posted in: Briefs, Aerospace, Defense, Manufacturing & Prototyping, Batteries, Electronic equipment, Ultracapacitors and supercapacitors, Fabrication

Modular Exhaust Design and Manufacturing Techniques for Build-to-Order Muffler Systems

Managing the acoustic signature of military vehicles can play a critical role in the safety of soldiers. Low-frequency sounds propagate through the atmosphere, resulting in unacceptable acoustic vehicle detection ranges, requiring relatively large silencer structures to mitigate. Currently, these requirements are met by using a custom muffler that is hand-assembled using low-volume prototyping manufacturing techniques. This method results in significant engineering and manufacturing time.

Posted in: Briefs, Aerospace, Defense, Manufacturing & Prototyping, Design processes, Manufacturing processes, Noise, Mufflers, Military vehicles and equipment

Silicon Microsphere Fabrication

The efficiency and methodology of coupling light into microcavities has improved exponentially in the last decade. One such advancement is coupling light onto silicon microspheres. The material, size, and shape of a silicon microsphere are ideal for optical devices. Silicon microspheres are not the primary material used to fabricate microspheres for optical coupling because current methods used for microsphere fabrication cannot produce single-crystal silicon in the 16-μm scale, which is best for current optical technology.

Posted in: Briefs, Aerospace, Defense, Manufacturing & Prototyping, Optics, Fabrication

Designing and Fabricating a Multiple-Decade Battery

There is a great need for energy sources that can power unattended sensors for more than a decade. Unattended sensors can be located in harsh and remote locations that are often dangerous for personnel maintenance and power source replacement. The power source must last the lifetime of the sensor. Unlike chemical batteries, the higher energy densities of radioisotopes allow the sensors to operate for infrastructure lifetimes (~150 years). Isotope batteries (iBATs) have the potential to become reliable, robust, and maintenance-free power sources for remote, long-term, low-power sensors. iBATs are different from chemical batteries because they are self-contained energy sources using radioisotope decay.

Posted in: Briefs, Aerospace, Defense, Manufacturing & Prototyping, Design processes, Batteries, Fabrication

Infrared Stereo Calibration for Unmanned Ground Vehicle Navigation

Many challenges still persist in the area of autonomous (and even semi-autonomous) vehicle navigation for unmanned ground vehicles (UGVs). One challenge is in detecting and classifying obstacles for avoidance and path planning. The use of laser-based sensors, such as lidar, has become quite common for assisting in such a task; however, lidar systems may be too expensive for certain applications, and are active, not passive sensors, so they may not be desirable in some missions. Lidar is adversely affected by smoke, dust, fog, and rain. Therefore, the use of passive camera sensors, such as typical color and infrared (IR) cameras, has become an important research topic in UGV navigation.

Posted in: Briefs, Defense, Sensors, Imaging, Optics, Sensors and actuators, Vibration

Simultaneous Vibration Suppression and Energy Harvesting for a Multifunctional UAV Spar

The goal of this work was to investigate using harvested energy to directly control the vibration response of flexible aerospace systems. Small, lightweight, flexible Micro Air Vehicles (MAVs) operate near flutter, providing both harvesting opportunities and vibration suppression requirements. The possibility that ambient energy might be harnessed and recycled to provide energy to mitigate the vibrations through various control laws was investigated. The goal was to integrate harvesting, storage, control, and computation into one multifunctional structure, and illustrate its benefits.

Posted in: Briefs, Aerospace, Vibration, Unmanned aerial vehicles

Development and Evaluation of the Stingray Amphibious Maritime Unmanned Ground Vehicle

Every year, the U.S. Navy and Marine Corps conduct thousands of Maritime Interdiction Operations (MIOs) to enforce embargoes, intercept contraband, prevent drug and human smuggling, and fight piracy. These operations are usually conducted by Visit, Board, Search, and Seizure (VBSS) teams using rigid-hull inflatable boats (RHIBs) or helicopters. Key performance parameters were developed for a portable, throwable robot that can best support their missions. This robot can be used for advanced reconnaissance as the team is about to board a target vessel, to assist in compartment clearing, and for inspection of flooded compartments and bilges.

Posted in: Briefs, Defense, Manufacturing & Prototyping, Product development, Autonomous vehicles, Marine vehicles and equipment

Pushbroom Stereo for High-Speed UAV Navigation in Cluttered Environments

Unmanned aerial vehicles (UAVs) rely on an external motion-capture apparatus that gives the vehicles almost perfect state information at high rates. Major challenges in gathering sensing data necessary for flight are the limited payload, computation, and battery life of the vehicles. Lightweight cameras are a good solution, but require computationally efficient machine vision algorithms that can run within the limits of these vehicles.

Posted in: Briefs, Aerospace, Software, Imaging, Navigation and guidance systems, Unmanned aerial vehicles

Modeling and Simulation of an Unmanned Ground Vehicle Power System

Robotic vehicles such as unmanned ground vehicles (UGVs) have multiple sources of power, including batteries, fuel cells, combustion engines, ultracapacitors, and solar cells to allow for extended periods of operation. Fuel-based power sources have a higher specific energy than batteries, which is why most current automobiles are gasoline-powered. Batteries have many other advantages in terms of low noise profile, easy replacement, and direct energy conversion. Solar charging allows for harvesting of natural resources to increase total energy reserves. Mission duration may be maximized using a combination of power systems.

Posted in: Briefs, Defense, Software, Simulation and modeling, Engines, Autonomous vehicles, Vehicle performance

Damping Measurement for Wafer-Level Packaged MEMS Acceleration Sensors

Microelectromechanical system (MEMS) three-axis acceleration threshold sensors have been developed to measure acceleration threshold levels using voltage switching when the threshold is reached. Determining damping coefficients is important for categorizing how each threshold sensor or switch operates. Switches with different damping coefficients result in different mechanical impedances and response times. Analytical and numerical methods to model damping coefficient values based on empirical data are needed to characterize three-axis acceleration sensors; traditional methods use the displacement of an underdamped system to calculate the damping ratio.

Posted in: Briefs, Defense, MEMs, Sensors, Measuring Instruments, Sensors and actuators, Switches

Sensing Suspicious Powders Using Noncontact Optical Methods

Suspicious powder incidents continue to be a disruptive and costly problem. In-situ assessment of suspicious powders within inorganic matrices, particularly with powders of biological origin, is currently limited to detection by biochemical methodologies that react with monomers such as amino acids, nucleic acids, lipids, or macromolecule compounds comprised of these basic subunits. Current optical methods such as Raman spectroscopy using excitation in the near infrared at 785 nm or visible at 532 nm, have not been able to detect or distinguish biological materials from background or other materials.

Posted in: Briefs, Defense, Sensors, Instrumentation, Test & Measurement, Optics, Biohazards

Isotope Beta-Battery Approaches for Long-Lived Sensors

The energy density of isotopes exceeds that of chemical energy storage by six orders of magnitude. Isotopes are used in many commercial applications, and are produced and available at modest prices. The power requirements of many sensors and communications equipment can greatly reduce the power requirements of many devices such as sensors, light sources, and transmitters. Chemical batteries are the mainstay of power for these devices. However, chemical batteries have limited lifetimes. This makes remote use and replacement difficult for applications extending the lifetime use.

Posted in: Briefs, Defense, Power Management, Sensors, Batteries, Sensors and actuators

Selective, Sensitive, and Robust Electrochemical Detection of Anthrax

There exists an unmet need for rapid, sensitive, and field-stable assays for pathogen detection. Bacillus anthracis is the causative agent of anthrax poisoning. This Gram-positive bacterium secretes a tripartite toxin including a cell-binding protective antigen (PA), and the delivered toxins edema factor (EF) and lethal factor (LF). Anthrax poisoning has high mortality and, when delivered in the form of B. anthracis spores, has a very high environmental stability.

Posted in: Briefs, Defense, Sensors, Biohazards