Scientists Create Optically Equivalent Synthetic Human Tissue

Lasers are an integral part of the modern battlefield, used for applications as diverse as point-to-point communications and ballistic missile defense. Their widespread use increases the warfighter's likelihood of being exposed to laser hazards, and damage to an individual's eyes and skin can be serious. AFRL has served as a leading authority on laser-induced damage thresholds for many years.

Posted in: Briefs, Medical

Dielectric Coolants

The Joint Strike Fighter (JSF) is the Department of Defense's affordable next-generation strike aircraft designed to meet the needs of the Air Force (AF), Navy, Marines, and US allies. Currently in development by Lockheed Martin, the multimission, supersonic, JSF aircraft will provide all services with enhanced lethality and survivability and reduced vulnerability (see figure). The JSF's unique, multiple-variant design pushes the threshold of fighter technology far beyond current limitations. The AF variant of the technology takes multirole fighter performance to new levels, offering improved stealth, increased range on internal fuel, and advanced avionics. The JSF's advanced avionics, as well as its flight control, target acquisition, and other sophisticated electronic systems rely on high-performance coolants to ensure proper operation. Designers employ dielectric coolants to dissipate heat from high-energy electronic components and therefore consider these fluids critical to aircraft operation and safety.

Posted in: Briefs, Materials

Weapon Data Link Demonstration

One of the US Air Force's goals is to reduce the time needed to strike timesensitive targets, thus minimizing the adversary's perceived mobility advantage and leaving concealment as that enemy's primary defensive measure. One potential way to meet this challenge relies on a capability to redirect and update weapons with new target coordinates while they are in flight—a solution that requires weapons developers to outfit weapons with a data link enabling communications between warfighters operating in the air and on the ground. This Weapon Data Link (WDL) approach would allow the warfighter to directly communicate with and control air-launched weapons to strike moving or otherwise time-sensitive targets, while continually gathering information about the weapon's performance against those targets. The scenario could involve something as simple as a weapon communicating its position and system status back to the release aircraft, or something as complex as a weapon operating in the Global Information Grid (GIG), wherein a secondary ground/air controller assumes the weapon's control after a positive handoff from the release platform, with the weapon's sensor and video information autonomously distributed throughout the GIG.

Figure 1. Depiction of WDLAFRL engineers recently accomplished a critical step in demonstrating the WDL approach. Held at Langley Air Force Base (AFB), Virginia, the demonstration's primary objective was to show that two WDL terminals, connected to Tactical Air Control Party (TACP) laptop computers, could successfully transmit and receive J-series messages within a Link-16 network (see Figures 1 and 2). The network included a legacy Fighter Data Link (FDL) terminal provided by the 46th Test Squadron (Eglin AFB, Florida), two WDL terminals, and local aircraft equipped with Link-16 radios.

Engineers from AFRL and Rockwell Collins partnered to develop the 50 in3, software-defined WDL radio used in the demonstration. This radio provides multiple operators with the flexibility to port and upload communication waveforms. The device has three software waveforms loaded into its memory; the operator can switch between these waveforms as required. Although the test team limited this demonstration to Link-16 operation, future demonstrations will highlight the radio's capacity to receive and transmit ultra-high-frequency satellite communications and line-of-sight waveforms as well. The TACP Modernization program supplied the TACPCASS (Close Air Support System) software, laptop computers, and a trained operator. During the first part of the demonstration, one TACP computer generated target coordinates and transmitted them as J-series messages from one WDL terminal to the other. The TACP-CASS software on the second TACP computer interpreted and displayed the transmitted messages as target tracks. This test showed that messages generated by the TACP-CASS software could be correctly interpreted by the two networked WDL terminals and that this information could be shared between them. In the second phase of the demonstration, test engineers integrated the FDL terminal into the network. One of the TACP computers transmitted target information via Link-16 network protocol to the FDL terminal, which correctly interpreted and displayed the information on the Improved Multilink Translator and Display System (IMTDS). In the next phase, both computers correctly received, interpreted, and displayed target messages transmitted by the FDL terminal. In a final demonstration of system capability, several aircraft from Langley AFB joined the network for short periods of time, transmitting information that was subsequently displayed on both the TACP and IMTDS computers.

Figure 2. Setup of WDL demonstration equipmentAll demonstration participants gained valuable insight into using Link-16 networks for passing J-series messages between aircraft, weapons, and ground troops. The test team did not intend for the demonstration to provide an in-depth look at integrating weapons into battlefield networks. Rather, its purpose was to provide a rudimentary understanding of how an aircraft, weapon, and TACP could join and operate in an existing Link-16 network, while specifically demonstrating the capability of a software-defined WDL radio to transmit and receive J-series messages. The demonstration achieved its twofold purpose, both providing overall insight regarding the system and establishing the flexibility of a softwaredefined WDL radio in processing J-series messages within a representative network.

Ms. Michelle White, of the Air Force Research Laboratory's Munitions Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn/index.htm. Reference document MN-H-05-14.


1 "China-America: The Great Game." Interview With Lt Gen Liu Yazhou. Eurasian Review of Geopolitics, Gruppo Editoriale L'Espresso/Cassan Press-HK, Jan 05.

Posted in: Briefs, Electronics & Computers, Data acquisition and handling, Personnel, Military aircraft

RASCAL Facility

AFRL's Radiation and Scattering Compact Antenna Laboratory (RASCAL) enables researchers to develop and evaluate advanced aperture technologies that support electronic warfare, radar, communication, and navigation— technologies supplementing a variety of applications as the "eyes and ears" of the warfighter. Current research efforts are concentrated on developing relatively small and inexpensive broadband, multifunctional antennas, as well as conformal and structurally integrated antennas for manned and unmanned air vehicles. Using the RASCAL facility, researchers can perform the necessary fabrication, simulation, testing, and measurement of aperture technologies.

Posted in: Briefs, Electronics & Computers, Antennas, Test facilities, Military aircraft

Response Surface Mapping Technique Aids Warfighters

When weaponeering a target, military planners pinpoint a detonation location that will result in the desired damage to the entire target, or even a particular area within the target. The warfighter then selects the most suitable delivery platform— aircraft, weapon, guidance package, release altitude, and speed— for inflicting the appropriate damage to the target. Determining the proper combination of variables capable of producing the desired effect on a hardened target requires the warfighter to understand the penetration dynamics of the weapon; it also relies on the individual's ability to adjust the variables within his or her control, as necessary. For a scenario in which the destruction of a specific target is often coupled with the mitigation of collateral damage, it is imperative that the warfighter make proper decisions regarding weapons selections. AFRL scientists, collaborating with other Department of Defense agencies, applied innovative data mining and visualization methods to aid warfighter efficiency and effectiveness in making these choices.

Posted in: Briefs, Information Technology, Cartography, Data acquisition and handling, Imaging, Terrain, Military vehicles and equipment

Microelectromechanical Systems Inertial Measurement Unit Flight Test

AFRL and Boeing engineers conducted successful flight tests of microelectromechanical systems (MEMS) inertial measurement units (IMU) on the Joint Direct Attack Munition (JDAM). They collected flight data and validated the MEMS IMU technology's capability to provide stable navigation performance and accurate weapon guidance, both with and without Global Positioning System (GPS) updates. Researchers will use this flight data to further refine MEMS IMU technology to enhance future capabilities of air-launched munitions.

Posted in: Briefs, Mechanical Components, Microelectricmechanical device, Navigation and guidance systems, Flight tests

Fruit Flies

He refers to them as "nature's fighter jets" and has devoted his life's work and an entire lab to monitor their every move. Thus is the relationship existing between Dr. Michael Dickinson and the objects of his attention—fruit flies. Career pursuits aside, Dr. Dickinson's connection to the insects is one he predicts will eventually lead to the development of flying robots capable of performing various covert tasks, such as spying and surveillance.

Posted in: Briefs, Mechanical Components, Surveillance, Biological sciences, Robotics

Active Flow Control Demonstrated on “Airborne Wind Tunnel”

AFRL engineers, collaborating with aerospace manufacturers and other Air Force groups, recently demonstrated the first-ever airborne active flow control system when they manipulated the airflow behind an F-16 external pod. They significantly altered the turbulent wake using small, electrically controlled, piezoelectric synthetic jet (PESJ) actuators. This demonstration is just one part of AFRL's multiphase Aeroelastic Load Control program aimed at reducing the weight, complexity, and signature of air vehicles through the introduction of active control technologies.

Posted in: Briefs, Mechanical Components, Aerodynamics

Coordination of Autonomous Unmanned Air Vehicles

Future autonomous unmanned air vehicles (UAV) will need to work in teams to share information and coordinate activities in much the same way as current manned air systems. Funded by AFRL, Professor Hugh Durrant-Whyte and his research staff (see Figure 1) at the Australian Research Council's Center of Excellence for Autonomous Systems have been developing mathematical models and simulation studies to understand—and ultimately provide— this future UAV capability.

The team's research focuses on coordination and cooperation for teams of autonomous UAVs engaged in information gathering and data fusion tasks, including cooperative tracking, ground picture compilation, area exploration, and target search. The underlying mathematical model for coordination and cooperation employs quantitative probabilistic and information-theoretic models of platform and sensor abilities. This information-theoretic approach builds on established principles for distributed data fusion in sensor networks, extending these ideas to problems in the distributed control of sensing resources. The researchers have made substantial progress towards formulating, solving, and demonstrating these methods for multi-UAV systems. In particular, they have developed distributed algorithms that enable UAV team-based search and exploration operations. These search and exploration algorithms can incorporate realistic constraints on platforms and sensors—a priori constraints from the environment and weak information from external sources. To date, Prof Durrant-Whyte's research team has successfully demonstrated these algorithms on a flight simulator of midlevel fidelity (see Figure 2).

Recently, the team presented its findings to AFRL researchers at Wright- Patterson Air Force Base (AFB), Ohio, and Eglin AFB, Florida. Based on the promising results of this research effort, AFRL is funding two additional projects to further explore the mathematical aspects of the technology and facilitate real-world application through demonstrations. The first round of demonstrations will involve high-fidelity, hardware-in-the-loop simulations, culminating in a large-scale demonstration involving a UAV fleet operated by the University of Sydney (see Figure 3). AFRL's two research projects will provide significant scientific and technical advancement in the cooperative control of autonomous systems.

The availability of autonomous UAV teams capable of complex cooperative behavior will enable warfighters to execute highly complex missions effectively and safely removed from harms way (i.e., remotely). In addition to providing these advantages, the UAV technology's imaging and atmospheric sampling capabilities have the potential to support both homeland security emergency scenarios and real-time forest fire monitoring tasks.

Dr. Tae-Woo Park, of the Air Force Research Laboratory's Air Force Office of Scientific Research, and Prof Hugh Durrant-Whyte, of the University of Sydney (Australian Research Council Federation Fellow), wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn/index.htm. Reference document OSR-H-05-06.

Posted in: Briefs, Information Technology, Mathematical models, Simulation and modeling, Unmanned aerial vehicles

Surface-Emitting Laser Arrays Bring Light to the Top

Laser diodes are an integral part of everyday life, incorporated into commonplace items as diverse in function as laser pointers, fiber-optic communications systems, and DVD players. Manufacturers make most laser diodes by layering specially doped semiconductor materials on a wafer. By slicing tiny chips from these wafers to attain two perfectly smooth, parallel edges, they create very thin (tens of microns) waveguides. These waveguides define a resonating cavity that causes stimulated light to combine in a way that embodies a "laser" and propagates its lasing action. Although this process represents a highly successful and wellengineered means for producing semiconductor lasers, the lasers do not produce an optimum beam. Beam emission occurs from the small rectangular opening at the end of the chip, a configuration that results in an elliptically distorted beam as well as the loss of output efficiency. In addition, the output aperture's relatively small size can lead to destruction of the cleaved and polished end facet during the laser's high-power operation. Laser diodes produced using this process are also susceptible to substantial fluctuations in output wavelength and beam quality as a function of temperature. Furthermore, since the chip emits beam output from an edge instead of its top or bottom surface, manufacturers experience difficulty both in packaging various diode configurations and in combining the output beams of multiple laser diodes.

Posted in: Briefs, Photonics, Fiber optics, Lasers