Naval Postgraduate School

A Back-surface, Alternating Contacts (BAC) Solar Cell featuring p-or-n type GaAs with alternating p-n junction regions on the back-surface of the cell, producing an improved, lighter-weight solar cell. The layers of p-or-n type GaAs are interfaced together to collect charge carriers, and a thin layer of AlGaAs is applied to the front and back surfaces to prevent recombination of charge carriers. Layer properties (thickness, material, doping, etc.) are optimized to improve overall conversion efficiency. The performance of the BAC Solar Cell is significantly improved by the arrangement of a GaAs-based emitter layer, heterojunction layer, and emitter-contact layer to facilitate a conduction band (CB) and valance band (VB) arrangement at layer interfaces that leads to dramatic improvements in BAC Solar Cell performance. Additionally, due to the very thin absorption layer, minority carriers have a much higher probability of reaching the electrical contacts and contributing to load current. The highly-reflective, back-surface, metal contacts improve solar cell efficiency by reflecting transiting or emitted photons back into the absorption layer. Additionally, a window layer and anti-reflective coating minimizes the escape cone at the front of the solar cell, effectively trapping photons and increasing the probability that they will create an electron-hole pair. These attributes provide better long-term performance in high-radiation environments; higher conversion efficiency at elevated temperatures; and a lighter, more flexible structure for mobile applications.

The Naval Postgraduate School has developed and patented a prototype hybrid vehicle that integrates features and capabilities of a drifting sonobuoy and a multirotor vertical take-off and landing UAV. As such, Aqua-Quad integrates a multicopter UAV with a tethered underwater vector sensor, environmentally hardened electronics, communication links for local (MANET) and global reach (Iridium), and a solar recharge system. A current application of the autonomous system is for detection, classification, and underwater target motion estimation using self-contained electronics and algorithms, for extended periods of time. The Aqua-Quads are intelligent, mobile, collaborative platforms that ride on ocean currents and fly over significant distances when required by the mission. Flight is triggered to enable rapid repositioning for underwater target tracking, collision avoidance, and communication with neighboring vehicles.

Conventional directional sound sensing systems use an array of spatially separated microphones to achieve directional sensing by monitoring the arrival times and amplitudes at each microphone. The accuracy of the directionality in this case is determined by the extent of spatial separation of the microphones making them bulky. On the other hand, the ears of Ormia ochracea fly are separated mere 0.5 mm yet it has remarkable sensitivity to direction of sound. The fly’s unique ear structure consists of two eardrums coupled at the center. The incident sound generates directionally dependent oscillations of the eardrums with large amplitudes at normal modes of the coupled system. In this work, a narrowband MEMS direction finding sensor has been developed based on the fly’s hearing system. The sensor consists of two wings coupled at the middle and attached to a substrate using two legs. The sensor operates at its bending resonance frequency and has cosine directional characteristics similar to that of a pressure gradient microphone. Thus, the directional response of the sensor is symmetric about the normal axis making the determination of the direction ambiguous. To overcome this shortcoming two sensors were assembled with a canted angle similar to that employed in radar bearing locators. The outputs of two sensors were processed together allowing direction finding with no requirement of knowing the incident sound pressure level. At the bending resonant frequency of the sensor an output voltage of about 10 V/Pa was measured which three orders of magnitude larger than conventional MEMS microphones. The accuracy of the bearing of sound is found to be about 2°. These findings indicate the great potential to use dual MEMS direction finding sensor assemblies to locate sound sources with high accuracy.

Navy researchers have developed a container and unique method of manufacturing that provides safe and secure storage of explosives. The method includes stacking tires one on top of another, filling the tires with a cement and locally obtained plant or synthetic fiber mixture to form a cylindrical sidewall of the container, and creating a bottom layer of the container with the cement and fiber mixture. In an event of unintended detonation of the explosives, the system should stop all ordnance-produced primary fragmentation (shrapnel from the ordinance itself), while eliminating or creating minimal secondary fragmentation from the storage system itself. The container is specifically adapted to redirect the thermal effects and blast overpressure wave away from people and mitigate its effects to a K-Factor of 24. A K-Factor (31 feet or 9 meters) is the minimum distance allowed between an individual and one pound TNT equivalent explosive detonation without receiving life-threatening or disabling injuries.

Navy researchers have developed a container and unique method of manufacturing it that provides safe and secure storage of explosives. The method includes stacking tires one on top of another, filling the tires with a cement and locally obtained plant or synthetic fiber mixture to form a cylindrical sidewall of the container, and creating a bottom layer of the container with the cement and fiber mixture. In the event of unintended detonation of the explosives, the system should stop all ordnance-produced primary fragmentation (shrapnel from the ordinance itself), while eliminating or creating minimal secondary fragmentation from the storage system itself. The container is specifically adapted to redirect the thermal effects and blast overpressure wave away from people and mitigate its effects to a K-Factor of 24. A K-Factor (31 feet or 9 meters) is the minimum distance allowed between an individual and one pound TNT equivalent explosive detonation without receiving life-threatening or disabling injuries.

This invention describes a dual propulsion system with a single-propellant source used for either a high specific impulse mode (an ion-thruster mode) or a low specific impulse mode (a cold-gas thruster mode). The high specific impulse mode utilizes a miniaturized positive-ion field-ionization chamber which consists of a grid or other permeable substrate material infused with properly oriented carbon nanotubes through which the propellant flows. Field-electron emission from a neutralizer, such as a carbon nanotube array neutralizer, positioned downstream of accelerator grids may be used for ion neutralization. The low specific impulse mode utilizes conventional supersonic nozzles.

When compared to conventional electron-bombardment-ionization, the invention’s chamber is more compact and its field ionization provides only singly-charged positive ions. The positive ions generated are electrostatically repelled from the ionizer surface because it is an anode, obviating the ion-impingement cathode damage that has plagued prior-art ionizers. This translates into longer lifetime. Further, no magnets are required and no extra propellant is wasted in neutralization when electron-field emission neutralizers are used. The ionization chamber’s compactness enables ion thruster applications to small satellites.

Nano- and pico-satellite applications require high specific impulses for orbit maintenance and low specific impulses for orbit maneuvers. The disclosure’s miniaturized ion thruster embodiment is useful for small satellites because the physical depth of the ionizer dimension may be decreased by as much as 80% (not the cross section) over the present state of the art for the same thruster performance. The use of a single propellant such as argon for both propulsion modes is both efficient and practical.

The Tactical Networked Communication Architecture Design (TaNCAD) lab at the Naval Postgraduate School has patented a methodology for integrating traditional Internet Protocol (IP) networks with Disruption-Tolerant Networks (DTNs). This is accomplished via a gateway router and software for application-aware automatic network selection, which translates data between networks and provides application-specific feedback. The router and method select between an IP network and a DTN (or other network module supported via plugins). This is accomplished by monitoring the state of both networks, intercepting IP packets which could otherwise not be delivered, responding to the application that sent the packet, and translating a group of such packets into a DTN bundle. The software implementing this system resides on a network router that functions as a node on both the IP and DTN networks. In other scenarios, the system selects between or among WAN accelerators, tactical networks, mobile ad hoc networks (MANETs), sensor networks, vehicular networks, and satellite and deep space networks. This bridges the gap between the vast array of legacy IP-based applications, and a number of domain-specific networking paradigms that are not natively IP-compatible.

A method is described that involves establishing a wireless network between a wireless access node of an existing network and a remote location by wirelessly linking a plurality of electronic processing circuits each transported by a respective parafoil. The wirelessly linked processing circuits are to route packets from the wireless access node to the remote location.

The Landing Signal Officer (LSO) Information Management and Trend Analysis (IMTA) System is a replacement for the legacy Automated Performance and Readiness Training System (APARTS), which is a Microsoft Access® database tool that is no longer supported. The LSO IMTA system is comprised of personal electronic devices (PEDs) and mobile laptops, each loaded with dedicated software, and shore based database server centers. The PED, such as a rugged handheld tablet, takes in shorthand symbology developed by the LSO community (normally recorded via paper logbook entries on the flight deck) which stores the quality of an aircraft landing aboard an aircraft carrier (trap). The pilot of the aircraft is graded for each trap. Thereafter, trend analysis can be performed on collected data and appropriate reports can be generated that are reviewed by Naval Air Systems Command (NASC), Carrier Air Wings (CAG), and individual squadron commanders. The data collected via PEDs is then transferred to intermediate storage until it can be uploaded to dedicated shore side database server centers that key stakeholders will have access to. This system can also automate the interaction between an aviation instructor and a student pilot in the training pipeline, propagate the information from disconnected handhelds to centralized databases for trend analysis, and allow for LSO shorthand capture during keyboard input with intelligent algorithms. The focus has been the naval aviator, however, the scope of data capture can also be applied to the commercial aviation sector.

A light activated generator having a rotor driven by mechanical power induced by the effects of light impingment.. The rotor utilizes a series of vanes rotatable around an axle, with each vane is separated into a first surface and a second surface having differing emissivities. Additionally, each vane includes an electrical conductor. When the light activated generator is illuminated with a radiant flux, the differing emissivities of the first and second surfaces produce thermal creep force across the planar vanes to revolve each vane and the attached conductor through a magnetic field to generate a voltage across the conductor. In typical applications, the magnetic field is generated using a permanent magnet. The Light Activated Generator has particular applicability as a microelectromechanical system (MEMS) device.