DARPA’s Tactical Undersea Network Architecture (TUNA) program recently completed its initial phase, successfully developing concepts and technologies aimed at restoring connectivity for U.S. forces when traditional tactical networks are knocked offline or otherwise unavailable. The program now enters the next phase, which calls for the demonstration of a prototype of the system at sea.
TUNA seeks to develop and demonstrate novel, optical-fiber-based technology options and designs to temporarily restore radio frequency (RF) tactical data networks in a contested environment via an undersea optical fiber backbone. The concept involves deploying RF network node buoys – dropped from aircraft or ships, for example – that would be connected via thin underwater fiber-optic cables. The very-small-diameter fiber-optic cables being developed are designed to last 30 days in the rough ocean environment – long enough to provide essential connectivity until primary methods of communications are restored.
«Phase 1 of the program included successful modeling, simulation, and at-sea tests of unique fiber-cable and buoy-component technologies needed to make such an undersea architecture work», said John Kamp, program manager in DARPA’s Strategic Technology Office. «Teams were able to design strong, hair-thin, buoyant fiber-optic cables able to withstand the pressure, saltwater, and currents of the ocean, as well as develop novel power generation concepts».
Supplying power to floating buoy nodes on the open sea presents a particular challenge. During the first phase of the program, the University of Washington’s Applied Physics Lab (APL) developed a unique concept called the Wave Energy Buoy that Self-deploys (WEBS), which generates electricity from wave movement. The WEBS system is designed to fit into a cylinder that could be deployed from a ship or aircraft.
Having now entered its second and final phase, the program is advancing to design and implement an integrated end-to-end system, and to test and evaluate this system in laboratory and at-sea demonstrations. As a test case for the TUNA concept, teams are using Link 16—a common tactical data network used by U.S. and allied forces’ aircraft, ships, and ground vehicles.
DARPA wraps up first phase of program developing temporary underwater fiber-optics communications networks to ensure connectivity when tactical networks are unavailable
The Mechanically Based Antenna program could enable radio communication through seawater and the ground and directly between warfighters hundreds and ultimately thousands of kilometers apart.
Here’s something easy to forget when you are chatting on your cell phone or flipping channels on your smart TV: although wireless communication seems nothing short of magic, it is a brilliant, reality-anchored application of physics and engineering in which radio signals travel from a transmitter to a receiver in the form of electric and magnetic fields woven into fast-as-light electromagnetic waves. That very same physics imposes some strict limits, including ones that frustrate the Department of Defense (DoD). Key among these is that radio frequency signals hit veritable and literal walls when they encounter materials like water, soil, and stone, which can block or otherwise ruin those radio signals. This is why scuba buddies rely on sign language and there are radio-dead zones inside tunnels and caves.
With his newly announced A MEchanically Based Antenna (AMEBA) effort, program manager Troy Olsson of DARPA’s Microsystems Technology Office is betting on a little-exploited aspect of electromagnetic physics that could expand wireless communication and data transfer into undersea, underground, and other settings where such capabilities essentially have been absent. The basis for these potential new abilities are ultra-low-frequency (ULF) electromagnetic waves, ones between hundreds of hertz and 3 kilohertz (KHz), which can penetrate some distance into media like water, soil, rock, metal, and building materials. A nearby band of very-low-frequency (VLF) signals (3 KHz to 30 KHz) opens additional communications possibilities because for these wavelengths the atmospheric corridor between the Earth’s surface and the ionosphere – the highest and electric-charge-rich portion of the upper atmosphere – behaves like a radio waveguide in which the signals can propagate halfway around the planet.
«If we are successful, scuba divers would be able to use a ULF channel for low bit-rate communications, like text messages, to communicate with each other or with nearby submarines, ships, relay buoys, Unmanned Aerial Vehicles (UAVs), and ground-based assets, Through-ground communication with people in deep bunkers, mines, or caves could also become possible», Olsson said. And because of that atmospheric waveguide effect, VLF systems might ultimately enable direct soldier-to-soldier text and voice communication across continents and oceans.
To date, there’s been a huge and expensive rub to actually pulling off low-frequency radio communication in the versatile ways that Olsson has in mind. The wavelengths of VLF and ULF radio signals rival the distances across cities and states, respectively. And since longer wavelengths have required taller antennas, communications in these frequency bands have entailed the construction of enormous and costly transmitter structures. A VLF antenna that the U.S. Navy built on a remote peninsula in Cutler, Maine, in the heat of the Cold War just to send a trickle of data to submarines makes the point: the gargantuan transmitter complex occupies 2,000 acres/8 square kilometers, features 26 towers up to 1,000 feet/305 m high, and operates with megawatt levels of power.
With the AMEBA program, Olsson aims to develop entirely new types of VLF and ULF transmitters that are sufficiently small, light, and power efficient to be carried by individual warfighters, whether they are on land, in the water, or underground. Rather than relying on electronic circuits and power amplifiers to create oscillating electric currents that, when driven into antennas, initiate radio signals, the new low-frequency VLF and ULF antennas sought in the AMEBA program would generate the signals by mechanically moving materials harboring strong electric or magnetic fields.
In principle, this is as simple as taking a bar magnet or an electret – an insulating substance, such as a cylinder of quartz (silica) glass, in which positive and negative electric charges are permanently segregated to create an electric dipole – and moving it at rates that will generate ULF and VLF frequencies. To open up practical new capabilities in national security contexts, however, the challenges include packing more powerful magnetic and electric fields into smaller volumes with smaller power requirements than has ever been achieved before for a ULF or VLF transmitter. That will require innovations in chemistry and materials (new magnets and electrets), design (shapes and packing geometries of these materials), and mechanical engineering (means of mechanically moving the magnets and electrets to generate the RF signals).
«Mobile low-frequency communication has been such a hard-technological problem, especially for long-distance linkages, that we have seen little progress in many years», said Olsson. «With AMEBA, we expect to change that. And if we do catalyze the innovations we have in mind, we should be able to give our warfighters extremely valuable mission-expanding channels of communications that no one has had before».
Tern, a joint program between DARPA and the U.S. Navy’s Office of Naval Research (ONR), seeks to greatly increase the effectiveness of forward-deployed small-deck ships such as destroyers and frigates by enabling them to serve as mobile launch and recovery sites for specially designed unmanned air systems (UASs). DARPA last year awarded Phase 3 of Tern to a team led by the Northrop Grumman Corporation to build a full-scale technology demonstration system. The program has since made significant advances on numerous fronts, including commencement of wing fabrication and completion of successful engine testing for its test vehicle, and DARPA has tasked Northrop Grumman with building a second test vehicle.
«DARPA has been thinking about building a second Tern test vehicle for well over a year», said Dan Patt, DARPA program manager. «Adding the second technology demonstrator enhances the robustness of the flight demonstration program and enables military partners to work with us on maturation, including testing different payloads and experimenting with different approaches to operational usage».
Tern envisions a new medium-altitude, long-endurance UAS that could operate from helicopter decks on smaller ships in rough seas or expeditionary settings while achieving efficient long-duration flight. To provide these and other previously unattainable capabilities, the Tern Phase 3 design is a tailsitting, flying-wing aircraft with a twin contra-rotating, nose-mounted propulsion system. The aircraft would lift off like a helicopter and then perform a transition maneuver to orient it for wing-borne flight for the duration of a mission. Upon mission completion, the aircraft would return to base, transition back to a vertical orientation, and land. The system is sized to fit securely inside a ship hangar for maintenance operations and storage.
Tern has accomplished the following technical milestones for its test vehicle in 2016:
Wing fabrication: Since Phase 3 work started at the beginning of 2016, Tern has finished fabricating major airframe components and anticipates final assembly in the first quarter of 2017. Once complete, the airframe will house propulsion, sensors, and other commercial off-the-shelf (COTS) systems to make up the full-scale technology demonstration vehicle.
Engine tests: In Phases 2 and 3, Tern has successfully tested numerous modifications to an existing General Electric engine to enable it to operate in both vertical and horizontal orientations. This type of engine was chosen because it is mature and powers multiple helicopter platforms currently in use.
Software integration: This summer, Tern opened its Software Integration Test Station (SITS), part of the System Integration Lab that supports software development for the program. The test station includes vehicle management system hardware and software, and uses high-fidelity simulation tools to enable rapid testing of aircraft control software in all phases of flight. The SITS is helping ensure the technology demonstration vehicle could fly safely in challenging conditions such as launch, recovery, and transition between horizontal and vertical flight.
Additional tests are about to start. A 1/5th-scale version of the approved vehicle model is in testing in the 80’ × 120’ wind tunnel at the NASA Ames Research Center’s National Full-Scale Aerodynamics Complex (NFAC). Data collected during this test will be used to better characterize aircraft aerodynamic performance and validate aerodynamic models.
«We’re making substantial progress toward our scheduled flight tests, with much of the hardware already fabricated and software development and integration in full swing», said Brad Tousley, director of DARPA’s Tactical Technology Office, which oversees Tern. «As we keep pressing into uncharted territory – no one has flown a large unmanned tailsitter before – we remain excited about the future capabilities a successful Tern demonstration could enable: organic, persistent, long-range reconnaissance, targeting, and strike support from most Navy ships».
Tern is currently scheduled to start integrated propulsion system testing in the first part of 2017, move to ground-based testing in early 2018, and culminate in a series of at-sea flight tests in late 2018.
DARPA and the Navy have a Memorandum of Agreement (MOA) to share responsibility for the development and testing of the Tern demonstrator system. The Marine Corps Warfighting Laboratory (MCWL) has also expressed interest in Tern’s potential capabilities and is providing support to the program.
In the decades-long quest to develop reusable aircraft that can reach hypersonic speeds – Mach 5 (approximately 3,300 miles per hour/5,300 kilometers per hour) and above – engineers have grappled with two intertwined, seemingly intractable challenges. The top speed of traditional jet-turbine engines maxes out at roughly Mach 2.5, while hypersonic engines such as scramjets cannot provide effective thrust at speeds much below Mach 3.5. This gap in capability means that any air-breathing hypersonic vehicles developed today would use disposable rockets for one-time boosts up to operating speed, limiting the vehicles’ usefulness.
To help remove these constraints and lay the framework for routine hypersonic flight with reusable vehicles, DARPA has launched its Advanced Full Range Engine (AFRE) program. AFRE seeks to develop and demonstrate a new aircraft propulsion system that could operate over the full range of speeds required from low-speed takeoff through hypersonic flight.
«Instead of designing an entirely new kind of engine, we’re envisioning an inventive hybrid system that would combine and improve upon the best of off-the-shelf turbine and ramjet/scramjet technologies», said Christopher Clay, DARPA program manager. «This won’t be the first time that ambitious engineers will attempt to combine turbine and ramjet technologies. But with recent advances in manufacturing methods, modeling, and other disciplines, we believe this potentially groundbreaking achievement may finally be within reach».
AFRE aims to explore a Turbine-Based Combined Cycle (TBCC) engine concept, which would use a turbine engine for low-speed operations and a dual-mode ramjet – which would work efficiently whether the air flowing through it is subsonic (as in a ramjet) or supersonic (as in a scramjet) – for high-speed operations. The two components of the hybrid engine would share a common forward-facing air intake and rear-facing exhaust nozzle to release thrust.
AFRE aims to develop critical technologies and culminate in ground-based testing of a full-scale, integrated technology demonstration system. If that testing is successful, further development of the AFRE technology would require flight testing in a potential follow-on demonstration program.
Systems that operate at hypersonic speeds offer the potential for military operations from longer ranges with shorter response times and enhanced effectiveness compared to current military systems. Such systems could provide significant payoff for future U.S. operations, particularly as adversaries’ capabilities advance.
On April 18, Aurora Flight Sciences announced that a Subscale Vehicle Demonstrator (SVD) of its LightningStrike, Vertical Take-off and Landing Experimental Plane (VTOL X-plane) for the Defense Advanced Research Projects Agency (DARPA) was successfully flown at a U.S. military facility at Manassas, Virginia. The flight of the subscale aircraft met an important DARPA risk reduction requirement, focusing on validation of the aerodynamic design and flight control system.
«The successful subscale aircraft flight was an important and exciting step for Aurora and our customer», said Tom Clancy, Aurora’s chief technology officer. «Our design’s distributed electric propulsion system involves breaking new ground with a flight control system requiring a complex set of control effectors. This first flight is an important, initial confirmation that both the flight controls and aerodynamic design are aligning with our design predictions».
The subscale aircraft weighs 325 pounds/147.4 kg and is a 20% scale flight model of the full scale demonstrator Aurora will build for DARPA in the next 24 months. The wing and canard of the subscale vehicle utilize a hybrid structure of carbon fiber and 3D printed FDM plastics to achieve highly complex structural and aerodynamic surfaces with minimal weight. The unmanned aircraft take-off, hover and landing was controlled by Aurora personnel located in a nearby ground control station with oversight and coordination by U.S. government officials including DARPA personnel.
On March 3, 2016, DARPA announced the award of the Phase II contract for the VTOL X-Plane contract to Aurora, following a multi-year, Phase I design competition. The program seeks to develop a vertical take-off and landing demonstrator aircraft that will achieve a top sustained flight speed of 300 knots/345 mph/556 km/h – 400 knots/460 mph/741 km/h, with 60-75% increase in hover efficiency over existing VTOL aircraft. Aurora’s design is for the first aircraft in aviation history to demonstrate distributed hybrid-electric propulsion using an innovative synchronous electric-drive system. Having successfully completed the subscale demonstrator flight, Aurora’s LightningStrike team will focus over the next year on further validation of flight control system and configuration of the full scale VTOL X-Plane demonstrator.
Aurora Flight Sciences’ subscale vehicle demonstrator successfully flew at a U.S. military facility
In an era of declining budgets and adversaries’ evolving capabilities, quick, affordable and routine access to space is increasingly critical for both national and economic security. Current satellite launch systems, however, require scheduling years in advance for an extremely limited inventory of available slots. Moreover, launches often cost hundreds of millions of dollars each, due in large part to the massive amounts of dedicated infrastructure and large number of personnel required. DARPA created its Experimental Spaceplane (XS-1) program to help overcome these challenges and create a new paradigm for more routine, responsive and affordable space operations, reducing the time to get capabilities to space.
In an important step toward these goals, DARPA has announced Phase 2 of the XS-1 program, which seeks to design and fabricate an experimental unmanned spaceplane using state-of-the-art technologies and streamlined processes, and fly the vehicle ten times in ten days. The reusable XS-1 would demonstrate the potential for low-cost and «aircraft-like» high-ops-tempo space flight, enabling a host of critical national security options while helping to launch a new and potentially fruitful commercial sector. A Special Notice was posted on April 7 on FedBizOpps announcing the XS-1 Phase 2 Proposers Day, to be held on Friday, April, 29, 2016, in Arlington, Virginia.
«During Phase 1 of the XS-1 program, the space industry has evolved rapidly and we intend to take advantage of multiple impressive technological and commercial advances», said Jess Sponable, DARPA program manager. «We intend to leverage those advances along with our Phase 1 progress to break the cycle of escalating DoD space system launch costs, catalyze lower-cost satellite architectures, and prove that routine and responsive access to space can be achieved at costs an order of magnitude lower than with today’s systems».
XS-1 envisions that a fully reusable unmanned booster vehicle would fly to high speeds at a suborbital altitude. At that point, one or more expendable upper stages would separate, boost and deploy a satellite into Low Earth Orbit (LEO). The reusable first stage would then return to earth, land and be prepared for the next flight. Although relatively small by conventional aircraft standards, the XS-1 flight booster size – akin to a business jet – would be sufficient to validate credible scaling to larger reusable launch systems. Moreover, demonstration of on-demand and routine access to space, akin to aircraft, is important for next-generation DoD needs.
XS-1 has four primary technical goals:
Fly 10 times in a 10-day period (not including weather, range and emergency delays) to demonstrate aircraft-like access to space and eliminate concerns about the cost-effectiveness and reliability of reusable launch.
Achieve flight velocity sufficiently high to enable use of a small (and therefore low-cost) expendable upper stage.
Launch a 900- to 1,500-pound/408- to 680-kilogram representative payload to demonstrate an immediate responsive launch capability able to support both DoD and commercial missions. The same XS-1 vehicle could eventually also launch future 3,000+-pound/1,361-kilogram payloads by using a larger expendable upper stage.
Reduce the cost of access to space for 3,000+-pound/1,361-kilogram payloads, with a goal of approximately $5 million per flight for the operational system, which would include a reusable booster and expendable upper stage(s).
Successful design would require integrating state-of-the-art technologies, processes and system approaches to deliver routine aircraft-like operability, reliability and cost efficiency. In particular, incorporation of autonomous technology and operations promises to significantly decrease the logistical footprint and enable rapid turnaround between flights. Structures made of advanced materials, cryogenic tanks, durable thermal protection, and modular subsystems would make possible a vehicle able to launch, fly to high speeds and then land in a condition amenable to rapid turnaround and launch with the next payload. Reusable, reliable propulsion would also be essential for a low-cost and recurring flight capability.
In Phase 1 of XS-1, DARPA sought to evaluate the technical feasibility and methods for achieving the program’s goals. To achieve that, it awarded prime contracts to three companies, each working in concert with a commercial launch provider: The Boeing Company (working with Blue Origin, LLC); Masten Space Systems (working with XCOR Aerospace); and Northrop Grumman Corporation (working with Virgin Galactic). Phases 2 and 3 will be competed as a full and open Program Solicitation mandating an Other Transaction Authority (OTA) agreement with the expectation of a single resulting award. Cost share is expected.
Specifically, the program is structured to directly transition any successful technology to the industrial and commercial launch sectors, with the goal of enabling new launch markets and sale of launch services back to the government at dramatically lower costs and more rapid time frames than are possible today. By ensuring the technologies and launch systems would be available through the commercial sector, government leaders would have the opportunity to begin relying on XS-1 and derived systems. Militarily-relevant applications of the technology may also spur adoption and help enable future capabilities such as disaggregated spacecraft architectures and next-generation, reusable space-access aircraft.
On April 7, DARPA is holding a christening ceremony for the technology demonstration vessel it has developed and built through the Agency’s Anti-Submarine Warfare (ASW) Continuous Trail Unmanned Vessel (ACTUV) program. Taking place in Portland, Oregon, the event marks the vessel’s formal transition from a DARPA-led design and construction project to a new stage of open-water testing to be conducted jointly with the Office of Naval Research (ONR). The christening, to include the traditional breaking of a ceremonial bottle over the bow by DARPA Director Arati Prabhakar, signifies the beginnings of an entirely new class of ocean-going vessel – one able to traverse thousands of kilometers over the open seas for month at a time, without a single crew member aboard. Potential missions include submarine tracking and countermine activities.
«Although ACTUV will sail unmanned, its story is entirely about people», said Scott Littlefield, DARPA program manager. «It will still be Sailors who are deciding how, when and where to use this new capability and the technology that has made it possible. And we could not have overcome the massive technical challenges to reaching this point without the creative, committed teamwork of our commercial partners and the Office of Naval Research».
In addition to Littlefield and Prabhakar, scheduled speakers at dockside ceremony include the Honorable Robert Work, Deputy Secretary of Defense; Rear Admiral Robert Girrier, Director, Unmanned Warfare Systems (OPNAV N99); and Rear Admiral Mathias Winter, Chief of Naval Research, Innovation Technology Requirements and Test & Evaluation (OPNAV N84).
The ceremony will culminate with Prabhakar’s swinging of the ceremonial «champagne» bottle (the contents will be non-alcoholic) to christen the vessel «Sea Hunter». The name both describes the technology demonstrator’s envisioned capabilities and also harks back to DARPA and U.S. Navy ship-development programs of years past, such as the Sea Shadow prototype vessel developed in the 1980s.
ACTUV is a 130-foot/39.6-meter twin-screw trimaran, designed for enhanced stability in all kinds of weather. It has a number of unusual features because it does not need to accommodate people. For example, interior spaces are accessible for maintenance but aren’t designed to support a permanent crew.
But of broader technical significance is that ACTUV embodies breakthroughs in autonomous navigational capabilities with the potential to change the nature of U.S. maritime operations. Through at-sea testing on a surrogate vessel, ACTUV’s autonomy suite has proven capable of operating the ship in compliance with maritime laws and conventions for safe navigation – including International Regulations for Preventing Collisions at Sea, or COLREGS. ACTUV accomplishes this feat through advanced software and hardware that serve as automated lookouts, enabling the ship to operate safely near manned maritime vessels in all weather and traffic conditions, day or night.
ACTUV is designed to normally operate under sparse remote supervisory control but can also serve as a remotely piloted vessel, should the mission or specific circumstances require it. In either case, it would operate at a fraction of the cost of manned vessels that are today deployed for similar missions.
In September 2014, DARPA signed a Memorandum of Agreement (MOA) with the Office of Naval Research to jointly fund an extended test phase of an ACTUV prototype. DARPA will collaborate with ONR to fully test the capabilities of the vessel and several innovative payloads during open-water testing scheduled to begin this summer off the California coast after preliminary checkout and movement to San Diego. Pending the results of those tests, the program could transition to the U.S. Navy by 2018.
«The Memorandum of Agreement is just one example of the strong relationship that exists between DARPA and the Office of Naval Research, where we are working together on a number of important projects», said Brad Tousley, director of DARPA’s Tactical Technology Office, which oversees ACTUV. «We look forward to strengthening and extending the relationship with ONR as we start testing ACTUV in San Diego later this spring and work jointly toward providing pivotal new capabilities for the Navy».
DARPA’s Anti-Submarine Warfare (ASW) Continuous Trail Unmanned Vessel (ACTUV) program has designed, developed and constructed an entirely new class of ocean-going vessel – one intended to traverse thousands of kilometers over the open seas for months at a time, all without a single crew member aboard.
The ACTUV technology demonstration vessel was recently transferred to water at its construction site in Portland, Oregon, and conducted speed tests in which it reached a top speed of 27 knots (31 mph/50 kph). The vessel is scheduled to be christened on April 7, 2016, with open-water testing planned to begin in summer 2016 off the California coast.
The Anti-Submarine Warfare Continuous Trail Unmanned Vessel is developing an unmanned vessel optimized to robustly track quiet diesel electric submarines. The program is structured around three primary goals.
Explore the performance potential of a surface platform conceived from concept to field demonstration under the premise that a human is never intended to step aboard at any point in its operating cycle. As a result, a new design paradigm emerges with reduced constraints on conventional naval architecture elements such as layout, accessibility, crew support systems, and reserve buoyancy. The objective is to generate a vessel design that exceeds state-of-the art platform performance to provide propulsive overmatch against diesel electric submarines at a fraction of their size and cost.
Advance unmanned maritime system autonomy to enable independently deploying systems capable of missions spanning thousands of kilometers of range and months of endurance under a sparse remote supervisory control model. This includes autonomous compliance with maritime laws and conventions for safe navigation, autonomous system management for operational reliability, and autonomous interactions with an intelligent adversary.
Demonstrate the capability of the ACTUV system to use its unique characteristics to employ non-conventional sensor technologies that achieve robust continuous track of the quietest submarine targets over their entire operating envelope.
While the ACTUV program is focused on demonstrating the ASW tracking capability in this configuration, the core platform and autonomy technologies are broadly extendable to underpin a wide range of missions and configurations for future unmanned naval vessels.
For decades, aircraft designers seeking to improve Vertical Take-Off and Landing (VTOL) capabilities have endured a substantial set of interrelated challenges. Dozens of attempts have been made to increase top speed without sacrificing range, efficiency or the ability to do useful work, with each effort struggling or failing in one way or another.
DARPA’s VTOL Experimental Plane (VTOL X-Plane) program aims to overcome these challenges through innovative cross-pollination between fixed-wing and rotary-wing technologies and by developing and integrating novel subsystems to enable radical improvements in vertical and cruising flight capabilities. In an important step toward that goal, DARPA has awarded the Phase 2 contract for VTOL X-Plane to Aurora Flight Sciences.
«Just when we thought it had all been done before, the Aurora team found room for invention – truly new elements of engineering and technology that show enormous promise for demonstration on actual flight vehicles», said Ashish Bagai, DARPA program manager. «This is an extremely novel approach», Bagai said of the selected design. «It will be very challenging to demonstrate, but it has the potential to move the technology needle the farthest and provide some of the greatest spinoff opportunities for other vertical flight and aviation products».
VTOL X-Plane seeks to develop a technology demonstrator that could:
Achieve a top sustained flight speed of 300 knot/345 mph/555 km/h to 400 knot/460 mph/740 km/h;
Raise aircraft hover efficiency from 60 percent to at least 75 percent;
Present a more favorable cruise lift-to-drag ratio of at least 10, up from 5-6;
Carry a useful load of at least 40 percent of the vehicle’s projected gross weight of 10,000-12,000 pounds/4,536-5,443 kg.
Aurora’s Phase 2 design for VTOL X-Plane envisions an unmanned aircraft with two large rear wings and two smaller front canards – short winglets mounted near the nose of the aircraft. A turboshaft engine – one used in V-22 Osprey tiltrotor aircraft – mounted in the fuselage would provide 3 megawatts (4,000 horsepower) of electrical power, the equivalent of an average commercial wind turbine. The engine would drive 24 ducted fans, nine integrated into each wing and three inside each canard. Both the wings and the canards would rotate to direct fan thrust as needed: rearward for forward flight, downward for hovering and at angles during transition between the two.
The design envisions an aircraft that could fly fast and far, hover when needed and accomplish diverse missions without the need for prepared landing areas. While the technology demonstrator would be unmanned, the technologies that VTOL X-Plane intends to develop could apply equally well to manned aircraft. The program has the goal of performing flight tests in the 2018 timeframe.
Aurora’s unique design is only possible through advances in technology over the past 60 years, in fields such as air vehicle and aeromechanics design and testing, adaptive and reconfigurable control systems, and highly integrated designs. It would also be impossible with the classical mechanical drive systems used in today’s vertical lift aircraft, Bagai said.
The Phase 2 design addresses in innovative ways many longstanding technical obstacles, the biggest of which is that the design characteristics that enable good hovering capabilities are completely different from those that enable fast forward flight. Among the revolutionary design advances to be incorporated in the technology demonstrator:
Electric power generation and distribution systems to enable multiple fans and transmission-agnostic air vehicle designs;
Modularized, cellular aerodynamic wing design with integrated propulsion to enable the wings to perform efficiently in forward flight, hover and when transitioning between them;
Overactuated flight control systems that could change the thrust of each fan to increase maneuverability and efficiency.
«This VTOL X-plane won’t be in volume production in the next few years but is important for the future capabilities it could enable», Bagai said. «Imagine electric aircraft that are more quiet, fuel-efficient and adaptable and are capable of runway-independent operations. We want to open up whole new design and mission spaces freed from prior constraints, and enable new VTOL aircraft systems and subsystems».
They may not have zoomed flawlessly around obstacles like the Millennium Falcon did as it careened through the hull of a crashed Star Destroyer in Star Wars VII. But the sensor-loaded quadcopters that recently got tested in a cluttered hangar in Massachusetts did manage to edge their way around obstacles and achieve their target speeds of 20 meters per second. Moreover, the quadcopters were unmanned … and real. Thus was the initial phase of data collection for DARPA’s Fast Lightweight Autonomy (FLA) program recently deemed an encouraging success.
DARPA’s FLA program aims to develop and test algorithms that could reduce the amount of processing power, communications, and human intervention needed for Unmanned Aerial Vehicles (UAVs) to accomplish low-level tasks, such as navigation around obstacles in a cluttered environment. If successful, FLA would reduce operator workload and stress and allow humans to focus on higher-level supervision of multiple formations of manned and unmanned platforms as part of a single system.
FLA technologies could be especially useful to address a pressing surveillance shortfall: Military teams patrolling dangerous overseas urban environments and rescue teams responding to disasters such as earthquakes or floods currently can use remotely piloted UAVs to provide a bird’s-eye view of the situation, but to know what’s going on inside an unstable building or a threatening indoor space often requires physical entry, which can put troops or civilian response teams in danger. The FLA program is developing a new class of algorithms aimed at enabling small UAVs to quickly navigate a labyrinth of rooms, stairways and corridors or other obstacle-filled environments without a remote pilot. The program seeks to develop and demonstrate autonomous UAVs small enough to fit through an open window and able to fly at speeds up to 20 meters per second (45 miles per hour) – while avoiding objects within complex indoor spaces independent of communication with outside operators or sensors and without reliance on GPS.
DARPA researchers recently completed the first flight data collection from the common quadcopter UAV platform that three research teams are using for the program. The flight test data validated that the platform – which uses a commercial DJI Flamewheel 450 airframe, E600 motors with 12″ propellers, and 3DR Pixhawk autopilot – is capable of achieving the required flight speed of 20 meters per second while carrying high-definition onboard cameras and other sensors, such as LIDAR, sonar and inertial measurement units. During the testing, researchers also demonstrated initial autonomous capabilities, such as «seeing» obstacles and flying around them at slow speed unaided by a human controller.
«We’re excited that we were able to validate the airspeed goal during this first-flight data collection», said Mark Micire, DARPA program manager. «The fact that some teams also demonstrated basic autonomous flight ahead of schedule was an added bonus. The challenge for the teams now is to advance the algorithms and onboard computational efficiency to extend the UAVs’ perception range and compensate for the vehicles’ mass to make extremely tight turns and abrupt maneuvers at high speeds».
The three performer teams are Draper, teamed with the Massachusetts Institute of Technology; University of Pennsylvania; and Scientific Systems Company, Inc. (SSCI), teamed with AeroVironment.
The test flight and data collection took place at Otis Air National Guard Base, Cape Cod, Massachusetts, in a former aircraft hangar that was transformed into a warehouse setting with simulated walls, boxes and other obstacles to test flight agility and speed. The test run also resulted in several crashes. «But the only way to achieve hard goals is to push physical systems and software to the limit», Micire said. «I expect there will be more flight failures and smashed quadcopters along the way».
With each successive program milestone flight test, the warehouse venue will be made more complicated by adding obstacles and clutter to create a more challenging and realistic environment for the UAVs to navigate autonomously.
«Very lightweight UAVs exist today that are agile and can fly faster than 20 meters per second, but they can’t carry the sensors and computation to fly autonomously in cluttered environments», Micire said. «And large UAVs exist that can fly high and fast with heavy computing payloads and sensors on board. What makes the FLA program so challenging is finding the sweet spot of a small size, weight and power air vehicle with limited onboard computing power to perform a complex mission completely autonomously».
The FLA program’s initial focus is on UAVs, but advances made through the program could potentially be applied to ground, marine and underwater systems, which could be especially useful in GPS-degraded or denied environments.
DARPA’s Fast Lightweight Autonomy (FLA) program recently demonstrated that a commercial quadcopter platform could achieve 20-meters-per-second flight while carrying a full load of sensors and cameras