Monday, March 21, 2016

Hybrid Drones - the Advantages of Operating in Multiple Domains

Classifying unmanned maritime systems by their operating domain: air, surface, or underwater - is both convenient and intuitive. But recently, navy and industry researchers have begun to explore the advantages of platforms that can operate in two domains, muddying the nomenclature.  In the past year, several prototype multi-domain unmanned vehicles have been introduced.  

The most popular combination of these hybrid drones is the air/sub-surface mixture - UAVs that float or swim. Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland introduced the Corrosion Resistant Aerial Covert Unmanned Nautical System (CRACUNS), a submersible UAV designed to operate in the littorals which can be launched from a fixed position underwater or from an unmanned underwater vehicle (UUV).

Rutger University's entry into the fray of flying/swimming drones is the Naviator, which can actually maneuver (sort of) underwater before surfacing and taking off. 

Naval Postgraduate School students built the Aqua-Quad, a small quadcopter with the ability to land and drift on the ocean's surface. Singapore's ST Engineering has produced the Unmanned Hybrid Vehicle (UHV), which can fly for short ranges then move at 4-5 knots underwater. Perhaps the most advanced air/sub-surface combo vehicle is the Naval Research Laboratory's FLIMMER. 

Another take on the multi-domain hybrid is American Unmanned Systems spherical Guardbot, an amphibious surveillance robot that can cross from the sea to land.

Unmanned  Hybrid Vehicle (image courtesy of Shepherd Media)
Currently, these vehicles are all prototypes in the testing stage. It's not clear, which, if any, will see practical application in maritime operations. What sort of tactical advantage might these vehicles bring to naval missions?  The ability to launch a fairly short-ranged UAV from a ship or a larger aircraft to rapidly and precisely deploy an unattended sensor in the water column could be important for anti-submarine warfare. For instance, deploying a hydrophone with acoustic sensors can be done directly - like when a maritime patrol aircraft dispenses a disposable sonobuoy.  But a hybrid UAV could deploy, listen, then move and listen in another place, using the same vehicle, and potentially recover to a mothership. The same situation could also be used to deploy hydrographic monitoring instruments, important for ASW, but also mine warfare.

Of course this versatility results in trade-offs. None of these platforms will excel performance-wise in either operating domain. The vehicles listed above have fairly short ranges compared to single purpose platforms. Flight ranges may be short, but in ASW and other applications, there is an advantage to being able to drift on or under the water and listen while consuming very little power.  The Aqua-Quad is designed to do just that, with the help of photo-voltaic cells.  

Though these smaller vehicles have limited range compared to say a MALE UAV, they will also be much less expensive than long-endurance vehicles, meaning they can be acquired and deployed in quantity.  Operating in swarms, hybrid vehicles can become a force multiplier, distributing many sensors -- and possibly weapons -- over wider ranges.  There are certainly situations in which the ability to move between the air, and on or under the water make sense.

Sunday, March 6, 2016

Unmanned Systems & Strategic Futures at the Naval War College

The Naval War College remains the center of the U.S. Navy's foremost strategic thinkers.  Later this month, various experts from the military, academia, and policy communities will convene in Newport for a maritime strategy symposium.   
Some of the presenters will focus on the impact that unmanned vehicles have produced on naval strategy.  From the Naval Post-graduate School, retired Navy Captain Jeff Kline will discuss his paper on Impacts of the Robotics Age on Naval Force Structure Planning."

Captain Kline’s paper emphasizes the importance of offensive “payload over platforms,” in order to overcome impediments to enhancing future force structure. In his words,
“This package focus” first is particularly applicable in the electromagnetic and cyber realm. Inexpensive, deposable UAVs employing radar reflectors or chirp jamming may be better delivery platforms for EM “packages” than an F-18 Growler. In the offense, developing “Left of kill chain” effects against an adversary need not be expensive, but does require synchronization with the movement of actual forces.
Retired Captain Jerry Hendrix, from the Center for New American Security, argues for investing in change by introducing innovative naval capabilities.  These technologies would bring future conflicts to a swift victory by targeting an enemy’s national leadership.
If the United States were to go to war again it must leverage the technologies it has, a superb intelligence-reconnaissance complex as well as a precision strike capability unlike any other nation on earth, and combine these with newly emerging capabilities; unmanned and man-machine platforms, directed energy weapons, electro-magnetic and hypersonics to identify, target and destroy the critical center of gravity within the enemy camp.
Joining Captain Hendrix on the force structure panel is Lena S. Andrews, a PhD candidate in Political Science and a member of the Security Studies Program at MIT, who recognizes that new technologies introduce new risks. In her War on the Rocks article, Ms. Andrews and her coauthor Julia Macdonald warn that the increased reliability on satellite data connections and space technologies which have enabled the unmanned intelligence, surveillance, and reconnaissance revolution create a cyber capability-vulnerability paradox. 

In the paper “Future Maritime Forces: Unmanned, Autonomous, and Lethal,” the War College’s own William F. Bundy foresees that the combination of distributed lethality and unmanned systems will revolutionize future naval warfare.  His vision is that advanced unmanned air, surface, and subsurface platforms operating off surface ships and governed by artificial intelligence will be able to conform to safety of flight and navigation and the laws of armed conflict.

Tuesday, February 23, 2016

Mitigating Cosite Interference in UAVs

by Doug King dking(at)

Military radios must be able to operate in severe cosite interference environments (Figure 1.1 defines cosite interference). Cosite interference is a problem faced by many RF and microwave communications platforms; including Unmanned Systems. Military radios often operate in close proximity to additional radios, giving rise to cosite interference. The following article explains the issues associated with military radios operating in close proximity to additional interferers and how Tunable Filters are utilized in real-time applications. Finally, MPG-Pole/Zero’s recent advances in mitigating cosite interference are summarized.

Issues associated with military radios operating in close proximity to additional interferers: 
Multiple transmitters coupled to antennas in close proximity create a condition called reverse intermodulation, characterized by the coupling of energy from one transmitter into the antenna of another, creating a simultaneous flow of reverse and forward energy. Coupled energy mixes in the nonlinearities in the output network of the transmitter to create an infinite number of intermodulation products. The products are then re-propagated to the collocated receivers, creating products of sufficient level to preclude reception at those frequencies. Thus, a cosite transmitter’s output carrier signal can significantly degrade the performance of the receiver.

How Tunable Filters are utilized in cosite interference applications: 
The use of a receive filter or filter/LNA cascade such as that introduced in the transmit chain can create “preselection” of the energy from the receive antenna and reduce the relative level of the cosite interferer to the desired signal. Under this condition, the debilitating effect of cosite interference is mitigated by the selectivity of the preselector

As in the transmit environment, nonlinear effects in the receive chain can be the source of additional cosite interference. The preselection filter serves to minimize the level of the interfering signals prior to the receive nonlinearity, thereby minimizing any resulting products created within the receiver. Pole/Zero designs and tests the filters and LNAs that comprise the cascade filter to ensure that acceptable levels of distortion occur under these conditions.

Greater isolation can effectively be achieved through the use of selective filtering at the transmitter to minimize broadband noise. Selective filtering is applied following the primary noise sources in the transmit signal chain, having the overall effect of lowering the broadband noise without necessitating an increase in antenna isolation.

For greater selectivity, multiple filters can be placed in cascade with low noise amplifiers (LNAs) for inter-filter isolation and filter loss recovery purposes, followed by a power amplifier designed for efficient operation and low noise output. Further reductions in broadband noise and improved immunity to reverse intermodulation distortion can be achieved with the addition of a high power tunable filter at the output of the PA.

Recent MPG-Pole/Zero tunable filter advances: 
MPG-Pole/Zero’s recent tunable filter advances for cosite interference mitigation solutions include:
• Highly integrated filter products with significant SWaP reduction, compared to legacy filters, that maintain 5W in-band power over the entire military tactical radio tuning range in single- and dual-channel configurations;
• Miniature SMT bandpass filter options from 30 MHz to 3GHz;
• Narrowband and wideband interference cancelers, some of which do not require an interferer reference, thereby enabling cancellation of off-platform interferers;
• Deep notch filters to create communications channels in wideband, high power signals;
• Miniature, light-weight filter and power amplifier cascades for cosite interference issues inherent in UAV retransmission applications.

Reprinted with permission from CRUSER NEWS. All opinions expressed are those of the respective author or authors and do not represent the official policy or positions of the Naval Postgraduate School, the United States Navy, or any other government entity. The inclusion of these links does not represent an endorsement of the organization, service, or product.

Monday, February 22, 2016

Joint Unmanned Aerial Vehicle (UAV) Swarming Integration Testing

by F. Patrick Filbert, Subject Matter Analyst-UAS, frederic.filbert.ctr(at)

As technology improves, so does the capacity to expand a defensive perimeter to ever increasing ranges both horizontally and vertically. Identifying ways to penetrate this perimeter with assets and capabilities that do not require ever more expensive solutions requires creative use of current and emerging technological advances. Potential adversaries understand the United States (U.S.) is extremely technologically advanced with its warfighting systems. This requires a thinking enemy to develop ways to keep America’s advanced systems outside their sphere of influence; specifically, to both deny and create an inability to gain access to specific areas of operation. In the current vernacular, this is called creating an anti-access/area denial (A2/AD) environment which has, as its backbone, advanced integrated air defense systems (IADS).

A Bit of History 
Being able to provide a “layered” offensive capability with manned kinetic/non-kinetic payload armed aircraft has been done for some time. One example is how a joint Army-Air Force helicopter team (Task Force Normandy: comprised of U.S. Air Force (AF) MH-53J/PAVE LOW III and Army AH-64/APACHE attack helicopters) blinded Iraqi IADS early warning radars with non-kinetic electronic attack (PAVE LOW IIIs) and destroyed the radars (APACHES) with kinetic weapon's strikes (i.e., HELLFIRE missile, HYDRA rocket, and 25mm cannon fire) in the opening minutes of Operation Desert Storm to allow follow-on USAF strike aircraft access through coverage “holes” in Iraqi IADS to attack key targets further into Iraq.1 Similarly, future use of an advanced wave of unmanned aircraft systems (UAS) equipped with electronic warfare (EW) payloads leading a subsequent wave of attacking aircraft from carrier strike groups is one potential way to enter and counter a potential adversary’s A2/AD environment.

Notional Air Defense Network
However, while emerging EW payload testing on UAS is occurring, mating electronic attack (EA) payloads onto a coordinated semi- or fully-autonomous swarm of smaller unmanned aircraft (UA) is still an emergent test environment effort. However, once such capabilities mature, being able to employ them requires that a foundational concept be in place. The Joint Unmanned Aerial Vehicle (UAV) Swarming Integration (JUSI) Quick Reaction Test (QRT) was directed on February 27, 2015 by the Deputy Director, Air Warfare under the authority of the Office of the Secretary of Defense, Director, Operational Test and Evaluation to address such a foundational approach.

The JUSI QRT was established under the Director of Operational Test and Evaluation’s Joint Test and Evaluation Program on July 29, 2015. It is colocated with U.S. Pacific Command’s (USPACOM) J8 Resources and Assessment Directorate, Camp H.M. Smith, Oahu, Hawaii. The JUSI QRT reports to the AF Joint Test Program Office (AFJO), Nellis Air Force Base, Nevada and receives support from USPACOM J81 (Joint Innovation and Experimentation Division). The JUSI QRT will develop, test, and validate a concept of employment (CONEMP) for the integration and synchronization of swarming UA performing EA in support of the joint force against an advanced IADS. The JUSI QRT effort is focused on a 2015-2020 timeframe to research and identify previous and ongoing swarm related efforts while building a swarming UA community of interest, concurrent with CONEMP development.

Advanced Integrated Air Defenses and How to Address Them – The Problem 
Modern surface-to-air missile (SAM) systems are an integral part of advanced IADS. These IADS are, in turn, integral parts of a potential adversary’s networked A2/AD environment. For the purpose of the JUSI QRT effort, IADS refers to a networked system of adversary capabilities (e.g., a series of detection and tracking radars coupled with SAMs) and not specific to one platform (i.e., an IADS on a warship by itself or a specific individual SAM such as an SA-20).

Notional Integrated Air Defense System 
The joint forces do not currently have adequate ways to fully plan, integrate, or synchronize the effects delivered by UA swarms. This requires development and testing of a foundational CONEMP offering an effective planning methodology for delivering integrated effects of UA swarms against advanced IADS protecting targets with threat SAM arrays.

The joint force is currently over-reliant on standoff weapons (SOW) and 4th/5th generation strike platforms to address the A2/AD challenge. UA swarms represent a potential additional approach, complementing existing platforms and weapons systems. Despite rapid technical advances in UA swarming development and demonstrations, the joint force lacks a CONEMP for operations requiring UA swarm-delivered effects. The lack of a CONEMP or other supporting documentation hinders requirements development, A2/ AD countering, and precludes integration and synchronization with the rest of the joint force.The joint force is currently over-reliant on standoff weapons (SOW) and 4th/5th generation strike platforms to address the A2/AD challenge. UA swarms represent a potential additional approach, complementing existing platforms and weapons systems. Despite rapid technical advances in UA swarming development and demonstrations, the joint force lacks a CONEMP for operations requiring UA swarm-delivered effects. The lack of a CONEMP or other supporting documentation hinders requirements development, A2/ AD countering, and precludes integration and synchronization with the rest of the joint force.

The Approach – Addressing the Problem 
Combat capable and survivable UA with the capability to perform swarming functions are a new but quickly growing aspect of modern warfare. The JUSI QRT will take the first step to characterize, develop, and evaluate a CONEMP for using multiple UA of various sizes to deliver coordinated EA to enable other weapons and platforms (i.e., various types of SOWs, decoys, jammers, and 4th/5th generation platforms) access to counter A2/AD approaches. With the short lifespan of the JUSI QRT—one year—the effort will focus on CONEMP development supported by a series of modeling and simulation (M&S) runs over the course of three test events. Integrated support by Johns Hopkins University’s Applied Physics Laboratory’s (JHU/APL) experienced M&S personnel during each of the test events will enable the QRT to gain data collection for the equivalent of hundreds of swarm flights; thus providing a cost saving aspect concurrent with data analysis to support CONEMP development. JHU/APL will provide M&S and analysis of the execution of UA with EA payloads against scenarios developed to test the UA’s ability to deliver desired effects against an advanced IADS as part of an A2/AD environment.

The resulting qualitative and empirical data, once analyzed, will enable the JUSI QRT Team to assess findings, conclusions, and recommendations to revise the CONEMP between each test event with JUSI QRT’s first test event, which wrapped up on November 20, 2015. Additionally, upon completion of each test event, a Joint Warfighter Advisory Group (JWAG) will be convened to receive test event results—the first JUSI QRT JWAG occurred on December 9, 2015. As the QRT process continues, it will lead to development of a finalized swarming UA CONEMP to provide the link to requirements development and capability integration for the joint force to have a distributed approach to complement existing solutions which focus on 4th/5th generation strike platforms and SOW.

The Way Ahead 
At the end of the JUSI QRT, the resulting CONEMP will provide an effective operational context to inform requirements development, roadmaps and, eventually, tactics, techniques, and procedures (TTP) in several areas, including communication, automation, UA, and EA to deliver intended effects. The CONEMP will also serve to help focus future Department of Defense and industry investment. Future considerations related to swarming UA with EA payloads may include development, testing, and validation of TTP for UA with EA payloads. Such TTP would further reinforce the use of swarming UA by empowering the commander to develop standards in the areas of man- ning, equipping, training, and planning in the joint force. In the interim, the JUSI QRT developed CONEMP will provide planners, trainers, and their supporters with a start point for employment of this capability.

JUSI QRT website:

The author would like to thank Lt Col Matthew “Bulldog” Nicholson, Andrew “Wooly” Wolcott, Don Murvin, Brendan “K-PED” Pederson, and Brock Schmalzel for their guidance and feedback during the writing of this article. 
1 Martin, Jerome V. Lt Col, USAF, “Victory from Above: Air Power Theory and the Conduct of Operations Desert Shield and Desert Storm,” Air University Press, Maxwell Air Force Base, AL, June 1994. 
2 “New Delhi could have anti-missile shield by 2014,”, August 29, 2011, http://defencenewsofindia.blogspot. com/2011/08/new-delhi-could-have-anti-missile.html#!/2011/08/new-delhicould-have-anti-missile.html, accessed October 8, 2015.

Reprinted with permission from CRUSER NEWS. All opinions expressed are those of the respective author or authors and do not represent the official policy or positions of the Naval Postgraduate School, the United States Navy, or any other government entity. The inclusion of these links does not represent an endorsement of the organization, service, or product.

Saturday, January 16, 2016

Flying Miniature Quad-Rotor Unmanned Aerial Systems over the Arctic Ocean

by Peter Guest, NPS Faculty, pguest(at)

This article describes meteorological measurements over the Arctic Ocean using a Miniature Quad-Rotor Unmanned Aerial System (MQRUAS). With support from the CRUSER program, the author and students have been testing the concept of using MQRUASs as platforms for measurements of temperature, humidity and pressure in the lower atmosphere using a radiosonde as a sensor. The author performed a series of tests at Camp Roberts that involved flying the InstantEye MQRUAS alongside a calibrated meteorological tower to test the accuracy of the measurements. These tests determined that such measurements were of sufficient accuracy and reliability to be used for scientific and operational studies of atmospheric structure near the surface.
Figure 1: InstantEye taking off from the fantail of the R/V Sikuliaq
An Office of Naval Research directed research initiative entitled “Sea State and Boundary Layers in the Emerging Arctic Ocean” (abbreviated as “Sea State”) provided the first opportunity for the author to use the MQRUAS to address scientific (rather than just feasibility) issues. The overall goal of the Sea State project was to understand the physics of the interaction between the atmosphere, the ocean and sea ice in the Arctic Ocean. Before about 10 years ago, the Arctic had been mostly ice-covered all year and therefore few surface waves were present. But recently, ice cover has dramatically decreased and as a result waves now exist where they did not previously and this is having significant effects on various physical processes such as ice formation, ocean mixing and shore erosion in the Arctic Ocean. The primary platform for this project was the R/V Sikuliaq, a newly-commissioned icebreaker operated by the University of Alaska, Fairbanks. The specific goals of the author in the Sea State project during the 1 October to 10 November 10, 2015 cruise was to quantify the role of the atmosphere in generating waves, creating and destroying ice and transferring heat, moisture and momentum to the surface. This was accomplished, in collaboration with other meteorologists, with a suite of measurements which included the MQRUAS/radiosonde system.
Figure 2: The author flying the InstantEye over a large ice flow in the Arctic Ocean

The MQRUAS meteorological measurements were the first of their kind in any polar region, to our knowledge. Also this was the first time the author has flown an MQRUAS from a vessel at sea and from sea ice floes. Flying in such an extreme and different environment presented several challenges. One challenge was to obtain the required interim flight clearance (IFC) for operation from vessels at sea and flying in international air space, neither of which had been performed by NPS researchers with any type of UAS. This was obtained just before the start of the Sea State cruise, not in time to perform any at sea testing before the Sea State cruise. Other challenges were operating (1) in cold conditions, (2) in potentially icing conditions and (3) where the magnetic field is nearly vertical due to proximity to the magnetic North Pole. The latter challenge was crucial because the navigation and control of the InstantEye depends on accurate compass readings.

There were three goals to the MQRUAS measurements:
  1. Testing the feasibility of such measurements in Arctic Ocean conditions 
  2. Quantifying the fine-scale atmospheric structure of the lower atmosphere 
  3. Quantifying the amount of heat and moisture coming from leads (openings in the ice pack).
The latter accomplished by comparing profiles of temperature and humidity upwind and downwind of a lead. The author performed flights from the deck of the Sikuliaq (Figure 1) and from ice floe surfaces (Figures 2 and 3). The flights involved horizontal transects over and on both sides of leads and also vertical profiles (up to 300 meters). A total of 18 MQRUAS 10 - 15 minute flights were performed. We choose to fly in periods with relatively light winds (less than 8 kts) and temperatures ranges from -3 C to -20 C (28 F to -3 F).
Figure 3: Close up of the InstantEye,
 with radiosonde instrument
 package attached underneath,
 over ice in the vicinity
 of a lead (seen in the background).

There were some operational issues encountered. During some of the flights over open water, ice crystals formed on the MQRUAS rotors. However, these did not appear to significantly affect performance and were easily cleaned off while changing batteries between flights. The cold conditions reduced the battery life from the usual 25-30 minutes to 12 - 15 minutes, at least as indicated by the control screen; we suspect the battery life was actually more than indicated. A more serious issue was compass performance. During three of the flights, the control screen indicated “Compass Error” and the MQRUAS became hard to control. In one case, when the MQRUAS was launched from the ship fantail, control became difficult and the author had to land on some thin ice alongside the ship. As the ship moved to recover the MQRUAS, it cracked the ice and the MQRUAS was pushed off into open water and sank before it could be rescued. (We had spares.) We believe the compass errors were a result of being so close to the magnetic North Pole, resulting in almost vertical magnetic force lines. Also the magnetic field generated by the ship may have caused distortions in the magnetic field.

Despite these issues, overall the experiment was a success. The meteorological data from the MQRUAS and fixed-wing UAS flights appeared to be accurate and we were able to quantify lead heat fluxes and also the fine scale-structure of the lower atmosphere and how it varies horizontally and temporally. These results are still being analyzed and will be published in a scientific journal article. Challenges remain, but the author believes that the MQRUAS shows great potential as a platform for scientific and operational meteorological measurements and he plans to continue testing the system in various marine environments including international waters off the coast of California in 2016 and in the seas surrounding Antarctica during a 2017 cruise.

Reprinted with permission from CRUSER News. All opinions expressed are those of the respective author or authors and do not represent the official policy or positions of the Naval Postgraduate School, the United States Navy, or any other government entity. The inclusion of these links does not represent an endorsement of the organization, service, or product.