Saturday, January 16, 2016

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

by Peter Guest, NPS Faculty, pguest(at)nps.edu

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.

Thursday, January 7, 2016

Write for Naval Drones

Do you enjoy writing? Are you interested in discussing the latest in unmanned systems and how they will impact future naval warfare? Great, because we're looking for guest contributors.  The range of topics we will publish here is broad, from systems and technology, to operational concepts, to the cultural changes that will be required to integrate drones into maritime warfare.

Please send your submissions to info@navaldrones.com for consideration.  Short form blog posts (500-800 words) or longer articles are acceptable.  International contributors are welcome.  Get your ideas in front of our large and growing global audience of industry and naval professionals.

Tuesday, December 29, 2015

Naval Drones - What to Expect in 2016

Looking Back at 2015 
Our highly unscientific Twitter poll below shows what some readers thought were the most significant events in unmanned naval systems for 2015.
For details on these stories, see: X-47B RefuelingRussian Kanyon Nuclear UUVUCLASS RFP

X-47B takes on fuel
And Forward to 2016

What follows are our expectations, hunches, and just wild guesses of the major developments to watch for in naval unmanned systems industry during the coming year.

Sanity Prevails - After spending nearly a billion dollars and more than two decades developing the troubled Remote Minehunting System, the U.S. Navy will cancel the program.  Lockheed's RMS, which was intended to be one of the Littoral Combat Ship's key mission packages, will be replaced by one or more of the growing number of versatile, less expensive mine-countermeasure UUVs.

Also, the Navy will finally make a decision to move forward with two different types of UCLASS aircraft - one optimized for deep penetrating strike, and the other for intelligence, surveillance, and reconnaissance.

Autonomy Tests - The Office of Naval Research’s Large Displacement Unmanned Underwater Vehicle Innovative Naval Prototype (LDUUV INP) will demonstrate navigation algorithms and sense-and-avoid technologies as it cruises from San Francisco to San Diego. Additionally, DARPA's Sea Hunter unmanned anti-submarine warfare surface vessel prototype will put to sea for the first time.
Sea Hunter ACTUV concept - DARPA Image
More Swarming Demonstrations - The development of low-cost, swarming air, surface, and sub-surface vehicles for naval warfare will continue to advance.  The LOCUST UAV system should be demonstrated at sea next year.

Armed Naval Drones - Land-based UAVs, such as the MQ-1 Predator, have routinely fired weapons in combat since at least 2001. However, no armed UAVs have put to sea since the QH-50 DASH of the 1950s and 1960s carried torpedoes.  This will change in next year, when the MQ-8C Fire Scout starts testing the Advanced Precision Kill Weapon System.

Industry consolidation - Large defense integrators will improve their unmanned systems portfolios by acquiring smaller upstart drone manufacturers.  We saw this earlier in 2015, when Huntington Ingalls purchased Columbia Group's UUV division.

More Hybrid Vehicles - Unmanned systems that operate in more than one domain (air, surface, or sub-surface) will continue to be an interest in 2016 to naval and industry researchers.  Examples such as the Naviator, Aqua-Quad, and Flimmer have begun to demonstrate the advantages of vehicles that can both swim and fly.  However, it will likely be years before these types of vehicles are developed into practical operational systems.

Tuesday, December 15, 2015

Development and Testing of the Aqua-Quad

by Dr Kevin Jones, NPS Faculty, kdjones<at>nps.edu 

Under CRUSER funding, a new energy-independent, ultra-long endurance, hybrid-mobility unmanned system has been under development called the Aqua-Quad. It is a concept platform that combines an ocean drifter with a quad-rotor air vehicle, and is intended to be a “launch and forget” asset, typically deployed in small groups or flocks that work as a team to more efficiently meet mission goals. While there are many mission sets where the Aqua-Quad might be advantageous, one in particular, underwater tracking with passive acoustic sensors, was previously addressed in simulation by LT Dillard (MAE, 2014). This has led to current work by LT Cason (USW, 2015), also with contributions by LT Fauci (SE, 2015).
Flyable prototype with lower shell removed and feet attached 
(image courtesy of CRUSER)

As seen in the figure, a 20-cell photovoltaic (PV) array is distributed around the four propeller disks. These monocrystalline Silicon Sun- Power E60 cells are the only source of energy that the copter has, but are the means to achieve endurances of 3 months or more. In a single day in June in the Monterey Bay, the NREL solar irradiance calculator, PVWatts, would suggest a total daily energy budget of about 0.5 kWh collected by the PV array, and this energy needs to be divided up amongst avionics, sensors, and propulsion for flight. This available daily energy budget will change depending on latitude, weather and other factors, but is representative of the energy available in a 24 hour period for all operational needs of the Aqua-Quad.

One of the most challenging aspects of the program has been identifying materials and manufacturing techniques to construct a device which is water-tight and tough enough to survive at sea, but still light enough to efficiently fly. The prototype weighs a little over 3 kg, including the water-tight enclosure and PV array, and is lifted by four water-tolerant motors spinning 360 mm diameter carbon fiber propellers. The outer ring is just over 1 m in diameter. Flight tests of a stripped down version of the prototype, with most of the water-tight enclosure and the solar array removed, demonstrated stable flight with a required power of about 340 W at full weight, indicating a maximum flight time of about 25 minutes with fully charged batteries. Flights have also been performed with the solar array support structure installed, as there were concerns regarding aerodynamic influences and possibly structural resonance – neither was a problem. The measured Figure of Merit (FOM) for the copter is pretty good, about 9 g/W, operating at roughly the same efficiency as a full size helicopter. The flying prototype with the PV array support structure installed is shown above.
Snapshots of the buoyance experiments in Monterey Bay. Upper left: John Joseph deploying the Aqua-Quad for the first time. Upper right: casually resting in calm waters. Lower left: just deployed in rougher seas. Lower right: riding down the back side of a 10 foot roller (images courtesy of CRUSER).
A test of the solar recharge sub-system was performed on the afternoon of October 18th, a fall day with mixed clouds. With the PV array aligned roughly normal to the Sunlight, a maximum power of about 63 W was measured, and with the array aligned horizontally, as it would be in use, an average power of about 35 W was recorded. PVWatts estimates values between about 30 and 45 W for that time of year and time of day, based on an archived year of data from NAF Monterey. During the test, a Genasun Maximum Power Point Tracker (MPPT) was utilized to optimize power output from the PV array and to charge the batteries. The stripped down MPPT weighed about 100g, and was relatively large, with a heavy inductor and several large electrolytic capacitors. The size and weight of the MPPT were known issues, as well as the limited lifespan of electrolytic capacitors. However, during the experiment, it was noted that the compass in the flight control system reported errors whenever the Sun was shining brightly. The running theory is that the inductor creates magnetic interference that is proportional to the current passing through the MPPT, which is proportional to the solar irradiance. The inductor is located just a few inches from the compass, and cannot easily be relocated due to the size of the Genasun MPPT. Fortunately, this last summer, LT Fauci was working with a MPPT from STMicroelectronicsfor the TaLEUAS project. It is a newer design with customizable output voltage (meaning that by swapping 4 resistors, we can tune it to act as a charge controller for the batteries). The STM board is actually purchased as a devboard, with 3 MPPT circuits either connected in series or parallel on a single board. We were able to cut the board into 3rds, obtaining 3 single-array MPPTs.  The weight of the STM board is under 25g, and the cost is about 1/10th of the Genasun. While not installed yet, the inductors on the STM board are much smaller, and there are no electrolytic capacitors, so we expect a longer life, and minimal compass interference. Due to its small size, the STM board can easily be relocated further from the compass.

On November 3rd, to gather data for LT Cason’s thesis, and with the support of John Joseph, Keith Wyckoff and Tarry Rago, we headed out onto Monterey Bay to perform float tests of the Aqua-Quad in various sea states. There was a small craft advisory posted for the day, with swells expected to reach 11-14 feet at 13 seconds, so a perfect day to make sure the design would stay afloat and keep the solar array above water while floating. We started about 100 m outside the harbor where the swell was around 3 to 4 feet, and everything looked good. As a backup, the Aqua-Quad was tied off to the buoy, and to represent actual fielded use, a dummy Acousonde sensor was hanging below the Aqua-Quad on a 10 m line. It provides a stabilizing effect, like a tail on a kite. After some sounding experiments in the harbor region, we recovered the equipment and moved out to rougher seas. At the second location swells were peaking at around 10 feet, and the Aqua-Quad still behaved perfectly.

Ongoing work on the Aqua-Quad includes obtaining an interim flight clearance to allow for autonomous outdoor flights with water launch and recovery tests, new developments on a self-righting capability in case the Aqua-Quad gets tumbled in rough seas, and collaborative behaviors to support realistic mission sets. There are a variety of interesting potential thesis topics, spanning from aerodynamic performance, to flight controls, to circuit design, to complete system optimization and operational applications. There may also be topics in USW, Cyber, and METOC where the AquaQuad might be of interest.



Reprinted with permission from the Naval Postgraduate School's CRUSER News.

Wednesday, November 18, 2015

Unmanned Maritime Systems Operations and Maintenance Lifecycle Costs

by Dr. Diana Angelis, NPS Faculty, diangeli(at) nps.edu 

The Navy currently has a number of Unmanned Maritime Systems (UMS) that perform a variety of missions including mine countermeasures, maritime security, hydrographic surveying, environmental analysis, special operations, and oceanographic research. While these unmanned systems were rapidly developed and fielded to meet immediate warfighter needs, some of the systems have not been subjected to the normal cost reviews associated with programs of record and in many cases the data required to develop rigorous cost models is limited or unavailable. As a result, the total ownership cost of unmanned maritime systems is not well defined, particularly the costs associated with operations and support.




Dr. Diana Angelis and Mr. Steve Koepenick from SPAWAR have been working on a CRUSER funded project to better understand UMS lifecycle costs with an emphasis on the operations and support costs associated with unmanned underwater vehicles (UUV). The first phase of the project brought together subject matter experts from various UMS programs in a warfare innovation workshop held at NPS in March 2015. The workshop participants identified several cost drivers of UUV O&S costs including fleet size, energy requirements, availability, security requirements (including cyber security), and training and retention.

Each of the major cost drivers was further decomposed into the system attributes that influence the magnitude of the cost driver. For example, energy is a function of:

Type of mission, which drives:
 • Area to be covered (which drives range)
 • Time constraints (which drives speed)

Type of energy source, which drives:
• Recharge requirements and # of recharge cycles
• Safety (certification)
• Storage and disposal
An influence diagram for energy costs is shown above. This will form the basis for further research into the factors that drive energy cost for UUVs.

The next steps are to collect data and build regression models that will quantify the relationships between the factors identified in the workshop and UUV O&S cost categories. When fully developed, these models can be used by program offices to forecast UUV O&S costs in support of analysis of alternatives and budgeting decisions.

Participating in the workshop were several NPS students, including four distance learning students in Systems Engineering. These students decided to use the findings of the workshop as a basis for further research in their capstone project. The capstone project will employ an array of systems engineering methodologies to investigate the specific UUV cost drivers associated with two unique mission types and explore the effect of mission requirements on O&S costs. The team has been working with PMS 408 and PMS 406 to develop point estimates and distributions for relevant O&S cost elements of the life cycle cost model. The project is expected to be completed in March 2016.

Reprinted with permission from the Naval Postgraduate School's CRUSER News.