Friday, February 13, 2015

Surf Zone Robotic Platform


Editor's note: Reprinted with permission from the Naval Postgraduate School's CRUSER News.
By Frederick E. Gaghan, Director of Program Development, Applied Research Associates 
Inc. 

The near-shore environment is one of the most dynamic and technically challenging for both man and machine. Significant research efforts have been conducted to investigate sea-floor crawling robots, but they usually involve “water-proofing” a standard ground robot and attempting to operate it underwater. These designs often experience difficulties in maintaining positional accuracy or operability due to the water flow and wave action.

Over the course of several months, ARA studied two key engineering concepts for the Strategic Environmental Research and Development Program (SERDP) that directly affect the ability of a
robotic system to operate in the surf-zone (SZ); 1) platform hull shape and, 2) propulsion.

To address platform shape a study was completed of a horseshoe crab’s carapace as a biomimetic representation for the hull shape of a robotic system (Figure 1). It was hypothesized that a hull shape based on a horseshoe crab would provide the appropriate balance between lift and drag, and allow hydrodynamic forces in the Very Shallow Water (VSW)/SZ to assist in the ability to station keep and maneuver without the need for excessive weight or a complex propulsion system to achieve platform stability and traction. The study focused on answering the following questions:

• Can a biomimetic hull design provide better stability in the dynamic wave conditions found in the VSW/SZ?
• Is the required scale of this hull design sufficient for carrying a usable payload and other system components?
• What are the maximum flow vectors for which the biomimetic hull can remain effective?
• What are the resultant forces from those maximum flow vectors?
Shape
Figure 1 (baseline model)                    Figure 2 (Archimedes Screw)
Several biomimetic hulls were modeled and underwent simulated and empirical testing in a water channel. The empirical testing was used to validate the data obtained from the Computational
Fluid Dynamics simulations used to identify a more effective hull shape.

To address locomotive factors a separate study was completed using an Archimedes screw drive as the mode of propulsion to assess platform traction and mobility (Figure 2). An Archimedes screw was chosen because of its ability to operate in various mediums with varying flow rates. It was hypothesized that an Archimedes screw with optimal geometry could provide the tractive force to propel a robotic system. Archimedes screw drives have been successfully used on larger underwater robots, such as those found in the deep sea mining industry, but it has not been widely applied to a robotic system in the near shore environment.


A test bed was designed to measure the speed, forces, and displacements created by an Archimedes screw interacting with various mediums. Several drive designs with different barrel diameters, flange heights, and flange depths were empirically tested to record efficacies in a range of mediums, including water, sand, and pebbles to answer the following questions:
Image
Figure 3
• Can the Archimedes screw drive be scaled appropriately for a small to medium robotic system?
• What performance characteristics (speed, efficiency, tractive force) would this system provide?
• How will the system perform across a variety of medium?

Results of the two studies confirmed that is possible to design a biomimetic hull shape to improve stability and an optimized geometry for an Archimedes screw that would provide good tractive force on the aquatic floor in the dynamic wave conditions found in the VSW/SZ (Figure 3).

Wednesday, February 11, 2015

Using Unmanned Systems For Anti-Piracy

Second Prize Winner, 2015 CIMSEC High School Essay Contest (reprinted with the permission of CIMSEC).
The issue I would like to address in this essay is piracy. Piracy has been a threat to the safety of the seas since the seas were first used for transport and it has been a danger ever since. From the Barbary Corsairs to the privateers of the Caribbean, pirates have found ways to succeed or even thrive no matter the situation. For years pirate skiffs from Somalia have been attacking marine traffic to hold the ships and/or their crews for ransom. These brazen attacks have drawn the attention of the media and even, in the case of the Maersk Alabama, Hollywood. Of course any security issue that comes to the attention of the general public has first passed through the halls of numerous defense ministries across the globe so it should come as no surprise that before, during, and after these events, efforts were made by various navies including the US Navy and a coalition task force from the European Union to combat this growing problem. In this essay I would like to address what they have done and how it could be done better and in a more sustainable manner.
The primaryMQ-4C Triton BAMS UAS approach was taken thus far is to use large surface combatants such as frigates and destroyers as escorts for merchant ships as well as touring African nations and training their respective navies in counter-piracy operations. These measures, when combined with better safety measures taken by commercial vessels, have been extremely effective since 2012 and attacks off Somalia have become almost vanishingly rare at this point in time.1 This being said, these measures are fairly expensive both in money and in combat forces and while the threat off the Horn of Africa has been put into remission temporarily, the underlying issues that lead to the growth of piracy in the region remain.2 Thus if the governments responsible for this crackdown on piracy wish to continue to suppress piracy without devoting significant monetary resources and a handful of large surface combatants to the region a change in strategy is required.
Currently the platforms responsible for this mission are surface combatants and Maritime Patrol and Reconnaissance Aircraft or MPRAs. These platforms belong to three multinational forces and four single state task forces are deployed in the region.3 This, in my opinion, is overkill. While the current system has worked, it is large and inefficient and when the political will runs out this bureaucratic nightmare will be one of the first things to go. Thus there is a need for immediate change.
First of all, the platforms now being used for security operations are not ideal for the job. The P-3s and other manned MPRAs used for wide area maritime surveillance in the area are high value assets in the navies of their respective countries and can be used for missions as diverse anti-submarine to search and rescue missions. In contrast, the MQ-4C Triton Unmanned Aerial System was designed without the anti-surface and anti-sub capabilities of most MPRAs and focused instead on long endurance patrol of large bodies of water. With an acquisition cost only 68% of the P-8A (the US Navy’s current MPRA)4 along with lower operational costs, the Triton is the clear choice for maritime patrol in low threat environments such as the coast of Somalia.
As for surface combatants, the frigates and destroyers currently allocated for these missions are large and often significantly over-armed for confrontations with pirates in small motorboats. An alternative would be smaller platforms, both manned and unmanned, which could provide sufficient armament and speed to effectively combat the threat while requiring significantly less time, money, and logistical support.
The manned platforms suited to this task that are available for use today are the Cyclone patrol ships, eight of which are currently forward based in the Persian Gulf, the Mk. VI Patrol Boat, and the Mk. V Special Operations craft. These craft could be used as a rapid response force, responding to threats at speeds of between 35 knots (the Cyclone) and 50 knots (the Mk V) with Intelligence, Surveillance, and Reconnaissance (or ISR) support from Triton UASs in the area. Of course these platforms unfortunately lack the persistence afforded by larger displacement surface combatants, which is where the Unmanned Surface Vehicle comes in. While the manned platforms listed above are an ideal and sufficient force to deal with crises such as the successful hijacking of a ship, they lack the ability to stay on station in the shipping lanes for long durations. Having these vessels in position to intercept any threats detected by airborne search radar is essential to prevent hijackings before they happen. The US Navy as well as a number of others have invested in the development of USVs primarily to protect large combatants from swarms of small, hostile boats armed with short range anti-ship missiles. Unfortunately the USVs currently in inventory are not armed but models in the near future will be.
With all these niches filled, a comprehensive anti-piracy strategy begins to emerge. First, a small, manned contingency response group, based in the gulf and rotated through ports in Yemen and other friendly nations will be constantly in the area to safeguard against crises. Second, the unmanned surface element will patrol threatened areas regularly to defend shipping against small-scale attacks and will be constantly on station, ready to intercept threats if and when directed to do so. Finally, the Triton element will provide a persistent “eye in the sky” for surface elements.
Piracy is an issue, both off the horn of Africa and around the world but as we have seen in the past few years it can be beaten. I believe that with a force such as the one described here, navies around the world could use the advantages of new technology to fight this age old threat.
Citations: 
1. US Office of Naval Intelligence, Piracy Analysis and Warning Weekly Report for 8-14 January 2015, pp. 2 Table 1, Available on-line:  http://www.oni.navy.mil/Intelligence_Community/piracy/pdf/20150114_PAWW.pdf 
2. Jon Gornall, Somali Piracy Threat Always on the Horizon, 16 December 2014, The National
4. US Government Accountability Office, Defense Acquisitions: Assessment of Selected Weapon Programs,  March 2013, pp. 109, 115, Available on-line: http://www.gao.gov/assets/660/653379.pdf 
 About the Author
Griffin Cannon is a senior at the Vermont Commons School in South Burlington, Vermont. His interests include spending time with his younger siblings, the outdoors, tennis, and skiing. He finds military and political issues fascinating and spends time every day keeping up to date on the defense world. As a graduating senior he plans on attending university at the Naval Academy or on a NROTC scholarship. Griffin hopes to pursue a career in either engineering or defense policy after serving in the Navy.