UUVs will foster fundamental change in naval warfare

Sea Power, Jul 2003 by Patton, James H Jr

Swarms of Mini-Vehicles Could Disable Enemy Mines Using Chemicals or Heat

During the Afghanistan and Iraq conflicts, the cameras of the press often were focused on the successes of various unmanned aerial vehicles (UAVs)-most notably the Predator and the Global Hawk-that performed a number of intelligence, surveillance, and reconnaissance missions. The Predator also has been successfully employed as an unmanned attack aircraft. Not surprisingly, many have asked why there is not an analogous family of Unmanned Underwater Vehicles (UUVs) to achieve similar successes for U.S. forces underwater.

In fact, UUVs have been around about the same length of time. In World War II, the Germans employed both UUVs (in the form of homing torpedoes) and UAVs (as radio-controlled "glide bombs"). Somewhat later in the war, the Allies employed variants of each. In recent years, however, UAVs have truly "stolen a march" on UUVs, and now point the way toward the broad utilization of various types and sizes of unmanned vehicles in the underwater realm.

Given the technology already at hand, for example, it would not be difficult to create swarms of small mini-vehicles that could attach themselves to enemy mines, penetrate their casings by chemical or thermal means, and destroy them without tipping off the enemy that its mine field is being neutralized. For other missions, the U.S. Navy's Advanced SEAL Delivery System, a mini-submarine now in development as a transporter, could be adapted to perform a variety of urveillance and reconnaissance tasks.

Fundamental Change to Warfare

Many UUVs are in development, and their future use will bring fundamental change to underwater warfare. But any assessment of the future of UUVs must include an explanation of the vernacular. The acronym UUV implies a degree of autonomy or, at the least, some enhanced level of embedded "intelligence." As is true in the domain of unmanned aircraft, different UUVs are equipped with different systems that give them different capabilities. These include a subset of tethered craft, called remotely operated vehicles (ROVs), that receive power or send and receive information via their tethers. They comprise a large percentage of the UUVs now in operation or being considered for future development or production. A second subset, called autonomous underwater vehicles (AUVs), comprises craft that are indeed completely free of any direct physical control by human operators, ships, or airplanes.

Differences between the two subsets, or classes, of UUVs are not always clear. For example, a UUV such as the Mk48 ADCAP (Advanced Capability) torpedo can begin its brief underwater career as an ROV, receiving orders and sending back status reports via a thin wire or fiber optic link. When that link is broken or deliberately cut while the torpedo is en route to a target, it converts to an AUV, operating on stored or self-generated information. In this article, specific UUVs will be described either as ROVs or as AUVs, depending on whether they employ a physical tether.

If provided with a tether somewhat heavier than a wire or fiber optic data link, ROVs are freed from the significant engineering difficulties associated with the storage of large amounts of energy. They are capable of conducting some significantly heavy work on or near the ocean bottom or of functioning there effectively for extended periods of time. The civilian offshore oil industry has been the clear leader in the ROV field for decades, and remains a fertile source of commercial-off-the-shelf hardware and concepts for other applications. Few have not seen, for instance, the video footage of the Titanic or the Bismarck that was retrieved by commercial ROVs operated by Dr. Robert Ballard.

New roles and missions for submarines, coupled with technological advances that can be employed by ROVs, are creating fresh opportunities for improved intelligence and surveillance. Submarines, particularly the nuclear-powered ballistic-missile submarines (SSBNs), have long used ROV-like objects to provide assured (but very low data rate) reception of communications while on patrol. These buoy-like devices are sent to the surface and towed by the SSBNs, which remain in the depths. Today, the Navy is placing increased emphasis on the need for submarines to be more integrated with surface forces and, thus, able to take on a wider variety of roles and missions. This creates a need for better connectivity. Today's submarines have to both transmit and receive at high data rates while operating at high speeds and greater depths. For that reason, the Navy is investigating variants of the sub-mariners' "legacy" towed buoy. Meanwhile, electro-optical and radio-frequency sensors are enjoying dramatic reductions in size and cost as performance improves geometrically.

British Look at Tethered Buoy

It is reasonable to assume that any mast or antenna that penetrates the ocean surface for communications purposes would be able to perform an additional role-for example, provide the manned platform below with a substantial degree of situational awareness in support of its intelligence, reconnaissance, and surveillance mission. The British are interested in an ROV called the Retrievable Tethered Optical Fiber (RTOF) buoy, which provides periodic communications windows of several minutes when allowed to float freely until the available tether line is fully deployed, at which time it is retrieved.