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By Norman Polmar, Author, The Ships and Aircraft of the U.S. Fleet
Robot Submarines
The War in the Persian Gulf demonstrated for U.S. forces the efficacy of remotely piloted vehicles (RPVs), or unmanned aerial vehicles (UAVs), as they are officially called. The U.S. Navy is now seriously exploring the potential role of unmanned underwater vehicles (UUVs).
In the underwater environment, unmanned craft—either tethered or autonomous underwater vehicles (AUVs)— would undertake several missions, some considered too dangerous to risk manned submarines. The missions being considered for UUVs include:
Submarine warfare: A variety of UUV configurations could support friendly submarine operations. They could serve as decoys to draw out hostile submarines, operate a sustained remote communication relay (as a link for radio or, in the future, lasers), act as an off-board platform for acoustic or wake sensors, perform area search and reconnaissance to expand a submarine’s “search horizon,” lay mines, and conduct specific intelligence collection (i.e., offshore of an enemy port or in a transit area).
Off-board acoustic sensors—i.e., AUV-carried active and passive systems— would permit submarines to use bistatic and multistatic low-frequency detection techniques. Surface ships that tow active low-frequency sonars currently use these techniques.
Antisubmarine warfare: In addition to the above operations, an ASW-config- ured AUV would perform barrier surveillance. It could tow an array through an area and automatically transmit detections to another platform (ship, submarine, or satellite). Future technology might enable an AUV to pick up and trail an enemy submarine as it leaves port or transits through a barrier line.
Ocean surveillance: In the ocean surveillance role, AUVs could be programmed to patrol wide ocean areas with passive sensors. Or they could be an active sound source with fixed underwater sound surveillance systems (SOSUS), or surface surveillance towed array sensor systems (SURTASS) monitoring reflections of their acoustic pulses.
Mine warfare: An autonomous mine countermeasure (MCM) vehicle could transit enemy minefields to map them for future reference or to guide a friendly submarine or surface ship through them. Active sonar would be used to detect the
Unmanned underwater vehicles may undertake future missions too risky for manned submarines.
mines, while a bottom-matching sonar coupled with an inertial navigation system would provide precise information on the UUV’s position.
The vehicle would maintain a minefield picture that could be transmitted back to friendly units through an acoustic datalink or a fiber-optic cable, or returned with the vehicle to a recovery ship, submarine, or even aircraft. The MCM vehicle could also provide “route maintenance,” periodically transiting a friendly minefield to ensure that an enemy submarine had not penetrated the field to plant mines on the safe routes used by friendly submarines.
And, as noted previously, mines could be laid by an AUV. This would be an extension of the existing Mk-67 submarine-launched mobile mine (SLMM) that can be launched from a standard 21-inch submarine torpedo tube and is capable of traveling several miles through the water on a preset course before reaching its target and becoming active.
Special warfare: In this role, the AUV could perform friendly harbor patrol/ defense, beach reconnaissance prior to a clandestine operation, and intelligence collection.
Non-combat operations: These AUV activities are primarily search and recovery of foreign or friendly objects dropped on the ocean floor. These could include satellites and weapons.
A number of unmanned underwater vehicles are already in foreign and U.S- naval use. Since the 1960s, the U.S. Navy has used cable-controlled torpedo recovery devices, the Mk-30 submarine target, the Mk-71 MOSS (mobile submarine simulator) decoy used by ballistic missile submarines, and tethered mine countermeasure vehicles. Classified deep-ocean search and recovery devices have also explored Soviet objects lost on the ocean floor. (Numerous commercial UUV-type vehicles are also in service, with most referred to as ROV for remote operating vehicles. These are used mostly for exploration and support of offshore oilfields. As an indication of the state-of- the-art, some of the commercial vehicles can operate to almost 10,000 feet and have a 350-hour mission duration at five or six knots.)
The new family of UUVs will expand the operational envelope of underwater drones. The Navy and Defense Advanced Research Projects Agency (DARPA) initiated a joint advanced-technology UUV program in 1986 that resulted in two prototypes for test bed/mission hardware demonstrations. One vehicle took the first mission “package”—a tactical acoustic decoy system developed by Martin Marietta—to sea in 1990 and has since been transferred to the Navy for testing. According to a Navy spokesman, increased submarine survivability will be ihe initial payoff, but it would also pave the way for UUV applications to a number of classified submarine scenarios. The second DARPA vehicle, also completed in 1990, has a Lockheed-developed mine-search system package. A third mission package for ocean surveillance is also being developed under darpa contract.
Several Navy laboratories are also Working in the UUV field. While most will not discuss their efforts, a notional vehicle for long-duration ocean surveillance is being designed by the David Taylor Research Center (DTRC) in Carder- °ek, Maryland. This vehicle would be much larger than the torpedo-like DARPA devices—68 feet long with a tail r'ng some ten feet in diameter that would stream a multiline passive acoustic array. Under the DTRC concept, the AUV Would operate in the deep ocean, powered by a hydrogen liquid-fuel cell power Plant that could provide a mission duration of several weeks. When a contact is teade and evaluated as a possible hostile tetruder, an expendable communications buoy would be launched, pop up to the surface, and broadcast the data or serve as a datalink.
The key to success in all the testing will be component or “enabling” technologies: navigation, composite hull materials, guidance, energy source, propulsion, communication links, and signal processing as well the specific mission packages. Advanced autonomous underwater vehicles will require enhanced sensor and decision-making capability. While these are within the scope of nearterm technologies, they could be very expensive.
The operating Navy, however, is cautious about moving toward UUVs. While most vehicles are considered to enhance submarine operations, the submarine may be the most difficult platform to support a UUV. Limited space, the problem of hull openings, the difficulty of maintenance on vehicles, and other factors contribute to the problem of submarines supporting UUVs. Even if they are sized for torpedo tubes—now 21-inch diameter and 30- inch diameter in the Seawolf (SSN-21) class—keeping UUVs on board submarines will displace torpedoes and missiles. A double-hull submarine configuration might better accommodate a UUV, but that design concept is an anathema to the Navy’s nuclear propulsion leadership. Further, underwater-to-underwater communications will be more difficult than communications from underwater to surface, air, or satellite platforms.
Surface ships and even aircraft (fixed- wing and helicopters) could also deploy and recover UUVs. A preliminary review of vehicle potential indicates that some UUVs, such as a DTRC-type area surveillance vehicle, would best be supported by surface ships. But for many UUV missions, the submarine is the ideal launch/support platform.
With the massive budget reductions, there is little enthusiasm among the Navy’s “platform sponsors” to invest money in developing operational UUVs and support gear. However, the fleet is being reduced—to some 450 ships, according to current plans; that number probably will be smaller, possibly as few as 400 ships in the next decade. There will be too few ships—and especially submarines—for the missions in 2000 and beyond. The risk is high in using manned platforms for the many missions that face threats from enemy submarines, mines, and other weapon systems that are now being proliferated. Therefore, the Navy should provide support for UUVs as well as other unmanned systems.
The U.S. Naval Institute and Kodak Present
the 30th Annual Naval & Maritime
■PHOTO CONTEST
The U.S. Naval Institute and Eastman Kodak Company ate proud to cosponsor the 30th Annual Naval & Maritime Photo Contest.
The contest is open to both amateur and professional photographers. The winning photographs will be published in a 1992 issue of Proceedings, the monthly magazine of the Naval Institute. Cash prizes will be awarded as follows: 1st Prize $500
2nd Prize $350
3rd Prize $250
Honorable Mention (15) $100 each
ENTRY RULES:
1 ■ Each photograph must pertain to a naval or maritime subject. (The photo is not limited to the calendar year of the contest.)
- Limit. 5 entries per person.
- Entries must be either black-and-white prints, color prints, or color transparencies.
- Minimum print size is 5" x 7".
- Minimum transparency size is 35 mm. (No glass- mounted transparencies, please.)
- Full captions and the photographer’s name, address, and social security number must be
printed or typed on a separate sheet of paper and attached to the back of each print or printed on the transparency mount. (Do not write directly on the back of a print. No staples, please.)
- Entries may not have been previously published, and winners may not be published prior to publication in Proceedings. Prior publication could result in the relinquishment of the prize awarded.
- Entries must arrive at the U.S. Naval Institute no later than 31 December 1991-
Only photographs accompanied by self- addressed, stamped envelopes will be returned. Photographs not awarded prizes may possibly be purchased by the Naval Institute.
DEADLINE: 31 DECEMBER 1991
Write for details or mail entries to:
NAVAL it MARITIME PHOTO CONTEST U.S. Naval Institute Annapolis. Ml) 21402 (301) 268-6110
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