The announcement called for technology so new it might exist only in the minds of inventors. Prospective contractors and analysts routinely compare the endeavor to the search for the Holy Grail.
In this case, the grail is an unmanned submarine smart enough to sense and avoid obstructions, powerful enough to stay out on months-long missions without detection, and cool enough to keep computers from overheating.
Those are among the challenges facing the companies and universities vying to provide ideas to the U.S. Navy about how to power and autonomously navigate a Large Displacement Unmanned Undersea Vehicle (LDUUV), a development project led by the U.S. Office of Naval Research (ONR).
Proposals were submitted to the office in late September, with winners informed Dec. 19, although they won't necessarily be publicly identified, ONR said. The Navy wants to gather up ideas and technologies from organizations that might not be equipped to build an entire vessel. A major company then could be hired to integrate the parts.
At the top of the list of challenges would be power and heat. Development of futuristic sensors and processing software will be moot if those issues cannot be managed. Complicating matters, the Navy has ruled out nuclear power because no human would be aboard to address an emergency.
"People might say, 'I've got the Holy Grail. I've got the engine and I've got the fuel,'" said Robert Nowak, an independent energy consultant who has run programs for ONR and the Defense Advanced Research Projects Agency. But that's only true if the heat that engine puts out from that fuel doesn't play havoc with the other systems onboard.
Once those issues are solved, "sensing and avoiding a fishing net are going to be the Holy Grail," said Jeff Smith, projects manager of Bluefin Robotics, which is working on autonomous control for unmanned submarines. "The number of dolphins and seals that get caught in nets is not insignificant. Let's face it: As smart as we are with unmanned vehicles, we're never going to come close to a dolphin or a seal when it comes to their situational awareness."
ONR's July announcement seeks ideas for enough energy for the craft to remain at sea for 70 days or longer in open-ocean transit with operations as deep as 800 feet. The craft will need the autonomy to conduct missions in littoral waters, amid local merchant shipping, fishing boats and nets. As a steppingstone, ONR has set a goal of power and autonomy for a 30-day mission, including operations at depths down to 400 feet.
These quests, particularly power generation and storage, have become the signature problems in building a prototype of what is envisioned as a 48-inch-diameter vehicle with a fiberglass hull to defeat sonar.
The Navy's Intelligence, Surveillance and Reconnaissance Roadmap calls for building an LDUUV by 2014 and having it on missions by 2017. It envisions a fleet of LDUUVs by the end of the decade. Job No. 1 will be proving the energy technologies required for such a vehicle. "The higher-ups in the Navy are emphasizing this and saying, 'If you can't develop the energy we need, we can't do the mission,'" said Nowak, who is not affiliated with the program.
The ISR Roadmap directs funding "UUV power and Endurance first," then "sensors, C3, networks and autonomy."
Chief among those higher-ups was now-retired Adm. Gary Roughead, who was chief of naval operations until September. Roughead laid out a vision of LDUUVs as submarine-force multipliers providing persistent ISR, a capability the Navy can't get from smaller unmanned subs that measure their mission capability in hours. "I cast the net widely in the continued pursuit of high-density underwater power," Roughead said at August's Association for Unmanned Vehicle Systems International conference in Washington. "That clearly is something that will be a game-changer for us."
As bait, he committed 50 percent of the Navy's research and development budget over the next five years to solving the energy problem for underwater vehicles, including LDUUV. The Navy is seeking $47 million for LDUUV work in the 2012 budget request.
The Navy is envisioning a different concept of operations for LDUUV compared with other robotic vehicles it has conceived of in the past, including the Long-term Mine Reconnaissance System and the Mission Reconfigurable UUV. The blueprint for those vehicles called for launching them from torpedo tubes and recovering them. The concept proved to be unworkable because, for example, the launch vehicles would have overcrowded torpedo rooms.
The Navy envisions the LDUUV leaving from a pier, doing its ISR work and returning, or perhaps being recovered by a surface ship away from the littorals. It sees a UUV that can loiter undetected long enough to map the sea bottom; track local submarine, merchant ship and fishing boat traffic; and detect mines, though a formal concept of operations has not yet been drafted.
With all of that in mind, the LDUUV will have an open software and hardware architecture to make it receptive to varying sensor suites to be replaced as missions change.
Smaller UUVs have done those missions for more than a decade, and the results have been subject to their range and payload capacity limitations. But the kind of endurance the Navy wants from the LDUUV requires the kind of energy that has remained elusive, and with cause, Nowak said. Conventional power systems, which in the case of other unmanned vehicles means batteries, need not apply. "You will find that there aren't any batteries that are capable of meeting the requirements the Navy is looking for," Nowak said.
But fuel-only probably isn't the answer either. The Navy has a contract with AlumiFuel Power to experiment with smaller undersea vehicles driven by hydrogen cylinders. But while hydrogen's energy potential is widely known, its storage under compression in thick-skinned cells would present weight and volume issues in the LDUUV. Other fuels are possible - much of industry and ONR were mum about their ideas while proposals were being evaluated - but Nowak posits that some combination of power is more likely.
The longevity issue can become complicated by problems accumulated along the way on a voyage. "Endurance is more than just putting out power," said Antoine Martin, president of Unmanned Vehicle Systems-Consulting, who recently completed a comprehensive study of power for robotic vehicles. "It's being able to manage the power you have, being able to play with the materials in the hull of the UUV so that it doesn't develop drag by accumulating particles at sea." Barnacles or algae growing on a slow-moving UUV could hamper its performance, as could saltwater corrosion, storm damage, ice and myriad other potential problems. "All of this is a long step from where we are today," Martin said.
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