On Aug. 2, 1943, U.S. motor torpedo boat PT 109 was on patrol off the Solomon Islands when it was struck amidships by the Japanese destroyer Amagiri, killing two U.S. crewmen and injuring two others. The PT was cut in half and sank, stranding 11 survivors, Lt. Junior Grade John F. Kennedy among them, on Plum Pudding Island for six days before they were rescued.

Thanks to recent advances in naval technology, this might not be a danger future sailors face.

Earlier this month, the U.S. Navy's Office of Naval Research revealed the results of an August demonstration of new "swarming" technology for small patrol boats. In it, 13 small, unmanned rigid-hulled inflatable boats, or RHIBs, were tasked with autonomously escorting a larger Navy warship as it transited a strait. In one exercise, the robo-boats were alerted to the presence of a potentially hostile vessel bearing down on their mother ship, and decided on their own to split their forces -- peeling off several boats to intercept the threat.

In actual practice, Chief of Naval Research Rear Adm. Matthew Klunder said, these boats might be armed with .50 caliber machine guns or directed energy weapons (such as Raytheon's (NYSE:RTN) "Silent Guardian" microwave beam weapon) to neutralize threats.

The Navy says its new device makes use of technology originally used by NASA on the Mars Rovers, crunching data gathered from sensors and radar to independently decide on a course of action. This suggests the Navy's tech could be even more advanced than that used by the Army to control iRobot (NASDAQ:IRBT) PackBot or QinetiQ Talon bomb disposal robots, or by the Air Force to control its Predator drones. With it, the Navy has shown that it, too, can remotely operate robots to perform missions that might be too dangerous for manned vessels.

Perhaps as important, it can do this on the cheap.

According to Navy officials, the device needed to turn a small manned patrol boat into a robotic killing machine, dubbed the Control Architecture for Robotic Agent Command and Sensing, or "CARACaS," costs only about $2,000. Needless to say, that's a far cry from the $3.5 billion price tag that defense contractors General Dynamics (NYSE:GD) and Huntington Ingalls (NYSE:HII) charge for a Zumwalt-class destroyer -- though admittedly we're only talking about the cost of the "brains" of the vessel, and a RHIB boat is far less capable than a Zumwalt.

But here's where the CARACaS program gets really interesting, and where the business models of traditional defense contractors such as General Dynamics and Huntington Ingalls begin to look vulnerable: We might be able to build an entire fleet of these robo-warriors for the cost of just one Zumwalt.

Robot warrior for hire: Will work cheap

Just this past summer -- around the time the Navy was putting CARACaS through its paces -- we heard word of a new military superboat designed by privately held Juliet Marine Systems. Dubbed the "Ghost," Juliet Marine's new high-speed patrol boat looks nothing like any naval warship you've ever seen. (It actually looks more like a stealth fighter jet on pontoons).

These pontoons, which contain one gas turbine engine each, are the only part of Ghost that actually touch the water. Separated from the 38-foot-long hull by 12-foot-long struts, they cut through water as Ghost races across the ocean, permitting the 38-foot-long hull to float above the waves, impervious to choppy seas that might upset a smaller, traditionally built boat.

And Ghost races fast. Juliet believes the vessel could reach speeds of up to 50 knots, outrunning even America's fleet of nuclear-powered aircraft carriers. According to news reports, the vessel moves this fast by using the principle of supercavitation to create an air bubble around each of its pontoon-engines. Within this bubble, friction is reduced, enabling the vessel to essentially "fly" through the medium.

Juliet founder and CEO Gregory Sancoff described Ghost as an "attack helicopter of the sea" and a perfect vessel for fending off attacks by swarming speedboats. Its angular-plane construction makes the vessel radar "stealthy" as well. And because it's much bigger than a standard 28-foot RHIB, it's a much more formidable, long-endurance adversary.

Reportedly, the vessel can carry enough fuel to remain in operation for up to 30 days. Ghost can also carry as many as 90 Nemesis surface-to-surface missiles, enough firepower to ensure the vessel greatly outguns its opponents (and outranges them as well. Lockheed Martin's (NYSE:LMT) Nemesis missile is said to have an effective range of more than seven miles).

Best of all, Juliet says the first prototype of Ghost cost just $5 million to build, and that it can deliver the Navy fully battle-ready versions of the boat for as little as $10 million per copy.

At that price, the Navy could literally build itself a 350-"ship" fleet... for the cost of just one Zumwalt.

Should defense investors be afraid of robotic Ghosts?

The good news for investors in defense contractors such as General Dynamics and Huntington Ingalls is that, to date, the U.S. Navy has shown zero interest in buying Ghost, sticking instead with more traditional ship designs. Indeed, some reports indicate Klunder's Office of Naval Research has in the past actively opposed the vessel's development, ordering Juliet to refrain from even discussing its design with investors.

ONR's development of the CARACaS technology, however, suggests the Navy could be coming around to Juliet's way of thinking -- that the Navy might now agree that a fleet of cheap, fast, stealthy, and armed-to-the-teeth patrol boats is something worth building. As Klunder himself has asserted, such robotic boats are "the future" of the Navy.

And Ghost just might be the boat that helps carry the Navy into that future.