The technology for seawater conversion is installed on a nuclear powered aircraft carrier. The submarines are included in a list of DARPA funded projects. The plan is for them to be mini-subs and unmanned. As for the practicality of any of this all I can say is DARPA funds some viable projects and others that utterly fail so it would not be a surprise if ideas conceived on a wish list turn out to be untenable.

“Seawater powered” naval vessels will have to be nuclear powered navel vessels. The large amount of energy required for the seawater “conversion” can only come from nuclear power, and the process would require large vessels to house and support the chemical plant. This boondoggle concept is less viable than Solendra.

Len says: “And robotic submarines that can attain speeds of up to 160 kilometers (100 miles) per hour.”

That sounds more like a “robotic” torpedo or naval mine than a submarine. Anything traveling 100 mph submerged must be expending energy at such a high rate that it must either be nuclear powered or very short-ranged. Seems unlikely any major power will build and operate unmanned nuclear-powered submarines. Supremacy at sea must depend on space-based assets, aircraft, missiles, and “smart” mines. Advanced SUBROCS and Harpoons are the most feasible solution to high-speed attack on warships by submarine. The Russians have invested heavily, and probably unwisely, into super cavitation high-speed torpedo technology, and many analysts speculate the required hazardous high energy density propellants led to the Kursk explosion and sinking. Western Navies well-understand this sort of technology, and view it as just too hazardous to deploy, and they have more effective alternatives. The Russians might have developed it with hopes of sales and influence with nations lacking space-based assets, and without industrial capability to produce SUBROCs and Harpoon missiles. It’s likely the Kursk disaster sank these hopes along with the Kursk.

All surface vessels are extremely vulnerable to missile attack, and for all practical purposes are defenseless against the present generation of first-world nation missiles. It’s already problematic whether a nuclear submarine can destroy an “enemy” nuclear submarine with a torpedo, regardless of the torpedo’s speed. The high-speed torpedo concept seems to be a hazardous solution in search of a problem that would justify the risks.