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Then come the unmanned submarines. Current, commercially available drone subs typically swim for several days at a time, according to Frank Herr, an Office of Naval Research department head who works on so-called unmanned underwater vehicles, or UUVs. That’s way behind the capabilities that successive Navy leaders want: crossing entire oceans without needing to refuel. So Klunder wants to raise the bar.

“The propulsion systems that I think you’re going to see within a year are going to [give] a UUV with over 30 days of endurance,” Klunder said. By 2016, a prototype drone sub for the office’s Long Duration Unmanned Underwater Vehicle program should be able to spend 60 days underwater at a time: “That’s ahead of schedule of what we told the secretary of the Navy a year ago.”

That’s a challenge for the subs’ propulsion and fuel systems. Typically, Herr explains, the commercially available batteries built into prototype drone subs take up a lot of the ship; but building bigger subs just increases the need for power. The nut that the Office of Naval Research has to crack is using more efficient fuel cells while designing subs that don’t need as much energy to run. “We’re thinking about power requirements for these systems as well as the power [sources] available for them,” Herr says.

“The breakthrough,” Klunder explains, “was really on getting past your more traditional lead-acid battery pieces to more technically robust but also mature lithium ion fuel cell technology and the hybrids of that.”