For decades, Pentagon mad science division Darpa as been at the forefront of robotics research -- including, and especially, the development of killer drones. But there are signs that agency's work on armed robotic planes and copters could be shrinking in the years to come.

Aerospace Daily reports that Darpa has been forced to cancel its project to develop an unmanned, heavily-armed helicopter. The Army, Darpa's partner in the Unmanned Combat Armed Rotorcraft (UCAR) program, lost interest. And so the agency can't afford the $160 million tab for the project's next phase.

"Designed for low- to medium-altitude reconnaissance and attack, the UCAR would have been the most autonomous unmanned aircraft ever built," Aerospace Daily's Jefferson Morris explains, "capable of coordinating with other UCARs and accepting high-level verbal commands from operators."

Darpa's fixed-wing drone program isn't quite as sophisticated. But its development is way, way more advanced. Today, the UCAR exists only in PowerPoint. There are working prototypes of the unmanned planes, called Unmanned Combat Air Vehicles (UCAVs) in Pentagonese.

Last spring, a Darpa-funded X45-A UCAV dropped a load of smart bombs on targets in the Mojave Desert. In December, a single human pilot was able to control two of the drones at once.

In cooperation with the Air Force and then Navy, Darpa recently committed to Boeing and Northrop Grumman about a billion bucks each to build the next killer drone models.

But whether those funds will actually come through is now an open question. In its recent Program Budget Decision, the Pentagon brass called for a billion dollars to be excised from the UCAV program over the next five fiscal years.

What's more, Darpa may be out of the killer drone effort. The remaining money for the project would be transferred out of Darpa coffers – and into the Air Force's kitty. According to the budget document, the Pentagon leadership wants a "restructur[ing]" of the program, "with emphasis on the development of air vehicles that will contribute to... future joint warfighting concepts of operations." That would seem to imply that Darpa's killer drones didn't really meet the Defense Department's future war plans.

Darpa tells Aerospace Daily it remains "committed" to building unmanned systems. But, when it comes to armed robots, the Pentagon higher-ups may not be committed to Darpa.