The navigational system used by the military for just about everything from guiding drones to dropping bombs is increasingly under threat of attack. Now, the Pentagon's desperate to replace it. Or, at least, reinforce it enough to stave off a looming storm of strikes.

That's the thrust of a new venture from Darpa, the military's premier research arm and the brains behind GPS' initial development in the 1950s. On Tuesday, the agency announced the second phase of their program, "All Source Positioning and Navigation (ASPN)," that's trying to "enable low-cost, robust and seamless navigation solutions ... with or without GPS."

The program, which Darpa quietly kicked off last year with two awards for theoretical research, is one part of a larger military effort that's trying to steer the Pentagon away from its GPS dependency.

Why? First off, there's the growing risk of GPS signals being jammed by adversarial forces. Enemies on the ground can also "spoof" a GPS system – essentially tricking it into showing an incorrect location. And these are far from hypothetical risks: Mere weeks ago, a fatal drone crash in South Korea was attributed to GPS signal jamming from north of the border. Last year, Iranians (perhaps dubiously) claimed they jammed the GPS signals navigating an American spy drone, then spoofed the system to land in Iran's clutches.

And those GPS-thwarting capabilities continue to grow – at a pace that's exceeded the military's ability to keep pace – largely because of a booming commercial market for GPS-jamming technology. Such electronic warfare "was once the province of a few peer-adversaries," Darpa deputy director Ken Gabriel told the House Armed Services Committee's panel on emerging threats earlier this year. "It is now possible to purchase commercial off-the-shelf components for more than 90 percent of the electronics needed in an [electronic warfare] system."

The risks now inherent in GPS are well-known, but it doesn't look like Darpa's ready to give up on the system altogether. Instead, they're after a navigational system that can swiftly move between different combos of devices, using a "plug-and-play" approach. Right now, the agency notes, the military's navigation systems primarily rely on a pairing of two devices: GPS, which uses satellite data, and what's known as an Inertial Navigation System (INS), which relies on "dead reckoning" (using estimates of speed and direction, without external references) to provide locational intel.

It's a tactic that's accompanied by several problems. For one, INS – because it uses internal, ongoing estimates – is notoriously error-prone without a GPS system to back it up, so it can't be relied upon exclusively. And INS systems often obtain their starting position and velocity from a GPS device. Which means if the GPS is under attack, the INS risks leading military personnel (or the drone or weapon they're navigating) astray.

These navigational systems are also extremely inflexible. Typically, Darpa notes, they're programmed to accommodate, maybe, one additional sensor (say, a magnetometer) and unable to plug into any others. As a result, personnel can't respond to "new threats or mission challenges" in real time. Not to mention that, even as consumer navigation tech becomes more sophisticated (Apple Maps, anyone?) the military can't take advantage of the most cutting-edge products.

Of course, there are already plenty of GPS alternatives available. Radio beacons, which transmit signals from static locations to receiving devices, allow the calculation of location based on proximity to various beacons. Ground feature navigation extracts the positions of tracked objects and then uses them as points of reference to gauge a vessel's locale. And stellar navigation systems use the coordinates of celestial bodies to assist in a vehicle's navigation.

Darpa's dream navigational system would go beyond those kinds of discreet systems – by incorporating pretty much all of them. The ASPN system, according to Darpa's announcement, should be able to accomodate any available sensor, and be versatile enough to incorporate new sensors "as they become available in the marketplace." The key benefit to such adaptability would be the mitigation of GPS-dependency. Personnel would instead have myriad sensors at their disposal, and be able to toggle between them as necessary. In other words, a suite of backup tools to work, in conjunction, as a safety net in case of GPS failure. Among the ton of gadgets that Darpa wants the system to utilize: 3-D imagers, LiDAR, temperature sensors ... and good old compasses.

It remains to be seen whether ASPN can restore the "spectrum dominance" that Gabriel and his Darpa cohorts are chasing. At the very least, though, it should help them keep pace with the commercial sector. Especially because, as Darpa's announcement notes, ASPN testing will rely on "the Android operating system."