How many giant experimental spy blimps does the military need over Afghanistan, exactly?

That’s one of many questions the Senate Armed Services Committee is asking after an intramilitary battle has erupted over what many expect to be the future of aerial surveillance. The Army and the Air Force each have their own football field-sized airships in the works; the Senate panel wants to know why it should pay for both — especially as the Air Force seems fickle about its model and keeps changing the spy sensors on board. Legislators are asking: What gives?

This is more than some obscure bureaucratic hair-pull. The answer to those questions — and the winners of those fights — could determine the direction of U.S. intelligence-gathering for years to come.

Here’s why. Surveillance drones like the Predator and the Reaper are starting to lose just a bit of their sheen in military circles, even though their number of “orbits,” or combat air patrols, has more than quadrupled in the last five years. Giant spy blimps are the new hotness. They can stay in the air for much longer than any drone. Instead of a Predator’s single camera, the blimps can carry a whole bunch of surveillance equipment, because they’re so freakin’ huge. Any one of those sensors could spy on an entire town at once. There’s even enough space on board the airship to process all that data in the sky, easing the burden on overloaded intelligence analysts.

A sign of the spy blimp’s rising stock: Retired Lt. Gen. David Deptula — who, until recently, was in charge of all Air Force intelligence, surveillance and reconnaissance (ISR) programs — is now the CEO of MAV6, a Vicksburg, Mississippi, startup building one of these next-gen airships for the military.

It’s part of a project called “Blue Devil.” The behemoth, 340-foot-long blimp and all of its spy gear should be ready for Air Force duty by January, Deptula promises. And if Blue Devil works as promised — staying four miles above Afghanistan for five days at a time — drones could suddenly seems like an expensive anachronism.

“It brings to bear a completely different concept for ISR: multiple sensors on one platform integrated with on-board processing and storage. It’s the first time we’re using a modular system on an aircraft to host a variety of sensors, and they can be rapidly changed for new or different sensors in a matter of hours,” Deptula tells Danger Room. “We’ve got the world’s largest ISR payload — and ‘real estate’ to host it, and nearly a supercomputer on board to process what they find.”

The Pentagon is planning to spend $4.5 billion to mount 15 more drone air patrols. The costs of operating, maintaining and processing the information from the roboplanes runs about $8,000 per hour. Deptula claims Blue Devil would run $1,000 per hour, because it requires fewer people (although that’s just an educated guess; the thing hasn’t flown yet). “A handful of Blue Devil orbits could achieve significantly greater ISR effectiveness for a fraction of that cost and save billions,” he insists. For now, the Air Force is spending $211 on one of Deptula’s blimps.

The Senate Armed Service Committee digs the idea. “There are many platforms and systems that advertise ‘multisensor integration,’ but almost always the different sensors … cannot view the same piece of terrain at the same time,” the committee notes in its recent report on next year’s Pentagon budget. “Blue Devil is different: this QRC [quick reaction capability] is designed to give ground forces a new capability to detect, locate, identify, and track targets seamlessly, building on concepts and practices pioneered by special forces to tightly integrate sensors and pursuit operations.”

But the committee “is concerned about recent turmoil in program plans,” according to the report. For starters, Blue Devil isn’t the only ginormous airship heading for Afghanistan. The Army has one in the works, too.

It’s called the Long Endurance Multi-Intelligence Vehicle, or LEMV. It’s being built by Northrop Grumman, the defense contracting behemoth. It’s allegedly going to start casting its “unblinking eye” by January. And the LEMV supposed to stay in the skies for weeks, thanks to a combination of lighter-than-air helium and the aerodynamic lift you’d ordinarily see in an airplane. Initial cost: $517 million, for three airships. But, according to InsideDefense.com, the Pentagon is already asking for another $28 million.

Which naturally has lead the Senate Armed Service to ask why we need both of these things.

“These developments raise the question of the value of Blue Devil Block 2,” the committee report reads.

“The Army now plans to deploy the LEMV to Afghanistan in the same timeframe as Blue Devil Block 2. Moreover, the Army is now planning to rapidly equip LEMV, after it is first demonstrated, with the same sensor systems that were originally planned for Blue Devil Block 2,” the committee adds. “The sensor changes raise questions about how effective and useful it will be, while progress in the LEMV program raises the issue of whether Blue Devil Block 2 funds would be better invested in LEMV program acceleration and expansion.”

LEMV may not be able to stay in the air quite as long as advertised. A recent technical presentation (.pdf) noted that the airship might stay aloft for a mere 10 days at a stretch.

Yet the Air Force is showing some signs of ambivalence about its Blue Devil airship. Turns out, the air service has grown rather attached to its current gaggle of spy planes.

That’s ironic, since it wasn’t that long ago that Defense Secretary Bob Gates complained that getting the Air Force to field more Predator and Reaper drones was like “pulling teeth.” The upstart robo-planes were a threat to the air service’s established, man-in-the-cockpit fleet. Now, however, the upstarts have become the establishment. Drones form the bedrock of the Air Force’s surveillance effort.

“Big Safari” — that’s the code name for the Air Force office in charge of special intelligence programs — doesn’t appear to be quite ready to shift gears again. Especially not when shifting gears means putting a small company like Deptula’s in the driver’s seat.

“The Air Force transferred responsibility for Blue Devil recently to the Big Safari Program Office, which promptly proposed wholesale changes to the program — an entirely different platform, continued use of legacy [c]ameras, and different SIGINT [signals intelligence] sensors,” the Senate report notes.

Most of those changes were ultimately beaten back. But there are still open issues about the future of Blue Devil — and how the airship relates to its past.

The Blue Devil program started by packing a bunch of sensors together onto a turboprop plane. That surveillance gear includes eavesdropping equipment that can pinpoint a chatty militant’s location, as well as the Angel Fire “wide-area airborne surveillance system,” or WAAS. It’s a hive of nine separate cameras, each one shooting at a very slow rate and at a slightly different angle — allowing a whole town to be watched at once.

On the Blue Devil turboprop plane, the WAAS sensors and the eavesdropping unit can tell each other where to look or listen. According to the committee, that combo is now “making significant contributions” in southern Afghanistan, “particularly in support of prosecuting high-value targets.” In other words, it’s helping the military hunt down and kill militants.

But Deptula — and the Air Force — don’t just want to move that gear onto the airship for the second phase of Blue Devil. There’s talk of upgrading the WAAS sensor, from nine cameras to 92. Plus, the blimp has room for more and bigger antennas. And the more and bigger antennas you have, the easier it is to pinpoint locations. The blimp could be a much better eavesdropper. The Air Force and the ear-men at the National Security Agency are still wrestling over which signals intelligence package will fly on the airship.

Even muddier is the Air Force plan for what to do if the spy blimp wows the military if and when it goes to Afghanistan; there’s no follow-on effort in the budget, at the moment.

Making things murkier still is that there are twomore giant blimp programs making their way through the military’s development chain.

The Armed Services Committee is kind of fed up. It’s demanding that the Pentagon appoint a single point person who can sort out which airship projects make sense, and which don’t. This is supposed to a time of coming budget cuts, after all. The sky is pretty big. But it’s not big enough for all these king-sized blimps.

Illo: Mav6