The Best Defense Against Cruise Missiles Might Be This Giant Surveillance Blimp

The North American Aerospace Defense Command (NORAD) will conduct a test exercise next week that involves some new high-power airborne surveillance gear: the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor, or JLENS for short.

JLENS is built around a pair of blimps that will be launched Monday from the US Army's Aberdeen Proving Ground in eastern Maryland. JLENS is basically a way for folks (like NORAD) to watch for low-flying cruise missiles (a.k.a. exploding drones without round trip tickets) and aircraft. The purpose of the exercise Monday will be to the test integration of these new sensors and platforms with existing air defense networks.

JLENS attracted attention earlier this year by agitating some privacy advocates, who were concerned by the fact that it's a flying thing with the potential to be outfitted with cameras. This time around, the introduction of the word "drone" has shifted the conversation: JLENS can watch for drones but is — get this — also a drone. Fixating on these aspects of JLENS is a bit of a pity, because the program is actually fascinating.

The JLENS craft are lighter than air (LTA) vehicles, called "aerostats." There are a number of different names for specific flavors of LTA aircraft, depending on whether or not they have a rigid body, have engines, generate lift, are tethered to the ground, and a variety of other factors. The US Government Accounting Office (GAO) classifies the JLENS craft as "aerostats" because they remain tethered to the ground.

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JLENS aerostats are deployed in pairs called "orbits." One blimp carries a giant search radar system while the other has high-powered targeting radar. The search radar looks for interesting stuff — up to 340 miles away — so that the tracking radar can pinpoint the interesting thing and pass that info along to other people in the air defense ecosystem, who can then check it out, shoot at it, or whatever.

At some point in the 1990s — back when people were flapping their gums about the pros and cons of defending against intercontinental ballistic missiles — during a periodic debate over missile defense, some bright spark observed that not all incoming nuclear missiles were necessarily going to be suborbital vehicles screaming in from space on ballistic trajectories. There's an entire universe of nuclear-armed cruise missiles that you need to pay attention to as well. If you're going to be doing "missile defense" you probably ought to defend against all the missiles — including cruise missiles.

Time-lapse of the inflation of a JLENS aerostat (blimp) at Aberdeen Proving Ground, Maryland, on December 14, 2014.

Spotting any incoming nuclear warhead involves (for the most part) looking up, because it's a lot easier to pick out an incoming missile or bomber against a backdrop of an empty sky. But cruise missiles fly fast and low to the ground, which requires looking out instead of up. The curvature of the Earth, however, limits the ability to look out to maybe a few dozen miles, meaning the missiles can't be spotted until they're relatively close.

Not being able to spot a high-speed, low-altitude missile until it's close means there's not much time to respond before the thing has already zipped past on its merry way to starting Armageddon.

You can see a lot more area and spot missiles a lot further away if you can get up high, but that means looking down and requires a much fancier kind of radar gear (although that has been around now for quite some time). Nonetheless, airborne radars allow you to see incoming threats a long way off.

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Getting up high usually means an airplane, but airplanes lack the ability to watch an area for very long periods of time — what defense folks like to call "persistence." Without a persistent observation capability, keeping a watch for incoming threats over a large area requires keeping several aircraft in the air, and also having a lot more aircraft on the ground for maintenance and backup.

Increasing the ability to monitor a super big area (a.k.a. "wide-area surveillance") and keep tabs on distant enemies (an "over-the-horizon" capability) over keep watching over a long period of time has been something of a Holy Grail since balloons were used in the US Civil War to watch enemy troops.

Folks haven't cracked this problem completely because designing and operating reconnaissance platforms involves making some pretty big design tradeoffs.

One of the important tradeoffs is safety/survivability. LTA craft are vulnerable to a lot of things (like any other flying vehicle) and those factors are a consideration. Still, LTA have got a lot less vulnerable in the last century or so.

However, instead of getting lost in the weeds on all the different trades, let's just simplify and say that LTA vehicles such as the JLENS offer the possibility (at least in theory) of a vehicle that can split the difference between a satellite and an aircraft. They combine a lot of features from both into a single platform. Like satellites, they provide persistence, large payloads, and wide-area observation. But like aircraft, they can get high-resolution images (without immense optics), an ability to repair and upgrade systems, and easily repositioning.

Even better, aerostats have capabilities that both satellites and aircraft lack. They can use their tethers to get power and transmit data, simplifying design and saving a lot of weight that can be used for things like more sensors.

The total result is that the JLENS is (theoretically) supposed to cover an area that might take four or five aircraft to monitor for weeks at a time, and do it a lot more cheaply.

In fact, the US Army has been using aerostats in Afghanistan for much of the last decade. The Persistent Ground Surveillance System (PGSS) and larger Persistent Threat Detection System (PTDS) have both been used successfully to provide battlefield information and monitor the area around bases by combining these different features.

Looking past reconnaissance, LTA craft also open the door to some very impressive logistical and cargo hauling capabilities. LTA cargo craft can combine the mobility of a helicopter with the cargo capacity of a train, and transport a large amount of goods very cheaply.

There's a lot of promise in LTA technology, so it's no wonder that the US Department of Defense (DoD) has invested more than $7 billion in LTA since 2007 to try to tease these advantages out and mature them into some pretty interesting capabilities. Unfortunately, much of that investment has gone into programs that have since been cancelled.

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For all the promise of LTAs, they've never really quite gelled as a fully mature technology. This latest round of research and development isn't even the first time that the DoD has tried to make them work, and it has fussed with this stuff for decades.

Although LTA advocates have been selling the merits of these technologies for ages, this latest round of enthusiasm hasn't quite been enough to get past all the technical and operational challenges and finally get LTAs off the sidelines in a big way. It's a shame — at least from a flying cars and fusion power point of view — but it should serve as a cautionary tale if you believe that DoD interest alone is enough to make tomorrow's technologies a reality today.

Follow Ryan Faith on Twitter: @Operation_Ryan

Image via US Army/dvidshub.net