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Nitty-Gritty Things
The first and most obvious challenge is how to enable increasingly autonomous operation. This may seem like a problem nearly solved. After all, for years even the most mundane commercial jets have included autopilot features that maintain trim and course during long flights and that can also perform essentially automated takeoffs and landings.

Importantly, though, ordinary planes still, of course, have pilots sitting in the cockpits. Pilots make countless decisions to handle little breakdowns on the plane – and decide whether or not it’s appropriate to engage automated systems at all. “It’s not so easy when you don’t have a pilot in there to take care of mishaps, faults, failures, and all that jazz,” says Eric Feron, an aeronautical engineer at MIT who is not connected to the current DARPA program. “It’s unbelievable how much the human is able to act as the glue between the technological gaps. The human covers so many nitty-gritty things, from frequency switching to target acquisition and recognition.”

Then there is the problem of constructing what amounts to an Internet in the atmosphere. On the ground, mobile communications networks are fast expanding, thanks to cellular and Wi-Fi networks. But when you get up to 10,500 meters at speeds of 700 kilometers per hour or faster, new challenges arise. To pick one technical example: today’s airborne radio links incur one bit error in every 10,000 bits sent. That’s far too unreliable for an airborne Internet. In fact, it’s 100 times worse than what’s needed for the ground-based Internet to provide even minimal service, says Dave Kenyon, an information architect at the air force’s Electronic Systems Center in Bedford, MA. The center is developing satellite-based networks that will be used by all kinds of military planes, including future unmanned planes.

But even when satellites are used, the fact remains that jets cover great distances, and that communication links will thus regularly break. “From a networking perspective, the frequent making and breaking of links will require new or improved network routing protocols,” Kenyon says.

In other words, the unmanned planes will require new ways for information to change communication pathways on the fly – literally. “We will not always have perfect communication and, in fact, will always have some form of latency,” says Paul Waugh, a DARPA deputy director of the X-47 program. “Thus, the system, in all its parts, demands some level of autonomy, which means we will need smart platforms, smart sensors, and smart data processing.” The plane needs to think for itself, at least during the gaps. “We recognize that we have entered perhaps the richest, deepest part of the information revolution that deals with mobile, wireless computing,” Waugh says.

To further reduce strain on the communications networks, the planes must be designed to do as much work on board as possible. For example, after collecting images of targets, a plane must do much of the processing and filtering, sending only the most relevant images back to the human controllers. “The lines of code [for flying the plane] are minuscule compared to the lines of code required for mission planning, sensor management, and getting aircraft to fly together as a team,” says Rick Ludwig, the business development manager for Northrop’s program.

Eric Feron is developing a key system that is generic to all unmanned aircraft: the human–machine interface. In the future, unmanned jets might be controlled by a pilot in a single manned fighter jet. Feron is working on a natural language interface, so that the pilot can “talk back and forth with the [unmanned jet] as if it were just another person,” Feron says.

But that’s only part of the task; once the spoken commands are conveyed, those commands must be translated into a set of electronic and mechanical actions. Feron is also writing software that sorts and prioritizes commands and turns them into instructions that the machine can act on. Last June this command-and-control part of the system was successfully tested – using typed commands – on surrogate aircraft.

Above all, the software – which DARPA calls the “common operating system” – must be adaptable. The Northrop and Boeing versions are supposed to connect to one another and to other military systems – including those only yet envisioned. In various corners of academic, corporate, and military labs, autonomous helicopters, desk-sized robotic planes, and even insect-sized, flapping-wing aircraft are in various stages of development. If the networking and control systems are worked out, any future aircraft could make use of them. Once the airborne networks are as reliable as the land-based Internet, the myrmidons can take any form that pleases the Pentagon.

David Talbot is Technology Review’s chief correspondent.

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