Two years ago, DARPA started developing self-destructing electronics as a way to prevent advanced military gear falling into the wrong hands. Now the agency is expanding on the idea with its Inbound, Controlled, Air-Releasable, Unrecoverable Systems (ICARUS) program, which is tasked with developing small, unmanned, single-use, unpowered air vehicles that can can be dropped from an aircraft to deliver supplies to isolated locations in the event of disasters, then evaporate into thin air once their job is done.

Delivering vitally needed supplies after disasters or to soldiers in the field isn't always a matter of slapping a parachute on a crate and pushing it out the back of a cargo plane. If the supplies are delicate, perishable, or need to be landed precisely, some sophisticated hardware and avionics are required to put it on target. Unfortunately, that sort of technology is precisely the sort that the US government prefers to keep out of hostile hands. Even if that isn't the case, retrieving such delivery craft from the back of beyond can be a bigger logistical headache than getting them there in the first place.

DARPA's answer is ICARUS, which is named after the mythical character who flew using wings made of feathers and wax, but fell to Earth when he soared too close to the Sun and his wings melted. The program evolved from the success of DARPA's VAnishing Programmable Resources (VAPR) program, which is developing a new class of self-destructing electronics designed to destroy themselves on command to prevent them from being captured by enemy forces.

According to DARPA, VAPR had already developed items like polymer panels that sublimate directly into a gas, and electronics-bearing glass strips that have high-stress inner anatomies like the famous Prince Rupert's Drop and can shatter into dust on command. This led to agency to consider new applications for the technology.

"With the progress made in VAPR, it became plausible to imagine building larger, more robust structures using these materials for an even wider array of applications," says VAPR and ICARUS program manager Troy Olsson. "And that led to the question, 'What sorts of things would be even more useful if they disappeared right after we used them?' In discussions with colleagues, we were able to identify a capability gap that we decided was worth trying to close."

The air delivery vehicles to be developed by the program need to meet certain criteria. These include the ability to drop payloads of up to 3 lb (1.4 kg) within 10 m (33 ft) of a target landing spot and cover a lateral distance of over 150 km (93 mi) when released from a stationary balloon at 10,670 m (35,000 ft). The vehicles must also completely vanish within four hours of delivering their payload during the day, or within 30 minutes of morning civil twilight (when the Sun is 6 degrees below the horizon) if dropped at night.

DARPA sees ICARUS has having a wide range of applications, from delivering food, perishable medicine such as insulin, water, and other supplies to isolated communities that have been struck by natural disasters or epidemics, as well as for supporting military units in the field. In both cases, the delivery vehicles would carry out their tasks, then evaporate or crumble into dust. This would not only prevent sophisticated technologies from falling into the wrong hands, but would also reduce costs as well as environmental and logistical problems by eliminating the need to disassemble the craft and haul them home again.

"Inventing transient materials, devising ways of scaling up their production, and combining those challenges with the hard control and aerodynamic requirements to reach the precision and soft-landing specs we need here makes for a challenging and compelling engineering problem," says Olsen.

ICARUS is a two-phase program scheduled to last 26 months that has a budget of US$8 million.