These Mushroom-Based Drones Eat Themselves at Mission’s End
Once the job is done, the tiny gliders are designed to disappear.
/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer/c3/4e/c34e8b55-a5d9-44dc-96b4-e3a1c29c9bda/apsara01.jpg)
How do you make a drone vanish after a one-way delivery flight? One answer is to have it eat itself.
A DARPA program called Inbound, Controlled, Air-Releasable, Unrecoverable Systems, or ICARUS, is exploring ways to make expendable drones disappear. The name is a nod to a character from Greek mythology who dies when he flies too close to the sun with wings of wax.
DARPA “seeks proposals for the design and prototyping of vanishing air delivery vehicles capable of precise, gentle drops of small payloads. These precision vehicles must be guaranteed to rapidly physically disappear following safe payload delivery. Proposed efforts must integrate engineered vanishing materials into advanced aerodynamic designs to produce an autonomously vanishing, field-testable prototype vehicle.”
Responding to DARPA’s call, the San Francisco-based R&D firm Otherlab developed a glider prototype with an 8:1 glide ratio, capable of delivering one kilogram of payload using onboard navigation and guidance. By using a glider the design eliminates motors and batteries, which allows more space and weight for cargo. The firm recently released a photograph of a cardboard prototype they call APSARA (for Aerial Platform Supporting Autonomous Resupply Actions).
According to Star Simpson, Otherlab’s APSARA project engineer, “we used cardboard as a prototyping material because it is easy to work with and resembled mycelium, the mushroom-based material that we intend for the future product.” That’s right. This drone will be made of mushrooms.
Mycelium, says Simpson, is very similar in texture to cardboard and can be machined in much the same way. To meet DARPA’s vanishing requirement the aircraft is designed to eat itself. “Our preliminary work on that indicated that you can basically impregnate [mycelium] with different types of spores [which] are activated just before the vehicle is released.” The activated spores immediately begin to feed on the airframe. “One thing that is great is what the spores do when they grow and meet.” When the different spores encounter each other they “compete with each other pretty strongly. Therefore they ingest the material quite rapidly” and the aircraft is gone in five to six days.
According to Simpson, APSARA is meant to be deployed by cargo airplanes such as the C-130 or C-17. Like the Perdix drones that recently demonstrated swarming behavior, Simpson says APSARA will be deployed from a canister ejected by a mother craft. Once the canister slows to a target airspeed, APSARA is released to begin the glide to its destination.
An aircraft that vanishes upon completing its missions offers real benefits to covert forces in need of supply. During parachute-based resupply missions, the parachutes are either buried or carried out to prevent discovery by hostile groups.
Simpson’s aircraft may also benefit from another DARPA program: Vanishing Programmable Resources, or VAPR. VAPR is looking for electronics that self-destruct, which could be useful for disposable drones. A Xerox firm, PARC, and IBM have both developed a way to use glass as a substrate to print computer circuits. On command, or at a predetermined time, the glass is shattered and the circuity along with embedded computer code is destroyed. Simpson says APSARA doesn't employ self-destructing electronics, but that it could.
Like mushrooms, Simpson says the design can grow. “We can currently carry up to a one-kilogram payload, and we know we can pretty directly scale the airplane up to about an 8-foot wingspan and carry 10 kilograms with no problems.” When asked if the mycelium technology limited aircraft size beyond that, she says “No, not from our perspective. The question of a higher payload is one we’d be happy to answer.”
