We first reported on Gremlins back in 2015, as one of those “DARPA wants” projects that seems like it might be a bit far-fetched—in this case, DARPA wanted swarms of nearly disposable UAVs that could launch and be retrieved from flying aircraft carrier motherships in mid-air. Over the last few years, we’ve seen some progress towardsdisposable drones, but the tricky part was always going to be the mid-air retrieval. We speculated a bit in our original post about how it might be done, but we didn’t get it quite right, which we know because DARPA has given a company called Dynetics a US $38.6 million contract to make Gremlins real.
The picture at the top of this article is concept artwork from Dynetics, showing how they plan to catch and release the Gremlin aircraft. Here’s a summary:
The Dynetics solution involves deploying a towed, stabilized capture device below and away from the C-130. The air vehicle docks with the device much like an airborne refueling operation. Once docked and powered off, the air vehicle is raised to the C-130, where it is mechanically secured and stowed. The key technologies can be straightforwardly adapted to allow under-wing recovery and bay recovery by other cargo aircraft.
This is a very pragmatic approach to take because of how much experience the Air Force already has with airborne refueling. It’ll be interesting to see how well the “mechanically secured” bit works behind a very large plane that’s flying very fast, but that’s what testing is for, right?
The Gremlin aircraft themselves are intended to be a compromise between the disposable single-use drones that both DARPA and the Marine Corps have been experimenting with, and traditional drones that are designed to last for years. Each Gremlin will be designed to function for perhaps 20 missions, with minor refurbishment between missions. They likely won’t be that much more expensive than a disposable drone, and the extra investment will make them much more useful. It’s a bit of a philosophical shift for the military, and makes the meaning of “military-grade hardware” potentially quite different.
It’s interesting to think about what kinds of design optimizations you could make for drones that never have to touch the ground—taking off and landing are usually the most stressful parts of an aircraft’s life, and if you do away with them, it’s not just about eliminating the need for landing gear. You could presumably lighten the whole structure, maybe rearrange some sensors, or even change the aerodynamics and control surfaces if your aircraft will never drop below some minimum speed. The drones in the concept images, for example, have much more of a missile look about them, and thinking of them as reusable cruise missiles may be fairly accurate.
Artist’s rendering showing aircraft launching the drones, which look like missiles.Image: Dynetics
Dynetics expects to conduct a series of ground and flight tests starting this year, and by the end of 2019, they’ll have demonstrated “the airborne launch and safe recovery of multiple unmanned aerial vehicles onto a C-130 aircraft.” And as for what these swarms of Gremlins will be doing? DARPA says that the drones will be designed to carry “intelligence, surveillance, and reconnaissance (ISR) and other modular, non-kinetic payloads.”
Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.