Two years ago, we spotted an interesting delivery drone concept at a military expo in Washington, D.C., called TACAD, or TACtical Air Delivery. The idea was to use gliders made out of cheap, disposable materials to deliver a substantial amount of supplies over long distances. You’d have to launch these gliders from larger aircraft, but they’d be able to deliver hundreds of kilograms of supplies over a hundred kilometers away, and then they’d just be left where they landed, simple as that.
Like many concepts that we see at trade shows, we didn’t necessarily expect much to come of this idea, but we’re delighted to report that the folks behind it—Logistic Gliders Inc. (LGI), based in Dixon, Calif.—have recently concluded a successful series of flight tests with the U.S. Marine Corps.
There are two different kinds of gliders that LGI is working on: The LG-1K, which can carry about 300 kg, and the larger LG-2K, which can carry over 700 kg. The bigger LG-2K glider is the one being tested in the videos above; it’s about 4 meters long with a 7-meter wingspan, and has a range of about 110 km at an optimal glide speed of 240 km/h. As the video shows, the glider can be dropped from a helicopter or pushed out the back of a cargo aircraft, and then it will deploy its wings and glide either autonomously or via radio control. Landing is a sort of controlled crash no matter what, but depending on how much room you have, the glider can either belly land or pop a parachute for a nose landing, with honeycomb paper cushioning the impact a bit.
The military already has a few different ways of delivering supplies to units in need, including the Container Delivery System (CDS) and the Joint Precision Airdrop System (JPADS). CDS is basically a pallet of stuff with a parachute attached that gets chucked out the back of a cargo aircraft. It’s not very expensive, but the cargo aircraft has to fly overhead, which can be a problem sometimes for obvious reasons. JPADS, meanwhile, is also a pallet of stuff with a parachute attached, but it’s a fancy autonomous steerable parachute with a range of 25 km. JPADS are expensive, though, and all the electronics need to be recovered and reused, which is a hassle for anyone on the receiving end.
Logistics gliders are designed to be more affordable than CDS, while also offering even longer range than JPADS, which is why the Marines are so interested in the idea. Even the smaller LG-1K has enough cargo capacity to deliver a day’s worth of supplies to a small unit of Marines, and since multiple gliders can be launched at once from a single cargo aircraft, it’s possible to resupply multiple units in different locations, or send a whole bunch of stuff to one location, distributed through a handful of gliders, without risk to the aircraft launching them.
What makes this supply strategy work is how cheap each individual glider is. As LGI says, each glider is “essentially a wooden box.” There are some electronics and a few servos that make up the autopilot and gas springs that help the wings deploy, but that’s it. The majority of the vehicle is weather-resistant plywood, and the entire thing only uses about 400 individual parts, which includes all the screws. The glider can be so cheap because it’s not designed to be reused—it performs one single delivery mission that involves a (hopefully gentle) crash at the end, the supplies are removed from the inside, and then the glider is abandoned. Plus, you save money on more than the glider itself, because you don’t have to risk a manned aircraft that likely costs thousands of dollars per hour to fly.
The testing that took place over the last year included 12 flights with full-scale LG-2Ks, six of which were dropped from a sling beneath a helicopter, and six that were deployed from a small cargo plane. Five gliders flew autonomously, and they all managed to land. LGI plans to continue its testing this year under a contract with the Marines, with loaded prototypes making test flights by the end of the year.
For more detail, we spoke with Marti Sarigul-Klijn, chief engineer at LGI, via email. And if some of his answers seem a little terse, it’s only because he had to get them approved by a couple different government agencies before we could publish them.
IEEE Spectrum: Can you estimate the final cost of both LK-1K and LG-2K gliders when produced in a reasonable volume?
Marti Sarigul-Klijn: LGI’ goal is to reduce the glider unit cost without sacrificing capacity to be comparable to a standard air-dropped parachute Container Delivery System (CDS). This could be especially true if gliders are eventually mass produced at the same numbers as CDS–for example, in 2013 about 250,000 CDS were produced for the U.S. military in that year alone.
CDS costs $4,500 to $11,000 a unit, depending upon the parachute used. Currently the glider prototypes cost much more since every part is made in-house using simple hand tools such as a jigsaw and hand drill. Our electronics contain many components that are needed for flight test only. Also we currently pay full retail for these parts. The production glider electronics may cost only a few hundred dollars if the customer allows us to continue to use commercial off-the-shelf components. The parachute is GFE [Government Furnished Equipment] and costs the government less than $1k.
Are there advantages that a standard air-dropped Container Delivery System has over a glider for delivering cargo? Under what circumstances would you want to use CDS or JPADS instead?
A cargo aircraft can carry more CDS or JPADS as compared to our glider. CDS or JPADS could be best in an environment where there are no Air Defense Systems (ADS) and all of the supplies go to one location. The glider could be best when delivering supplies from a single cargo aircraft to multiple dispersed locations.
How did you decide on what compromises to make between affordable construction and redundancy/reliability?
Logistic Gliders’ focus is on optimizing the performance for the lowest cost. Our idea is to send multiple very low cost gliders to one point of need to ensure delivery of supplies in an ADS environment. Reliability must be high enough to ensure safe operations in and around the carrying platform to avoid any mishaps or material damage but does not have to stand up to the repeated reliability and redundancy of a traditional aircraft as it is a single one time use device.
What are the constraints on the supplies that the gliders can deliver? How forceful are the landings? Could a glider safely deliver a human?
In LGI’s opinion, the glider can physically deliver the same supplies as CDS. Landing impact is similar to CDS. A human could fit inside the glider, but would need to jump out of the glider and land with a personal parachute because landing impact for both CDS and our glider is too high for humans.
You can find lots more information, some of it very detailed, in this AAAI paper, as well as at the website below.