What is it that’s not quite either a plane or a boat, but has characteristics of both? There are probably a lot of things that fit that description, but the one that [Nick Rehm] is working on is known as an ekranoplan. Specifically, he’s looking to make the surface-skimming ground-effect vehicle operate autonomously.
If you think you’ve heard about ekranoplans around here before, you’d be right — we’ve covered a cool LIDAR-controlled model ekranoplan that [rctestflight] worked on about a year ago, and more recently, [ThinkFlight]’s attempts to make an autonomous ekranoplan that can follow behind a boat. The latter is where [Nick] enters the collaboration, and the featherweight foam ground-effect vehicle shown in the video below is his test platform.
After sorting out the basic airframe design and getting the LIDAR integrated, he turned his attention to the autonomous bit, which relies on a Raspberry Pi 4 running ROS and a camera with a wide-angle lens. The Pi uses machine vision algorithms to find an “AprilTag” fiducial marker in the scene, which gives the flight controller information about the relative orientation of the ekranoplan to the tag. [Nick] tested tag tracking using an electric longboard, and the model ekranoplan did an admirable job of not only managing the ground-effect, but also staying on target right behind him. And hats off to [Nick] for keeping all the balls in the air and not breaking his neck in the process.
We’re looking forward to seeing what [Nick] built here end up in [ThinkFlight]’s big ekranoplan build. Ground-effect vehicles like these are undeniably cool, and it seems like they’ve got the potential to solve some interesting transportation problems.
Ground effect vehicles, or ekranoplans, have the advantage of being more efficient than normal aircraft and faster than boats, but so far haven’t been developed beyond experimental prototypes. Fortunately, this doesn’t stop companies from trying, which has led to a collaboration between [ThinkFlight] and [rctestflight] to create a small-scale demonstrator for the Flying Ship Company.
The Flying Ship Company wants to use unmanned electric ekranoplans as high-speed marine cargo carriers that can use existing maritime infrastructure for loading and unloading. For the scale model, [rctestflight] was responsible for the electronics and software, while [ThinkFlight] built the airframe. As with his previous ekranoplan build, [ThinkFlight] designed it in XFLR5, cut the parts from foam using a CNC hot wire cutter (which we still want a better look at), and laminated it with Kevlar for strength. One of the challenges of ground effect vehicles is that the center of pressure will shift rearward as they leave a ground effect, causing them to pitch up. To maintain control when moving into and out of ground effect, these crafts often use a large horizontal stabilizer high up on the tail, out of ground effect.
A major feature of this demonstrator is automatic altitude control using a LIDAR sensor mounted on the bottom. This was developed by [rctestflight] using a simple foam board ekranoplan and [Think Flighs]’s previous airframe, with some custom code added to ArduPilot. It works very well on smooth, calm water, but waves introduce a lot of noise into the LIDAR data. It looks like they were able to overcome this challenge, and completed several successful test flights in calm and rough conditions.
The final product looks good, flies smoothly, and is easy to control since the pilot doesn’t need to worry about pitch or throttle control. It remains to be seen if The Flying Boat will overcome the challenges required to turn it into a successful commercial craft, and we will be following the project closely.
There are a number of famous (yet fictional) sea monsters in the lakes and oceans around the world, but in the Caspian Sea one turned out to be real. This is where the first vehicles specifically built to take advantage of the ground effect were built by the Soviet Union, and one of the first was known as the Caspian Sea Monster due to the mystery surrounding its discovery. While these unique airplane/boat hybrids were eventually abandoned after several were built for military use, the style of aircraft still has some niche uses and can even be used as a platform for autonomous drones.
This build from [Think Flight] started off as a simple foam model of just such a ground effect vehicle (or “ekranoplan”) in his driveway. With a few test flights the model was refined enough to attach a small propeller and battery. The location of the propeller changed from rear-mounted to front-mounted and then back to rear-mounted for the final version, with each configuration having different advantages and disadvantages. The final model includes an Arudino running an autopilot program called Ardupilot, and with an air speed sensor installed the drone is able to maintain flight in the ground effect and autonomously navigate pre-programmed waypoints around a lake at high speed.
For a Cold War technology that’s been largely abandoned by militaries in favor of other modes of transportation due to its limited use case and extremely narrow flight tolerances, ground effect vehicles are relatively popular as remote controlled vehicles. This RC ekranoplan used the same Ardupilot software but paired with a LIDAR system instead of GPS to navigate its way around its environment.
Ekranoplans are a curious class of vehicle; most well known for several Soviet craft designed to operate at sea, flying just above the waves in ground effect. [rctestflight] had accidentally come across the ground effect flight regime himself years ago, and decided it was time to build an ekranoplan of his own.
While ground-effect flight can be quite stable for a heavy, human-scale craft, the smaller RC version suffered more from minor perturbations from the wind and such. Thus, a Pixracer autopilot was installed, and combined with a small LIDAR device to accurately measure altitude above the ground. With some custom tweaks to the Ardupilot firmware, the craft was able to cleanly fly along barely a foot off the ground.
The final effect is almost mesmerizing; it appears as if the craft is hovering via some heretofore unknown technology rather than just flying in the usual sense. It’s still sensitive to breezes and sudden drops in the terrain lead to a temporary escape from the ground effect region, but the effect is nonetheless impressive. It’s a nerve wracking video at times, though, with quite a few near misses with traffic and children. Regardless of the nature of your experimental craft, be cognisant of your surroundings. We’ve seen [rctestflight]’s Ardupilot experiments before, too. Video after the break.
In the 1960s the Soviet Union began experimenting with what they called ekranoplans, ground effect vehicles (GEVs) that were something of a hybrid between a ship and a large airplane. Their stubby wings didn’t provide enough lift for the vehicle to fly in the traditional sense, the craft essentially rode on a cushion of pressurized air produced by the aerodynamic interaction between the wings and the surface of the water. But after decades of testing, the ekranoplan never became much more than a curiosity for American intelligence agencies to ponder over.
Now [Peter Sripol] has built his own version of what the CIA dubbed the “Caspian Sea Monster”, and judging by the video of him “flying” it around a lake, the design seems to tick all the boxes. The advantage of a GEV is that it’s far faster than a ship and more fuel efficient than an aircraft of similar size. They also operate low enough to avoid enemy radar, which made them very appealing for military applications. Not that any of those characteristics apply to an RC vehicle, but at least it looks cool.
Ironically, it took some extra effort for [Peter] to keep his scratch built ekranoplan from getting airborne. Built out of foam covered with aluminum tape, the craft was light enough that even the tiny wings were enough to break it free from the ground effect if it got going fast enough. It didn’t help that the electric ducted fan motors used were probably a bit too powerful as well.
But by carefully adjusting the throttle and control surfaces, [Peter] was able to keep his craft firmly planted in the ground effect most of the time. Seeing the large RC craft floating just a few inches over the water is very impressive, and thanks to the application of some Soviet-style iconography on its burnished aluminum body, it looks like found-footage from a Cold War test program.