Why the Seaglider craft succeeds where the ekranoplan failed

We often receive the question: Are Seaglider vessels just modern-day ekranoplans?

Ekranoplans are wing-in-ground (WIG) effect craft that rose to prominence in the late 1960s, most notably with the Soviet Union’s experimental KM, also known as the Caspian Sea Monster, which was over 300 feet long. Despite decades of experimentation, the ekranoplan program never matured into a scalable or commercially viable mode of transportation.  

While both the ekranoplan and the Seaglider vessel operate within ground effect, the similarities end there.  

Seaglider craft represent a new category of maritime vehicle, one that solves the core aerodynamic and operational challenges that limited the potential of earlier WIG designs.

Why did the ekranoplan fail?

Ground effect has historically been difficult to fly in because it's unstable. Earlier WIG designs suffered from three key challenges: 

1. Poor wave tolerance: They were very sensitive to weather and could not be reliably dispatched.
2. Low maneuverability: They could not operate in littoral (near coastal) environments or around other vessels. Taking off and landing was especially dangerous, as ekranoplans were traveling in excess of 150 mph during these transitions, and had to do so very close to the harbors where they were operating, which often meant high trafficked areas.
3. Manual control and low safety: They relied on captains, who had to be trained pilots, to make nonstop adjustments to hold the ekranoplan low over the water, and introduced large risk risk of human error. Ground effect and low alititude flight is difficult to manually control.  Ekranoplans and past WIGs tried to address this instability with wacky wing designs that added stability at the expense of losing all the efficiency they gained from flying in the ground effect in the first place!

How the Seaglider succeeds

1. High wave tolerance: The addition of a hydrofoil provides wave tolerance, allowing the vessel to rise above rocky seas of up to 5 feet and seamlessly transition from the hull to the wing. The Seaglider can reliably dispatch and operate in most weather conditions.
2. High maneuverability: Hydrofoiling also gives the Seaglider high maneuverability in harbors and near-coastal areas. The vessel can operate on the water, like a boat, when it is near other boats. Taking off and landing can also be moved outside the harbor, because the hydrofoiling mode allows a “high speed taxi”, at up to 50 mph, between inner harbor operations on the hull, and open water operations on the wing.
3. Digital flight control systems: Seaglider vessels leverage autonomous digital flight control systems that fully control stability and ensure safety. The captain drives the craft like a boat – left and right, fast and slow, and the triple-redundant software system controls every aspect of flight. This automatic control enables the efficiency of a standard wing design, for very high efficiency and therefore long range, while still being safe and controllable in ground effect.

Dive deeper into the physics of how the Seaglider wing differs from previous WIG wing designs.