Abstract.

A proposed watercraft that can outperform aircraft and ships at the majority of over-sea transport needs. This can be achieved by improving upon ground-effect vehicle technology to make it passively safe, stable and able to handle rough weather.

Introduction

The world’s waterways were the main transport routes for millennia and 50% of the world’s population still lives within 200km of the sea. Yet over-sea travel is now almost exclusively by aircraft and 35% of global freight by value is transported via aircraft.

Generally speaking, the usefulness of any transport system is its cost of mass per velocity:

                          $/kg  
Transport Utility =   -----------
                        km/hour

• Aircraft have a high speed but a very high cost per kg.
• Ships have a very slow speed but a low cost per kg

The result is that transportation is a choice between speed or weight. A watercraft that is able to achieve a low cost/kg in combination with a high speed could expect to replace the existing transportation modes for a large share of over-sea transport.

From a consumer’s point of view, 85% of the world’s population cannot realistically afford passenger air travel and over 99% cannot afford private air travel. Unfortunately, travel via ship isn’t an option either as it is slow and impractical due to the costs of supporting passengers for long time-periods. Ships also cannot outrun bad weather, thus they require extra size and reinforcement.

The physics of watercraft

So what is possible? There are four types of dynamic movement over or through water. These are displacement, hydrofoiling, planing, and the wing in ground effect.  Displacement is the default method used by traditional ship hulls. Hydrofoils are underwater wings that produce lift by redirecting the flow of water around them. Planing hulls generate lift through high-speed movement of water below them, e.g. speedboats and water skis. Lastly, the wing-in ground effect occurs when a ground/sea surface limits the displacement of air below a wing, creating a high-pressure cushion of air that supports greater lift.

History

During the 20th Century a number of innovations were made to attempt to solve the problem of speed, comfort and fuel efficiency in sea transport. Hydrofoils were promising at first and studied extensively in the US by Alexander Graham Bell and others as well as in the Soviet Union. The key limitation of hydrofoils is their vulnerability to collision and a phenomenon called cavitation at higher speeds. Cavitation occurs where the water around a foil separates into microvoids and the collapse of these voids causes pressure waves that damage the foils. Ground effect vehicles, on the other hand, seemed to have much more promise. They are able to travel at aircraft-like speeds, carry twice the weight of a comparable aircraft, while using half as much fuel.

In the Soviet Union, ground effect vehicles were given a lot of attention as a way to counter US Aircraft Carriers. The chief designer, Rostislav Alexeyev headed the hydrofoil design bureau and started working on ground effect vehicles after frustration with the limitations of hydrofoils. The monstrous “Ekranoplans” were the result. These vehicles worked exactly as predicted but the collapse of the Soviet Union eventually led to the demise of their efforts. Alexyev died from injuries sustained in a Ekranoplan crash in 1980 and these vehicles never reached their potential.

The main limitations of the Soviet Ekranoplans were pilot fatigue and vulnerability to large waves. Flying at 200 km/h a few meters above the surface without any form of autopilot is an extremely difficult task. The Soviet vehicles also weren’t practical in oceans because they weren’t designed to handle rough seas. Over the last 40 years, work has continued on ground effect vehicles but these main limitations have still not been solved.

Solution

I propose a vehicle that is able to overcome all the requirements discussed and thus offer a from factor that is a superior solution for over sea transport needs - as measured in cost per kg per km per hour.

Promised properties

• Travels at 5x the speed of a ship
• Able to carry twice the weight of a comparable aircraft.
• Able to use half the fuel of an aircraft
• Able to effortlessly absorb bumps and handle waves
• Able to outrun storms and bad weather conditions
• Passive stability and safety to prevent pilot fatigue
• No license required to operate
• Low maintenance costs vs aircraft or ships

Prototype key features

1. Canard design

An elongated speedboat style bow and front-stabiliser reduces the craft’s susceptibility to sea-surface impacts.

2. Large ram-effect wings

For optimal performance in ground effect, radically different wings are needed. Unlike regular long and thin wings, these wings are specially designed to produce lift via a high-pressure pocket of air underneath them. If these wings gets too high above the surface, lift falls away, making them a great source of natural stability.

3. Stabilization

Eventually we want to continuously scan the oncoming sea surface and actively stabilize the craft by adjusting the angle of the rear elevators.

4. Raised point of propulsion

Having a raised point of propulsion in the rear helps to keep the craft passively stable by keeping the nose down. This prevents the craft from being able to backflip on accident like high-performance speed boats often do. The rear position also minimizes the effect of sea-spray and water hitting the propeller.

Market

As a craft that requires no license to operate, an obvious entry point is people who would want to privately travel over sea but cannot afford or deal with the complexity of owning their own aircraft. Starting with smaller vehicles also means our development costs are lower, iteration cycles are faster and profitability can be reached sooner. Eventually, the basic design can scale to vehicles much larger than todays largest commercial jets.

Development and Production Plan

As displayed by SpaceX recently with their development of Starship, I believe an iterative approach is the fastest way to acquire and apply the lessons needed to reach production. We will start by building relatively simple test vehicles and iterate quickly from there.

Competitors

There are several competitors out there also building ground effect vehicles. However these are focused on building something more along the lines of a traditional airplane with limited low-flying efficiency gains. I believe this is due to a long-standing underappreciation and lack of research into ram-wings. Wings fully optimised for pure ground-effect mode will outperform traditional airfoils.

Conclusion

We have proposed a watercraft with performance characteristics that offer a better solution than air transport for most over-sea transport use cases. We started with ground effect vehicles but their significant shortcomings have prevented widespread adoption in over 60 years of existence. To solve the two main shortcomings, an inherent lack of safety, and the inability to handle large wave conditions, we developed a novel form factor that is passively safe, easy to operate and able to handle rough sea conditions by safely falling back to “skiing” in case of any hard contact with the sea surface.