Could seagliders be the next big thing for New Zealand passenger transport?

In the news recently there’s been a number of articles about a New Zealand transport start up called Ocean Flyer, proposing to deliver revolutionary new intercity public transport on coastal routes to take a big bite into the domestic passenger market. This company has placed an order with American firm Regent to purchase a fleet of their new Seagliders, a ground-effect craft that is sort of a cross between a boat, a hovercraft and an airplane.

While it’s clear this is a media blitz from the start up, I wanted to dig into whether this is actually a promising technology that can deliver on its claims, or if it’s just another hype-cycle transport technology that is big on promise and small on feasibility. Many so-called transport revolutions focus on some ephemeral high tech vehicle, and fall over on the nuts and bolts of regulation, routing, operations and service planning.

The craft

In appearance these “seagliders” are quite similar to a seaplane, and have the similar benefit of being able to operate out of just about any wharf or dock with access to the sea. For a maritime nation like New Zealand this has the potential for very convenient access right to the downtowns of our many seaside cities, and to provide effective passenger transport to coastal towns and villages that can’t justify an airport of their own.

Unlike a seaplane, they don’t really fly so much as hover on a bubble of high-pressure air between the vehicle and the surface. They can’t actually take off like an aircraft because they rely on this ground effect bubble for lift, which dissipates once you are a more than a few metres above the surface. However, because of this they are much less energy intensive, and the manufacturers claim the seagliders will have twice the range of an electric aircraft of the same size and weight.

There are some fancy looking renders of the vehicles, and some videos of them flying gliding, although so far these are only scale models of test articles. Nonetheless, wing-in-ground-effect craft are actually a pretty mature technology with examples having existed since the 1960s, not least the giant jet powered ekranoplan missile cruisers of the soviet navy. However, the current proposal is for a much more efficient passenger vehicle, utilizing electric propulsion, hydrofoil technology and light weight carbon construction.

Operations and speed... aren't the just very fast ferries?

So how would they operate? From what I have read the Regent seagliders will have three distinct modes of operation. At idle the vehicles will float on their hulls, and while maneuvering around docks and harbours at speeds of 5 to 20 knots (10-37 km/h) they’ll function much like a normal boat, pushing its way through the water. In this mode they’ll have a reported wave tolerance of one to two metres, similar to a regular ferry boat.

Outside of harbours the craft will transition to hydrofoils, lifting the hull out of the water like an Americas Cup boat to minimizing contact with the water. The proponents don’t state exactly what at what speed this will be, but we can expect it would be in the range of 20 to 50 knots (40 to 100 km/h) like other hydrofoil vessels. However the low height of the hydrofoils in the renders does suggest they'll still be limited to quite calm seas in mode.

The third mode is the transition to ground effect. Here the speed is increased, the hydrofoils retract and the seaglider lifts entirely out of the water, cruising at 160 knots (300km/h) less than ten metres above the surface. Presumably this mode could only be used once the craft are clear of busy shipping lanes and other places with high marine traffic.

In that regard these gliders are equivalent to very fast hydrofoil ferries, which means they need to be considered as sea traffic rather than air traffic. The International Maritime Organization treats them as such, although there appears to be some disagreement on exactly what rules they need to follow. However, it is clear that these seagliders will need to navigate a marine environment with much the same hazards and restrictions as fast ferries, including:

• Boats and ships. Even though the craft are travelling above the surface of the sea, they won’t be able ‘fly over’ other vessels, and will have to avoid them entirely as any other ferry or ship would. For a start most ships and many yachts are over ten metres tall, but even for smaller sea craft being hit by the ground-effect pressure wave of a seaglider travelling at 300km/h could be as catastrophic as any sea level collision. This does suggest that the pilots will have to rely on radar while gliding at that speed, I don’t expect boat-style visual navigation would be sufficient when moving almost 100m every second!
• ?Speed limits. New Zealand maritime law restricts all vessels to five knots (about 10km/h) when travelling within 200m of shore, or within 50m of any other vessel or person in the water. Furthermore, several places have an additional speed limit such as the twelve-knot (22km/h) restriction in the Waitemata Harbour. In effect this means two things, the seagliders will have to stay in boat mode until they are clear of inner harbours, and they’ll be unable to speed up to glide mode in busy navigation channels where there is a significant chance of coming within 50m of another vessel.
• ?Marine life. While hydrofoiling the craft will pose a risk to dolphins and other marine life, which are commonplace around New Zealand’s coasts. The hydrofoils remain in the water, but unlike most boats they’ll be travelling much faster than the creatures themselves, so they’d have less chance to avoid an impact.
• Debris. There is also the risk of impact with debris in the water while hydrofoiling.?Logs and lost shipping containers are not unheard of around our harbours and have a nasty habit of floating just below the surface.
• Sea birds. Seabirds cruise along at the same altitudes as the seagliders are proposed to glide at so there is a risk of birdstrike. While this would not be as catastrophic as it is with jet aircraft, it would still be plenty catastrophic for the birds, and damaging to the craft.

These problems are not new, nor insurmountable, but like fast ferries this does mean there will be operational constraints that limit how and where they can travel and the routes they can use. This leads us to the claims around journey times that have been mentioned in the media, I wanted to look at this because I’m not sure it’s quite as good as the marketing department might have you believe.

Can they deliver the promise in reality?

First of all, these are electric craft with a purported range of 300 kilometres. ?Two routes have been mentioned as examples: Auckland to Whangarei in half an hour, and Auckland to Whitianga in half an hour. Both of these routes are just under 150km distance by sea, so it seems they are suggesting an operations plan where the gliders are based in a main port and make a 300km return trip on each charge of the batteries.?That makes a lot of sense, and it is the same sort of operational model used by electric ferries.

What doesn’t make sense is that these journeys would take only thirty minutes. Of course, by simple math a distance of 150km to Whangarei would take only half an hour at 300 km/h, but they clearly won’t be able to maintain full top speed the whole way. Departing Auckland they’ll initially be limited to five knots around the wharves, then no more than twelve knots until they are clear of the inner harbour at North Head. Then I expect they’d have to limit speeds through the busy Rangitoto channel to something relatively boat-like, say forty knots. After that they could get up to full hydrofoil speed out to open water, then transition to full speed gliding perhaps once they are a few miles out from Tiritiri Matangi.

After a high speed run up the coast they process would have to happen in reverse. Somewhere off Mangawhai Heads, the craft would have to slow down to land back on its foils, then approaching Marsden Point it would have to slow again for the run up the relatively narrow and busy Whangarei harbour. Finally, they’ll be back into five knot territory for the last bit up the river past the marina and into downtown Whangarei.

A potential route for the Auckland to Whangarei run, with limited speeds in harbours and high speed gliding out on the gulf.

Factoring in some estimates on a likely route and the range of speeds involved, I estimate the journey from Auckland to Whanagarei would actually be more like 65 minutes from go to whoa, less than half of which would be spent at full glide speed. While it would rapidly cover a lot of distance at full speed once out over the open ocean, the majority of the time would be spent getting in and out of the harbours at much lower speeds. All together I’d expect a return trip from Auckland to Whangarei and back would be a three-hour cycle, once you account for including for loading and unloading at both ends, and recharging and servicing at one end.

The timeframe is also questionable, with the suggestion of going from the current scale model through prototyping to passenger service within three years. My experience is that even if the technical designs are sorted, working through approvals and regulations on new transport initiatives can take a very long time.

Likewise, I’m skeptical about the suggestion that tickets to Whangarei could cost $30. The proposed craft are twelve seaters and require two crew. If a return cycle takes about three hours all up, that’s three hours of operational time and six person-hours for crew, for a maximum of twenty-four seats sold. Doing the math a $30 ticket equals only $240 of revenue (less GST) per operating hour, and that is at 100% occupancy. I image that’s not even enough to pay the crew, who will need training and certification at least as onerous as a ship captain, if not an airline pilot. So rather than thirty dollars for a thirty-minute trip, I expect the break even point would be more like a $99 ticket for trip of an hour and a bit.

Having said that the twelve-seaters are presumably just the trial model, they also talk about larger 100-seaters as a future model, one that can glide at over 500km/h with longer range. That is where the concept would start to make operational and financial sense, this later stage is perhaps where $30 tickets might happen… if the second generation of craft pan out.

A conclusion: definitely maybe!

My take is these seagliders should be considered as fast ferries in operational terms, albeit ones that can go very fast under the right conditions. That means like other ferries they'll have various operational constraints, not least the need to go slow in harbours and at boat-like speeds in shipping lanes, and only hit full speed out in open ocean. So, if the tech eventuates the concept would probably still deliver, but it will undoubtedly cost more and won't be as fast a trip as they say. Nonetheless, this might still be affordable and competitive for intercity public transport on a number of routes, we can only wait to see if they can turn the concept into reality.