Should Airships Make A Comeback?

• Airships seem like a bad idea. Exhibit A. (bright upbeat music)

• It's the greatest of miracles that anyone came out of the disaster alive.

• The Hindenberg was filled with over 200 million liters of hydrogen, but it also had an iron oxide and aluminum powder coating on its outer shell, two of the ingredients that make thermite—a mixture that undergoes such a strongly exothermic reaction, it is used to weld train tracks together.

But even if airships weren't giant sacks of flammable gas encased in questionable coatings, they would still seem like a bad idea because they are big and slow.

But right now, a handful of companies around the world are competing to build a new generation of airships. So why are they doing it?

I came across the following argument in a blog by Eli Dourado, and I found it compelling, so I wanted to explore it.

Think about how goods, all the different types of stuff, are transported around the U.S. A large amount of money is spent moving things around by airplane, but this doesn't translate into a huge volume of goods because air transport is really expensive.

It's the fastest way to get something from one place to another, but you pay a premium for that speed. If you want to save money, you can transport your goods on ships using the waterways in and around the country, but that will be much slower.

Still, since it's significantly cheaper, far more goods are transported this way, and more money is spent on it overall. Rail provides an even better option.

It's faster than ships and cheaper than planes, so more goods are sent by train than by air and water combined.

But by far, the way that most goods are moved around the U.S. is by truck.

What's interesting about this is that trucks are not as fast as planes; they take several days to get across the country.

They are also not as cheap as ships, but the combination of speed and price puts them in this sweet spot of cheap enough and fast enough, which is why they transport the vast majority of goods. They are like the baby bears' porridge of transport options—just right.

Now consider how goods are transported internationally. The only options are planes and ships.

Again, a lot of money is spent sending goods by air, but because it's so expensive, the actual volume of goods is low.

And most goods, both in terms of dollars and weight, are sent via ocean freight.

But what if there were a third option—faster than ships and cheaper than planes?

It seems likely that most customers would prefer this new truck-like method of transport.

Airships could be this option. (bright upbeat music)

They could be the trucks of the sky. (bright upbeat music)

They would transport cargo across oceans in around a week rather than a month for freighters.

And theoretically, they would be several times cheaper than sending goods by plane.

And they would achieve all this while emitting significantly less emissions than planes.

See, while planes get their lift from their wings and so they need to burn a lot of jet fuel just to stay in the air, airships get their lift effectively for free.

The buoyancy of lighter-than-air gas keeps them up, so they don't need to move forward to stay aloft.

As a result, modern airship manufacturers estimate airships can reduce carbon emissions by 90% or more.

But for airships to become the trucks of the sky, they would have to carry a lot of weight, and historically, that has not been a particular strength of airships.

But that's where the physics comes in.

The lift of an airship depends on the volume of light of an air gas it contains, so lift is proportional to radius cubed.

Whereas drag depends on a combination of the cross-sectional and wetted area—that is basically the surface area of the craft.

So it's proportional to radius squared.

This means the bigger you make an airship, the more efficient it becomes.

Lift goes up proportional to radius cubed, whereas drag only goes up proportional to radius squared.

So there's a cubed squared advantage for larger airships.

Want to boost the performance of your airship?

Well, just double it in size.

The area grows by a factor of four, the volume by a factor of eight.

So your lift-to-drag ratio doubles.

If that's not enough, just double it again.

To make airships the trucks of the sky, we'd need to build the largest airships the world has ever seen.

There are three different kinds of airships.

The first is a blimp, which is basically a balloon with a gondola and motors attached.

Like a balloon, it is over-pressurized to maintain its shape.

Therefore, the skin of a blimp is in constant tension.

As the blimp becomes larger, this tension increases.

Moreover, it becomes increasingly difficult for larger blimps to maintain their shape.

So you can't scale up blimps forever.

The second option is semi-rigid.

Just like a blimp, the hull is still in tension yet now there's some added structural support to maintain the shape.

The last variety is a rigid body airship.

These have an internal structure to maintain their shape.

Inside the hull, there are a series of gas cells filled with a lifting gas like hydrogen or helium.

In this case, the gas cells are not over-pressurized, so making them larger is no issue.

The great thing about rigid airships is that they don't run into the same scaling limits.

Want a bigger airship?

Just scale up the structure and add some extra gas bags.

In fact, the weight of the structure actually decreases as a fraction of the total weight, so rigid airships scale even better than square cubed.

So it's this last option that is best suited for the cargo market.

And that's what Eli proposes: to build a 388 meter long rigid airship to conquer the cargo market.

It would be capable of carrying 500 tons of goods at a speed of 90 kilometers per hour.

That's enough to carry two Statues of Liberty at the speed you drive down the highway.

If built, it would be the largest aircraft by far, both in size and in how much weight it could carry.

Not bad for an airship.

But to take a significant piece of the cargo market, you don't need just one airship; you need a fleet of thousands constantly moving goods around the globe.

And if they take over half of the ocean freight container market at a price comparable to trucks, say 10 cents per ton-kilometer, that would equal $650 billion of revenue per year.

And if that was all served by one company, it would be the biggest company in the world by revenue.

Bigger than Apple or Amazon or Walmart.

So who is building these monster airships?

Well, at the moment, no one.

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While transporting cargo is probably the largest market for airships, it's also one that's driven by fierce competition and low margins.

And that's not ideal when you need to spend a lot of money to first build, develop, and certify your airship.

What you want is a market with less competition and better margins.

This is the Airlander 10, and it's built by the U.K. company Hybrid Air Vehicles.

Can you tell me about the envisioned use of the Airlander?

• They'll be going on extraordinary experiential holidays.

So going to the North Pole, going on a safari, going over the Amazon, knowing that they're making almost no environmental impact, being able to travel in some luxury and see things that you just can't do another way.

• The first trips are scheduled for no later than 2026.

Want to go on this trip?

Well, you'd better start saving because getting a cabin for two will cost you about $200,000.

And while a few companies are focusing on the luxury travel markets, others plan to make use of another unique advantage of airships.

Think about what it normally takes to move things around.

Trucks need roads, ships need water and ports, trains need railways and stations, and planes need long runways and airports.

Airships, on the other hand, require very little infrastructure.

The most important thing they need is a reasonably flat surface to land on, like grass, sand, ice, or even water.

And it's this unique ability that allows them to deliver goods where no truck, boat, train, or plane can go.

Airships can connect parts of the world that have been disconnected forever, such as remote villages in Canada or Alaska, and they can do this with little to no infrastructure.

Or what if the roads, rails, and ports have been destroyed by a natural disaster?

Help is urgently needed to find and support the survivors, but there seems to be no way to get there and no methods of communications once you are there.

Well, then airships could quickly rush to the scene to deliver rescue workers and supplies, or to provide cellular service from the sky.

Disaster relief missions like these are what LTA Research, which is backed by Google co-founder Sergey Brin, is focusing on, and they're making great progress.

Their current prototype, the Pathfinder 1, has completed multiple indoor flight tests and it's scheduled to fly outside sometime in the next few months.

They plan to take the lessons they learn from these tests and build a series of airships that can provide help to disaster-stricken areas.

Other times, roads may be available, but what you're transporting just isn't that compatible with roads, like long, clunky, and fragile turbine blades.

To get them from the factory to the destination requires careful planning and perfectly choreographed maneuvers, and this process is what often limits the size of wind turbines.

Airships don't have that problem; they can simply mount turbine blades of any size to the bottom and carry them to the destination.

So it's much faster, easier, and it allows you to build more powerful wind turbines.

Plus, airships can also easily transport other structures that are hard to move.

But sometimes, instead of delivering goods, you need to pick them up.

France is full of natural resources like wood, yet many of their forests can't be reached by truck, so they can't actually extract the wood they've chopped down.

The French company Flying Whales, backed by the French government, is hoping to change that.

They are developing this 200-meter-long cargo ship that's capable of carrying a 60-ton payload.

It was designed to be able to hover above remote forests and pick up logs, which could then be carried off and turned into timber.

But loading and unloading from the sky comes with significant problems.

For starters, you need to make sure that during this process your airship stays still, which is more difficult than it sounds.

• So a very large airship has what we call sail effect.

Even a relatively light current of wind, when multiplied by a really, really large area, is going to have a huge effect.

That makes airships difficult to control, especially close to the ground and at low speeds.

So they are a little bit unwieldy.

• To overcome this, the airship is fitted with propellers all around the hull that can stabilize it.

But still, this limits the use of most airships to places with stable weather.

A bigger problem comes from the fundamental reason why airships work in the first place.

And this issue is particularly bad for large cargo airships.

See, when an airship is carrying a heavy load, the combined weight of the load and the airship are offset by the lift.

The problem arises when you release that heavy load because now the airship is suddenly much lighter, and so it wants to shoot up into the sky.

So you need some way to stop that from happening.

• Unless we can solve that problem, we're kind of dead in the water in terms of airships for cargo.

A few methods have been proposed to solve this problem.

The easiest one is to decrease lift by venting lifting gas.

The only issue is that most modern airships use helium.

And to offset, say, 60 tons of weight, you would need to release about 54,000 cubic meters of helium, which costs a few hundred thousand dollars.

Not to mention that helium is scarce, so venting it isn't really a practical option.

Now, you could use propellers to push the airship down, but that ends up burning so much fuel it negates much of the advantage of using airships in the first place.

• The real dream has been to compress and decompress lifting gas because you take a lifting gas and when it is in gaseous form, it lifts.

When it is compressed, it's ballast—it's heavy—but there are some real problems with that.

So you're talking about a very large airship with a very large volume of lifting gas; now you need a compressor that's capable of compressing a tremendous amount of gas very quickly, and that is just a technological problem we haven't really developed.

• Until then, the short-term solution is to replace the weight you're releasing.

So if you're dropping 60 tons of supplies, you need to pick up 60 tons of ballast.

If you want to pick up 60 tons of wood, you'd carry 60 tons of, say, water on board and release it at the pickup location.

But there's another innovative way to solve this problem, and it's the secret behind how the Airlander 10 works.

It relies on a combination of lift from helium and aerodynamic lift created by its hull.

• We can lift the whole weight of the aircraft with the helium inside, so that effectively, when you're flying, that weighs nothing.

• And the aerodynamic lift is just there to lift the payload.

• So if we've, say, got 100 people on board, we take off like a conventional aircraft, just at very low speed and we generate the aerodynamic lift to lift those people.

The advantage then is that when we come down on the ground and those people get off, we don't float away 'cause we used aerodynamic lift, which you can turn on and off.

• While hybrid airships work well for relatively light payloads, they're not ideal for carrying heavy payloads over long distances because you would lose the advantage of using free lift to carry all that weight.

So for large cargo airships, the current best solution to the load exchange problem is to replace the weight you're releasing.

But there are harder problems that you need to overcome to make airships the trucks of the sky.

See, no one has ever built a 388 meter long airship before.

So how do you do it?

Well, normally airships are built in humongous hangars to protect them from the elements.

But the largest airship hangar that's ever been built was only 360 meters long, so it wouldn't even fit.

And since you need to build thousands of these airships, you either have to find a way to magically construct scores of fragile airships outside or build lots and lots of the world's largest hangars.

If that wasn't hard enough, there's also another problem that needs to be solved because each one of those airships must be filled with over one million cubic meters of lifting gas.

Which raises the age-old question: do you use hydrogen or helium?

• Helium's really expensive and it has a lower lifting ability, right?

Hydrogen's really cheap, but it'll kill you.

• After the Hindenburg burned down in less than 40 seconds, the choice seemed obvious.

Only inert helium should be used for airships.

The Federal Aviation Administration agreed, and hydrogen as a lifting gas has been banned for many years now.

But what many people don't realize is that of the 97 people on board, more than 60 miraculously survived.

Just a few years earlier, another airship, the USS Akron, crashed off the coast of New Jersey, killing 73 of the 76 people on board.

And that airship was filled with helium.

So perhaps the issue wasn't that hydrogen airships were inherently unsafe; maybe we just didn't know how to build safe airships.

I mean, we also didn't know how to build safe planes, and now they're one of the safest ways to travel.

And for any plan that includes building and filling thousands of large-scale airships, hydrogen is the only realistic option because helium is too scarce and expensive.

Hydrogen, on the other hand, is easy to produce, cheap, and it provides about 8% more lift.

And then there's the issue of certification.

• In general, certificating any new aircraft is a really lengthy and expensive process.

If you're talking about certificating an airship, not only are you talking about a brand new aircraft, you're talking about a brand new type of aircraft.

No one has certificated a large rigid airship in, well, sort of ever.

• Combine that with building the largest aircraft the world has ever seen and filling it with tremendous amounts of a highly flammable gas and you've got yourself another pretty big challenge.

But all of these problems may not even matter because it might not be possible to build a 500-ton cargo ship of that size.

• I mean, the most important thing of an airship structure is it needs to be light; it needs to be robust, it needs to be strong, it needs to have really good structural integrity, but it needs to be light enough to get off the ground, or there's no point.

And at a certain point of size, the weight you need to add to create the structural integrity you need to operate safely, you know, you reach a point where those curves just intersect in a bad way.

So there is a structural size limitation due to weight issues.

• So how large is that size?

We are not sure. What we do know is that right now, several companies around the world are developing and building the next generation of airships.

For now, none of them are setting out to develop the trucks of the sky.

Instead, they're focusing on areas where airships have a distinct advantage; markets with less competition and decent margins.

Who knows, perhaps as airships mature, one company will take the leap and set out to develop these trucks of the sky.

It certainly won't be easy, but the reward could be huge.

Do you think we'll see a future where we've got these airships roaming all over our skies?

• I know it may sound crazy, but we really do.

• It won't be very, very long before we get to see some stuff in the sky, which will make a lot of people, including me, have really big smiles and a lot of happy nostalgia for the great airships of the past.

• It's very hard to break into the world with a new thing that the world's not ready for.

I mean, there are many other things that have become normal after a bit of time. And there's no reason why this shouldn't.

• I hope when that day comes someone will invite me to come along and at least take a look; if not, have a ride in it. (soft upbeat music)