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This August, Greta Thunberg sailed across the Atlantic in a zero-emission sailboat to protest the high carbon footprint of plane travel. But there’s good reason to think she may someday travel to climate protests via airship — the same giant aircraft, buoyed by gas-filled balloons, that were popular in the early 20th century. Faster than cargo ships and able to alight inland as well as on a beach, many airships, also known as dirigibles, have fewer emissions than boats, and all are much more carbon efficient than planes.

While interest in early dirigibles waned after they proved too slow and, occasionally, too dangerous, climate change is making plane travel increasingly contentious. Now some scientists are considering airships as a serious transportation solution.

Unlike planes, airships don’t need to burn much fuel to take off and propel themselves. Because they move more slowly than planes, they’re being eyed as a much more carbon-efficient way to move air cargo, which is set to triple in the coming decades, according to the International Air Cargo Association. “An airship produces 80% to 90% fewer emissions than conventional aircraft,” said Jean Baptiste Meusnier, spokesperson for the International Air Transport Association.

paper in the journal Energy Conservation and Management published in September posits that just one airship could move 21,000 tons of stuff using almost no energy at all if we used airships to harness the free winds of the jet stream, the narrow band of fast-moving air above the troposphere, where planes fly. These winds, which average 100 miles per hour and can be as speedy as 250 mph, could propel an airship from Denver to China in about seven days or from Los Angeles to Tokyo in four, says Julian David Hunt, of Austria’s International Institute of Applied Systems Analysis and the paper’s first author.

The airships Hunt proposes would fly in the stratosphere, where there are additional advantages besides free wind. “You can plan a long time in advance, because the weather forecasting is much better — there are fewer disturbances, and it’s easier to predict wind patterns in the stratosphere,” he says. He envisions a round-the-world drop-off and pickup route for airships to deliver cargo for little to no energetic cost, and he’s not alone.

“You don’t really need to fly above the weather.”

Bob Boyd, a program manager at Lockheed Martin’s Skunk Works, explains that the physics of airships makes them inherently energy efficient. “Buoyant lift is a much more efficient method to move through the sky than direct lift,” he says. Planes and helicopters rely on direct lift, which is powered by burning fossil fuels, while buoyant lift relies on the natural properties of gases like hydrogen and helium, which are lighter than air and don’t need to be burned.

However, Hunt’s high-altitude vision for soaring through the jet stream requires ultra-flexible materials for the ship envelope that do not yet exist. The air pressure is lower above the stratosphere, creating pressurization issues for airship design. “Materials that are structurally sound has been one of the challenges,” says Jason Rhodes, a senior research scientist at NASA’s Jet Propulsion Lab. That’s one reason most companies gearing up to build commercial airships are looking to fly below the stratosphere, at an altitude of 5,000 to 6,000 feet, which will eliminate pressurization issues and reduce time spent on vertical travel.

These lower-flying vehicles, known as hybrids, are likely what we’ll see in the nearer future. Aerospace company Lockheed Martin’s hybrid prototype sports three cartoonish bubbles up front to help with navigation and engines to assist with maneuverability. The company’s hybrid design uses 20% aerodynamic lift — a lightly fuel-powered boost for a bit of a “plane-like effect” — and helium for the remaining 80% buoyant lift, Boyd says. The end result uses significantly less fuel than a plane and can access many areas other vehicles can’t.

Already, there are a number of opportunities for airships to transform transportation. Cargo, for one thing, doesn’t need to move as fast as planes fly. “It’s wasteful to spend all the money and energy to bring cargo from Asia to North America at 500 miles an hour to then sit for days in a warehouse before it gets moved,” says Barry Prentice, a professor of supply chain management at the University of Manitoba and president of Buoyant Aircraft Systems International (BASI). From an environmental perspective, we are paying “a huge cost, since jet engines are the most polluting of any form of transport,” he says. Using an airship can slash both fuel use and carbon production by up to 90%, according to the International Air Transport Association.

In addition to mitigating the causes of climate change, airships can also alleviate the effects, Prentice says. In northern Canada, he says, the ice roads — highways formed by frozen lakes — are melting, and it will soon become harder to reach the difficult-to-access communities that already lack adequate housing and affordable food. BASI is building airships to carry large, heavy loads like produce, construction equipment, and modular housing without the need for roads or runways, bridging distances for remote communities and areas without reliable roads. They may eliminate the need for roads altogether, which would reduce construction and pollution in sensitive ecosystems where thoroughfares are often built and avoid the high costs of road-building for cash-strapped remote communities. Likewise, runways won’t be needed because most airships can land anywhere that’s flat enough — whether on water, snow pack, beach, or field.

Their ability to land anywhere makes up for their lack of speed. Container ships wait in notoriously backed-up lines before their goods are unloaded onto trucks, which themselves are prone to traffic jams. Airships could pick up goods for regional distribution directly from a factory if the payload is big enough (like an order of new cars and trucks), skipping congested cities and avoiding travel through the waterways where sea animals make their homes.

Furthermore, airships aren’t limited by the size of truck containers or train beds, making it possible to move large vehicles and machines directly to hard-to-reach locations, like construction projects, congested cities, or mines. “Transport massive loads — like fully assembled heavy equipment,” brags Lockheed Martin’s site. “Cargo will have a weight limit, but no practical size limit,” according to U.K.-based Varialift Airships.

These characteristics make them useful for humanitarian and disaster missions. “Infrastructure is one of the first things that goes in a hurricane, tidal wave, or earthquake. An airship is ideal for getting aid in and refugees out,” says Boyd, pointing to the devastation caused by the tsunami that hit India in 2004. With 2,000 miles of coastline devastated, even a massive helicopter lift wasn’t enough to move heavy supplies like fresh water and food quickly enough to the millions in need. “[Airships] are more capable than helicopters — safer, more environmentally friendly, and with a longer operational range,” says Mark Dorey, COO of Straightline Aviation, which is set up to be an operator for Lockheed Martin’s hybrid dirigibles.

Staying aloft for as long as airships can — most models easily go for a week — means they can also be used for long-term work: surveys, border security in remote areas, and, importantly, scientific monitoring. Currently, low-Earth orbit satellites that can capture great detail move past a site only every two hours, while images from higher, geostationary satellites have lower resolution because they’re farther away. Airships could fill the need for continuous, detailed monitoring in one location. “You could look at how vegetation changes over a season, at ocean surface changes, or agriculture,” says NASA’s Rhodes. “[An airship] could provide fire detection over the whole fire season; it could watch fire and understand its effects over days and months.”

It’s important not to overlook the fact that dirigibles are significantly quieter than planes, making only as much noise as a big car engine, thousands of feet above the ground.

Anumber of companies are already working on commercial airships, but their designs vary greatly. Which gas is best to use to fill an airship’s balloons is up for debate. Among those relying on helium for lift are Lockheed Martin, Varialift, and Flying Whales, which has investors from China and France. Meanwhile, Hunt’s jet-stream model relies on hydrogen, as does BASI’s design, which also incorporates solar panels. Hydrogen has major advantages: It’s cheap, it can be created using renewable energy, and it has greater lifting ability — about 6% to 8% more than helium — but it’s also flammable. Helium is not, and so it’s the safer choice, though Prentice says today’s technology can keep airships safe from explosions, pointing out that ignition occurs only at hydrogen concentrations greater than 4% — unlikely from a small leak. Gasoline, he notes, ignites at 1% concentration, making it “much more dangerous than hydrogen.” To some, the risk isn’t worth it. “[Hydrogen] doesn’t give that much more lift, so is that really worth it to go from something that is entirely safe and inert to something that’s flammable?” Boyd asks.

Because of safety concerns, helium is more likely to help the industry move forward in the near future. Though there are concerns that the world is running out of the buoyant gas, Boyd’s research on USGS reports of helium supplies suggests this is a “misunderstanding.” Hydrogen may not be safe to use for lift, but he says it would be useful as a carbon-free fuel to power airship navigation.

Though bad weather caused some crashes in the early days of airships, concerns that one might get caught like a balloon in a storm today shouldn’t be taken too seriously because the airships being built are so huge. “You don’t really need to fly above the weather,” Prentice says. “A really big airship, like the kind we’d use for cargo, it has plenty of inertia and isn’t going to get pushed around much.” To airships, the cruise ships of the skies, even big waves will be negligible.

A world where giant airships drift overhead may seem like a throwback to a long-forgotten past, but it also feels incredibly futuristic. Lockheed Martin’s certification plan has already been approved by the Federal Aviation Administration, and Boyd estimates it will take two to three years to update aviation regulations to allow for commercial airships. But airship ordering is open. “You can buy one for $40 million to $50 million, depending on the options,” he says. “That’s about half the cost of an airplane of similar size.” And a lot less carbon spewed into the sky.