Stratoplanes: The Aircraft That Will Fly at The Edge of Space

For a long time, there was only one option if you wanted to explore the stratosphere, and that was a balloon. Balloons could climb to the ceiling of the world, where there is too little oxygen for wings, or air-breathing engines. The problem then was staying alive at those altitudes, and a good number of balloonists failed trying.

In 1931, humanity finally reached the stratosphere, with one balloonistachieving a height of 52,000ft(15,800m) in a pressurised gondola attached to a hydrogen-filled balloon. Two years later, Jeannette Piccard became the first woman to reach the stratosphere, with an ascent to 57,600ft (17,600m).

From the 1950s it was the turn of expensive, state-financed and top-secret spy planes like the U-2, the SR-71, and recently the RQ-170 drone. Now the stratosphere is also home to weather balloons, amateur high-altitude balloonists, Chinese spy balloons and marketing stunts. A group ofCornish schoolchildrenused a weather balloon to lift a Cornish pasty to an incredible 116,410ft (35,500m). It returned, frozen.

Yet the age of exploration isn’t over. The pressurisedWindward Performance Perlan 2 gliderset a new altitude record of 73,800ft (23,500m) in September 2018. It flew higher than any glider has ever flown, and even the maximum record altitude of a U-2 spy plane, using the waves created by the Andes mountain peaks to lift the glider all the way up to the stratosphere.

The British-builtAalto Zephyr(the company was recently spun-out of Airbus) is one of a new type of flying machine designed to reconquer the stratosphere through eternal flight. Aircraft that, when combined with miniaturisation of components and powerful new computer models of the atmosphere, give humanity the possibility of a near-permanent presence at these high altitudes for the first time.

Known as Haps (high altitude pseudo-satellites), these autonomous, super-lightweight aircraft range from solar-powered gliders to solar-powered silver zeppelins.

Their jobs include providing 4G or 5G phone coverage and internet service after a disaster, spotting forest fires, and tracking the movement of enemy forces during wartime. All the while, they can do it better, more cheaply, faster, and more flexibly than satellites.

Technological improvements, especially in the development of lightweight materials, solar panels, and battery technology, make the “long endurance” part of the brief a reality.

“The challenge for their designers,” says Robert “Bob” Kraus, dean of the John D Odegard School of Aerospace Sciences at the University of Dakota, “is to find the sweet spot of having an aircraft that is light and strong enough to stay up at those altitudes for long enough, can haul enough payload to be useful to paying customers, and can survive the ascent – and descent – through the troposphere.”

Even in Low Earth orbit, micro-satellites orbit the Earth around 340 miles (547km) higher than an aircraft such as the Zephyr. This means there is still a slight latency – a delay to communication that can impede high-speed broadband communication. There are also some fundamental limitations in the use of satellites for remote sensing in terms of resolution, speed and flexibility that make the case even stronger for the use of Haps.

Some are now beginning to take physical shape.

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Inside a large cylinder-like structure in Roswell, New Mexico, for instance, is a large silver zeppelin Haps. It is another “eternal” aircraft. Its aluminium parts have been replaced with carbon. A Goodyear Blimp built to the same size would be 12 times heavier.

“We started small, with a 9ft (2.7m) version that couldn’t lift its own weight, so we had to attach it to a balloon just to start generating data,” says Mikkel Vestergaard, founder of Sceye, the materials science company behind the stratospheric zeppelin. “Then in November 2020, we opened the hangar doors for the first time to a 270ft (82m) version.”

By May 2021, the zeppelin had made it to its target altitude of 65,000ft (19,800m) at an average rate of 1,000ft (305m) a minute, and this year alone they have six flights. What really sets the zeppelin apart is the payload it can carry. While the Zephyr can lift around 5kg (11lb), the zeppelin can already lift more than 100kg (220lb). Future versions could lift 300kg (660lb), or a communication array to broadcast broadband direct to a large number of people. Broadband services can be provided by zeppelin instead of masts.

So far Sceye has run two flights for broadband-to-smartphone. This September will see its first demonstration flight for methane leaks monitoring.(Read aboutthe growing fleet of satellites identifying methane leaks from space)

“We’re very big,” he laughs. “We’re very visible. And so we work best at home in a friendly territory, to connect people, to help people.

“At the end of the day, once you get to the stratosphere, there’s no point in staying unless you can turn that into a business.”

Some of the balloons used to carry humans to the stratosphere have been the size of a football stadium. Not soUrban Sky‘s. Inflated on the ground, these reusable microballoons are the size of a car, with a payload attached underneath.

As the images show, they offer the high-res aerial imagery needed to monitor the aftermath of wildfires, and to even image entire cities, which insurance companies or city planners might need.

“We can literally launch from the back of the pick-up truck,” says Jared Leidich, co-founder and chief technology officer of Urban Sky. “We figure out from the weather models where we would need to launch a balloon from to have it passively float over its target, and drive there. Twenty to 30 years ago the models were not good enough to do this.”

But climatologists are starting to worry about the impact all this increased activity may have on the stratosphere. Water vapour is present in minute amounts. So, any increase in its use due to the use of hydrogen powered aircraft may have a disproportionate affect, especially contributing to the destruction of ozone layer.

“Pollutants will remain in the stratosphere much longer because atmospheric mixing is a lot slower,” says Michaela I Hegglin, a professor in atmospheric chemistry at the University of Reading in the UK and a member of the Forschungszentrum Juelich in Germany.

“So, you must consider how you might disturb the stratosphere if you suddenly start building a big aircraft fleet that will fly up there every day,” says Hegglin.

At around 4am on 19 August 2022, the Zephyr finally succumbed to gravity after an incredible three-month flight of 35,000 miles (56,300km) at around 70,000ft (21,300m) and over 64 days aloft – only hours away from breaking the 1959 endurance record.

“The flight was a huge success,” says Chris McLaughlin of the Aalto Haps programme. “It flew all the way down to South America on a mission and all the way back again. And the US Army pronounced themselves happy, but we are not allowed to open up on what they did with it.”

Its success was due to the singular focus of Aalto’s engineers at Farnborough in the UK, says McLaughlin. “One of the great skills of the team in Farnborough is they are obsessive about reducing weight. How do we reduce the weight of that wiring loom? Is there a better piece of carbon that we can put in place to strengthen this and at the same time reduce weight?”

The eight-to-10 hours the Zephyr takes to ascend to the stratosphere means that the aircraft needs a very stable weather environment to fly in. “We are planning to build several ‘Aalto ports’ around the world in countries with very good, stable weather at different times of the year,” says McLaughlin. “So we’ll always be able to get access to the stratosphere, and that was all part of Chris Kelleher’s original concept.”