Patagonia, Argentina, is one of the windiest places on Earth. Gusts can do more than just make for bad hair days. They stretch trees sideways and can knock planes from the sky. (See: the movie Alive.)
To the pilots and scientists of the Perlan Project, an aviation expedition under way this month in El Calafate, Argentina, the harder the wind blows, the better. It’s a sign that an atmospheric condition called stratospheric mountain waves are forming in the skies above the Andes Mountains.
By the end of this month, the pilots hope to begin flights in a three-million-dollar experimental glider. The craft arrived by container ship from the United States this week. Within days, the team will attempt soaring to an altitude of 90,000 feet (27,432 meters)—the edge of space.
If successful, Perlan will beat the world altitude record for a fixed-wing aircraft of 85,068 feet (25,929 meters), set 50 years ago by the SR-71 Blackbird.
The Perlan mission is about more than just exploration. The pilots will test the experimental glider at an altitude where the air density is similar to that on the surface of Mars. The glider is outfitted with scientific equipment so it can take measurements of the Earth’s atmosphere along the way. The data will help meteorologists better understand the ozone hole and the polar vortex, features of the Earth’s atmosphere being impacted by climate change.
If successful, the Perlan flight will break the altitude record set by a jet-powered spy plane. Except that, unlike the Blackbird, the Perlan glider will have achieved that height without consuming a drop of fuel. (Learn about the record-breaking Solar Impulse project.)
The Perfect Wave
Mountain waves occur wherever a jet stream collides with a mountain range. As the jet stream ramps up and over it, a column of air is pushed upward, creating lifters for gliders to soar. (Perlan is an Icelandic word for the pearl-shaped clouds that sometimes form over mountain waves.)
In the United States, the Sierra Nevadas produce one of the world’s most powerful and consistent mountain waves. In 1986, pilot Bob Harris soared to 49,009 feet (14,938 meters), a record for gliders. That’s about as high as the Sierra wave can go before it hits the tropopause, the ceiling to the Earth’s lower atmosphere, and dissipates.
Elizabeth Austin, Perlan’s chief meteorologist, knew that the team would need help getting through the tropopause, either in the form of a secondary boost or a lessening of its dampening effect on mountain waves. Scouring maps of the Earth’s climate, topography, and weather systems, she noticed a high-altitude air current called the Stratospheric Polar Night Jet. Oval-shaped, it rotated west to east so that the longer ends swept across the 55th parallel with every revolution. She and Einar Enevoldson, a former NASA test pilot, theorized that conditions could arise where the polar night jet could line up directly over a low-altitude jet, allowing the Perlan pilots to stair-step into the stratosphere.
A Blast of Air, Then Quiet
Perlan’s Phase I flight was made by Enevoldson and Steve Fossett, the millionaire adventurer who funded the expedition. On August 30, 2006, they soared to an altitude of 50,724 feet (15,460 meters) in the skies over Patagonia, breaking Harris’s soaring record from the Sierras. The flight proved Enevoldson’s theory and Austin’s atmospheric model correct.
“It felt quite graceful,” Fossett said after the flight, speaking with me at an airport hangar in Patagonia. “The hardest part was getting into the wave because we had to go through a lot of turbulence that stressed the glider to around 5 g's. But once we connected with the wave, the air went smooth and there was an eerie silence. We were just climbing. That’s the wave: Once you’re there it’s easy.”
Tragically, Fossett was killed one year later, in an unrelated plane crash in the Sierra Nevadas.
“I couldn’t have asked for a better sponsor or colleague than Steve Fossett,” says Enevoldson. “We owe him for taking on the project and giving it respectability.”
For Phase II, Perlan needed to build an experimental glider, from scratch. Members of the gliding community donated a million dollars, but the project needed a lot more. In 2014, Enevoldson announced that Airbus Group, the European plane manufacturer, had agreed to be Perlan’s corporate sponsor. Airbus covered the costs for completing the sailplane, its test flights in California, and two years of flight attempts in Argentina.
“The prospect of winged flight on Mars is becoming more real,” says James Darcy, a spokesman for Airbus. “This glider could create a technology road map for use 30 years into the future.”
Stretched to the Limit
The glider’s most obvious feature is the cockpit’s round windows. Square windows would’ve created stress at the corners, causing the frame to buckle or a window to pop out. For testing, the engineers built a replica model and tested it to 25 psi. In the stratosphere, the sailplane will experience only 8.5 psi, giving the design a safety factor of three, NASA’s standard for spacecraft.
“We spent hundreds of engineering hours eliminating every risk we can,” says Jim Payne, the project’s chief pilot. “There’s always a small chance of some unknown danger.”
The unknowns increase the higher Perlan goes. Payne tested the glider at 20,000 feet (6,096 meters), in the Sierra Nevadas. It performed to specs, giving him confidence the design will perform at 90,000 feet (27,432 meters). But at that altitude, the plane will be pushed to the limits of its ability. Because the air will be thin, the sailplane will risk stalling. But if it goes too fast, the relative ground speed will be such that the plane could easily go Mach I, and break the sound barrier, which would send damaging shock waves through the craft.
As Austin succinctly puts it: “Go too slow, and you fall out of the sky. Go too fast, and you fall out of the sky.”
In either scenario, the Perlan cockpit doesn’t eject, but the pilots can release a ballistic recovery chute that will bring the plane down to Earth safely. The best insurance against that is for qualified pilots to be in command of the craft.
Enevoldson, age 84, believes it is unwise for him to fly the mission he dreamed up 20 years ago. So he recruited Payne, a retired Air Force test pilot with 2,000 hours of mountain wave experience. (Payne also spent parts of his career as a flight trainer, playing the role of a Soviet MiG in real-life versions of the dog fight scene in the movie Top Gun.)
As exciting as the flight will be, the Perlan team expects to spend a lot of time waiting around the hangar in El Calafate, Argentina.
“A lot of stars have to line up for us to get a shot at 90,000 feet,” Austin says. “Really, there’s just a handful of chances in a season when that will happen.”
But the worse the wind gets, the better their odds will be of making aviation history.