Airbus Wants to Replace Satellites With High-Flying Drones
When Sputnik 1 reached low Earth orbit in 1957, it did more than kick-start America’s space program and send American schoolchildren scurrying for cover under their desks. It launched the satellite age. The orbiting platforms, which now number in the thousands, revolutionized communication, navigation, and watching football.
Satellites, though, are expensive to build, expensive to launch, and difficult to update once in orbit. Drones are another story. They’re relatively cheap, easily launched, and readily updated. Of course, they can’t stay aloft very long.
Or can they?
Airbus recently announced the successful maiden flight of its Zephyr T aircraft, a drone powered only by sunshine. Six decades after Sputnik launched the space race, the European firm joins the likes of NASA and Facebook in a race to build high-altitude drones that combine the advantages of a satellite and the flexibility of a plane. “You don’t have to go through the rigor that current space-based satellite systems use,” says John Del Frate, an aerospace engineer at NASA’s Armstrong Flight Research Center.
These “high altitude pseudo satellites,” as Airbus calls them, won’t drop bombs or deliver packages. They’ll do many of the things satellites do and return periodically for new batteries or new tech. One day, swarms of solar-powered drones could monitor military or intelligence targets, track forest fires, or provide communications in an emergency. By flying far lower than satellites, drones could provide sharper photos of Earth. They could provide high-bandwidth links, using lasers to relay information to other drones or receivers on the ground, providing the sort of line-of-sight communication isn’t possible with satellites that orbit the planet and disappear over the horizon.
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NASA’s 1999 Helios prototype was among the first forays into this technology. In one experiment, NASA used boomerang-like aircraft, made of carbon fiber and Styrofoam, as an airborne cell phone tower. It was funky but graceful, with a wingspan of 247 feet and 14 electric propellers, but crashed into the Pacific near Kauai in 2003. Helios topped out at more than 96,000 feet, and was designed to stay in the air for at least 24 hours.
Flying something at those extreme altitudes, for long stretches, and on solar power, poses new challenges. For Helios, the killer was power storage. The team experimented with fuel cells, but batteries are a better choice. “Endurance is huge,” says Del Frate, who managed the program. “Anything you put up there has to be ultra-reliable. It’s kind of like your refrigerator, you just want to plug it in and forget it.”
Airbus started working on pseudo satellites in 2008, aiming to fill the “capability gap” between satellites in orbit and the low-altitude, limited drones of the day. In 2010, Zephyr 7 smashed the world record for longest flight without refueling (14 days). After that, the company decided to move to commercialization with two new models, the Zephyr S and Zephyr T. The British Ministry of Defense has dibs on the first two S models, and will likely use them for surveillance. Airbus just tested a one-quarter scale model of the T, which will stretch the Zephyr S’s 82-foot wingspan to 108 feet. It will quadruple its payload capacity to 44 pounds, enough to carry the radar and other gear military customers will want to keep airborne.
The solar-powered planes are designed to cruise at around 65,000 feet, nearly twice the altitude of commercial airliners. The Zephyr 7 prototype can fly for 14 days on end. Airbus plans to get that up to at least a month.
To achieve that, the team is taking cues from nature, says Steve Whitby, head of business development for the Zephyr program. Instead of the upturned winglets now common on commercial aircraft, his aircraft sport downturned tips, like a buzzard’s wings. “Because of the speed we’re flying at, which is quite slow, we want to gain the maximum lift,” he says. This aerodynamic trick effectively gathers wind beneath the wings, for a 15 percent efficiency gain. Weighing as little as possible helps, too: The S model—which resembles a wire hanger that’s figured out how to fly—is just 143 pounds. The twin-tailed T weighs just over 300, counting its payload.
The biggest issue impacting endurance is what happens in the dark, when photovoltaic cells can’t generate power. A solar plane currently circumnavigating the planet offers one idea: Solar Impulse 2 spends the day at about 30,000 feet, then slowly descends to 5,000 at night, trading altitude for distance. Zephyr can’t drift down quite so much, or it will enter commercial airspace and spend all day returning to its operational height. Airbus says the electric propulsion it uses is already efficient, but expects improves as battery tech advances.
There’s plenty of competition here. The Solar Impulse team says its next project will focus on a lightweight solar drone capable of remaining aloft for six months. Google is experimenting with high-altitude drones and balloons to provide wireless service. Facebook is developing a solar drone called Aquila, which would fly for three months at a time to provide Internet access to remote areas.
Airbus hopes to combine the lessons from Zephyr program with its experience building conventional satellites to launch and maintain a fleet of forever drones. This isn’t a concept anymore—the Zephyr S is already in production, and before long will be pinging above our heads, just like Sputnik 1.