There's a new race in space, but it's not where you might expect. It's happening close to home, right at the edge of Earth's atmosphere.
High above Earth, a new space race is taking place. Here, just above the line where space begins, companies are working to create a new kind of satellite. These aren't quite high-altitude planes or low-orbit satellites. Instead, these sky skimmers are designed to circle our planet in an unexplored area, offering potentially huge benefits.
Currently, about 10,000 satellites are orbiting our planet at speeds of up to 17,000 mph (27,000 km/h). Each of these delicate machines is in constant free-fall and would fall back to Earth if not for their incredible speed. It's their strong sideways momentum, perfectly balanced against Earth's gravitational pull, that keeps them in orbit.
A new class of satellites aims to push the limits of this balancing act by flying in a much lower orbit that skims the top of Earth's atmosphere. Known as Very Low Earth Orbit (VLEO), these spacecraft must contend with much greater air resistance in the upper atmosphere than higher-altitude satellites, to avoid being pushed out of the sky. If successful, these satellites could achieve something remarkable—they might potentially fly indefinitely.
"When you start describing it to people, it sounds like a perpetual motion machine," says Spence Wise, senior vice-president at Redwire, an aerospace company in Florida. A perpetual motion machine is supposed to be impossible, but in this case, it almost is.
A few pioneering companies have started designing satellites that might orbit the planet at these unusually low altitudes while collecting air and using it to create propellant—literally while flying. This new generation of satellites could enable ultra-high-definition surveillance of ground activities or superfast satellite-based communications.
If you want to send something into orbit, you need to decide how high your satellite will fly. Earth orbits are generally described by altitude and divided into different categories. In high orbits, 22,000 miles (36,000 km) above Earth, satellites enter a geostationary position, meaning they stay above the same spot on Earth. This is useful for telecommunications and weather monitoring. Next is Medium Earth orbit, which ranges from about 22,000 miles (36,000 km) down to 1,200 miles (2,000 km) above the planet. Below this is Low Earth orbit, extending down to altitudes of 250 miles (400 km), where the International Space Station (ISS) is located. Even lower is VLEO, loosely defined as anything below the ISS down to about 60 miles (100 km). Operating here is challenging because of Earth's atmosphere. "The atmosphere will increase exponentially as you come down," says Hugh Lewis, a professor of astronautics and a space debris expert at the University of Southampton in the UK.
This creates more drag on your satellite, which can be disastrous. As molecules in the atmosphere collide with the satellite, they reduce its momentum, causing Earth's gravity to pull it towards the ground.