Sky-Crane
The rocket-powered platform that lowers a rover to the surface on tethers, then flies away — the landing system that put Curiosity and Perseverance on Mars.
101 · zoom in
Early Mars rovers were small enough to bounce down inside a cocoon of airbags. But Curiosity was the size of a car — far too heavy for airbags — and putting big landing legs under the rover would have meant perching it high on a bulky platform, then somehow driving it off. NASA's answer was stranger and more elegant: the sky-crane.
After the heat shield and parachute have done their work, a rocket-powered descent stage takes over, firing eight engines to slow to a near-hover a few metres up. Then, instead of landing itself, it lowers the rover beneath it on a set of tethers — like a helicopter placing a load — until the rover's wheels touch the ground. The rover is its own landing gear.
The instant the rover is down and its weight comes off the tethers, the descent stage cuts the cords and flies away to crash a safe distance off, so its exhaust and its wreckage never touch the rover. The whole sequence — hover, lower, touchdown, fly-away — takes only seconds, and it has now worked twice: for Curiosity in 2012 and Perseverance in 2021.
The sky-crane solves two problems at once. It keeps the rocket engines high, so their plumes do not dig a crater or throw debris up at the rover, and it delivers the rover directly onto its wheels, ready to drive — no ramps, no lander deck to descend. The cost is a choreography with zero margin for error, executed autonomously, minutes after a fiery entry, with Earth too far away to help in real time.
It is the terminal chapter of the seven minutes of terror: entry heating, then the supersonic parachute, then heat-shield separation, then the powered descent, then the sky-crane lower and fly-away — each step must fire on cue or the mission is lost on landing. Only a handful of nations have soft-landed on Mars at all; the sky-crane is the most audacious way it has been done.
On `/fly`, fly Curiosity or Perseverance in `?descent=1` and watch the descent stage's tethers pay out below the parachute-and-retro sequence, lowering the rover to the surface before the stage flies clear — the sky-crane beat made visible.
SEE IN THE APP
- /fly Fly Curiosity or Perseverance in ?descent=1 to watch the sky-crane lower the rover on tethers