How Perseverance’s Sky‑Crane and Ingenuity Drone Redefined Mars Exploration

Sky‑Crane Landing

On 4:55 a.m. UTC 18 Feb 2021, NASA’s Perseverance rover entered the Martian atmosphere without a pre‑deceleration burn and performed a sky‑crane descent similar to Curiosity. The descent stage consists of an aerial crane with eight retrorockets and the rover suspended by a nylon rope and a data cable. After touchdown the rope and cable are cut and the crane flies away.

Two new technologies were used:

Distance‑triggered safety : rapid imaging to estimate altitude and trigger events.

Terrain‑relative navigation (TRN) : onboard cameras compare images to a pre‑loaded map to select a safe landing site in Jezero crater.

Mission Objectives

Perseverance carries seven scientific instruments: a panoramic camera, lidar, X‑ray and UV spectrometers, a MOXIE oxygen generator, weather sensors, and a ground‑penetrating radar. Primary goals are to search for biosignatures in ancient lake deposits, collect and cache rock and soil samples for a future return mission, and characterize geological diversity while demonstrating new technologies such as the Ingenuity helicopter.

Ingenuity Helicopter – Technical Overview

Ingenuity (“机智号”) is a 1.8 kg, 0.5 m tall rotorcraft with two pairs of carbon‑fiber rotors (1.2 m diameter) that spin up to 2400 rpm, delivering about 350 W. The thin Martian atmosphere (≈1 % of Earth’s density) and a sound speed of 240 m s⁻¹ require blade tip speeds below 40 rev s⁻¹ to avoid flutter.

The flight controller runs on a Qualcomm Snapdragon 801 processor (the same SoC used in the 2014 Xiaomi 4 smartphone). The processor was selected for its small form factor, radiation tolerance, and computational capability far exceeding the rover’s CPU.

Navigation hardware (IMU, laser rangefinder, etc.) is commercial‑off‑the‑shelf, demonstrating that consumer‑grade components can survive Mars conditions.

Because of the ~10‑minute light‑time delay, Ingenuity operates autonomously from a pre‑loaded instruction list stored on Perseverance. Each of the four test flights stays within 50 m of the rover, lasts ≤90 s, and is documented by rover‑borne images.

Open‑Source Flight Software

For the first time a Mars mission carried an open‑source Linux operating system. NASA JPL released the flight control software (F′Prime) on GitHub: https://github.com/nasa/fprime The repository contains the Linux‑based flight stack used by Ingenuity, enabling external developers to study and reuse the code.

China’s Tianwen‑1 Landing Concept

Tianwen‑1 entered Mars orbit on 10 Feb 2021 and plans a rover landing around May 2021. Unlike Perseverance’s sky‑crane, Tianwen‑1 will use a powered‑descent (retro‑propulsion) system, requiring larger fuel tanks and a wider‑stance landing‑leg array.

The Chinese rover is solar‑powered with a design life of 90 days, aiming to achieve the first complete “orbit‑landing‑rover” sequence for China.

Reference Links

https://github.com/nasa/fprime

https://www.wired.com/story/nasa-lands-the-perseverance-rover-on-mars/

https://www.nature.com/articles/d41586-021-00432-1

https://arstechnica.com/science/2021/02/what-to-expect-from-the-dramatic-mars-perseverance-landing-on-thursday/

https://spectrum.ieee.org/automaton/aerospace/robotic-exploration/nasa-designed-perseverance-helicopter-rover-fly-autonomously-mars

https://www.futurezone.de/science/article216775269/Der-Mars-Hubschrauber-funktioniert-die-NASA-hats-bewiesen.html