Mars Helicopter (before it went to Mars)
Why Hacker News recommends it
HN repeatedly recommends it as an excellent explanation of why flying on Mars is hard and how the helicopter was built.
What it is
Veritasium's Derek Muller visits NASA JPL to see the Mars helicopter Ingenuity before it was mounted on the rover. He explains how it can fly in Mars's thin atmosphere with large, fast-spinning contra-rotating rotors and low mass, and covers power and cold.
Recommended by 10 HN commenters across 4 different months, 2020 to 2021.
What Hacker News said
Strong rec kibwen · 2021-02 · on “Perseverance Rover lands on Mars [video]”
Here's a really excellent video that answers all your questions: [this video] TL;DW: Martian atmosphere is so sparse that it's equivalent to flying at 100,000 feet on Earth. (The altitude record on Earth is 85,000 feet, set by the SR-71.) In order to fly at all the blades have to spin at nearly the (Martian) speed of sound. The drone wouldn't fly on Earth because the atmosphere is so dense that the blades would never make it up to speed.
Recommends jcims · 2020-06 · on “NASA rushing to complete Mars launch before planet moves out of range”
Totally agree. It's obviously a high risk portion of the mission but I'm glad someone had the guts to propose it. Derek from Veritasium did a nice little story on it last summer - [this video]
Recommends manicdee · 2021-02 · on “How NASA Designed a Helicopter That Could Fly Autonomously on Mars”
Veritasium did an episode 'Mars Helicopter' containing some interesting discussions with the team that built it. [this video] nm it was already linked elsewhere
Recommends kibwen · 2021-02 · on “Perseverance Rover lands on Mars [video]”
A great video where the host visits the drone, interviews its makers, and goes over the cool technical aspects of it and its mission: [this video]
Recommends Brajeshwar · 2021-02 · on “The Mars Helicopter Is Online and Getting Ready to Fly”
You should watch Dr. Derek Muller of Veritasium, who did a video (2019) details of the Helicopter while it was being built. [this video]
Recommends kingo55 · 2021-02 · on “The Mars Helicopter Is Online and Getting Ready to Fly”
It's not just atmosphere and g-forces. The cold temperatures mean the helicopter spends 2/3 of its battery power keeping the batteries and electronics from freezing. Good rundown of how it was built: [this video]
Recommends jshmrsn · 2021-04 · on “NASA's Mars helicopter Ingenuity touches down on the Red Planet”
Veritasium has a great video on the helicopter. Early on in the video they explain that Mars’ atmosphere is equivalent in density to Earth’s atmosphere at 100,000 feet, and the record altitude for helicopters on earth is 40,000 feet. [this video]
Recommends ortusdux · 2021-04 · on “NASA's helicopter survives first freezing night on Mars”
On top of what others have said, we need advancement it batteries that can withstand low temperatures. Lithium ion batteries generally need to be kept above freezing temps. There have been some advances in capacitors that operate down to -100C, but their energy density makes them a non-ideal option for weight limited applications. This video from Veritasium does a good job of covering the helicopter power system: [this video]