Why local flight on Mars is a big deal
There are several technological challenges to conducting a helicopter flight on another world. First, and most significantly, helicopters need an atmosphere to fly.
The blades, or “rotors” of a helicopter must spin fast enough to generate a force called “lift”. But lift can only be generated in the presence of some kind of atmosphere. While Mars does have an atmosphere, it’s much, much thinner than Earth’s — about 100 times thinner, in fact.
Flying Ingenuity in Mars’s atmosphere is therefore the equivalent of flying a helicopter on Earth at a height of 100,000 feet. For reference, commercial aircraft fly between 30,000-40,000 feet above the Earth’s surface and the highest we’ve ever been in a helicopter on Earth is 42,000 feet.
Testing the craft on Earth required a pressurised room, from which a lot of air would have been extracted to emulate Mars’s atmosphere.
Then there’s the Martian gravity to consider, which is about one-third the strength of gravity on Earth. This actually gives us a slight advantage. If Mars had the same atmosphere as Earth, it’s lesser gravity means we’d be able to lift Ingenuity with less power than would be required here.
But while Mars’s gravity works to our advantage, this is offset by the lack of atmosphere.
Ingenuity’s success marks the first time such a flight has even been attempted outside of Earth. And the reason for this may simply be that, as laid out above, this task is very, very difficult.
There are two main ways Ingenuity was able to overcome the hurdles presented in Mars’s atmosphere. Firstly, to generate lift, the two rotors (made from carbon fibre) had to spin much faster than any helicopters on Earth.
On Earth, most helicopters and drones have rotors that spin at about 400-500 revolutions per minute. The Ingenuity’s rotor spun at about 2,400 revolutions per minute.
It also has a distinct aircraft-to-wingspan ratio. While Ingenuity’s body is about the size of a tissue box, its blades are 1.2m from tip to tip.
Even transmitting the signal for the flight to begin required an array of advanced technology. Whilst it only requires minutes for radio signals to travel between Earth and Mars, there was still a delay of hours for those signals to reach the helicopter.
This makes sense when you consider the journey those signals have to take – from a computer on Earth, to a satellite dish, to the Mars Reconnaissance Orbiter, to the Perseverance rover and then, finally, to the helicopter.