Yesterday, on April 19, 2021, at 07:15 UTC, the NASA’s Ingenuity Team did it. In a moment comparable to the Wright’s Brothers first flight in 1903, a little helicopter, about half a meter high, received the instructions from 287 million kilometers (at the time, Mars-Earth distance varies a lot) away to take off vertically 3 m high, hoover for 40 seconds and then return to original position. They succeeded!
Imagine being on that team, you send the instructions, you know you have to wait around 15 minutes for the signal to reach Mars, then you have no way of telling if the Helicopter did what was intended or not until after it has sent back a message basically saying: “Everything ok guys, don’t worry, flight went well, take care, XOXO.” So you had to wait for around half an hour before realizing if it either worked or not. That’s pretty stressful. I think about moms when they call their kids to check if they are ok and get no answer until half an hour later, worrying sick meanwhile.
This helicopter flew to Mars in the belly of the Mars Perseverance Rover, which arrived to the red planet on February 18, 2021.
It is an engineering masterpiece for many reasons. First of all, it is light, very light, with just 1.8 kg it weights the same as my ASUS laptop! Which funny enough is promoted as “Ultra-light weight”… Anyways, that is amazing considering the span of its blades is 1.2 m and is half a meter high, has a solar panel, box of circuits, CPU, cameras, battery, sensors, etc… They managed this by using carbon fiber blades, and carbon compound legs. Carbon fiber is approximately 5 times stronger than steel but 8 times less dense, which relates the weight of a material to the volume it occupies. For instance carbon fiber has a density of around1.6 g/cm³ while steel of around 8 g/cm³. Basically, a little bar of carbon fiber will be 5 times harder and 8 times lighter than a similar steel bar. Awesome, right?
Let’s continue. So yes light is cool, carbon fibers are cool too, but why is that so important? Because flying in Mars is very, very hard. Imagine, for instance, trying to swim up in the AIR. Sounds crazy I know, but it’s just to give you an idea. I would dare say confidently that it is extremely hard to swim in air. And I like this comparison to understand the importance of the density of the medium you are planning to move through. With a gas, like air, think of density as the amount of molecules you would expect to find in a defined volume. In Mars the “air” is almost 100 times less dense than on Earth at sea level. So of course it is not as drastic as my “swimming in air” example, because air is around 1000 times less dense than water, but it helps make the problem more tangible. To test the Ingenuity, they used a big vacuum chamber filled with CO2 with 0.68% the atmospheric pressure of Earth, because Mars’ atmosphere is 95 % CO2. Although the red planet is smaller than Earth and therefore, according to Newton’s law of gravitational motion, its gravity is only 38% of that of ours (an 80 kg person would weight 30 kg in Mars) which helps with our flight purpose. But still, it is really hard, so you need light weight, and very fast spinning blades, at around 2400 rpm.
The other big challenge is communication. I hope it is now obvious to you that it is not possible to fly this helicopter with a joystick or a PlayStation like controller. No, no real-time flying. But we humans are very smart (sometimes) and we came up with cool algorithms that make flight almost autonomous. (You can check more about algorithms on my other article). So how it works is you break the problem into smaller chunks. Applicable to life. Basically you decompose flight into a series of small steps: make the helicopter able to autonomously do just certain very concrete actions. For instance, something like “test blades rotation”, “lift to 3 m high”, “stay there for 40 seconds”, “land”. Which is similar to how modern drones work. But this requires very complex algorithms that permanently monitor the sensors on the helicopter for altitude, balance, orientation, etc. and are constantly tweaking the rotation of the blades accordingly. Exactly like how you move your body according to your inner ear’s semicircular canals that allow you to feel when your head is straight or when you are tilting forward. Even more awesome is that they used open-source code (here) for the software and a Linux system on a pretty common smartphone processor (Qualcomm Snapdragon 801). A great day for open-source software!
The Ingenuity mission is just a proof of concept, a test of the possibility of future air missions on other planets. A gigantic first step towards new ways of exploring the Solar System. I like to imagine the engineers at JPL (Jet Propulsion Laboratory) saying something like, — ok we are sending a big rover to Mars, we might as well attach a little helicopter to it and see what happens. Oh! And since we are doing that, we might as well add a little 13 megapixel camera in case it does fly, so we can take maybe some nice pictures too, what do you say? — Indeed it has 2 cameras, one pointing downwards which is a 0.5 megapixels, black and white camera used for navigation, and a 13 megapixel color camera that points horizontally. Can’t wait for the upcoming pictures!
Finally, a little touch of poetry: they attached a little stamp size piece of fabric from the Wright’s brothers airplane wing and wrapped it around one of the cables under the solar panel on top of the Ingenuity. Because it is a comparable success! This is a historic moment, and I am proud to be part of the generations that were able to witness it. Congratulations to NASA’s Perseverance and Ingenuity teams and everyone that is and was involved with its operation and development. Thank you.
References and further reading:
- Ingenuity Mars Helicopter Preflight Briefing (press conference livestreamed on YouTube). NASA Jet Propulsion Laboratory. 9 April 2021.
- Balaram, Bob (8 April 2021). “When Should Ingenuity Fly?”. NASA Mars Helicopter Tech Demo. NASA.
- Chang, Kenneth (23 June 2020). “Mars Is About to Have Its “Wright Brothers Moment” — As part of its next Mars mission, NASA is sending an experimental helicopter to fly through the red planet’s thin atmosphere”. The New York Times.
- “How NASA Designed a Helicopter That Could Fly Autonomously on Mars”. IEEE Spectrum. 17 February 2021.
- “Ingenuity Mars Helicopter Landing Press Kit” (PDF). NASA. January 2021
- “Mars Helicopter Fact Sheet” (PDF). NASA. February 2020.