Breathe the air, the higher you fly

Of course, this is even more of a factor for climbers trying to climb Mount Everest. Because at the top of that mountain, a cubic meter of air weighs only 400 grams—about a third of the sea level figure. Climbers must not only take the time to hike as they ever climb a mountain, but they also often carry oxygen along to help them breathe at those heights.

To understand all this, let’s start with how much air you breathe in: about eight liters per minute. That much air at sea level weighs about 10 grams. Twenty percent of that is oxygen, or about 2 grams. So for normal functioning 2 grams of oxygen per minute of normal breathing is required. At the top of Everest, you’d need to take three minutes or more of deep breaths to get that much oxygen. hard work. No wonder most climbers carry tanks of oxygen near the top.

So imagine reaching a place where the air around you is so thin that a cubic meter weighs just 18 grams. Not more than a kilo, not 400 grams, but only 18 grams. If you were still on Earth, the 8 liters of water you consume each minute would weigh only 0.15 grams, of which 0.03 grams is oxygen. How hard would you have to work to get your regular dose of 2 g/min of oxygen? No amount of adaptation will help you survive in that thin air, even if the air is pure oxygen. You will have to carry and breathe through the oxygen tank at all times.

There is actually one place where the density of air is so low, although it is nowhere on Earth. This is Mars, and if the thinness of its air was not a sufficient constraint, there is an added complication. Twenty percent of Earth’s air is oxygen, but Mars has only 0.16% air. So for every minute you breathe on Mars, you’ll only breathe 0.00024 g—0.24 micrograms—of oxygen. The truth is that you’ll be inhaling almost pure carbon dioxide because that’s 95% of the Martian air.

The truth is, unless you strap on those oxygen tanks you dug out of the earth, you’ll die quickly.

Again, there’s an instrument called MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) that travels to Mars with NASA’s Perseverance rover that landed there earlier this year. The team that designed this toaster-shaped device describes it as an “electric tree,” which is pretty accurate. Trees on Earth absorb carbon dioxide and release oxygen, and that’s exactly what Moxie is designed to do. Remember that carbon dioxide is created. above carbon and oxygen (CO2). MOXIE “breathes” in the carbon dioxide and breaks the molecules down into those components, thus producing oxygen. But if it’s just theory, last April Moxie went to work and actually produced about 10 grams of oxygen an hour. Just five minutes’ worth of, sure, but actual breathing oxygen all the same for your average human. And in doing so, Moxie showed that future humans on Mars would not need to carry massive amounts of oxygen from Earth. It would be an almost impossible task anyway. The moxie, or indeed a moxie on a large scale, can produce oxygen for them.

Even so, the main reason oxygen is produced there, at least with the first many arrivals on Mars and to allow for any long-term human presence on the planet, is not so much because human visitors need to breathe. . Even with 100 women and men on Mars, you’d need less than 300 kilograms of oxygen per day for all their breathing needs. In contrast, to lift a rocket from Mars and take some of those humans back to Earth – a journey that will certainly be repeated – would require 25,000 kilograms of oxygen.

There is no way to carry so much oxygen to Mars. Instead, the scaled-up moxie will have to be moved there several months before the first humans arrive and put them to work. Even though this hyper-moxy can generate one kilo of oxygen in an hour instead of 10 grams, it would take about three years for a rocket to produce enough oxygen for lift-off. Then, of course, facilities are needed to store all that oxygen, something else that would need to be carried to Mars. This is all just to tell you what it would mean to send humans to Mars. And yet, this pillar was not really driven by the needs of humans on Mars, but by problems that have already become thin air for anything on Mars.

I’m referring to – you might have guessed it – to Ingenuity, a small helicopter that also made the journey to Mars with perseverance. But, like Moxie, it was really – as I wrote in a column on Ingenuity (bit.ly/2XKmdKA) – “just an experiment, designed to answer the question: Will Mars But is it possible to fly?”

Why was this question? Precisely because the air on Mars is so thin. Are the blades of the Ingenuity strong enough to lift the helicopter off the surface? This was answered in April when Ingenuity took off for half a minute. Since then, it has flown more than a dozen times, some of them spending nearly three minutes on flights. It has reached a height of 12 meters above the ground, and in its ninth flight in July, it flew over 600 meters horizontally.

Yet its 14th flight, which will happen any day now, will be a test run. This is because the density of air is falling as the “seasons” on Mars change. NASA estimates that “in the coming months, we may see a density as low as 0.012 kilograms per cubic meter during the afternoon hours, which is better. Flight” (go.nasa.gov/2W8VuXc)—that is, one cubic meter The air would weigh only 12 grams. 18 no. Can Simplicity handle that fall?

Thin air would need ingenuity to spin its blades faster than it has ever been: 2,800 rpm compared to the roughly 2,500 rpm used so far. would it be possible? Can a small helicopter maintain the rotor speed that high? There are various potential side effects to consider, some potentially damaging to Ingenuity’s delicate system. Nevertheless, on September 17, NASA confirmed that Ingenuity conducted a rotor spin test at 2,800 rpm (bit.ly/3CGTCOK) without taking off. Thus we know that the blades can spin so fast. So Ingenuity is ready to attempt flight again. However when this happens, the 14th flight will operate at 2,700 rpm, to release the buffer at some point when needed. It will be a brief flight – climb up to 5 metres, take off and land a short distance sideways.

So much so that it would prove that even when the air on Mars is still thin, it is capable of flying smoothly. But it’s probably a good thing that Ingenuity doesn’t need any oxygen.

Dilip D’Souza, once a computer scientist, now lives in Mumbai and writes for his dinner. His Twitter handle is @DeathEndsFun