NASA will fly in the air on another planet.
As part of its next mission to Mars, which will leave Earth this summer, the space agency will try to do something that has never been done before: flying a helicopter through the dilute atmosphere of Mars.
If it works, the small helicopter called Ingenuity will give future robot researchers a new way to get a bird's eye view of Mars and other worlds in the solar system.
"This is very analogous to the Wright brothers moment, but on a different planet," said MiMi Aung, project manager of the Mars helicopter at NASA's Jet Propulsion Laboratory for the past six years.
Flying on Mars is not a trivial undertaking. There is not a lot of air there that you can press against to create buoyancy. The atmosphere on the surface of Mars is only 1/100 as dense as that of the Earth. The lower gravity – a third of what you feel here – helps get up into the air. However, taking off from the surface of Mars is equivalent to flying at 100,000 feet on Earth. No land helicopter has ever flown so high, more than double the height that jetliners normally fly.
The helicopter will use Perseverance, the fifth robot rover that NASA sent there, to couple a trip to the red planet. The mission is scheduled to launch on July 20, one of three missions to Mars this year.
At a press conference last week that previewed the Perseverance mission, NASA administrator Jim Bridenstine emphasized Ingenuity. "I'm telling you the thing that thrills me most as a NASA administrator is to prepare to see a helicopter fly to another world," he said.
By 1997 all spaceships had been sent to the surface by Mars had been stationary landers. But in 1997, the Pathfinder mission included something that was revolutionary for NASA: a robot with wheels. This rover, Sojourner, was about the size of a short filing cabinet. This success was followed by two golf cart-sized rovers, Spirit and Opportunity, that arrived on Mars in 2004, and Curiosity, about the size of a car, in 2012.
For a robot researcher on another planet, the ability to move around offers great advantages.
Planetary scientists no longer stare at one place. A rover can drive through the landscape and take a closer look at fascinating rocks. This freedom was key to the current understanding of early Mars that the planet, now cold and dry, was once wet and had at least some environments that might have been habitable for life.
Ingenuity is essentially the counterpart of Sojourner from the air, a demonstration of a new technology that may be used on a larger scale in later missions. Ingenuity's body is about the size of a softball with four protruding spindle-shaped legs. Two sets of blades, each about 4 feet from tip to tip, rotate in opposite directions. It weighs only 4 pounds and is about a foot and a half tall.
Bob Balaram, the chief engineer of the helicopter, started working on the idea with some colleagues in the 1990s.
"That wasn't really like going anywhere," said Dr. Balaram. "We did some small tests, but then it was on the shelf until about six or seven years ago."
He said Charles Elachi, then director of the Jet Propulsion Laboratory, was interested and provided money for further studies. "And that got us going," said Dr. Balaram.
Doing something that had never been done before was a technical challenge that Ms. Aung addressed, who joined in mid-2014 as a project manager.
"About 20 years ago it wasn't actually possible due to the math," said Ms. Aung, who was the deputy head of the autonomous systems department at the Jet Propulsion Laboratory before joining the Mars project.
But a number of advances, such as miniaturization of electronics, batteries that store more energy, and materials that could be shaped into light blades, had finally made the dream of Mars flying machines a technological possibility, Ms. said Aung.
Seizing the opportunity Getting into a working helicopter took years of trial and error.
By the end of 2014, the engineers had built a small prototype. The small helicopter was placed in a chamber in which most of the air was extracted, which simulated the density of the Martian atmosphere. Since they had not yet written software for the helicopter to fly themselves, a member of the team tried to control their movement with a joystick, like a hobbyist flying a drone.
When the leaves turned, the helicopter rose. It got out of control immediately.
They had buoyancy but no control.
"It did exactly what we had to do at the time, namely to say that we can actually take off the ground," said Havard Grip. the engineer who led the work on aerodynamics and achieving a controlled flight. “In this way it was a success. But it was also clear that there was still a lot to do here to understand how this thing behaved. "
Dr. Balaram and Dr. Grip said one problem was that the blades bobbed up and down at 2,000 to 3,000 revolutions per minute. On earth, the pressure of the air that presses against the blades minimizes the impact. But in the thin Martian atmosphere, the impact caused an instability that made it difficult to control the movement of the helicopter.
The solution turned out to be that the blades became a bit stiffer, but that added some weight.
"Arrival I think a suitable design for this was one of the biggest problems early on," said Dr. Grip. Finally, they found a solution.
“It is quite amazing when you lift one of these blades. When you hold it in your hand, you think you will be lifting something essential and it is as light as air and air at the same time extremely stiff. “
Engineering involved a number of trade-offs that were necessary to meet size, weight, and battery performance constraints.
Dr. At the same time, Grip led the development of computer algorithms with which the helicopter's flight can be controlled and adjusted quickly enough to automatically respond to changing atmospheric conditions on Mars.
The next prototype was ready in May 2016. In the same chamber that simulated the transparent Martian atmosphere, the helicopter rose, then hovered steadily and landed gently. For the first time, a prototype helicopter had flown under conditions that simulated the Martian atmosphere, although it was still connected to an external power source and a computer.
The Complete Design Using the Batteries of a Qualcomm Snapdragon Processor To mimic the weaker gravitational pull of Mars, a pulley was pulled up to counter some of Earth's gravity. The air density in the chamber was pumped out again. But this time, a bit of carbon dioxide – the main component of the Martian air – was pumped in instead of leaving a piece of natural air.
The helicopter climbed and flew.
Half a year later, NASA gave the go-ahead to add the helicopter to NASA's next Mars rover mission, Perseverance.
Ingenuity is now linked to Perseverance's belly, which is making the final preparations for the launch from Cape Canaveral, Florida.
In the meantime, Ms. Aung and her team have rehearsed what they will do when Ingenuity is on Mars. Since the Jet Propulsion Laboratory was largely closed due to the coronavirus pandemic, all work was done via conference call, with all team members working from home.
About two months after Perseverance landed on Mars in February, testing by Ingenuity will begin. The rover finds a reasonably flat place, drops the helicopter onto the ground, and then drives away at least 100 meters away. "The helicopter never returns to the rover," said Ms. Aung.
The helicopter will carry out up to five flights over 30 days. Most of the time, people sit around and wait for solar panels to charge the batteries.
The first is to go up a few feet and hover for up to 30 seconds and then land. Subsequent flights will be longer, higher and further. If everything works on the fifth flight, Ingenuity rises about 15 feet, flies 500 feet, and then returns to where it started. It has two cameras: a black-and-white, down-facing camera that lets you track where it is; and a color for oblique views of the landscape. The flight will take a minute and a half.
Once the flights are completed, Ingenuity will be left at its final landing site and Perseverance will leave for the rest of its mission.
Mr. Aung said the technology could be adapted to a larger vehicle, weighing up to 30 pounds instead of four. That could be big enough to carry a few pounds of cameras and other instruments.
NASA already has plans to send Dragonfly, a nuclear aircraft, to Titan Saturn's largest moon. But Titan has a thick atmosphere, so flying there doesn't pose the same technological challenges as Mars.
Even if future helicopters fly to Mars, they will almost certainly never be a viable means of transportation for astronauts.
"You wouldn't imagine expanding it so that you can fly people as you can on Earth," said Ms. Aung. "There's just not enough atmosphere."