NASA’s Perseverance rover made its Martian debut this week—and strapped to its underbelly is one of NASA’s most daring scientific creations. Weighing at just four-pounds (or 1.5 pounds on Mars), Ingenuity will become the first rotorcraft to explore the skies of another world.
To ensure the helicopter would be ready for its Red Planet debut, engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, developed two Ingenuity prototypes. They subjected one prototype to rigorous environmental testing to see whether it could survive chilling temperatures and vibrations associated with lift-off and landing. The other was developed specifically for flight tests, which took place in a 25-foot- diameter vacuum-sealed space simulation chamber on JPL’s campus.
Now, it’s almost show time. Once separated from the rover, Percy’s otherworldly helo will have just 30 martian solar days (commonly called sols, which are each 24 hours, 39 minutes, and 35 seconds) to conduct a series of up to five test flights, each lasting anywhere from 30 to 90 seconds. The helicopter’s most ambitious hops, nearly all of which will be choreographed by Ingenuity itself, could take it as high as a single-story building and far as 1,000 feet.
While Ingenuity is a technology demonstration—meaning its only goal, really, is to safely get off the ground—a successful flight could forever change the way we explore our solar system.
Ingenuity’s 2-foot-long blades are specially designed for the Martian atmosphere, which is 1 percent the density of Earth’s.
“As the blades rotate, they tend to flap up and down a little bit, which interferes with control,” Balaram tells Popular Mechanics. “On Earth, [this motion] gets stamped out. On Mars, in the thin air, it doesn’t get stamped out.”
Grip, a research technologist also at NASA’s Jet Propulsion Laboratory, likens the unsteady motion to riding a bicycle with heavy grocery bags hanging from the handle bars. To counteract the wobble and make the flight smoother, the blades, which have a foam core and a carbon fiber coating, are crafted to be lightweight but extremely stiff.
The rotor system’s distinguishing feature is its hulking size compared to the rest of the vehicle.
“That’s one of the effects of the density being as low as it is,” Grip says. “You just have to have a larger rotor—basically as much rotor as you can fit.”
And it has to spin the blades quickly—2,800 revolutions per minute, or more than 10 times faster than chopper blades spin on Earth—but not too quickly. Because the speed of sound is lower on Mars,around 540 miles per hour, compared to Earth’s 760 miles per hour, the helicopter has to abide by a lower speed limit.
How Percy Will Deploy Ingenuity on Mars
“When you get too close to the speed of sound, you start getting very high drag at the tips [of the blades],” Grip says. “At that point, the power that’s needed to drive the rotors shoots through the roof.”
Ingenuity features an upper and lower rotor assembly. Each assembly includes a propulsion motor, pitch links, and three servo motors, which work together to direct the helo where it needs to go. Four additional weights, two for each assembly, create a “restoring force on the blades when under centrifugal loads…reducing the torque requirements” for Ingenuity, according to a NASA research paper.
Engineers settled on the coaxial rotor configuration as opposed to tail rotor or quadcopter design because it’s incredibly compact, meaning it could easily fit in the belly of the rover. That doesn’t mean quadcopter or hexacopter configurations are off the table for future missions.
“We are investigating different vehicle designs that would allow us to go further, faster and carry more payload,” Grip says.
The helicopter’s four carbon fiber and epoxy legs are extremely lightweight and attach to the landing plate with deformable aluminum elements at the hinges that help dampen the force of impact and prevent the rotorcraft from bouncing.
“We want to touchdown confidently, but without bouncing too much,” Grip says. “The legs are designed to accomplish that.” Ingenuity’s test team tried out the legs on a number of analog Martian surfaces including rock and sand.
The advanced quadruple-junction metamorphic solar cells that cap Ingenuity are specially “tuned to the Mars spectrum,” Balaram says, meaning they’re optimized to absorb the most energy from the light found on Mars.
The solar panels will charge Ingenuity’s six Sony Lithium-ion batteries. If needed, the battery pack can generate around 500 Watts, Balaram says. It takes roughly one Martian sol—depending on factors like the season and the scope of the mission—to recharge the helicopter’s batteries.
Because Mars doesn’t have a magnetic field, compasses and GPS systems are obsolete. Instead, the helicopter uses a black and white navigation camera that snaps pictures of the surface as it flies. “In that camera frame, we detect features on the ground that we track over time,” Grip says. “That helps us see how we’re moving relative to the ground.” The Return-to-Earth camera, a 13 megapixel Sony color camera, will snap images of the horizon and send them back to Earth for review.”
Those images, paired with observations from a LIDAR altimeter and an inertial measurement unit will help Ingenuity make decisions about where to fly and, ultimately, where to land.
“With those three sensors, we’re able to keep track of what the helicopter is doing at any point in time and where it is,” Grip says.
Fuselage Electronics Box
The fuselage contains an upper sensor assembly, affixed to Ingenuity’s mast, which includes of an inclinometer, an IMU, and elements that minimize flight vibration to protect the helicopter’s electronics. The lower sensor assembly contains an altimeter, navigation cameras, and a secondary IMU.
One of the most significant challenges the helicopter will face is simply staying warm. The average temperature on the Martian surface is roughly -64 degrees Fahrenheit. Balaram and his team have devised a few clever techniques to keep all of Ingenuity’s sensitive electronic equipment warm enough to operate.
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Click (or touch) and drag to interact with this 3D model of the Mars 2020 Ingenuity Helicopter.
The battery pack, which must be kept at at least 5 degrees Fahrenheit, is buried deep within the helicopter’s shiny fuselage and is surrounded by heaters and a series of baffles, or pockets of Martian air.
“It turns out that gaseous carbon dioxide is a pretty good insulator,” Balaram says. Additionally, the exterior of the fuselage is coated in a high-absorptivity tungsten film which, according to Balaram, is “designed to harvest the natural warmth of the sun.”
Ingenuity is packing serious processing power. The brains of the operation—one of four processors on board—is a Qualcomm 2.26 GHz Quad-core Snapdragon 801 processor. It’s the same type of processor found in smartphones and, according to Balaram, provides more than two orders of magnitude more computing power than any other spacecraft.
“We have more computing on Ingenuity than probably all of the other NASA spacecraft out there put together,” says Balaram.
The gold-sheathed cube includes the Battery Interface Board, which regulates power to the battery and motors. Other boards include the Helicopter Power Board, Field-Programmable Gate Array (FPGA) Flight Control Board, Nav/Servo Controller Board (which houses the Snapdragon processor), and the Telecom Board.
All these boards work together to form the electronic brain behind the entire mission.
Like other spacecraft, Ingenuity will occasionally phone home. Through an antenna fixed atop its solar panel, the helicopter will send data to a receiver aboard the Perseverance rover, which has a range of almost 1,000 feet.