The small helicopter will lift about three meters from Martian soil, hover, turn toward Perseverance, and snap a picture, then settle carefully back to the ground. It’s the aviation equivalent of Neil Armstrong’s one small step.
Ingenuity carries no science instruments — the helicopter itself is the experiment. It's what engineers call a technology demonstrator, or as NASA put it "a project that seeks to test a new capability for the first time, with limited scope."
In this case, the “capability” is something that seems superficially easy — flying a helicopter on another world — but presents daunting challenges. The atmosphere on Mars is just 1 percent the density of Earth’s and the planet has about 38 percent the gravity of our homeworld, meaning engineers have to hope the four-pound helicopter that looks equal parts NASA and 1980s Radio Shack catalog can achieve enough lift. Punishingly cold temperatures on Mars also mean it has to survive nights that make Antarctica look balmy.
And then there’s the fact that communications take place on a 20-minute delay, thanks to the 171 million mile distance to Mars. This means the helicopter won’t be controlled by a joystick by a live operator. It will have to fly autonomously with a set of instructions sent by flight controllers long before.
MiMi Aung, Ingenuity project manager at the Jet Propulsion Laboratory (JPL), says during a press briefing on Friday that it’s just the latest in a long line of flight tests to build toward the future.
“Flight experiments are as old as flying,” Aung says. “The Wright brothers’ first successful powered, controlled flight was a flight experiment.”
How was the Mars helicopter Ingenuity designed?
An aircraft built to fly on Earth couldn’t fly on Mars, because its wings (or rotor blades) wouldn’t generate enough lift. Here’s the simplified version of how helicopter flight works on Earth:
- The curved shape of a wing forces air flowing over the top to move faster than air flowing across the bottom
- This creates a difference in air pressure that pushes against the bottom of a wing, creating lift
But in the thin Martian atmosphere, it takes a much larger surface, moving much faster, to produce enough of a difference in pressure to create lift.
In Ingenuity’s case, it takes two pairs of four-foot-long carbon fiber blades, spinning in opposite directions at 2,537 RPM, just to get four pounds of craft off the ground. The helicopter itself is only about one-and-a-half feet tall, meaning most of the size of Ingenuity is blades.
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Teddy Tzanetos, deputy operations lead for Ingenuity Mars Helicopter at JPL, says that helicopter flight on Earth doesn’t need quite this much speed.
“A comparable mass rotorcraft on Earth would spin much slower due to the comparatively thick atmosphere of Earth, spinning at hundreds of RPM, not thousands,” Tzanetos tells Inverse.
The second planned rotorcraft on another world, the Dragonfly mission to Titan set to launch in 2027, will face the opposite challenge. Titan’s atmosphere is about 45% denser than the one on Earth.
How was the Mars helicopter Ingenuity tested?
In order to test a helicopter bound for Mars, the engineers needed to build an environment as close as possible here on Earth.
The first step was to create a computer model, which then helped them retrofit a four-story simulation tower at JPL, compensating for differences in gravity and air pressure between Mars and Earth.
“We pumped out the air to simulate the density, and drove the temperatures down to match the thermal environment, and even built a gravity-offload system to balance out the difference in gravity," Tzanetos says. "We even installed our own Mars-like wind tunnel inside this chamber to determine how Ingenuity would react to wind on Mars."
Now it's time for the real test, on the real planet.
Ingenuity has already passed its first big milestone. Just surviving its first night in the open on Mars, without the protective warmth of Perseverance looming over it, was an accomplishment. Temperatures in Jezero Crater drop to -90 degrees centigrade (-130 degrees F) at night, and the cold can be deadly to electronics. That’s equivalent to the lowest temperatures ever recorded on Earth, but it’s just a day in the life on Mars.
Ingenuity's engineers faced the challenge of designing an aircraft sturdy enough to keep its systems warm in the bitter Martian cold, but still light enough to stow away on Perseverance's undercarriage for the ride to Mars.
Ingenuity’s rotors spun up for the first time on Thursday night, and now all that remains is to see if it flies.
What is the Mars helicopter Ingenuity's first flight date and time?
NASA reported on Friday, April 17 that Ingenuity successfully completed its high-speed rotor spin test. That's the same test that triggered the delay announced on April 12, so it appears a software update to fix technical issues was successful. The agency is now targeting a flight around 3:30 a.m. on Monday, April 17, with a live stream to follow three hours later.
The delay follows an unexpected shutdown during a high-speed rotor spin test on Friday. While Ingenuity’s onboard computer systems tried to transition from pre-flight mode to flight mode, a “watchdog” program noticed a problem with the command sequence and ended the test – which is exactly what it was supposed to do. If the test had been an actual fight, the “watchdog” code would have just saved Ingenuity from a mission-ending crash.
In a blog post, the agency added that technology demonstrations like Ingenuity often have to discover and fix problems on the fly. Or before flying, in this case. After reviewing the data from the test, Ingenuity’s engineers have made a minor modification to the helicopter’s flight software, which will change how Ingenuity’s flight control systems boot up. That’s good news, but it’s going to take several days to double-check the software and upload it to Ingenuity.
At this point, NASA says, “Our best estimate of a targeted flight data is fluid right now.” The agency hopes to announce a new flight plan sometime this week.
This article was updated on April 10, April 13, and April 17. We will update it further as new information is revealed.
The day before the flight, chief pilot Håvard Fjær Grip and his team will program a sequence of commands for Ingenuity to follow during flight, including waypoints, altitude, positioning instructions, timers, and thermostat setpoints. They’ll send that flight plan to Perseverance, and the rover will transmit it to Ingenuity when it’s time to fly.
Grip is an aircraft pilot here on Earth, but he can’t fly Ingenuity in real-time the way drone pilots can fly Predators on another continent. It takes about 20 minutes for commands to reach Mars at the speed of light, so everything has to be programmed and transmitted in advance. Ingenuity’s computer can make an early landing or abort the entire flight if it detects “non-optimal conditions,” but there’s no way for the team at JPL to make corrections on the fly.
The team at JPL doesn't even get to watch the flight live, and neither will the rest of us. Several hours after the flight, Ingenuity will send sensor data from its accelerometer, altimeter, gyroscope, inclinometer, and cameras back to Perseverance, who will then beam it to Mars Reconnaissance Orbiter, which will relay it to Earth.
Perseverance will send along some photos and video from its navigation cameras and Mastcam-Z, the high-res camera aboard the rover. Grip and the team will rely on that data to tell them whether Ingenuity lifted off, turned, and landed safely.
“A crash would likely result in the end of the mission,” Tzanetos says. Even a bad landing would put an end to future flights because Ingenuity lacks the ability to right itself if it tips over, and Perseverance has no way to help its tiny companion.
But even a catastrophic failure will, in its way, be useful. Aung pointed out that the Wright Brothers crashed several times before their first successful flight in 1903. From those attempts, they learned the principles of flight. (The helicopter has a small piece of the Wright Brothers flyer aboard, adding special symbolism to this flight.)
“Ingenuity has already returned back a treasure trove of engineering data from the handful of days it has been on the surface,” Tzanetos told Inverse. “The most critical data will be used to compare our models and simulation to the real world results observed on Mars.”
What comes next for the Mars helicopter Ingenuity?
More engineering data from the flight will reach Earth on Monday, along with a low-resolution black-and-white photo from the helicopter's navigation camera. We'll finally get two high-resolution color images from the helicopter in the next sol's downlink, slated for Tuesday. (The rover will also be sending back a video of Ingenuity in flight over the coming days.)
If the first flight succeeds, Ingenuity will make a series of longer flights over the next 30 Martian days, or sols (about 31 Earth days). Ingenuity's longest flight will last about 90 seconds and cover 980 feet of Martian terrain at an altitude of 15 feet.
That duration is determined by the limits of the helicopter's onboard battery, which is charged by the square solar panel perched like a jaunty robot hat atop the rotors. The lithium-ion battery holds enough power for about 90 seconds of flight, and then Ingenuity has to land and recharge.
When all is said and done, Perseverance will trundle on across Jezero crater to continue doing science, leaving Ingenuity in its tracks. That will be the end of the helicopter's mission because it relies on Perseverance to relay commands from Earth and send flight data and images back via the Mars Reconnaissance Orbiter. Without Perseverance, Ingenuity can only sit there on its empty Martian "airfield."
NASA didn't spend $85 million building a tiny helicopter and sending it to Mars just to set a record, however. If Ingenuity works, future missions could use uncrewed aerial vehicles like Ingenuity to scout potential routes for rovers or — eventually — human crews.
“It’s possible for one day larger, more capable rotorcraft to carry meaningful science payloads and even help the first human explorers on Mars,” Tzanetos says. An aircraft can fly over rough terrain that a rover can't safely traverse, and it offers a viewpoint in between distant orbiters and rovers on the ground.
That future now depends on what happens next. "If we don't make the first attempt, for sure we will not make progress forward," says Aung.
This article was updated on April 10. We will update it further as new information is revealed.