NASA Perseverance rover recording Mars helicopter’s historic flights
The Ingenuity helicopter made its fourth successful Mars flight on April 30, longer in distance and duration than its first three, which were impressive enough to extend the craft’s mission time.
Ingenuity will fly an additional 30 days to test the vehicle’s ability as an aerial scout for the Perseverance rover, NASA’s Jet Propulsion Laboratory said in a briefing. The craft was originally scheduled to fly for 30 days.
JPL announced the extension as it was waiting for results of the fourth attempt.
In that flight, the 4-pound craft rose to an altitude of 16 feet and executed an out-and-back flight of about 436 feet from its helipad, NASA’s Jet Propulsion Laboratory reported, for a total distance of approximately 872 feet.
Its top speed was about 8 mph, or 78% faster than the 4.5 mph third flight.
Ingenuity lifted off at 10:49 a.m. EDT and flew for about 117 seconds, about 37 more than its third flight on April 25.
The helicopter’s “flawless” performances are giving engineers at NASA’s Jet Propulsion Laboratory confidence to attempt more ambitious flights. At least two more are planned.
“We do want to push it to the limit,” said MiMi Aung, helicopter project manager. “The (second) flight perfectly matched what we were predicting. We want to know what the limits are.”
“We will be stretching the capabilities of the helicopter,” said Håvard Grip, Ingenuity’s chief pilot.
First two flights paved the way
Sixty days after landing on Mars, Perseverance recorded Ingenuity as it made – in a test evoking the Wright brothers at Kitty Hawk in 1903 – its historic flight on April 19.
In the first flight, Ingenuity rose to a height of nearly 10 feet, hovered about 39 seconds and rotated 96 degrees toward the waiting Perseverance rover before landing, NASA said.
The flight took place at about 12:33 p.m. Mars time, 3:34 a.m. EDT on Earth.
In the second flight, on April 22, Ingenuity rose to an altitude of 16 feet, hovered a moment, then tilted itself 5 degrees and flew 7 feet. Then it stopped to hover in place and rotated to take photographs before returning to its take-off point.
The flight lasted 51.9 seconds, 13 more than the first.
More: Mars sites named after author Octavia Butler, JPL engineer Jakob van Zyl.
A glitch in Ingenuity’s onboard computer during a high-speed rotor test on April 9 forced JPL to postponed the first flight. Engineers came up with a software fix that was transmitted to the craft.
JPL engineers responded with cheers and applause at the arrival of the first photo, a black-and-white image of Ingenuity’s shadow as it hovered above the Martian surface. A series of color images taken by the rover showed the helicopter landing.
“Ingenuity is extremely healthy at this point,” said Bob Balaram, Mars helicopter chief engineer at the briefing.
“In fact, she’s even healthier than before the flight since she shook off some of the dust that had been covering her solar panel,” Balaram said. The craft is “producing more solar energy than before.”
Anxious engineers couldn’t wait to learn if the flight was a success but had to wait more than three hours. And they were sweating it out.
“We operate on what’s called ‘Earth receive time,’” says Robert Braun, JPL director for planetary science. “What we’re watching on the livestream is the signal that’s coming back in real time from Mars. In reality, the helicopter will have flown autonomously several hours earlier.”
It’s the only way to fly a robotic craft on a planet 178 million miles away. Data and photos will continue to come in over several days.
While waiting, “we have to sit and chew our nails to the bone until we get all this data that tells us whether the flight worked or not,” says Tim Canham, Mars helicopter operations lead.
It took about 14 minutes for JPL to get a radio signal confirming the rover’s safe landing Feb. 18. For Ingenuity, “we hope to find out within a few hours,” says Håvard Grip, Ingenuity chief pilot at JPL.
NASA/JPL streamed the flight results live. “It’s a livestream, as we get the information how the helicopter did,” Braun says.
Base of flight operations
Flight controllers were finicky about choosing the helicopter’s testing area. The space had to be large enough for ambitious flights and devoid of large rocks that could endanger the craft while landing.
“We’ve already done a fair bit of homework in terms of identifying, in broad terms, what the areas would be suitable for flight zones,” Grip says. “A satellite in Mars orbit takes the first photos of the area. Then we get more precise images from the rover on the surface.”
“This site is very good, because it has a lot of barely submerged bedrock,” Canham says. “It provides texture for the navigation camera, but there are very few rocks that pose a hazard.”
Flights are taking place inside a nested collection of sites: the helipad, a launch and landing site for the helicopter; the airfield, a space surrounding the helipad; and the flight zone, an oval-shaped area in which the helicopter will fly.
The first step was getting the helicopter to the Martian surface.
About 60 feet from the edge of the helipad, the rover released a 10-foot-square protective shield from its underside and let it drop to the surface March 21.
“We wanted to drop the shield a minimum distance away to make sure it didn’t confuse our navigation,” Canham says.
- The rover rolled to the center of the helipad and rotated the helicopter 90 degrees until its legs pointed down.
- The rover released the helicopter to the surface, an easy drop of about 6 inches, on April 3.
- The rover retreated to the Van Zyl Overlook, a designated observation point nearly 200 feet away from, and about 3 feet higher than, the flight zone. (The point was named in honor of Jakob van Zyl, a former member of the JPL team who died in August 2020.)
“That distance was deemed far enough away so we won’t be risking the rover if the helicopter has a bad day,” Canham says.
After that, helicopter was on its own and began to charge its batteries with its solar panel.
NASA calls the Mars helicopter a technology demonstration and an engineering test but not a science experiment. Ingenuity carries two cameras but no scientific instruments in a box-shaped fuselage below its rotors.
Ingenuity and the Wright brothers’ Flyer are 118 years apart and vastly different, but both are milestones in aviation.
They’re also connected. Ingenuity carries a piece of muslin about the size of a postage stamp from the bottom left wing of the original Wright plane. Insulation tape attaches the fabric to a cable on the underside of the helicopter’s solar panel.
In another tribute, Ingenuity’s airfield has been named Wright Brothers Field, said Thomas Zurbuchen, NASA Associate Administrator for Science.
“While these two iconic moments in aviation history may be separated by time and 173 million miles of space, they now will forever be linked,” Zurbuchen said.
“I feel very confident we’ve done everything we can to set ourselves up for success,” Grip says. “But of course, when that time comes, I’m not going to deny my heart will be pounding.”
Picking the best time to fly
JPL uses the rover to monitor weather conditions on Mars. It looks at the strength of sunlight for the helicopter’s solar panel and wind velocities during the day.
“We’re playing a balancing game,” Canham says. Too early and “we won’t have charged the batteries enough from the morning charge-up.” But if they go too late, the winds could pick up and make flying difficult.
Flight controllers determine the best day and time to fly. Then they tell the helicopter what to do.
NASA Ingenuity helicopter makes historic first flight on Mars
NASA makes history with the “first flight of a powered aircraft on another planet,” Mars.
Staff video, USA TODAY
Ingenuity gets flight plan from rover
Because of the distance, the JPL flight team doesn’t control the helicopter in real time. The commands are sent directly to the rover during the Martian morning. Later in the Martian day, all data from the rover is sent back to Earth via an orbiter, since it has greater data bandwidth.
“The helicopter team has an instrument on the rover called the helicopter base station,” Canham says. “The helicopter doesn’t really know what it’s doing that day until we tell it.”
Across millions of miles, the relay works this way:
- JPL packs a series of flight commands into a file called a sequence.
- The file is sent by radio to the helicopter base station on the rover.
- On the morning of the flight, the rover activates the base station.
- The base station sends the file to the helicopter, which carries out the commands.
The first flight: Simple but most important
JPL originally set aside a month for up to five test flights. The first was deceptively simple and each successive flight was built on what was learned from the previous ones. Time is scheduled in between flights to allow the batteries to recharge and for analysis of flight data.
Ingenuity’s flights have a ceiling of about 16 feet, even though the craft is mechanically capable of flying higher.
“The helicopter can go pretty high,” Canham says. “We limit ourselves between 3-5 meters (10-16 feet) because we start to lose the ability to track the ground with certainty. So we want to stay within that sweet spot.”
The flights are designed to last about 90 seconds. “Given our energy estimate, that’s as long as we can fly before we have to land and recharge,” Canham says.
The actual flights may show the navigational system can work at higher altitudes. As for the flight paths, “the helicopter will fly in straight line segments,” Grip says.
The flight plans are:
First flight | April 19: 39.1 seconds
Second flight | April 22: 51.9 seconds
Third flight | April 25: 80 seconds
Fourth flight | April 30: 117 seconds
- Take off.
- Climb to 16 feet.
- Fly horizontally for 436 feet.
- Return to same space above helipad.
- Land in same place.
Fifth and sixth flights
JPL says it will plan the remaining flights to expand the flight envelope further after analyzing data from the first four.
Taking pictures like a tourist
The helicopter has two cameras. One is a black-and-white navigational camera mounted in the fuselage floor and aimed at the ground.
During flight, “it’s taking pictures 30 times a second, and the guidance software does what we call feature tracking,” Canham says. The craft analyzes the images to figure out its location.
The second is a color camera that’s “more like a tourist camera,” Canham says. “It’s tilted mostly to the horizon, so we can get some views in front of the helicopter.”
The color camera is 13 megapixels; by comparison, an Apple iPhone camera is 12 megapixels. It’s mounted next to the navigational camera.
Instruments on board control changes in the helicopter’s position, altitude and orientation.
Ingenuity anatomy: Fast-spinning rotors needed for Mars flight
Conventional helicopters won’t work on Mars because of the thin atmosphere. A helicopter on Mars needs larger rotors, spinning at much higher speed.
Here is what Ingenuity has:
Rotors: 2 carbon-fiber blades, about 4 feet in length. They spin in opposite directions at about 2,400 rpm, much faster than standard helicopter rotors, which run at about 500 rpm. (Ingenuity’s blade rotation spin is closer to that of blades in a high-end food processor.)
The helicopter’s computer can adjust the angle, or pitch, of the blades for optimal flight.
The blades are super light, Canham says. “You can pick one up with one finger. They’re very light but very stiff, so they can capture the Martian air.”
Weight: 4 pounds on Earth; 1.5 pounds on Mars.
Power: Solar panel charges 6 lithium-ion batteries.
Body: The box-shaped fuselage measuring 5.4 x 7.7 x 6.4 inches is insulated and has heaters to warm the onboard electronics – the batteries, two computers and cameras.
“The batteries are the most temperature-sensitive thing we have,” Canham says. “Temperatures at night can drop below -100 degrees (Fahrenheit), so we put a series of heaters around the batteries and use a thermostat-controlled heater to keep them at a minimum temperature.”
Ingenuity is designed to overcome the extreme differences between Mars and Earth
Atmosphere is thinner: The Martian atmosphere is just 1% of Earth’s, which makes flying on Mars roughly equal to flying 18 miles high on Earth. Special helicopters have a ceiling of 25,000 feet, or 4.7 miles.
Air is colder: At the rover’s location, temperatures range from a high of -7.6 degrees Fahrenheit to a low of -117 degrees F. That was recorded over a two-day period. (Temperatures near the Martian poles can plummet to -284 degrees F.)
Earth is much warmer, with a total temperature range from 136 degrees F to -126 degrees F.
Gravity is less: Mars is half the size of Earth, but its gravity is about a third of Earth’s. A 200-pound person on Earth would weigh 76 pounds on Mars.
How will Ingenuity flights compare with those of the Wright brothers?
Though circumstances are obviously different, it’s irresistible to compare the flights of Ingenuity with the Wright brothers’ first attempts on Dec. 17, 1903. It’s possible that Ingenuity could travel a greater distance on Mars during its third flight than the Wrights traveled during their first.
“When we landed Perseverance, we had direct-to-Earth communication,” Braun says. “But in this case, Ingenuity doesn’t have enough power to send a signal all the way back to Earth. So, we have to use a complicated relay.”
Ingenuity sends data to the rover that details flight performance. Then the rover sends the data, as well as the images it has collected, to a satellite orbiting Mars. “And then that orbiter turns and sends the information back to Earth,” Braun says.
An eager JPL staff will be waiting.
“Most of us have been working remote the whole time,” Canham says. “And we sit in our offices or our living rooms or our breakfast tables or whatever, and we pore over the data. And we have that moment when we’re like, wow, it actually worked. They’re going to have live coverage of us when we review the data. So there’s a lot of drama in that.
“And then there’s always the real risk of failure. There’s a chance it won’t work. Then we, as a team, will live through that together, too.”
SOURCE USA TODAY Network reporting and research; NASA/Jet Propulsion Laboratory; Smithsonian Air and Space Museum; Federal Aviation Administration; wright-brothers.org; thewrightbrothers.org; The Associated Press; theskylive.com
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