NASA’s Perseverance rover will soon release a small rotorcraft onto the surface of Mars and drive a safe distance away to observe a series of historic test flights in the ultra-thin Martian atmosphere, which could begin around April 8, officials said this week.
The Mars Helicopter, named Ingenuity, has been stowed underneath the deck of the Perseverance rover for nearly one year. Ground crews at the Kennedy Space Center installed the 4-pound (1.8-kilogram) rotorcraft onto the belly of the rover April 6, 2020, during preparations for Perseverance’s launch last July.
Controllers at NASA’s Jet Propulsion Laboratory are now preparing to send commands to release the Ingenuity helicopter. The rover released a debris cover March 21 to reveal the helicopter. The carbon-fiber shield protected Ingenuity from rocks and dust kicked up during the rover’s landing on Mars on Feb. 18.
The rotorcraft was a relatively late addition to Perseverance’s mission. NASA approved the helicopter technology demonstration to fly to Mars with the Perseverance rover in 2018, just two years before launch.
NASA spent $80 million developing and building the helicopter, which will stand about 1.6 feet (0.5 meters) tall and has counter-rotating rotors that will span about 4 feet (1.2 meters) tip-to-tip. Another $5 million is devoted to operating the helicopter during a 31-day test campaign, which officially begins when Perseverance releases Ingenuity in the coming days.
Ingenuity’s test flight is scheduled for around April 8, but that date could change as the helicopter goes through its deployment and testing milestones, according to Bob Balaram, helicopoter’s chief engineer at JPL.
The helicopter’s first hop is designed to reach an altitude of about 10 feet, or 3 meters. Ingenuity will hover in place for about 30 seconds, then make a turn while it’s hovering before descending back to the surface of Mars.
“The first flight is special,” said Håvard Grip, Ingenuity’s chief pilot at JPL, during a press conference Tuesday. “It’s by far the most important flight that we plan to do. It will be the first powered flight by an aircraft on another planet.”
Bobby Braun, director of planetary science at JPL, said the helicopter and its support team back on Earth will attempt to produce a “Wright brothers’ moment” on another world.
Recognizing Ingenuity’s flight as another aviation first, NASA installed a postage stamp-size piece of fabric from the Wright brothers’ first aircraft, known as the Flyer, onto the Mars helicopter. The fabric covered one of the aircraft’s wings during its first flight at Kitty Hawk, North Carolina, on Dec. 17, 1903.
Another piece of fabric and a fragment of spruce wood from the Wright Flyer flew to the moon on the Apollo 11 mission in 1969. While the Wright brothers used fabric and wood for their aircraft, Ingenuity is made of carbon-fiber skins and “exotic metals,” Balaram said.
“This is, in effect, an aircraft that also happens to be a spacecraft,” Balaram said. “It has survived launch. It has survived the journey through space, the vacuum and radiation, it has survived the entry, descent and landing onto the surface on the bottom of the Perseverance rover, and it has survived all the challenges and design issues that are necessary for a spacecraft.
“But most of all I think of Ingenuity also as an experimental aircraft,” he said.
The surface pressure of the Martian atmosphere is about 1% that of Earth’s, meaning Ingenuity’s rotors will have to generate extra lift to allow the helicopter to take off. The Mars helicopter’s rotors will spin about five-to-ten times faster than a typical helicopter flying in Earth’s atmosphere.
Lori Glaze, head of NASA’s planetary science division, described the Ingenuity helicopter as a “high-risk, high-reward” experiment that could pave the way for future aerial vehicles to explore Mars and other planets.
Before it can attempt to make history, the helicopter will through a series of deployment and checkout steps. It will take about six days to fully release the rotorcraft from the rover, first releasing a launch lock that kept Ingenuity firmly attached to the rover during the trip to Mars.
Then a pyrotechnic device will cut a table to allow Ingenuity to begin rotating out of its horizontal position, and the helicopter will extend two of its four landing legs. By the third day, an electric motor will fully rotate Ingenuity into a vertical orientation underneath the rover, and the other two landing legs will unfurl into position on the fourth day of the helicopter’s deployment sequence, according to NASA.
At that point, the helicopter will remain attached to the rover by a single bolt and a couple of tiny electrical connectors, NASA said.
NASA says a wide angle camera at the end of the rover’s robotic arm will take pictures of Ingenuity throughout the sequence to confirm everything looks good.
On the day before Perseverance releases the helicopter, the Ingenuity team at JPL will fully charge the rotorcraft’s six battery cells using electricity from the rover’s plutonium power source. Then the rover will sever its connection to the helicopter to drop about 5 inches (13 centimeters) down to the Martian surface.
“Then there will the deposition of the helicopter on the surface, and then there will be that first exposure to sunlight where we have to charge the batteries by ourselves,” Balaram said. “We are no longer part of the Perseverance rover and connected safely and we are completely on our own, fully autonomous, waiting to receive commands.
Once Ingenuity is on the ground, the Perseverance begin driving away from the helicopter. Its destination will be an observation point at least 200 feet, or 60 meters, away from Ingenuity’s flight zone, which itself is about the length of a football field. The flight zone includes an airfield, a 33-by-33-foot (10-by-10-meter) area where the helicopter will take off and land.
Ground teams selected the location for the airfield with the help of imagery from Perseverance’s cameras, which surveyed the landscape at its landing site at Jezero Crater over the last month. The region chosen for the test flights is flat, with few rocks or obstacles that could pose a threat to the helicopter.
There will be a bit of drama after the rover releases the helicopter onto the surface.
Ingenuity’s batteries can power the helicopter and keep its internal electronics warm for about 25 hours before they need recharged. The rover will be shading Ingenuity’s solar panels after it releases the aircraft, so it will have to drive away within a day to allow sunlight to illuminate the helicopter, according to Farah Alibay, an engineer who oversees Perseverance’s integration with the Ingenuity helicopter.
“We will go through a number of days of commissioning, approximately a week, where we test out sensors, we test out solar mechanisms, we test the motors to make sure they spin right, and we will be very methodical and even driven as this engineering experiment unfolds,” Balaram said. “And then we will be at a point where we will undertake our first flight and then we will progressively undertake more aggressive flights once we understand and analyze all the behaviors on that first flight.”
Ingenuity’s counter-rotating rotors will spin up to 2,537 rpm — more than 40 times per second — while the helicopter remains on the ground, a final test before engineers commit the aircraft to flight.
“Our current best estimate of when the (first) flight could happen is no earlier than about April 8, but things are fluid,” Balaram said. “We are very event and experiment driven, so that could be changed by a few days in either direction, but the best guess that we have right now is about April 8.”
Mars is currently about 159 million miles, or 259 million kilometers, from Earth. It takes communications signals about 14 minutes make a one-way trip between the planets, eliminating any chance for ground teams to fly Ingenuity in real-time.
Instead, engineers will uplink commands for each of the helicopter’s flights, and Ingenuity will autonomously take off and land, using a vision-based navigation system to help guide its flights.
Engineers tested the helicopter in a low-pressure chamber at JPL, which simulates the atmospheric conditions on Mars.
Before committing the helicopter to flight, engineers will assess wind conditions and other weather parameters, such as atmospheric density, to maximize the chances of success. Controllers at JPL can adjust the rotor speed to best match the atmospheric conditions on the day of each flight.
“I think the biggest challenge will be that we are are flying in the atmosphere of Mars, which has its own dynamics, its own winds, with gusts and so forth,” Balaram said. “These are things which we tested with wind tunnels in our chamber. We have some confidence that everything will be good, but there’s nothing that beats actually being in the real environment of Mars to see how well the … aerodynamics actually work out.”
Balaram said there are also challenges related to surviving the cold Martian nights, when temperatures dip well below zero.
“It’s difficult to keep a small system warm through the night. So just to see how well that thermal system protects us through the night, how well does the solar panel work?” he said. “There are a number of engineering aspects before you even get to the flight. But when it comes to the actual flying, it’s really the winds and the dynamics of how that all interacts with the helicopter that will be most interesting for us to learn.”
Assuming the first flight goes well, Ingenuity could fly up to four more times, reaching a higher altitude of about 16 feet (5 meters) and traversing downrange along the pre-selected flight zone, before returning to its “helipad” for landing.
The 16-foot limit for Ingenuity’s flights is largely driven by the performance limitations of a laser rangefinder on-board that measures the helicopter’s distance to the ground, according to Grip.
“We’re focusing on demonstrating basic capability to hover and then traversing and going longer distances, where we go down the flight zone and back again,” Grip said. “And then if we get past those, we will assess did we meet all tho objectives during those flights, do we want to back and retry some of those things, or if everything goes really well, then we might try to stretch our capabilities.”
NASA has set aside just one month for Ingenuity’s test flights because the $2.4 billion Perseverance mission needs to get moving in pursuit of its own higher-priority scientific objectives. The rover is designed to collect rock samples for return to Earth by a future mission set to arrive at Mars in the late 2020s.
Scientists back on Earth will analyze the specimens and search for signs of ancient Martian life.
“Ingenuity is a limited time project,” Glaze said. “It will have 31 Earth days to attempt to be the first helicopter to fly on another planet. It isn’t intended to collect science, but because its mission is so focused, it is, at its core, innovative.”
NASA’s first Mars rover, named Sojourner, landed on the Red Planet in 1997 and proved the usefulness of surface mobility in exploring other worlds.
“Sojourner redefined what we thought was possible on the surface of Mars and completely transformed our approach to how we explore it,” Glaze said. “That small rover enabled all the missions to follow, and now Perseverance — the size of a small car — is able to carry other technology demonstrations, like Ingenuity, which will further expand our horizons.”
Future rotorcraft could be dispatched to other planets with more sophisticated scientific instruments.
NASA has selected a robotic mission named Dragonfly to explore Saturn’s largest moon Titan. But Titan has a much thicker atmosphere than Mars, which eases the difficulty of rotor-driven flight.
“If we can scout and scientifically survey Mars from the air with a thin atmosphere, we can certainly do the same in a number of other destinations across the solar system, like Titan or Venus,” Braun said.
Airborne drones could survey regions on other planets not reachable by rovers driving on the ground.
“The future of powered flight in space exploration is solid and strong,” Braun said.
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