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The Mastcam-Z camera on the Perseverance rover captured this image of Ingenuity during its second flight on Mars April 22. (credit: NASA/JPL-Caltech/ASU/MSSS)

The little Mars helicopter that could

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In the last decade, drones have become almost ubiquitous. They have found roles from providing aerial photography to delivery services to entertainment. You can go on Amazon and find a low-end quadcopter, with limited range and performance but still sporting high-definition cameras, for less than $100, and maybe under $50.

“It’s been great just watching Ingenuity take flight in the Martian skies,” Balaram said. “To see it fly freely in the Martian atmosphere in Jezero Crater is fantastic.”

Mars, though, is a far more challenging environment for a helicopter. The benefit of reduced gravity is outweighed by cold temperatures and, more importantly, an atmosphere whose surface pressure is less than 1% of Earth. Many engineers were skeptical that a rotorcraft could be small enough and also powerful enough to generate enough lift to fly in that atmosphere.

Those skeptics have been proved wrong. On Friday a tiny helicopter called Ingenuity, developed at JPL and flown to Mars along with the Perseverance rover, made its fourth flight in 12 days the tenuous Martian atmosphere. Each flight stretched the helicopter’s boundaries in terms of distance, duration, and speed. By the fourth flight, Ingenuity flew for 117 seconds, going 133 meters from its “airstrip” or landing zone and back, reaching top speeds of several meters per second.

Even before the data arrived confirming a successful fourth flight, NASA had declared the project a success. “I want to start off by congratulating the amazing Ingenuity team. They have achieved the unbelievable and inspired the next generation of explorers with their Wright Brothers moment last week,” Lori Glaze, director of NASA’s planetary science division, said at the start of a press conference Friday about the status of the project.

“It’s been great just watching Ingenuity take flight in the Martian skies,” Bob Balaram, chief engineer for Ingenuity, said at the briefing. “To see it fly freely in the Martian atmosphere in Jezero Crater is fantastic.” He later noted that everything on the helicopter “is working very well.”

Almost too well, as it turns out. The plan for Ingenuity was to make up to five flights in a one-month period that started when the helicopter was deployed from Perseverance in early April. Those flights would be increasingly complex, and project officials warned earlier in the month that the final flights would likely result in the loss of the helicopter. That was perfectly fine, they added: Ingenuity is strictly a technology demonstration, designed to simply see if it was possible to fly on Mars.

After three flights that went perfectly, though, NASA decided to change direction. Ingenuity, in the final days of its month-long mission, would get an extension and a new mission. The helicopter will now test the ability of a small helicopter to support a larger rover mission by serving as an aerial scout.

“After assessing the Perseverance science strategy, there’s room to expand the Ingenuity demonstration into a new phase,” Glaze said. “Ingenuity is going to transition from a technology demonstration, where we prove the technical capabilities of the helicopter, to an operations demonstration.”

“Now it’s like Ingenuity is graduating from the tech demo phase to now the new ops demo phase, where we can show how a rotorcraft can be used and show products that only an aerial platform, from an aerial dimension, can give,” said MiMi Aung, Ingenuity project manager.

“Now it’s like Ingenuity is graduating from the tech demo phase to now the new ops demo phase,” said Aung.

This operations demo will run for another month—30 sols, or Martian days—with the possibility of extending it further. It will run at a slower pace than the technology demonstration phase so that Perseverance, which has spent the last month largely supporting those test flights, can move ahead on its science mission. After a flight likely late this week where Ingenuity will make a one-way trip to a new airstrip, only a couple additional flights are planned for the next month.

Project officials were vague about how Ingenuity will support Perseverance, suggesting that the helicopter could use its color and black-and-white cameras to scout paths for the rover to follow, or look at terrain inaccessible to the rover, and collect lessons to support future missions. “We can inform how to design the helicopter, how to design the mission scenario, how to design this mission to be very effective,” Jennifer Trosper, Perseverance rover deputy project manager, said at the briefing.

That was only possible, despite the excellent performance of Ingenuity, by a change in plans for Perseverance. “Originally, we thought we would be driving away from the location that we landed it,” Trosper said. “But that’s not true. The science team is very interested in getting the initial samples from this region that we’re in right now.”

Perseverance, whose primary mission is to collect Martian rock samples for later return to Earth, was going to head towards the base of the former river delta that flowed into Jezero Crater shortly after landing. However, Ken Farley, chief scientist for the mission, said some of the oldest material in the crater is likely in this region, including rocks deposited when the crater was a lake early in the planet’s history.

“This is the kind of environment that we expect to be the most habitable by organisms that might have existed on Mars billions of years ago, as well as having the capability to preserve biosignatures over the billions of years since the climate changed and the lake dried,” he said.

It all sounded like a happy ending for Ingenuity, which demonstrated its ability to fly on Mars after years of development and testing on Earth. Glaze, in her remarks, drew comparisons to Sojourner, the small rover included as a technology demonstration on the Mars Pathfinder Lander in the mid-1990s, a comparison that others at the agency had also made in recent weeks.

“It completely shifted our paradigm, ever changing how we think about exploring the surface of Mars,” she said of Sojourner. “Ingenuity is going to do the same thing. We’ve learned so much from this little technology demonstration that will enable future aerial systems and explorers.”

“It completely shifted our paradigm, ever changing how we think about exploring the surface of Mars,” Glaze said of Sojourner. “Ingenuity is going to do the same thing.”

Such comment support an ideal model of technology development and demonstration, one where new technologies make their way up the one-to-nine ladder of technology readiness levels, from concept to flight demonstration and, thus, adoption. Reality is far more complex, with advances often met with setbacks not just because of engineering but also due to shifting funding priorities and a lack of flight demonstrations.

Ingenuity, for example, struggled to get a ride to Mars. While the project was making progress in ground testing, a long debate on whether to include it on Perseverance was not resolved until May 2018, a little more than two years before launch. NASA officials would often note in briefings that Ingenuity was added “somewhat late to the project, which made really challenging,” as acting NASA administrator Steve Jurczyk put it at an April 19 briefing.

The reason why it was late was not discussed, but back in 2018 the Perseverance science team was opposed to adding Ingenuity. “I am not an advocate for the helicopter, and I don’t believe the Mars 2020 project has been an advocate for the helicopter,” Farley said at a Space Studies Board meeting in early May, shortly before NASA decided to add the helicopter.

His opposition was based on the impact it would have on the mission’s science. “This comes right out of science time,” he said. “I have personally been opposed to it because we are working very hard for efficiencies, and spending 30 days working on a technology demonstration does not further those goals directly from the science point of view.”

At last Friday’s briefing, Farley, if not a convert to the helicopter, was open to further tests to see how it might be useful in future missions. “We really do have to see whether it is possible to carry out the science mission and support the helicopter simultaneously,” he said. “That’s why we’re going to do this operational demonstration, just to see how it works.”

If Ingenuity does demonstrate how a helicopter will be useful on Mars, that concept could be used on future missions, just as Sojourner led to larger rovers. The catch is that, right now, it’s not clear when that next opportunity might be. NASA’s future plans for Mars exploration revolve almost entirely around Mars sample return, with two missions planned for launch as soon as 2026 to return the samples collected by Perseverance. No other lander missions are currently being developed or even formally studied by NASA (see “The future of Mars exploration, from sample return to human missions”, The Space Review, December 7, 2020).

Adding a helicopter to the Sample Return Lander mission that will collect those samples gathered by Perseverance and launch them into Mars orbit might, at first glance, seem useful. Perseverance will cache at least some of the samples in “depots” on the Martian surface that a European-built rover will collect and return to the lander. That helicopter could scout the path the rover will follow and confirm the location of the cached samples, for example.

NASA officials, though, seem reticent to add a helicopter to that lander. “The Mars sample return mission is a very, very ambitious mission,” Glaze said. “So, I think it’s really important that that mission stays very focused on its mission to collect those samples.”

“There’s just not a lot of room to add additional things onto that mission,” she added after a pause. “It’s already got an incredible scope and an incredible tasking just to bring those samples back. I don’t expect to see any additional flight elements going along with sample return.”

“We really do have to see whether it is possible to carry out the science mission and support the helicopter simultaneously,” Farley said. “That’s why we’re going to do this operational demonstration, just to see how it works.”

Developing a technology and then trying to find a use for it is not new. In 2019, NASA launched the Green Propellant Infusion Mission, a spacecraft designed to test non-toxic “green” spacecraft propellants that could replace hydrazine. That mission ended in October 2020 after successfully demonstrating the performance of that green propellant, known by the Air Force Research Laboratory designation of AF-M315E.

However, while the propellant—which now has the friendlier name of ASCENT, for Advanced Spacecraft Energetic Non-Toxic—has demonstrated its performance, it’s still finding its place in the market. At an AIAA conference in January, those involved with the mission said in a panel session they’re working on various versions of ASCENT that could be used on everything from smallsats to Mars missions, but didn’t identify any specific customers or missions.

While the long-term future of rotorcraft like Ingenuity on Mars is uncertain, the path ahead is clear: additional flights as long as the helicopter continues to operate and is useful. “We are hoping we can operate Ingenuity in a not-to-interfere basis with the science mission, in a way that, as long as it’s available and alive, that we’ll be able to continue,” Trosper said.

It’s possible that, at some point soon, the helicopter could break down, having been designed for only a 30-day mission. Balaram suggested the temperature changes from the day-night cycle will eventually cause something to break, given that the helicopter used commercial components not designed for the rigors of a long surface mission. “The expectation is that, at some point with enough thermal cycling, something—a joint or something—will snap,” he said.

“We really do expect some finite life” for Ingenuity, Aung said, “so it will be a race between how long these parts surprise us in surviving and, in doing these operational scenarios, we will naturally be pushing the limits of Ingenuity.”

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