So, you want to try flying a helicopter on Mars.
You work at NASA’s Jet Propulsion Laboratory (JPL) in California and have proven time and again that when it comes to landing and operating robotic probes and rovers on the distant Red Planet you pretty much know what you’re doing.
This illustration shows Ingenuity awaiting takeoff on Mars. NASA’s aviation experts in atmospheric flight shared their experience with the helicopter’s designers to help ensure the technology demonstration on the Red Planet will be a success. Credits: NASA/JPL-Caltech
But it’s never a sure thing when it comes to planetary exploration.
Even as smart as you are about designing and building spacecraft, you realize you might need a little extra engineering help to make sure your newly designed helicopter will fly in an alien atmosphere the way you want it to.
So, who are you going to call? NASA’s aeronautical innovators of course.
“When it came to determining if this would work the JPL project team had to learn rotor dynamics, so they came to us for help,” said Wayne Johnson, a senior researcher with the rotorcraft aeromechanics group at NASA’s Ames Research Center in California.
Vertical lift aircraft, which includes helicopters, is something NASA researchers have studied since the earliest days of flight, beginning with NASA’s predecessor organization, the National Advisory Committee for Aeronautics.
“The problems you have to solve to fly a helicopter aren’t all that different whether you’re talking about Earth or Mars. We were able to help them better understand their design and refine their methods and the tools they used for testing it,” Johnson said.
Five years later, the Ingenuity helicopter is securely fastened to the Perseverance Mars rover awaiting a launch attempt from Cape Canaveral Air Force Station in Florida no earlier than 7:50 a.m. EDT on July 30. The Atlas 5 rocket’s launch window that day extends until 9:50 a.m. EDT.
“This is so exciting for us. It really is,” said Carlos Malpica, an aerospace engineer at Ames who is a rotorcraft flight dynamics and control expert for NASA’s Revolutionary Vertical Lift Technology project.
“When we started working on the project, we started doing it with a lot of uncertainty about whether it would even be possible to do. There were significant technical challenges to overcome,” Malpica said.
Among them was to ensure the vehicle could take off in a controlled manner in a thin Martian atmosphere that is equivalent to about 100,000 feet high on Earth – an altitude that no Earth-based helicopter has reached even half that distance.
Others had to do with designing the vehicle to survive bitterly cold Martian nights where temperatures plunge to minus 130 degrees Fahrenheit, and to operate largely on its own since direct pilot control isn’t possible given the distance between Mars and Earth.
“But as we went along and we started realizing this is realistic, this can happen, and that it could work. And when we reached that point it was like wow, this feels like one of those Wright Brothers moments in aviation history,” Malpica said.
Indeed, if all goes well with the mission after its targeted landing on Mars in February 2021, Ingenuity’s inaugural technology demonstration flight will echo the Wright Brothers’ 1903 achievement on Earth by making the first powered flight of an aircraft in another planet’s atmosphere.
The Right Tools
Serious ideas for flying over Mars’ rusty surface pre-date the official beginning of the Space Age in 1958. Most concepts involved fixed-wing aircraft, including gliders with inflatable wings.
Much later, one such prototype flew over Oregon in 2001 while another idea was investigated above the California high desert as recently as 2015. It was around this time that JPL engineers had finished their design of Ingenuity and came to NASA Aeronautics looking for help.
Since then, the aeronautics researchers consulted on a wide range of subjects but ultimately the work fell into two broad areas: demonstrating controllability and improving and verifying computer models used in testing.
Larry Young, an aerospace engineer assigned to NASA Ames’ aeromechanics branch, was a key player in helping JPL deal with both.
“It wasn’t only figuring out how to operate Ingenuity so it was stable as it hovered or flew forward, but that we could also figure out how to demonstrate that ability with the test facilities and computer simulation codes we were using,” Young said.
The primary testing facility available to Ingenuity was a vacuum chamber at JPL that could simulate the actual temperatures and pressures at the Martian surface – but it wasn’t set up to be a wind tunnel.
For example, airflow created by the spinning rotors would recirculate along the chamber’s walls and ceiling and then flow back into the rotors and compromise the test data, something that is better managed in a wind tunnel.
“So early on we had a lot of questions about that and how representative this was of actual flight operating conditions,” Young said.
Through a combination of computer analysis and his own testing and experiment experience, Young was able to come up with the best way to configure the chamber and do system integration testing that demonstrated the helicopter would perform as predicted.
“We have a lot of confidence that we’ve done the work the right way. We’ve done our due diligence,” Malpica said. “Of course, this is something that no one has ever attempted so there’s always a risk of something going wrong.”
If all does go according to plan, after being gently deployed from Perseverance, Ingenuity will make at least five short hops over the Martian surface, flying as high as about 15 feet.
Additional flights are not out of the question – NASA’s Mars spacecraft tend to enjoy long lives – and the aeronautics researchers are ready to continue helping with advice and engineering insight, although they won’t have an active role in the flights as they happen.
“We’ll be nervous and filled with anticipation. And some of us hope to be at JPL to cheer on Ingenuity, but we’re not part of the flight control team. For now, we’re just hoping for a safe launch, cruise to Mars, and landing,” Johnson said.
But even if there is a problem that prevents the actual helicopter flight on Mars, whatever the reason may be, Johnson and his colleagues feel they can already declare success.
“Whatever problem may occur on Mars, it won’t change the fact that we’ve already proven with the testing we’ve done that, yeah, you can fly a helicopter on Mars,” Johnson said.
A Look Ahead
Weighing less than four pounds with a main body the size of a softball, there’s no room for any science experiments on Ingenuity. Martian science was never the goal of the helicopter in the first place.
“This is just a demonstration of technology to show that flying on Mars is possible, but eventually we’d like to design and fly a helicopter on Mars that actually has a science mission,” Johnson said.
Already, NASA’s aeronautics and space experts are thinking about what a future Mars helicopter might look like and what kind of explorations it could do if loaded with science instruments.
It’s a dream that Johnson, whose long career at NASA working on helicopters has reached “legendary” status, wholeheartedly embraces.
“I’ve been at this a long time. It’s exciting to see how this project might inspire new engineers to be interested in aeronautics. A lot of graduates coming out of school, when they think about NASA, they look at the space side of things,” he said.
“Well, this is sort of a space thing, but it’s really an airplane; and it really does get new engineers excited just for the fact that it is Mars we are talking about flying over,” Johnson said.
Some of those future aerospace engineers may be among the students who had a hand with Ingenuity.
“At Ames we relied a lot on student interns, undergraduate and graduate interns, to help assist us in making Ingenuity a success throughout its five-year development cycle – and they deserve our thanks,” Young said.
“Hopefully, they will be the ones to take this forward into the future.”