Since the Wright brothers first took to the skies of Kitty Hawk, North Carolina on December 17, 1903, the first flight has become an important milestone for any vehicle designed for air travel. While it’s one thing to design an aircraft and make it fly on paper (or computer), it’s another to put all the pieces together and watch them get off the ground.

In late January 2019, all the pieces making up the NASA’s Mars Helicopter flight model (the actual vehicle going to the Red Planet) were put to the test.

Weighing in at 1.8 kilograms (4 pounds), the helicopter is currently undergoing the rigorous process that will certify it for Mars.

The majority of the testing will assess how the helicopter operates on Mars, including how it performs at Mars-like temperatures. Can it survive — and function — in cold temperatures, including nights with temperatures as low as -90°C (-130°F)?

All of the testing is in preparation for February 2021, when the helicopter will reach the surface of the Red Planet as part of the Mars 2020 rover. A few months later, it will be deployed and test flights (up to 90 seconds long) will begin — the first from the surface of another world.

“Gearing up for that first flight on Mars, we have logged over 75 minutes of flying time with an engineering model, which was a close approximation of our helicopter,” said MiMi Aung, project manager for the Mars Helicopter at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “But this recent test of the flight model was the real deal. This is our helicopter bound for Mars. We needed to see that it worked as advertised.”

Flying helicopters is commonplace here on Earth, but flying hundreds of millions of miles away in the thin martian atmosphere is something else entirely. Creating the right conditions for testing here on Earth presents its own set of challenges.

“The martian atmosphere is only about one percent the density of Earth’s,” said Aung. “Our test flights could have similar atmospheric density here on Earth — if you put your airfield 100000 feet [30480 meters] up. So you can’t go somewhere and find that. You have to make it.”

Aung and her Mars Helicopter team did just that in JPL’s Space Simulator, a 7.62-meter-wide (25-foot-wide) vacuum chamber. First, the team created a vacuum that sucks out all the nitrogen, oxygen, and other gases from the air inside the mammoth cylinder. In their place, the team injected carbon dioxide, the chief ingredient of Mars’ atmosphere.

“Getting our helicopter into an extremely thin atmosphere is only part of the challenge,” said Teddy Tzanetos, test conductor for the Mars Helicopter at JPL. “To truly simulate flying on Mars we have to take away two-thirds of Earth’s gravity, because Mars’ gravity is that much weaker.”

The team accomplished this with a gravity offload system — a motorized lanyard attached to the top of the helicopter to provide an uninterrupted tug equivalent to two-thirds of Earth’s gravity. While the team was understandably concerned with how the helicopter would fare on its first flight, they were equally concerned with how the gravity offload system would perform.

“The gravity offload system performed perfectly, just like our helicopter,” said Tzanetos. “We only required a 5-centimeter [2-inch] hover to obtain all the data sets needed to confirm that our Mars helicopter flies autonomously as designed in a thin Mars-like atmosphere; there was no need to go higher. It was a heck of a first flight.”

The Mars Helicopter completed its second flight in the vacuum chamber the following day. Logging a grand total of one minute of flight time at an altitude of 5 centimeters (2 inches), more than 1500 individual pieces of carbon fiber, flight-grade aluminum, silicon, copper, foil, and foam have proven that they can work together as a cohesive unit.

“The next time we fly, we fly on Mars,” said Aung. “Watching our helicopter go through its paces in the chamber, I couldn’t help but think about the historic vehicles that have been in there in the past. The chamber hosted missions from the Ranger Moon probes to the Voyagers to Cassini, and every Mars rover ever flown. To see our helicopter in there reminded me we are on our way to making a little chunk of space history as well.”

For more about the Mars 2020 mission, visit https://mars.nasa.gov/mars2020/.