Flying the Martian Skies

Something New Arrives on Mars

On July 30, 2020, NASA launched its fifth rover mission to the Red Planet. In terms of its size and appearance, the Perseverance rover wasn’t much different from its robotic cousin, Curiosity, which landed on Mars in 2012 and has since been exploring Gale Crater. Perseverance distinguished itself in other ways—it carried a different suite of instruments and experiments, some of which were oriented toward the eventual return of Martian soil and rock samples to Earth, or the materials and technologies necessary to send humans to Mars.

Perseverance also carried something completely new to Mars—something that has the potential to change Mars exploration forever: A small helicopter named Ingenuity. Ingenuity was what NASA calls a “technology demonstration.” Its primary purpose was to show that robotic flight was feasible on Mars and test the technologies involved. In this way, it was very similar to the first rover NASA ever sent to the Red Planet—the small Sojourner rover that hitched a ride on the 1997 Pathfinder mission. Sojourner paved the way for Perseverance, on which Ingenuity has now hitched its ride.

Ingenuity is one of the smallest robotic craft ever sent to Mars. On Earth, it weighs only about 4 pounds (1.8 kg). Its rotors stretch about 4 feet (1.2 m) from tip to tip and it  is less than 2 feet (0.6 m) tall. All of this was by design—Ingenuity had to be as small and light as possible in order to fit onto Perseverance without adding much mass or taking space away from other mission critical components. But despite its small size, the helicopter continues to reach great heights.

Deploying on Mars, Testing New Technology

When Perseverance arrived on Mars on February 18, 2021, Ingenuity landed with it, tucked away in a compartment on the bottom of the rover’s body. After the rover team performed their systems checks and prepared for the beginning of Perseverance’s mission, it was time to let the little helicopter go solo. On April 3, 2021, Perseverance slowly lowered and released the helicopter on the surface of Mars, then drove a safe distance away so the helicopter could perform its first experimental flight on Mars.

Of course, engineers working on Earth in the NASA-Caltech Jet Propulsion Laboratory (JPL) had already flown Ingenuity—or test versions of Ingenuity—at home, in simulated Martian conditions. They had to determine whether a rotorcraft could be flown, and how it would be controlled, in the thin CO₂ atmosphere of Mars.

The average atmospheric pressure at the Martian surface is less than 1% the atmospheric pressure found at sea-level on Earth. To simulate these conditions, the JPL engineers used the Lab’s 25-foot Space Simulator thermal vacuum chamber. The chamber was evacuated of atmosphere and backfilled with CO₂ to produce a 7 Torr pressure environment. Flight tests in this environment showed that the thin atmosphere made lift more challenging and made the helicopter respond differently to controls than what one would expect in Earth conditions.

What became quickly apparent was that human response time was insufficient to control the helicopter. Human pilots crashed the first prototype. Even on Earth it would have to be controlled by a quick-thinking computer that could respond instantaneously to data collected by sensors mounted on the helicopter.

The helicopter would have to be computer controlled on Mars as well. With a significant time delay in communicating with spacecraft (between 4.3 and 21 minutes, depending on the relative positions of Earth and Mars), it is impossible to control even the slow-moving Mars rovers in real-time from Earth. Years of testing with prototypes, engineering models, and versions identical to the helicopter that would fly to Mars allowed the JPL engineers to refine the rotor shape, the design of the helicopter, and the electronic control system that would fly it, for Ingenuity.

First Flights on Mars, Not the Last

By the time Ingenuity was ready to take off for its first flight on April 19, 2021, the JPL engineers had done everything they could to prepare for this moment. They had spin tested Ingenuity’s rotors three days earlier. Now they had five demonstration flights planned, hoping that the helicopter performed as expected. If successful, this would be the first powered, controlled flight on another planet and could add a new capability to the exploration toolkit. If it failed, then the future of flight on other worlds would be uncertain.

The first flight was a success. Ingenuity took off and hovered in place 9.8 feet (3 m) above the ground for 39.1 seconds, executing the commands sent by the flight team. Two more successful flights followed, each a bit more ambitious than the last. Before even reaching their fourth flight, NASA decided to transition Ingenuity’s mission from a technology demonstration to an operational contribution to Perseverance’s mission. The helicopter flights would now be used to scout ahead for new exploration sites and to map the surrounding terrain. After completing the final two of its first five flights, Ingenuity started this new phase of its mission.

Although NASA engineers believed that the helicopter mission could be cut short by the intense cold of the Martian winter, Ingenuity was able to keep itself warm with electricity generated by the small solar panel mounted above its rotors. It survived and continued flying as part of the Perseverance mission. As of today (December 14, 2023), it has flown 67 flights with a combined total of 121.1 flying minutes, covered a total distance of 9.5 miles (15.3 km), and reached altitudes as high as 78.7 ft (24.0 m).

Ingenuity’s successes on Mars have far exceeded the hopes of the engineers who planned and designed this ambitious technology demonstration. It has been so successful that plans for future Mars missions—including plans to return samples from Mars—now include helicopters that will build on the achievements of Ingenuity.

It Started with a Prototype

None of Ingenuity’s accomplishments would have been possible without the years of development and testing described above. This required a series of prototypes and engineering and flight models to learn and better understand design challenges and work through solutions. The Smithsonian’s National Air and Space Museum is excited to bring a crucial piece of this story into our collection. The Museum has acquired from JPL the prototype that, on May 31, 2016, achieved the first successful free flight under simulated Martian conditions.

The prototype is full-scale, and its dimensions are very similar to Ingenuity. Because it is a prototype, its components differ slightly from its flown counterpart. For example, the prototype has no solar panel or battery because it was connected to an external power source, and its computer and avionics were also kept off-board. Keeping these components external to the prototype reduced its mass and helped to correct for the difference in gravity between Earth and Mars (Mars gravity is about one third what we experience on Earth).

Like the flight version of Ingenuity, this prototype is built around a central hollow mast that runs from the helicopter’s top to its bottom. Along the mast are the propulsion motor and servo elements that control and spin the rotor blades. The two sets of co-axial rotor blades connect to hubs attached to the mast. Four small legs allow the helicopter to land and stand upright.

JPL has called Ingenuity’s first flight on Mars a “Wright brothers moment,” likening the first powered, controlled flight on Mars to the first powered, controlled flight on Earth (and a piece of fabric from the Wright Flyer is even attached to Ingenuity on Mars!). Like the JPL engineers, the Wrights relied on extensive testing and prototyping to perfect the design of their 1903 Wright Flyer—a story that now fills an entire gallery in the Museum. With future helicopter missions already being planned, the story of flight on Mars may one day be worthy of its own gallery, too. If so, this prototype will be the first object to help us tell that story. Even today, not knowing what will come next, it represents a leap forward in our power to explore new worlds and a promise of new technologies to come.