Seasonal Variations Make Flying Harder for Ingenuity

With summer coming to an end across the northern hemisphere, many of us are getting ready for a chilly winter. But it’s not only us humans on Earth who are at the mercy of the seasons: NASA’s Ingenuity helicopter is also facing challenges from the changing seasons on Mars.

Mars’s atmosphere is very thin at the best of times, being just over 1% of the density of the atmosphere on Earth. That presents a challenge for a vehicle that keeps itself off the ground by moving air. Ingenuity was built to be extremely light to handle this, as well as having large rotor blades. But the changing Mars seasons means that soon the atmospheric density will drop even lower, which could be a challenge for the plucky helicopter.

An image acquired by NASA's Ingenuity Mars Helicopter using its navigation camera during its 13th flight on Sep. 5, 2021.
NASA’s Ingenuity Mars Helicopter acquired this image using its navigation camera during its 13th flight on September 5, 2021 (Sol 193 of the Perseverance rover mission) at the local mean solar time of 12:06:30. NASA/JPL-Caltech

Ingenuity has been something of a victim of its own success, as it was originally only designed for a mission of five flights. It has now well surpassed that, recently making its thirteenth flight – with the flights becoming longer and more complex as well. But its extended lifespan means it has to contend with more difficult conditions on Mars.

“When we designed and tested Ingenuity on Earth, we expected Ingenuity’s five-flight mission to be completed within the first few months after Perseverance’s landing in February 2021. We therefore prepared for flights at atmospheric densities between 0.0145 and 0.0185 kg/m3, which is equivalent to 1.2-1.5% of Earth’s atmospheric density at sea level,” Håvard Grip, Ingenuity Mars Helicopter Chief Pilot, wrote in a mission update.

“With Ingenuity in its sixth month of operation, however, we have entered a season where the densities in Jezero Crater are dropping to even lower levels. In the coming months, we may see densities as low as 0.012 kg/m3 (1.0% of Earth’s density) during the afternoon hours that are preferable for flight. The difference may seem small, but it has a significant impact on Ingenuity’s ability to fly.”

The Ingenuity team does have a plan to address this issue if the atmospheric density does drop to low levels by spinning the helicopter’s rotors faster than ever before to enable it to keep flying. However, such a move is risky as it involves spinning the rotors even faster than has been done with helicopters tested on Earth. The higher speeds could create significant aerodynamic drag or even create resonances that could shake the helicopter and damage its hardware, not to mention the requirement for more power and higher loads.

To ease into these more demanding rotor speeds, the team will try out a high-speed spin test with a 10% increase in peak rotor speed, and if that goes well then the fourteenth test flight will use a higher rotor speed to see how the helicopter handles it. Hopefully, Ingenuity will be able to continue exploring Mars and gathering data, even with all the challenges of the Martian environment.

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