Two Worlds, One Goal: NASA’s Testing of Mars Helicopter Designs

Teddy Tzanetos, the project manager for Ingenuity and overseer of the Mars Sample Recovery Helicopters, emphasized the unique advantages of testing next-generation Mars helicopters on both Earth and Mars. Earth provides an ideal environment for testing aircraft components, offering comprehensive instrumentation and immediate hands-on capabilities. On the other hand, Mars presents the invaluable opportunity to experience genuine off-world conditions, featuring an extremely thin atmosphere and considerably lower gravity compared to Earth. This dual-testing approach allows for a comprehensive assessment that combines the advantages of controlled Earth-based testing with the authenticity of Martian conditions.

Currently undergoing testing on Earth, the next-generation carbon fiber rotor blades are poised to revolutionize Mars helicopter capabilities. These blades, boasting a length nearly 4 inches longer than those on Ingenuity, feature enhanced strength and a redesigned structure. NASA envisions that these advancements could pave the way for larger and more capable Mars helicopters. However, a significant challenge arises as the blade tips approach supersonic speeds, where the potential for turbulence-induced vibrations becomes a critical concern.

In the quest to replicate Martian atmospheric conditions on Earth, engineers turned to JPL’s space simulator—a colossal chamber measuring 25 feet in width and 85 feet in height (8 meters by 26 meters). This space simulator, renowned for providing Surveyor, Voyager, and Cassini with their initial exposure to space-like environments, became the designated area for testing. Over a three-week period in September, a dedicated team meticulously observed sensors, meters, and cameras as the newly designed rotor blades underwent successive runs, progressively reaching higher speeds and steeper pitch angles.

Tyler Del Sesto, the deputy test conductor for the Sample Recovery Helicopter at JPL, revealed that the rotor blades were spun up to an impressive 3,500 rpm. This speed surpasses the Ingenuity blades by 750 revolutions per minute, showcasing the enhanced capabilities of these more efficient blades. Del Sesto emphasized that these advanced rotor blades have transcended the realm of a theoretical concept and are now deemed flight-ready, marking a significant milestone in their development and testing.

Simultaneously, roughly 100 million miles (161 million kilometers) distant, the Ingenuity helicopter received commands to undertake tasks that the Mars Helicopter team had never envisioned they would have the opportunity to execute.

Fourth rock flight testing

Initially designated for a maximum of five flights, Ingenuity, with its inaugural flight recorded over two and a half years ago, has surpassed expectations by completing 66 flights, extending well beyond its planned 30-day mission duration. Each time Ingenuity takes flight, it ventures into new territory, providing a unique perspective previously unattainable in planetary missions. Recently, Team Ingenuity has been pushing the boundaries, sending their solar-powered rotorcraft on increasingly novel and unprecedented maneuvers.

In the span of the last nine months, Ingenuity’s achievements have been notable. The maximum airspeed and altitude have been doubled, accompanied by advancements in both vertical and horizontal acceleration rates. Notably, the team has successfully implemented techniques for slower landings. Travis Brown, the chief engineer for Ingenuity at JPL, highlights that this expansion of the helicopter’s operational capabilities has yielded valuable data. This data, gained through pushing the boundaries of Ingenuity’s capabilities, becomes a crucial resource for mission designers in shaping the trajectories of future Mars helicopters.

Constrained by available energy and considerations related to motor temperature, the typical duration of Ingenuity flights spans approximately two to three minutes. While increasing the helicopter’s speed could potentially allow for a broader coverage area in a single flight, there’s a delicate balance. Flying too fast poses a challenge for the onboard navigation system, which relies on a camera to identify and track rocks and surface features within its field of view. If these features pass by too rapidly, the navigation system may encounter difficulties in maintaining its orientation and accurate positioning.

To attain a higher maximum ground speed, the team employs a strategic approach: instructing Ingenuity to fly at elevated altitudes. These instructions are meticulously sent to the helicopter before each flight, ensuring that surface features remain in view for an extended duration. During Flight 61, a new altitude record was achieved at 78.7 feet (24 meters), allowing for a comprehensive examination of Martian wind patterns. Subsequently, Flight 62 marked a speed milestone, reaching 22.3 mph (10 meters per second). Beyond speed accomplishments, this flight served the purpose of scouting a location for the Perseverance rover’s science team, underscoring the versatility of Ingenuity in supporting broader mission objectives.

The team has been actively exploring variations in Ingenuity’s landing speed. Originally designed to make contact with the surface at a brisk 2.2 mph (1 mps), this intentional speed ensures that the helicopter’s onboard sensors can promptly verify a successful touchdown. This deliberate approach helps prevent any inadvertent bouncing back into the air before the rotors are safely shut down.

The team embarked on an exploration during Flights 57, 58, and 59, investigating the feasibility of designing a helicopter with lighter landing gear by enabling slower landings. In this experimental phase, Ingenuity demonstrated its capability to successfully land at speeds 25% slower than the originally designated landing speeds, showcasing adaptability and potential design enhancements for future iterations.

The series of Martian maneuvers reminiscent of Chuck Yeager’s feats is set to continue. Anticipated for December, post-solar conjunction, Ingenuity is poised to engage in two high-speed flights. These flights will involve executing a distinctive combination of pitch-and-roll angles meticulously designed to gauge and assess the helicopter’s performance under specific conditions.

Brown highlighted the significance of the upcoming high-speed flights in December, emphasizing that the data collected will play a crucial role in refining aero-mechanical models detailing the behavior of rotorcraft on Mars. Typically, on Earth, such testing is conducted in the initial flights. However, given the unique challenges of operating on Mars, caution is paramount, as there are no opportunities for do-overs when you are operating far from the nearest repair shop. This underscores the careful and meticulous approach required in the remote Martian environment to ensure the success and longevity of the Ingenuity helicopter.

Resources

1. ^{ONLINE NEWS} NASA. (2023, November 22). NASA uses two worlds to test future Mars helicopter designs. Phys.org. [Phys.org]