NASA’s Mars helicopter Ingenuity canceled flight 14 due to failures in its flight control system. Originally, Ingenuity was designed to live one month and execute five demonstration test flights. Like other NASA technology, Ingenuity pushed beyond its initial limits. Today the Mars helicopter has more than doubled its original intended lifespan and number of flights.
Weeks before the canceled flight NASA had warned that flying on Mars was becoming more difficult with each passing day due to the variations of the Red Planet’s seasons. Seasonal variations on Mars are so extreme that they affect atmospheric density. Like all helicopters, Ingenuity must boost performance to overcome atmospheric changes.
Ingenuity made the autonomous decision of canceling flight 14 after detecting an “anomaly” with its main control mechanisms. The helicopter is programmed to run pre-flight tests. During the last test, it detected that two flight-control servo motors did not respond as they should. The two upper rotor swashplate servos oscillated with an amplitude of approximately 1 degree compared to their commanded position. A change in 1 degree may seem small but from the perspective of the small helicopter about to fly on Mars, it was critical enough to shut down the flight.
Three days before the canceled flight the helicopter had conducted a high-speed test required to compensate for atmospheric density changes in Mars. The test pushed Ingenuity’s rpm to the highest level ever, reaching 2,800 rpm. The high-speed test was needed to know if it was safe to fly with high rpm levels.
Servos are a critical part of Ingenuity’s anatomy. They control a swashplate mechanism that adjusts the pitch of rotor blades which in turn controls the helicopter’s position and orientation during flights. Ingenuity has six servos, three on each swashplate. “Servos are critical to stable and controlled flight,” NASA said. NASA is working on two theories to understand what went wrong and how to solve it. One theory is that the helicopter has doubled its original flight design capabilities and the stress begins to show. The second theory is that during the high-speed rpm test the servos were affected.
On Earth, the solution is an easy fix, replacing servos in drone helicopters is normal. However, Ingenuity is millions of kilometers away from Earth, which rules out running to the store for a new servo. NASA is left with two main solutions, including the possibility of disabling “abnormal” servos if they have redundant systems, or programming flight commands to adjust to the servo malfunction. All vehicles on Mars, including Ingenuity, will be on a communication blackout due to the Solar Conjunction. The team will use these two weeks to test solutions and get back Ingenuity on the game by the time communications with Mars are reestablished.