As NASA’s newest Mars rover, Persistence, continues its own cash registers and tests, work begins for a new phase of the mission – the Ingenuity helicopter. This first piece of hardware of its kind will demonstrate for the first time a (non-rocket) powered flight on a world other than Earth. Data from these flights – expected to begin in 30-60 days – will aid in the development of future programs for missions to Mars and beyond.
Ingenuity is an experimental addition to the Mars 2020 mission. Regardless of the results of the test campaign, it will not have a significant effect on the primary mission.
Teams schedule a 30-day flight window for the helicopter. They are currently aiming for at least one flight, but it can be extended if necessary. The maiden flight involves a relatively simple 20-30 second glide test at low altitude before landing. After that, flights will take longer and travel further.
Ingenuity equipped with a pair of coaxial, 1.2 meter long carbon fiber rotors. “Coaxial” means that the rotors are stacked on top of each other and rotate in opposite directions, dramatically increasing lift with minimal increase in area.
The rotors spin at a speed of 2,400 revolutions per minute (RPM) – much higher than the roughly 500 RPM of many helicopters on Earth. The rotors have to rotate quickly to take into account the extremely thin Martian atmosphere.
Ingenuity after mounting in NASA’s Jet Propulsion Laboratory (JPL). The carbon fiber patterns on the rotors and legs are visible. Credit: NASA.
The helicopter is powered by a single solar panel above the rotors that charges six lithium-ion batteries. These batteries will turn on Ingenuity to fly for a maximum of 90 seconds at a time. A single flight of 90 seconds – the maximum flight time of Ingenuity – consumes approximately 8.75 WHr – less energy than in an iPhone 12 battery.
Four carbon fiber legs protruding from the corners of the main body absorb any extra speed and impact upon landing.
The combination of its small size and large amount of composite materials makes Ingenuity particularly light, with a weight of 1.8 kilograms. On Earth, this equates to 17.7 Newtons (4.0 pounds), but in the lower gravity of Mars, Ingenuity weighs only 6.7 Newtons (1.5 pounds).
Once deployed from Persistence Ingenuity communicates with Earth through the rover. Each has a small antenna to talk to each other, and the rover sends data back to Earth using its more powerful communications suite.
During the cruise to Mars, Ingenuity communicated and received power directly through Persistence
On August 13, 2020, NASA announced that the helicopter was first turned on and charged in space. This was about two weeks after the launch. The batteries were only charged to 35%, as each full charge and discharge of lithium-ion batteries slightly shortens their life. Keeping them at a low to medium charge level minimizes this impact.
Engineers then repeated this test approximately every two weeks during the cruise to Mars.
Persistence – with Ingenuity attached to his stomach – hit Mars on February 18, 2021.
The helicopter is currently still connected to Persistenceas the latter completes its checkouts and initial operations on the surface of Mars.
On March 2, the rover successfully deployed and tested its robotic arm. The arm contains various tools and cameras, most notably the rover’s drill. It also features the PIXL and SHERLOC instruments – with an X-ray and ultraviolet spectrometer, respectively. These will allow a more detailed analysis of surface materials.
A view of the surface of Mars – with new tire tracks – as seen by Perseverance after the first ride on March 4. Credit: NASA.
Two days later, on March 4, Persistence completed its first trip over Mars. The 6.5-meter (21.3-foot) trek gave rover operators and mission planners from NASA’s Jet Propulsion Laboratory (JPL) their first chance to test and calibrate the rover’s engines. The short drive consisted of a four meter drive forward, a 150 degree left turn and a final 2.5 meter drive backwards. The team reported that the rover’s performance was excellent.
They now begin the search for a flat and clear piece of land – appropriately nicknamed ‘helipad’ – on which Ingenuity will be deployed. Once Persistence finds and moves to such a location, the team will order the robber to deploy IngenuityThis happens approximately 30 days after landing.
The deployment process consists of several steps to bring the helicopter to the surface of Mars.
First, the cover protects Ingenuity will be thrown overboard, and Persistence will drive away. Then the first connections to the helicopter are broken and two of the landing legs are deployed – by turning them away from the rover’s belly. It will then be rotated to a fully upright position under the robber where the last two legs will be deployed.
Persistence will then fall Ingenuity on the surface and drive away to a safe distance.
IngenuityThe solo test campaign begins with a series of internal checkouts, testing in particular whether it can maintain a stable temperature and charge its batteries using its tiny solar panel.
Successfully completing all of these steps will spin the rotors at high speed, although not fast enough to lift the vehicle off the surface. This ensures that the engines are running at nominal level and clears the vehicle for flight.
As discussed earlier, the first flight lasts 20-30 seconds and consists of Ingenuity floating at a small height above the surface. If that flight is successful, the helicopter will later perform more complex operations.
The current test window only lasts 30 days, but that will likely be extended as Ingenuity performs well.
Ingenuity marks the start of an alien flight. Regardless of the outcome, it will provide a wealth of data to aid the designers of future off-Earth helicopters.
The first of this mission is Dragonfly, a large eight-rotor drone that will explore part of Saturn’s largest moon, Titan. Dragonfly will be similar in size to Persistence, and actually use an identical Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for power.
The MMRTG charges Dragonfly’s batteries during the Titan night, allowing for 30-minute flights and data downlink during the day.
Dragonfly will feature a host of experiments to study Titan’s atmosphere, surface composition and seismology. It will then be the second mission to Titan Huygens in 2005.
Dragonfly will launch in 2027 and land on Titan in 2036.
(Lead display of persistence and ingenuity – via Mack Crawford for NSF / L2)