ExoMars rover twin rehearses first drive
Before the Rosalind Franklin rover can explore Mars, it must first get off its lander.
A full-size model of the rover tackled slopes, boulders and Mars-like gravity as it stepped onto a simulated martian terrain during a two-month test campaign on Earth.
Amalia, a twin model of Rosalind Franklin, rehearsed driving off the landing platform and reaching the surface over 20 times. This will be one of the most critical moments of the ExoMars rover mission.
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The test recreated some of the challenges Rosalind Franklin will face on the Red Planet, from reduced gravity and a 20-degree incline to uneven ground and obstacles beneath its ramps.
Exit ramps
This operation, called egress, is not simply a matter of driving down the ramps. Moving the rover safely from the lander to the surface is a carefully choreographed procedure.
The landing platform has two pairs of ramps for the rover to descend: one at the front and another one at the back. The rover is designed to negotiate steep inclines on these ramps, but it is up to ground control on Earth to decide which is the safest way to drive off.
“Because we will have to rely only on orbital images, we won’t know exactly what the conditions around the rover will be after landing. Depending on where and how we land, one of the exits could be blocked by rocks or slopes. The first and most crucial decision of all will be which direction to drive down,” explains Eric Zekri, ESA’s ExoMars rover team leader.
“On Mars, we will only have one chance. Once we egress, there is no way back, so we have to get it right,” he adds.
Engineers practised the most extreme scenarios, leaving the ramps from both sides and setting extra challenges for Amalia.
Extra challenges
First, teams used a lifting device to simulate Mars gravity, which is about one-third of Earth’s. A device in the ceiling held the rover like a puppet, carrying two-thirds of its weight. The rover’s total weight on Earth is 300 kg.
Next came a tilted descent. A hydraulic platform inclined the rover and its lander module 20 degrees.
Finally, engineers placed obstacles under the ramps, as if the lander had come to rest on a boulder or a slope. The rover is designed to handle steep, uneven terrain.
“It is incredibly rewarding to see the rover driving off the platform successfully in such challenging conditions and in a Mars-like scenario. The excellent performance of the ramps reflects the quality of the design, taking us another important step closer to the martian surface,” says Chiara Lombardi, ExoMars rover and lander interface engineer.
The three-metre-long ramps, developed by the Polish space company Astronika, are made of aluminium with a honeycomb pattern for better grip.
The campaign helped engineers gather operational experience that will keep Rosalind Franklin safe in 2030, when its real journey on the martian surface begins.
Teams from Thales Alenia Space, industrial prime contractor for the ExoMars mission, conducted this egress test campaign at ALTEC’s facilities in Turin, Italy. They used a mock-up of the landing platform and a fully representative model of the rover.