ExoMars: Good News From Parachute Tests (Astronomy)

The parachute system that will help to land ExoMars Rosalind Franklin’s rover on Mars has completed recent dynamic ground extraction tests on the first main parachute. Apart from a small problem, which can be solved in a few days, the ESA says, the tests were carried out correctly, confirming the functionality of the upgrade carried out after the last failed tests. High-altitude tests on both main parachutes are scheduled in the coming months

Good news for the ExoMars 2022 mission : the first main parachute, essential to slow down the lander before landing on the Red Planet, has passed the ground extraction tests, which leaves the expected schedule unchanged, with the launch of the mission scheduled in the window that runs from 20 September to 1 October 2022.

The descent module of the Esa-Roscosmos ExoMars 2022 mission, consisting of the Rosalind Franklin rover , designed to search for signs of life on the planet, and the Kazachok surface platform, which will be responsible for monitoring the landing site – requires two main parachutes – each with your own extraction pilot parachute – to slow it down as it plunges into the Martian atmosphere.

The first of the two main parachutes, with a diameter of 15 meters, will be deployed while the descent module still travels at supersonic speeds. The second main parachute, with a diameter of 35 meters (it will be the largest ever deployed on Mars), will open about 20 seconds later, when the module has reached a speed of about 400 km / h.

Tests carried out at NASA’s Jet Propulsion Laboratory in California involved the first of the main parachutes and its containment and release bag.

These are dynamic ground extraction tests: tests that reproduce the high speeds at which the parachute will be extracted from the bags during the descent to Mars. This made it possible to verify the changes made to the project by Airborne Systems and Arescosmo after the criticalities that emerged in the latest high-altitude tests .

The Jpl Earth Dynamic Mining Test Facility, California. Credits: Nasa / Jpl-Caltech

In these tests, the parachute assembly (the white circular structure in the image opposite), with one end tied to a special machine and the other anchored to a structure suspended on a long cable, is literally fired at high speed by a system compressed air. When the extraction mechanism is activated, the parachute is released from the bag at the target speed, mimicking the deployment on Mars. At higher speeds, the tests allow for extraction at more than 200 km / h.

Those to which the parachute has been subjected is actually a double draw test. In the first, which took place on April 27, Arescosmo evaluated the modifications made to the prototype after the previous unsuccessful tests: the new design of the release bag and the new way of folding the parachute inside to avoid twisting and damage to the tissue during extraction. In the second, which took place three days later, Airborne Systems validated the extraction process.

“Both prototypes performed very well in testing,” says Thierry Blancquaert , head of ExoMars’ Spacecraft Systems Engineering team. “The inspection showed that some small areas of the parachute had been subjected to friction during the extraction process of the bag, reducing the resistance of the fabric in those points. Analysis of the video footage allowed the Airborne Systems team to pinpoint when the damage occurred and to make changes to the parachute bag and packaging. These changes – continues Blancquaert – could be made quickly, just a couple of days, to soon reach a successful result ».

The first main parachute of the ExoMars 2022 mission on the ground after a dynamic extraction test at the test bench of the Jpl. Credits: Nasa / Jpl-Caltech

The parachute was originally packed inside the bag around the central structure that contains its pilot parachute, so that after extraction it opened to 360 degrees. Folding the canopy in two parts, so that one half unfolds first and then the other half, has been shown to reduce the friction that the canopy undergoes as it unwinds around the core structure, prior to deployment.

This time, compared to the previous tests, there are therefore significant steps forward.

Once the changes are made, Airborne Systems will conduct the first high-altitude drop tests on this parachute. Tests scheduled in early June in Kiruna, Sweden. In these tests, a test vehicle is brought to about 29 km altitude by a sounding balloon and from there it is released, then sequentially opening the parachutes so as to subject them in the most likely possible way to the stress they will experience in the rarefied atmosphere of Mars.

Arescosmo will also conduct tests at high altitudes in the coming months, but its attention will be on the second main parachute, the one with a diameter of 35 meters. The improvements made to this parachute and its bag, which include the use of stronger canopy tensors and reinforced fabric around the apex of the parachute, have already been implemented and tested in dynamic extraction tests conducted in December 2020.

The high-altitude test involves the use of a pilot parachute – auxiliary to the second main parachute – slightly smaller: 3.7 meters in diameter instead of 4.5 meters. A decision taken with the aim of reducing the friction generated by the extraction of the main parachute from its bag. This parachute cannot be pre-tested with ground pull tests, as these focus only on pulling the main parachutes out of their bag.

But the tests that the ESA and Roscosmos intend to conduct do not end there. Further dynamic ground extraction tests are planned for August. After that, another couple of high-altitude drop tests will take place between October and November of this year in Oregon, United States. Other high-altitude tests could also take place during the first half of 2022, the configuration of which will largely depend on the outcome of the next tests in Kiruna.

«Our strategy of having two highly qualified teams working on the parachutes, together with the availability of the test bench on the ground, is already paying off» concludes Blancquaert. «We are ready and we can’t wait to carry out the next high altitude drop tests. Landing safely on Mars is notoriously difficult. Investing our efforts in this test strategy is essential to ensure the success of the mission when we arrive on Mars in 2023 ».

Featured image: The sequence of deployment of the two pilot parachutes and the two main parachutes (15 and 35 meters) of the second ExoMars mission. Credits: Esa

Provided by INAF

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