The European Space Agency (ESA) has reported that the first successful high-altitude drop tests for the braking parachutes for the joint ESA/Roscosmos ExoMars probe have taken place. The ExoMars mission is scheduled for launch in September 2022 and will be composed of ESA’s Rosalind Franklin rover and Russian space agency Roscosmos’ Kazachok lander, which will not only transport the Rosalind Franklin to the surface of Mars but then also function as a scientific platform in its own right.
The parachutes are an essential part of the ExoMars braking and landing system. After travelling nine months through space, the descent module containing the rover and the lander will be released by the ‘cruise stage’ which carried it from Earth, and enter the Martian atmosphere at a speed of 21 000 km/h. Initial deceleration will be by the resistance of the Martian atmosphere itself, with the descent module protected from the concomitant heating by a thermal shield.
It is once the atmosphere is thick enough for them to function that the parachutes come into play. There are two of them: a 15-m-diameter first stage main parachute, which will deploy while the descent module is still moving at supersonic speeds; and a 35-m-diameter second stage main parachute that will open after the descent module has been decelerated to subsonic speeds and has jettisoned the first stage parachute. Both parachutes will have ‘pilot’ or ‘drogue’ parachutes to help them deploy properly. The final stage of landing will see retro rockets fire during the last 20 seconds, to ensure a soft landing.
The parachute tests took place on June 24 and June 25 at the Esrange facility of the Swedish Space Corporation at Kiruna. A mock-up of the descent module was carried aloft to an altitude of 29 000 m by a helium-filled stratospheric balloon. Previous drop tests in 2019 and 2020 had failed. Consequently, last year the ESA team undertook ground-based ‘dynamic extraction’ tests at the US National Aeronautics and Space Administration’s (Nasa’s) Jet Propulsion Laboratory (JPL) in the state of California. These ‘fast turnaround’ tests allowed the ESA team to improve its designs.
“We’re very happy to report that the first main parachute performed perfectly: we have a supersonic parachute design that can fly to Mars,” reported ExoMars programme leader Thierry Blancquaert. “The performance of the second main parachute was not perfect but much improved thanks to the adjustments made to the [parachute] bag and canopy. After a smooth extraction from the bag, we experienced an unexpected detachment of the pilot chute during final inflation. This likely means that the main parachute canopy suffered extra pressure in certain parts. This created a tear that was contained by a Kevlar reinforcement ring. Despite that, it fulfilled its expected deceleration and the descent module was recovered in good state.”
The team will now focus on determining the cause of the new ‘anomaly’. Should countering it require any changes to the parachute system, these will be tested at the Nasa/JPL test rig before new drop tests are carried out. The next pair of drop tests are currently expected to take place in October and/or November, in the US state of Oregon.