16. August 2019
As the second ExoMars mission, comprising a rover and surface science platform, progresses towards launch next year, teams continue to troubleshoot the parachute design following an unsuccessful high-altitude drop test last week
The European-built Rosalind Franklin rover and the Russian-led surface platform, Kazachok, are nearing completion. They will be encapsulated in a descent module, and transported to Mars by a carrier module, following launch on a Proton rocket from Baikonur.
The descent module needs two parachutes – each with its own pilot chute for extraction – to help slow the craft prior to landing. Following separation of the parachutes, the speed must be suitable for the braking engines to safely deliver the landing platform and the rover onto the surface of Mars. The entire sequence from atmospheric entry to landing takes just six minutes.
As part of the planned testing prior to launch, several parachute tests were scheduled at the Swedish Space Corporation Esrange site. The first took place last year and demonstrated the successful deployment and inflation of the largest main parachute in a low-altitude drop test from 1.2 km, deployed by a helicopter. The parachute has a diameter of 35 m, which is the largest parachute ever to fly on a Mars mission.
On 28 May this year, the deployment sequence of all four parachutes was tested for the first time from a height of 29 km – released from a stratospheric helium balloon. While the deployment mechanisms activated correctly, and the overall sequence was completed, both main parachute canopies suffered damage.
Following hardware inspection, adaptations were implemented to the design of the parachutes and bags ready for the next high-altitude test, which was conducted on 5 August, this time just focusing on the larger, 35 m diameter, parachute.
Preliminary assessment shows that the initial steps were completed correctly, however damages to the canopy were observed prior to inflation, similar to the previous test. As a result, the test module descended under the drag of the pilot chute alone.
“It is disappointing that the precautionary design adaptations introduced following the anomalies of the last test have not helped us to pass the second test successfully, but as always we remain focused and are working to understand and correct the flaw in order to launch next year,” says Francois Spoto, ESA’s ExoMars Team Leader.
All hardware, videos and recorded telemetries have now been recovered and are currently under evaluation. The analysis should reveal the root cause of the anomaly and will be able to guide the way forward in terms of further modifications that might be required to the parachute system before subsequent test opportunities.
A further high-altitude test is already foreseen for the first main parachute before the end of this year. The next qualification attempt of the second main parachute is then anticipated for early 2020.
In parallel, the teams are investigating the possibility to manufacture additional parachute test models and conducting ground-based simulations to mimic the dynamic nature of parachute extraction, since there are not many opportunities for full-scale high-altitude drop tests.
Furthermore, in addition to the regular forum of exchanges between ESA and NASA experts, a workshop of Mars parachute specialists will convene next month to share knowledge.
“Getting to Mars and in particular landing on Mars is very difficult,” adds Francois. “We are committed to flying a system that will safely deliver our payload to the surface of the Mars in order to conduct its unique science mission.”
The mission is scheduled for launch in the window 25 July–13 August 2020, arriving at Mars in March 2021. After driving off the surface platform, Rosalind Franklin rover will explore the surface of Mars, seeking out geologically interesting sites to drill below the surface, to determine if life ever existed on our neighbour planet.
The rover is currently nearing completion at Airbus Defence and Space, Stevenage, UK, and will soon begin its environmental test campaign at Airbus Toulouse, France. At the same time, the flight carrier module comprising the descent module and lander platform will begin its final round of testing at Thales Alenia Space, Cannes, France. The rover will be integrated into the spacecraft in early 2020.
The ExoMars programme is a joint endeavour between ESA and Roscosmos. In addition to the 2020 mission, it also includes the Trace Gas Orbiter (TGO) launched in 2016. The TGO is already both delivering important scientific results of its own and relaying data from NASA’s Curiosity Mars rover and Insight lander. It will also relay the data from the 2020 mission once it arrives at Mars in March 2021.
Images: ExoMars 2020 parachute deployment sequence. The ExoMars parachute deployment sequence that will deliver a surface platform and rover to the surface of Mars in 2021 (following launch in 2020). The graphic is not to scale, and the colours of the parachutes are for illustrative purposes only. The graphic highlights the main events concerning the parachutes, a sequence that is initiated after significant slowing of the 3.8 m-wide entry module in the atmosphere with the aeroshell’s heatshields. Then the first pilot parachute is deployed, and shortly after the first main stage parachute, which measures 15 m in diameter and has a disc-gap band design. It will open while the module is still travelling at supersonic speed and will be jettisoned prior to the deployment of the second pilot chute and second stage main parachute once at subsonic speeds. The second stage main parachute has a ring-slot design and is 35 m in diameter, the largest to ever fly on Mars. The second pilot chute remains attached to the main parachute in order to prevent rebound of the deployed parachute. During latter stages of the descent (not pictured) the aeroshell’s front heatshield will be discarded, and the landing platform will be released for its final descent and propulsive braking phase. Once safely on the surface, it will subsequently deploy ramps for the rover to drive down and on to Mars.
How big is the ExoMars 2020 mission? Sizes of key components of the ExoMars 2020 mission. The parachutes that will help slow the descent module through the martian atmosphere are compared in size to the iconic landmark of Elizabeth Tower (‚Big Ben‘), in London, UK. The descent module, which will deliver the surface platform and rover to the martian surface, is compared with the height of a human. The rover is stowed inside the surface platform, and will drive off one of the two ramps that will be deployed after landing.The ExoMars Trace Gas Orbiter, which launched in 2016 and is already in orbit around Mars analysing its atmosphere, is also included in this graphic. It will relay data from the rover mission back to Earth.