ESA turns to NASA to assist in crucial ExoMars parachute tests
HELSINKI — The European Space Agency has sought assistance from NASA in a bid to qualify problematic parachutes that threaten the launch of the ExoMars 2020 mission.
ESA is preparing two new high-altitude tests of the supersonic and subsonic main chutes for the entry, descent and landing phase of the ExoMars mission, following failures in August and May.
The new tests, to be held in December and February, will test the 15-meter-diamater supersonic and 35-meter-wide subsonic parachutes needed to slow the descent of the ExoMars lander.
Both tests, to be held at high altitude to simulate the Martian atmosphere, need to succeed in order for the parachutes to pass qualification. TheExoMars mission faces a final review scheduled April 2020, Francois Spoto, ExoMars program manager, told SpaceNews.
“Now the situation is critical, of course, because we have limited time and no margin,” Spoto says.
If one of the tests fails, the ExoMars mission will miss the narrow July 25 to Aug. 13 launch window next year and slip to the next window, in late 2022. The lander and rover segments are meanwhile progressing well and ready for environmental testing.
ExoMars is to launch on a Russian Proton rocket and reach Mars in March 2021. It will employ a complex system of four parachutes, with two small pilot chutes used to sequential deploy the supersonic ‘disc–gap band’ chute and subsonic main chute.
In the first failed test, main chutes were found to have suffered damage prior to full loads being exerted. Measures to address the issues, including the addition of teflon to reduce frictional effects during release from bags, did not prevent damage being sustained during a second test.
ESA convened a workshop early September as part of efforts to identify and address the issues. Following this, inspectors from the Jet Propulsion Laboratory visited facilities involved in the parachute systems, Spoto says.
The findings from the JPL team indicate that the damage to the chutes was caused at the point of extraction from their bags. The failed tests also saw damage to cables holding the parachutes, but this was likely related to asymmetries resulting from the damage to the canopies.
“The focus is on adapting and simplifying the bag than touching the parachutes,” says Spoto. A meeting at European Space Research and Technology Center, ESTEC, in the Netherlands with industry partners involved in the parachute project was to be held Wednesday to decide the measures to be taken ahead of the next tests.
New tests in Oregon
While previous tests were held at the Esrange Space Center, northern Sweden, the new tests will take place in Oregon in the United States. Esrange closes late August due to conditions in the upper atmosphere and safety concerns related to dropping heavy components following the start of the local hunting season.
The ExoMars 2020 mission is a collaboration between ESA and Russia. The latter took the place of NASA, which pulled out of the mission in 2012 due to budgetary constraints.
The unprecedented size and complexity of the parachute system is related to the lander, being provided by Roscosmos. A more powerful retropropulsive system on the lander could have allowed the mission to require only one main chute, Spoto says.
The chutes will slow descent for the six-minute entry, descent and landing process, with the retropropulsion stage starting around 30-40 seconds prior to landing.
Spoto states that, given the apparent readiness of the Rosalind Franklin rover and lander spacecraft, missing the launch window due to the parachute would be a shame.
He adds however that Europe does not have a long line of planetary missions utilising parachutes, and the ExoMars missions are something of a one-off, making development a challenge.
A Mars sample return mission in collaboration with NASA will be one of the proposals for ESA’s Ministerial Council in November this year but, if approved, will not utilise a European-developed parachute.
NASA, China and the United Arab Emirates are also preparing to use the short launch window next year, determined by the relative positions of Mars and the Earth, to launch missions to the Red Planet.