NASA's latest mission on Mars will study the atmosphere and listen to phenomena like the "marsquake".

WASHINGTON – NASA's director, James Bridenstine, said he's still waiting for astronauts to leave the US ground floor. The International Space Station by the end of next year, although an unprepared test flight scheduled for January 7 may well be completed in the spring.

Bridenstine's statement that the month of January is a "very low probability" is the first time that the agency has publicly questioned the timing of the planned launch of the Kennedy Space Center in Florida. The test flight of the SpaceX rocket and capsule is a key step in NASA's efforts to resume US transport into Earth orbit nearly a decade after the Space Shuttle slowdown.

The administrator attributed this delay to problems related to several components, including landing parachutes. Some of these systems could be tested without flying them during the initial flight.

It's a matter of determining "what configuration are we willing to accept as an agency and are we willing to give up some elements (and) how are we going to test these elements," Bridenstine told reporters at the headquarters of The NASA.

But he added that the test flight "will certainly take place in the first half of 2019", a program that will still be able to host a crewed flight by the end of the year.

Earlier this year, Bridenstine declared "unquestionably" that such launches would resume in 2019.

The multi-billion dollar NASA program to resume rocket launches on the ISS, known as the commercial crew, has become a priority since Atlantis completed the last mission of the space shuttle in 2011.

Since then, US taxpayers have been paying Russia to transport astronauts to the Soyuz rocket-in-orbit laboratory at a cost exceeding $ 80 million per seat. At the same time, two companies are collaborating with NASA – Boeing and SpaceX – to develop a shuttle replacement system at a lower price.

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Boeing is also working on a test flight next year.

The test flight of the SpaceX Falcon 9 rocket and its Crew Dragon spacecraft is designed to evaluate ground systems, mooring and landing operations. It will also provide valuable data to NASA certifying the SpaceX crew transportation system for transporting astronauts to and from the space station.

The replacement program for the Space Shuttle did not proceed smoothly.

Even though a crewed launch arrives at the space station in 2019, it will be four years behind schedule.

When the commercial crew was unveiled in 2010 under the Obama administration, the target date was 2015. But the lack of total funding of the Republican-controlled Congress resulted in delays. When Boeing and SpaceX won contracts in 2014, the date was pushed back to 2017. New delays have delayed the schedules in the next year.

Bridenstine also said that he was confident that the space station was "absolutely" safe.

On 29 August, ground crews detected what NASA described as a "slight" pressure drop onboard the 250-km-orbiting laboratory complex housing three NASA astronauts, two Russian cosmonauts and one European.

An investigation revealed that the leak was an isolated incident.

"This has been evaluated in many different ways," said Bridenstine. "It is not leaking now, it has been sealed and we all agree that it is safe."

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