A few weeks ago, NASA placed a $ 2.9 billion contract with SpaceX to use Starship to bring astronauts from lunar orbit to the lunar surface. The contract is part of the Artemis program, and NASA was expected to select more than one company to build a lunar lander. This reflects the approach the space agency has taken in hiring companies to move cargo and now astronauts to the International Space Station.

Following the announcement, NASA’s decision was challenged by the other two companies vying for the contract: Blue Origin, the private company founded by Jeff Bezos, Amazon’s chief executive officer; and Dynetics, a defense company in Huntsville, Ala. NASA has now ordered SpaceX to cease work on the lunar spacecraft until the Government Accountability Office makes a decision on the protests. The challenge does not affect SpaceX’s work on the Starship models that are currently being tested in Texas.

Mr. Musk’s company has become successful in the start-up business and is now one of the most valuable private companies in the world. Its Falcon 9 rockets have become a dominant workhorse for launching satellites into orbit. It routinely transports cargo and astronauts to the International Space Station. Last month she took four astronauts to the space station for NASA and later on Saturday brought another crew home in a nightly splashdown.

However, many are skeptical of Mr. Musk’s claim that the company is only a few years away from sending a spaceship to Mars, and note that he has repeatedly set schedules for SpaceX that have proven far too optimistic.

When he released an update on Starship’s development in 2019, he said that an altitude test would take place within months and that orbital flights could take place in early 2020.

Instead, several catastrophic failures occurred due to faulty welding. When the fuel tanks stopped bursting, two of the prototypes made short successful flights last year. These earlier Starship prototypes resembled spray paint cans with the labels removed and soared nearly 500 feet on a single rocket engine before being returned to the test site in Texas.

Despite being lifted from the ground many times, Starship is still a long way from being ready for a trip into orbit. But SpaceX already has future tests in mind that will send subsequent Starship prototypes to much greater heights. In March, Mr. Musk shared a picture of a prototype of the large booster stage needed for a trip into space. It’s over 200 feet tall.