Sierra Nevada Corporation's Space Systems' Dream Chaser spacecraft. (Sierra Nevada Corporation)

NASA has ordered Boeing Co. and SpaceX to stop work on crewed spacecraft that may someday ferry astronauts to the International Space Station while a bid protest filed by Sierra Nevada Corp.'s Louisville-based Space Systems is being investigated.

NASA spokeswoman Stephanie Martin confirmed the stop-work order, calling it a "typical process" with a bid protest, but declined to comment further.

Space Systems filed the formal protest with the U.S. Government Accountability Office on Sept. 26 over rejection of its bid for NASA's commercial crew contract to shuttle astronauts to the space station.

An artist's rendition of the Crew Space Transportation (CST)-100 next to the International Space Station (ISS). (The Boeing Company )

The National Aeronautics and Space Administration on Sept. 16 announced the $6.8 billion total contract would be split between Chicago-based Boeing's CST 100 capsule and Elon Musk's SpaceX Dragon spacecraft.

No documents related to the protest have been made public. Space Systems, SpaceX and Boeing all declined to comment.

The GAO appeal process was created by Congress to give businesses the ability to protest without filing a full legal claim in federal court, said Ralph White, GAO's managing associate general counsel.

"A disappointed bidder can challenge the terms of solicitation or outcome of procurement, and in return we will hear those cases or provide an answer within 100 days," White said. "It's a nonpartisan and objective place for the review of contracts."

During the first 30 days, NASA will decide whether to request that the protest be dismissed or to defend its decision by submitting answers to each of Space Systems' claims. The response is due by Oct. 27.

Continued here:

So Sierra Nevada protested NASA space-taxi contract, but what's next?