When NASA awarded crew transport contracts to Boeing CST-100 and the SpaceX Dragon v2, a lot of you asked, "What about Sierra Nevada's Dream Chaser?" Sierra Nevada is asking the same question, filing a legal challenge claiming their craft was ranked equally proficient and a hefty $900 million cheaper than Boeing.

Dream Chaser at dawn on a runway at Dryden Flight Research Center. Image credit: NASA

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Sierra Nevada filed a legal challenge on September 26th, requesting a review of the selection process. In the associated press release, they explain that the proposals were supposed to be ranked on three criteria: price, mission suitability, and past performance. Of the three, price was the most heavily weighted, equal to suitability and performance combined. SpaceX and Sierra Nevada were by far the cheapest, which meant that in a fair competition, Boeing must have substantially out-performed Sierra Nevada on both mission suitability and past performance.

Dream Chaser [right] and the Space Shuttle Atlantis [left]. Image credit: Sierra Nevada Corporation

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Sierra Nevada is alleging that their Dream Chaser is more technically suited to commercial crew transport to the International Space Station than the CST-100, with a wider array of capabilities. The Dream Chaser was the only non-capsule design remaining in the competition: although Dream Chaser launches atop a rocket, it builds on the shuttle's heritage as a piloted, reusable, lifting-body spacecraft that makes soft runway landings. Officially, all three programs scored comparably, with a reportedly small range between highest-ranking and lowest-ranking project.

They also allege that their past performance record is on par with Boeing, and certainly not so low as to justify picking the more expensive project, claiming that selecting CST-100 over Dream Chaser will result in "a substantial increased cost to the public despite near equivalent technical and past performance scores."

A suspended Dream Chaser taking a test flight. Image credit: NASA

In response to the challenge, NASA has ordered a stop to any work under the contracts, halting publicly-funded development of CST-100 or the Dragon v2 until the situation is resolved. As Stephen Clark of SpaceflightNow points out, it is unclear if that also interrupts internally-funded development on the projects.

Artist's concept of the Dream Chaser atop a United Launch Alliance Atlas V rocket. Image credit: Sierra Nevada Corporation

The Government Accountability Office has until January 5th to respond to the challenge. The odds are split on if the challenge will be upheld or dismissed: in recent years, just over 40% of challenges are typically sustained or resolved through voluntary action. If the challenge is sustained, NASA may change its decision, or re-compete the contract.

Will the Dream Chaser ever dock with the International Space Station, or is it doomed to remain an artist's concept forever? Image credit: Sierra Nevada Corporation

Read more on SpaceFlight Now.