In September, NASA announced it would be funding two private spacecraft designed to ferry astronauts to and from Earth orbit: Boeing's CST-100 and the SpaceX Dragon V2. A third competitor, Sierra Nevada's Dream Chaser, wasn't picked, and as a result, Sierra Nevada is challenging the decision, placing all projects on hold.

The challenge comes in the form of a Government Accountability Office (GAO) protest filed by Sierra Nevada. The case will be heard and/or answered within 100 days. In the first 30 NASA will decide to defend its position or dismiss the protest, Sierra Nevada will then have 10 days to respond, and then the GAO can take 60 days to make its decision.

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According to Sierra Nevada's press release, here's why they decided to protest the decision:

SNC, Boeing and SpaceX submitted separate proposals for the CCtCap program. While all three competitors were found to be compliant and awardable under the criteria set forth in the request for proposal (RFP), only two proposals were selected (Boeing and SpaceX), one of which would result in a substantial increased cost to the public despite near equivalent technical and past performance scores.

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The company believes that, in this time of critical budget limits, it is more important than ever to deliver the best value to the American public. With the current awards, the U.S. government would spend up to $900 million more at the publicly announced contracted level for a space program equivalent to the program that SNC proposed. Given those facts, we believe that a thorough review must be conducted of the award decision. The company feels it owes this extra effort to their employees, the over 30 Dream Team U.S. industry partners, 10 university partners, 10 international space agency and industry partners – all of whom believe in Dream Chaser® and that the proposal that was submitted by SNC is the best choice for NASA and the American public.

Importantly, the official NASA solicitation for the CCtCap contract prioritized price as the primary evaluation criteria for the proposals, setting it equal to the combined value of the other two primary evaluation criteria: mission suitability and past performance. SNC's Dream Chaser proposal was the second lowest priced proposal in the CCtCap competition. SNC's proposal also achieved mission suitability scores comparable to the other two proposals. In fact, out of a possible 1,000 total points, the highest ranked and lowest ranked offerors were separated by a minor amount of total points and other factors were equally comparable.

SNC's Dream Chaser design provides a wider range of capabilities and value including preserving the heritage of the space shuttle program through its design as a piloted, reusable, lifting-body spacecraft that embodies the advanced technologies of today and flexibility that enables the innovations of the future. It was also the only vehicle remaining in the Commercial Crew Program that was not a capsule.

SNC's filing seeks a further detailed review and evaluation of the submitted proposals and capabilities. SNC takes the nation's human spaceflight capability and taxpayer's money very seriously. SNC believes the result of further evaluation of the proposals submitted will be that America ends up with a more capable vehicle, at a much lower cost, with a robust and sustainable future.

Of course they think their spacecraft is the best and should have been chosen. As rocket scientists say, "duh." What is interesting to consider is that NASA's decision seems to be one that tacitly chooses capsule designs for travel to and from orbit over winged, spaceplane/lifting body designs, possibly as a result of lessons learned from 30 years of shuttle flying.

The Dream Chaser is, of course, the only non-capsule design submitted, but it also has a long history with NASA. Where you can argue that both Boeing and SpaceX's craft are derived from NASA's old Apollo capsules, the Dream Chaser is also derived from an old NASA design: the HL-20 spaceplane, which in turn shares (or owes) a lot of design similarities to the Soviet BOR-4, and both of those can trace their designs back to earlier lifting-body experimental craft like Northrop's HL-10.

As a spaceplane design, the Dream Chaser can land on a runway like an aircraft, and likely can also have greater flexibility in choosing where to land as well, thanks to its greater ability to glide and fly. Even so, both the CST-100 and the Dragon V2 are testing and planning for ground-based recovery, like a Soyuz, as opposed to a water-based landing, like an Apollo, which makes the appeal of the runway landing a bit less important.

I think technically, the Dream Chaser probably is a more refined, advanced basic design than a capsule, but I suspect that after years of dealing with an expensive, somewhat fragile fleet of spaceplanes, NASA has seen the economy and simplicity of a capsule-based design for an orbital ferry, and their decision reflects that.

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It's not clear if Boeing or SpaceX can continue development with private funds at this point or not. As far as the outcome of Sierra Nevada's appeal, it looks like we'll know more within, oh, 100 days or so.