As Boeing and Space Exploration Technologies (SpaceX) restart work on commercial crew contracts following NASA’s Oct 9. decision to lift a stop-work order, details of an internal agency document reveal why the bid from losing competitor Sierra Nevada lost out.

The three companies competed for $6.8 billion worth of Commercial Crew Transportation Capability (CctCap) contracts to transport NASA astronauts to the international space station (ISS) starting in 2017. However, following the awards of work to Boeing for the CST-100 and to SpaceX for the Dragon V2, Sierra Nevada -- which proposed the Dream Chaser lifting body -- filed a protest with the U.S. Government Accountability Office (GAO) on Sept 26, citing “inconsistencies in the source selection process.”

In response, NASA issued a stop-work order to Boeing and SpaceX on Oct 2, only to rescind it a week later on the grounds that a delay to development of the transportation service, “poses risks to the ISS crew, jeopardizes continued operation of the ISS, would delay meeting critical crew size requirements, and may result in the U.S. failing to perform the commitments it made in its international agreements.” The GAO has until Jan. 5, 2015, to rule on Sierra Nevada’s protest.

The internal document, signed by NASA Associate Administrator William Gerstenmaier on Sept. 15, the day before the contract awards were announced, says, “I consider SNC’s (Sierra Nevada Corp.) design to be the lowest level of maturity, with significantly more technical work and critical design decisions to accomplish. The proposal did not thoroughly address these design challenges and trades.” Gerstenmaier goes on to say that Sierra’s proposal “has more schedule uncertainty. For example, some of the testing planned after the crewed flight could be required before the crewed flight, and the impact of this movement will greatly stress the schedule.”

A copy of Gerstenmaier’s document was obtained by Aviation Week.

Although the document praises Sierra’s “strong management approach to ensure the technical work and schedule are accomplished,” it cautions that the company’s Dream Chaser had “the longest schedule for completing certification.” The letter also states that “it also has the most work to accomplish which is likely to further extend its schedule beyond 2017, and is most likely to reach certification and begin service missions later than the other ‘Offerors’.”

Discussing costs, Gerstenmaier says that “although SNC’s price is lower than Boeing’s price, its technical and management approaches and its past performance are not as high and I see considerably more schedule risk with its proposal. Both SNC and SpaceX had high past performance, and very good technical and management approaches, but SNC’s price is significantly higher than SpaceX’s price.”

 Touching on why Boeing received a $4.2 billion contract, versus $2.6 billion for SpaceX, he adds “I consider Boeing’s superior proposal, with regard to both its technical and management approach and its past performance, to be worth the additional price in comparison to the SNC proposal.”

Commenting on the two winning capsule concepts, Gerstenmaier clearly singles out the Boeing design for most praise, being “the strongest of all three proposals in both mission suitability and past performance. Boeing’s system offers the most useful inherent capabilities for operational flexibility in trading cargo and crew for individual missions. It is also based on a spacecraft design that is fairly mature in design.” He also points to Boeing’s “well-defined plan for addressing the specific issues from Phase 1,” and says of the three bidders Boeing “has the best management approach, with very comprehensive and integrated program management, and an effective organizational structure, further ensuring they will be able to accomplish the technical work in a manner that meets NASA’s standards.” Phase 1, the Certification Products Contract (CPC), covered hazard reports, plans for verification, validation and certification.

Space X had the best price of the three contenders and Gerstenmaier expressed a “high” overall level of confidence in the company’s ability to successfully perform the CctCap contract. However he acknowledged “some technical concerns about this proposal,” and worries that the schedule could be affected by having to tackle redesign issues late in the program. 

 While praising SpaceX’s strong approach for incremental development and testing with risk reduction, Gerstenmaier expressed a worry that the company has “the least robust approach for addressing the actual specific feedback on the Phase 1 products that are the foundations of certification in this second phase.” He added there could be a risk that “problems not yet well understood, and design trades made late in the development process, will result in the system not being certified and ready for missions in the needed timeframe.”

Despite SpaceX only showing “satisfactory” performance during CPC, Gerstenmaier says the young space company has “performed very well” on other relevant work and has the benefit of more schedule margin than the other companies.

Boeing plans to launch the CST-100 on a United Launch Alliance Atlas V from Space Launch Complex (SLC) 41 at Cape Canaveral Air Force Station, while SpaceX will launch its Dragon V2 atop its Falcon 9 v1.1 rocket from the adjacent SLC 39A. Sierra Nevada, which recently announced new studies of a scaled, three-person version of the Dream Chaser for launch from the Stratolaunch air launch system, continues to pursue internationally-backed development plans and remains committed to a sub-orbital test planned for November 2016.

Editor's note: SpaceX's launch pad has been corrected above.