Updated 5 p.m. Eastern to correct Northrop Grumman and Sierra Nevada Corp. price rankings.

WASHINGTON — SpaceX won a NASA contract to deliver cargo to the lunar Gateway by offering what the agency determined to be the most effective solution and at the lowest price.

NASA announced March 27 that it awarded SpaceX for a Gateway Logistics Services (GLS) contract to deliver cargo to the lunar Gateway. The agency did not disclose specific contract terms, but said that the overall program had at maximum value of $7 billion over 15 years.

At the time of the announcement, NASA did not reveal the other bidders for the contract. However, in a source selection statement released by NASA April 9, the agency said that Boeing, Northrop Grumman and Sierra Nevada Corporation (SNC) all submitted proposals, along with SpaceX, for the program.

The evaluation was based on three factors: mission suitability, past performance and price. Mission suitability, in turn, was based on technical approach, management plan and small business utilization, with technical approach the most important. Price was the most important factor in the final evaluation, approximately equal to the combination of mission suitability and past performance.

SpaceX performed the best of the four companies in mission suitability, followed by Northrop, SNC and Boeing. The company had a “Very Good” score in its technical approach, while Northrop and SNC both were “Good” and Boeing “Fair.” All the companies were rated Good in their management plans other than Northrop, which was Fair, and all were Good in their small business utilization ratings other than SNC, which was Very Good.

NASA found “significant weaknesses” in the technical approach for all the companies but SpaceX. Boeing’s vehicle, identified as the CLS-250 but not described in detail in the document, had three significant weaknesses, one of which was heavily redacted in the public version of the document but appears to involve its approach to cargo stowage. NASA also cited Boeing for failing to meet agency requirements for insight into the program, as well as access to source code for flight software.

Northrop, which offered a version of its Cygnus cargo spacecraft called Exploration Cygnus, was praised by NASA for a vehicle that significantly exceeded cargo requirements. However, NASA identified a significant weakness in the design that is redacted in the public version of the document, but was considered serious by NASA.

“This is a significant concern that could ultimately lead to significant degradation (or even total failure) of the Exploration Cygnus, the launch vehicle, or both,” Ken Bowersox, deputy associate administrator for human exploration and operations, and the source selection official for the contract, wrote in the document. “This significant weakness is a key discriminator in my selection decision.”

SNC’s design was not identified by name in the document, although company executives said in January that they were looking at opportunities to repurpose the “Shooting Star” cargo module it developed for its Dream Chaser cargo vehicle. NASA’s evaluation of that design found a significant weakness that appeared to raise doubts about the vehicle’s ability to meet the pressurized cargo requirements of the contract, although key passages were redacted.

“Without any additional information than what was proposed, there is a high likelihood SNC will be unable to meet the minimum cargo requirement if it cannot achieve this seemingly [redacted],” Bowersox wrote.

NASA found significant strengths SpaceX’s design for its Dragon XL vehicle, both in the total amount of cargo it can carry, exceeding the other three proposals, and its cargo stowage design. While the agency found no significant weaknesses, it did find five lesser weaknesses, such as a lack of definition of the interface between the spacecraft and its Falcon Heavy launch vehicle and a design that requires astronauts to go through the spacecraft’s service module to access its cargo hold.

Another weakness involved the performance of the Falcon Heavy, and suggested a new version of that rocket would be used for Dragon XL. “SpaceX could have been clearer in stating its launch vehicle’s performance capability, especially since this configuration has not yet flown and thus, performance margins for lifting its Dragon XL are uncertain,” Bowersox wrote. SpaceX did not respond to questions April 10 about any changes to the Falcon Heavy planned for Dragon XL missions.

“However,” Bowersox added, “because these weaknesses are minor and correctable, I do not consider them to be an obstacle to SpaceX’s successful contract performance.”

For past performance, all the companies received “High” scores except SNC, which received a score of “Moderate” in part because the company didn’t offer examples of past week that evaluators “found to be relevant and similar in size, content, and complexity compared to the entire scope of work” of the Gateway contract. NASA noted delays by both Boeing and SpaceX in their commercial crew work, but said that project was “significantly more complex” that the proposed Gateway cargo effort.

The statement did not disclose specific prices the companies proposed. However, it said that SpaceX provided the lowest price, followed by SNC, which was “significantly higher” than SpaceX. Northrop had the next lowest price, and Boeing the highest price. Evaluators added that Boeing used an incorrect assumption in its price estimate and included two exceptions to contract terms that made NASA “unable to determine whether Boeing’s proposed price was reasonable.”

In his final evaluation, Bowersox immediately eliminated Boeing because its mission suitability score was the lowest and its price the highest. Of the remaining three, SpaceX stood out, he concluded, based on its low price and high mission suitability score.

Bowersox noted that the proposal terms allowed him to selection more than one company for the program, just as NASA has selected two or more companies for commercial cargo and crew services for the International Space Station. He decided, though, that “awarding more than one GLS contract at this time is not in the Government’s best interest.” There will be opportunities to “on ramp” additional companies in the future if NASA decides it needs more suppliers.