WASHINGTON — The Dragon cargo capsule developed by Space Exploration Technologies Corp. (SpaceX) will have to prove its ability to conduct precise orbital maneuvers to the satisfaction of the international space station partnership before it will be permitted to berth with the orbiting outpost in a proposed two-step demonstration anticipated later this year, according to NASA officials.

SpaceX has been developing Dragon and its Falcon 9 medium-lift launcher under a 2006 agreement with NASA that calls for three flight demonstrations of the hardware before the company can begin routine resupply runs to the orbiting outpost next year under a separate contract valued at $1.6 billion.

The Hawthorne, Calif.-based startup proposed combining the second and third Commercial Orbital Transportation Services (COTS) demonstration flights for NASA following a successful maiden flight of Falcon 9 last June. But NASA did not seriously consider the SpaceX proposal until the company successfully sent Dragon into orbit atop a Falcon 9 in its first COTS demonstration Dec. 8.

Douglas Cooke, head of NASA’s Exploration Systems Mission Directorate, said the agency is still considering the SpaceX proposal.

“Basically, the approach would be that [Dragon] would have to satisfy all the Demo 2 objectives, which are primarily [proximity-operations] related, but without docking,” Cooke said during an April 26 meeting of the NASA Advisory Council’s exploration subcommittee. “They would have to satisfy the Demo 2 objectives, and those would be evaluated for how well they performed before they would be allowed to do the Demo 3 objectives.”

As currently planned, SpaceX’s second COTS demo would be a five-day mission during which Dragon would approach to within 10 kilometers of the space station and use its radio cross-link to allow the station’s crew to receive telemetry from the capsule and send commands. In the third and final COTS demo, Dragon is supposed to berth to the station for the first time.

“We know that based on their analysis, they have enough fuel to do all that,” Cooke said of the proposed combined COTS mission. “So those conversations are ongoing.”

Russia, a key space station partner, recently made clear that the decision on SpaceX’s proposal is not solely NASA’s to make.

Alexei Krasov, head of manned spaceflight for the Russian space agency, Roscosmos, said the agency would not grant permission for new commercial vessels to dock with the orbiting outpost “unless the necessary level of reliability and safety [of the spacecraft] is proven,” Russia’s RIA Novosti news agency reported April 22. “So far we have no proof that those spacecraft duly comply with the accepted norms of spaceflight safety,” he said.

NASA officials say SpaceX and fellow COTS provider Orbital Sciences Corp. of Dulles, Va., which is developing the Cygnus cargo vehicle and Taurus 2 launcher, will be held to the same safety standards as other visiting vessels such as Europe’s ATV and Japan’s HTV.

“Dragon and Cygnus will be subject to the same procedures as any visiting vehicle to the space station would be,” NASA spokesman Joshua Buck said in an April 28 email, adding that the international space station partners routinely coordinate to ensure that crew and station safety are not compromised by any visiting cargo or crew vehicle.

“U.S. commercial vehicles will not be unique in this regard; we will work through our normal procedures and ensure the safety of the planned operations,” he said.

Buck said the space station partnership “will be involved to allow approach and docking” to the space station, an activity he said is already covered under visiting vehicle requirements. “Plans are in work to complete these activities in time to support the SpaceX docking,” he said.

Although NASA has yet to officially sign-off on the SpaceX proposal, Alan Lindenmoyer, head of NASA’s Commercial Crew and Cargo Program Office at the Johnson Space Center in Houston, and COTS program manager, said the agency is boosting its investment in SpaceX by some $128 million this year to help pay for previously unplanned ground tests that would facilitate the combined COTS demonstration.

“In the next month or two we’ll make the decision whether or not we’re going to proceed with the actual combined [demo flight] planning,” Lindenmoyer said in a March 28 interview, adding that the new test milestones will serve as prerequisites for conducting what would be the second and final test flight of the Falcon 9 and Dragon. “These are things we would want to do anyway, but the fact that you’re getting potentially one less test flight, well, yeah, you want to be sure they’re done.”