WASHINGTON — NASA will decide in the coming weeks whether or not to combine two scheduled flight demonstrations of the commercial rocket and space capsule developed by Space Exploration Technologies (SpaceX) to ferry cargo to the international space station.

Last year the Hawthorne, Calif.-based startup proposed combining the second and third of three planned Commercial Orbital Transportation Services (COTS) demonstration flights for NASA before beginning routine resupply runs to the station under a separate $1.6 billion fixed-price contract with the space agency. Although NASA has yet to officially sign-off on the company’s 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 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 become the second and final test flight of SpaceX’s Falcon 9 rocket and Dragon capsule. “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.”

SpaceX is more than two years behind in completing its COTS demonstration flights, but successfully flew the first one Dec. 8; Dragon launched atop the Falcon 9 from Cape Canaveral Air Force Station, Fla., and completed two full orbits before splashing down near its intended target in the Pacific Ocean. But even before that mission SpaceX founder and Chief Executive Elon Musk proposed combining the second and third demonstrations under the company’s $278 million COTS agreement.

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.

Lindenmoyer said NASA is still working out how combining the mission would affect NASA’s COTS payments to SpaceX. Under the current scheme, SpaceX is to receive a cash payout of $10 million upon completion of each demonstration.

“My feeling is if they met the objective of both missions and everything went really well they should be able to get paid for those objectives,” Lindenmoyer said. “But it’s just a little too early to say.”

Regardless, he said, SpaceX will need to conduct a full-up thermal vacuum test and electromagnetic interference test of Dragon in addition to completing a closed-loop demonstration of the capsule’s proximity operations sensors before the objectives of the two COTS demo missions can be merged.

In addition, the company must upgrade its production operation in Hawthorne, add engine test stands at its facility in McGregor, Texas, and make improvements to its launch pad at the Cape, Lindenmoyer said.

SpaceX and fellow COTS provider Orbital Sciences Corp. of Dulles, Va., have earned a combined $80 million in milestone payments since the fiscal year began Oct. 1, money that comes in addition to the payouts negotiated in their original COTS agreements. Although both firms are running behind in meeting milestone objectives, they have received the bulk of the funding anticipated under their original COTS contracts, which total $448 million combined.

Doug Cooke, NASA associate administrator for exploration systems, said the additional funds for both firms are intended to keep them on track to begin cargo resupply missions to the space station in early 2012. NASA will be heavily reliant on these companies for station cargo delivery once the space shuttle is retired later this year.

“By the conclusion of the COTS effort, NASA anticipates it will have invested $800 million in the COTS program,” Cooke said in prepared testimony before the House Science, Space and Technology Committee March 30.

The added COTS milestones and corresponding cash payments were proposed as part of the 2011 budget blueprint U.S. President Barack Obama sent lawmakers last year. Although Congress has yet to approve that plan, leaving NASA and other agencies operating under a series of stopgap appropriations that limit spending to last year’s levels, Cooke said the request for extra COTS money is supported in a three-year authorization bill enacted in October, despite concerns among some lawmakers that the roughly 62 percent increase to the original $500 million COTS budget was excessive.

Currently SpaceX’s remaining COTS demonstration flights are scheduled for July 2011 and January 2012, but Cooke said if NASA approves the company’s proposal, “the combined mission could be flown as early as November 2011.”

Lindenmoyer said SpaceX is developing a plan, worth a $5 million cash payout, for completing the thermal vacuum test of Dragon and is negotiating with an aerospace contractor in Southern California to lease facilities for the test. He said the ground test is important given that Dragon “will be on orbit longer if we execute this combined mission.”

Whereas Dragon spent hours in orbit on its maiden flight, “now we’re talking about weeks on orbit,” Lindenmoyer said. During the December flight, he said, the capsule “didn’t achieve the thermal balance that it’ll see” during the combined COTS demo.

“You’re going to see longer cold-soaks, you’re going to see longer hotter periods and you’re just going to see general exposure to the vacuum of space and these thermal cycles,” he said. “So this is what you want to test; you want to make sure you’re good to go for that longer mission.”

Meanwhile, SpaceX is assessing whether or not to conduct the closed-loop test of Dragon’s proximity and rendezvous sensor system at NASA’s Marshall Space Flight Center in Huntsville, Ala., or at the company’s Hawthorne facilities.

“They want to be able to do this in-house,” Lindenmoyer said. “The question is whether or not they can do it quickly enough to take that on in-house, but we’re still just waiting to see what their assessment will be and we’ll decide the right way to go.”

Regardless of the location, Lindenmoyer said the actual test is not planned until July at the earliest.

“One of the longest poles in getting to the flight is finishing up all the rendezvous and proximity ops software and testing that with the hardware,” he said.

SpaceX will get another $10 million COTS payout for developing a plan for improvements to its production, test and launch facilities.

“It’s to improve the throughput at the facilities, reduce schedule risk and make sure they are set up to complete these demos as fast as possible,” Lindenmoyer said. “As an investor we’re saying, ‘Hey, we think it’s important to get this done quickly’ and that’s part of our investment — to accelerate some of that work.”

Orbital Sciences, which is developing the Taurus 2 rocket and Cygnus spacecraft under its $170 million original COTS agreement, also garnered an extra $40 million in new milestone payments since Oct. 1. NASA says the new money will help Orbital prepare for an additional test flight of the Taurus 2, which Lindenmoyer said would loft a dummy Cygnus capsule in September. Under Orbital’s original COTS agreement, the company is slated to conduct just a single test flight of Taurus 2 that would deliver a cargo-laden Cygnus capsule to the space station. However, that mission has been bumped to the end of the year to make room for the additional flight demo.

“They’ve started ordering all the additional elements for the second flight and getting ready for the first flight, too,” Lindenmoyer said. “They had to put all those parts on order to make sure they can meet their obligations for the demo flight. They had to do all the work and the analysis for the design of the simulator. That’s the benefit [of the added test flight] — not risking a flight spacecraft.”

Lindenmoyer said Orbital expects to receive new milestone payouts during the next six months for test plans and delivery of the Taurus 2 first stage and upper stage, delivery of the Cygnus mass simulator for the added demo flight, and for the inaugural flight itself.

In his testimony Cooke said NASA sees no reason to doubt either company’s ability to succeed in fulfilling the terms of its COTS agreements.

“While each has experienced milestone delays, this is not unexpected, since both partners have aggressive, success-oriented schedules, and are facing challenges typical of a space flight development program,” he said in his prepared testimony. “These delays have not required any additional NASA funding of specific milestones, since the partners are paid only fixed amounts for achieving milestones. Additional development costs have been borne by the companies and/or other investors.”