With the International Space Station stocked with food and clothing by the last space shuttle mission, SpaceX and Orbital Sciences are gearing up for test flights of their cargo freighters to the orbiting lab in December and February, government and industry officials said.

Artist's concept of a SpaceX Dragon spacecraft approaching the International Space Station. Credit: NASA
 
The commercial automated cargo vehicles are in the final stages of development and testing before moving to their launch sites in Florida and Virginia.

NASA has "technically" agreed to combine SpaceX's next two demonstration flights of the company's Falcon 9 rocket and Dragon capsule, electing to send the next mission all the way to the space station, according to Bill Gerstenmaier, the head of the agency's human space programs.

"We technically have agreed with SpaceX that we want to combine those flights, but we haven't given them formal approval yet," Gerstenmaier said last week. "We still want to go through some more analysis to go take and look and define exactly what criteria makes up that combined mission, what objectives are there, what the go/no go criteria is."

The unmanned flight would blast off Nov. 30 from Cape Canaveral and reach the space station about one week later, where the lab's Canadian robot arm would reach out and grapple the approaching Dragon spaceship.

SpaceX and NASA are reviewing plans for the mission, which would deliver some limited cargo to the complex. If everything goes as planned, SpaceX's first operational resupply flight would launch in the first half of 2012.

Working under a funded Space Act Agreement with NASA, SpaceX tested the medium-lift Falcon 9 rocket on two flights in 2010. The second launch in December demonstrated the blunt Dragon capsule on two orbits around Earth, culminating in a successful splashdown and recovery in the Pacific Ocean.

Under the initial agreement, SpaceX's next mission would have approached within the vicinity of the space station before backing away after checking out navigation and communications equipment. On the eve of the December flight, SpaceX asked NASA to accelerate the demo mission schedule and fly the next Dragon to the space station.

"Overall, what we want to do is we want to get to cargo delivery as fast as we can, and if the systems are mature enough and the design is mature enough, combining those two flights is that best way to get cargo to ISS in the fastest manner possible," Gerstenmaier said.

NASA added an extra space shuttle mission to haul food, clothes and other supplies to the station, putting the outpost on solid footing for more than a year even without further deliveries by NASA's budding commercial partners.

Mike Suffredini, NASA's space station program manager, said the additional shuttle visit gives the agency wiggle room in case SpaceX and Orbital Sciences fall behind. The gear delivered by the shuttle Atlantis ensures the complex can remain at full operational capability through 2012.

"This most recent space shuttle mission...was able to stock up the space station with supplies and consumables to buy some time for both us and SpaceX to get our cargo systems operational, but the pressure is on to get both of these delivery systems proven and into service over the course of the next year," said David Thompson, chairman and CEO of Orbital Sciences.

Atlantis returned from the resupply flight July 21, wrapping up the shuttle program's 30 years of service.

File photo of the International Space Station. Credit: NASA
 
Speaking to reporters after the shuttle's last landing, Gerstenmaier said NASA is analyzing SpaceX's flight software using Monte Carlo methods. SpaceX's flight design for the mission is also being reviewed, particularly regarding two small Orbcomm communications satellites to be carried as secondary payloads on the mission.

The first and second stages of the Falcon 9 rocket for SpaceX's cargo flight are already at the company's Cape Canaveral launch pad. The Dragon spacecraft is due to arrive in August or September.

"We're doing all the planning to go ahead and combine those missions," Gerstenmaier said. "The capsule is being designed that way and the software is being built that way, and we're just kind of waiting for the right formal time where we collectively agree that this is the right thing to go forward."

Two months after SpaceX's first mission to the space station, Orbital Sciences plans to launch its inaugural Cygnus resupply ship. The company foresees the mission launching in February 2012, according to Thompson.

SpaceX and Orbital's missions will fly to the space station soon before or after European and Japanese cargo freighters dock to the outpost.

Orbital Sciences holds a $1.9 billion Commercial Resupply Services contract with NASA to serve the International Space Station with eight flights of the Taurus 2 rocket and the robotic Cygnus cargo freighter. The contract requires Orbital to deliver 20 metric tons, or about 44,000 pounds, of equipment to the complex over the eight missions.

SpaceX signed a similar contract worth $1.6 billion for 12 flights of the Falcon 9 rocket and Dragon capsule.

Both companies have Space Act Agreements, funneling government financing to help design, build and test commercial spacecraft for cargo resupply missions to the space station. The NASA funding is coupled with private investment.

The public-private partnership is called the Commercial Orbital Transportation Services, or COTS, program.

Orbital Sciences will launch the Cygnus spacecraft on the Taurus 2 rocket from a new pad at Wallops Island, Va.

Delays in installing and checking out the Wallops launch complex's propellant and pressurization systems has pushed back the Taurus 2 rocket's debut flight from October to December, Thompson said July 21.

The launch pad should be completed in August, and a pathfinder version of the Taurus 2 rocket will be moved to the complex in October.

The December test launch was added with the help of NASA funding to reduce the risk in Orbital's rocket and spacecraft development programs. If the launch is successful, Orbital aims to bolt the first Cygnus craft to the second Taurus 2 rocket for liftoff in February.

Artist's concept of a Taurus 2 rocket launch. Credit: Orbital Sciences
 
Thompson said a failure during a June ground test of Aerojet's kerosene-fueled AJ26 engine is also unlikely to cause any significant delays in the Taurus 2 launch manifest. Each Taurus 2 rocket first stage is powered by two AJ26 engines, which were built in Russia for the Soviet Union's moon program in the 1960s and 1970s.

Aerojet acquired and modified the engines for U.S. launches.

"Orbital, Aerojet and NASA have substantially completed our analysis of the cause of this test failure and have developed a screening process which is now being applied to an initial batch of the three dozen or so AJ26 engines that are in inventory at Aerojet," Thompson said in a conference call with financial analysts.

Thompson said about two-thirds of Aerojet's AJ26 inventory are ready for flight as is, with the remaining engines needing "some level of rework or repair" before being cleared for launch.

The June testing mishap occurred at NASA's Stennis Space Center in Mississippi. The AJ26 engine caught fire after a leak in one the powerplant's fuel lines.

According to Thompson, two Taurus 2 first stages built in Ukraine are already at the Wallops launch site. One solid-fueled Castor 30 second stage motor is also now at Wallops.

The Cygnus mass simulator and instrumentation package that will fly on the Taurus 2 rocket's December test flight has also been shipped to the coastal Virginia launch site.