The first SpaceX demonstration flight to the International Space Station will launch no sooner than January as NASA awaits final delivery of flight software before clearing the mission to proceed, according to space agency sources.

Artist's concept of a Dragon spaceship approaching the International Space Station. Credit: NASA
 
A NASA manifest document shows the launch set for Jan. 12. SpaceX has a date on the Air Force-run Eastern Range for liftoff Jan. 7, at the earliest.

But an agency official familiar with the mission described the date as challenging and said February is a more likely timeframe for the flight.

SpaceX and NASA previously stated Dec. 19 was the earliest the mission could blast off from Cape Canaveral, Fla.

SpaceX officials, including founder and CEO Elon Musk, have consistently cautioned media and observers the test flight would likely occur in January, at the earliest.

During the test flight, an unmanned Dragon capsule will lift off from Florida on a Falcon 9 rocket and reach the International Space Station a few days later. After making sure the Dragon's systems are healthy with a flyby of the space station, NASA will approve the spacecraft's final approach within about 30 feet the complex.

Then astronaut Don Pettit will grapple the Dragon with the space station's Canadian-built robotic arm and berth the automated cargo ship to the lab's Harmony module.

SpaceX holds a $1.6 billion NASA contract to supply the space station with food, crew logistics, experiments, spare parts and other necessities with 12 flights of the company's Dragon cargo craft.

But SpaceX must first show the spacecraft works and can safely reach the space station.

The Dragon cargo vehicle for the upcoming demonstration mission arrived at the Florida launch site Oct. 23. The Dragon's trunk, or service module, arrived at Cape Canaveral on Nov. 11. The trunk will house two small Orbcomm communications satellites and the craft's solar panels and propulsion system.

But the spacecraft itself is not driving the schedule.

NASA must review SpaceX's flight plan, test the Dragon's software algorithms and issue a series of safety reports demonstrating the mission poses no unacceptable threat to the $100 billion orbiting laboratory or its six-person crew.

Before NASA approves the launch, the space agency is putting the Dragon spacecraft through a comprehensive safety review to ensure it meets standards for vehicles visiting the station.

NASA's oversight team is now in Phase 3 of the safety review, which will conclude the agency's engineering audit of the flight's safety risks. The review includes a series of "hazard reports" designed to address specific threats during the mission.

Spacecraft approaching within a few miles of the outpost must have at least one level of redundancy in systems to avoid a critical mission-jeopardizing hazard. Two levels of back-up systems are required for catastrophic or safety-related threats, according to NASA.

NASA is also running its own Monte Carlo analysis of SpaceX's software and must obtain approval for the mission from international partners.

According to a senior NASA manager, SpaceX has not delivered the final version of software for the mission. In addition to testing of the software itself, some of the hazard reports can't be finished until the software is delivered and studied, the manager told Spaceflight Now.

Josh Byerly, a NASA spokesperson, said the SpaceX software is due to NASA by Nov. 27 and integrated testing is scheduled to begin the next day.

SpaceX is flying the test mission under NASA's Commercial Orbital Transportation Services program, which is designed to prove out commercial resupply vehicles for the station after the retirement of the space shuttle.

The COTS program partners with SpaceX and Orbital Sciences Corp., which is developing its own rocket and cargo craft, under Space Act Agreements. The agreements form a public-private partnership in which the companies can receive U.S. government investment to complement private capital.

So far, the government has pledged $396 million to SpaceX. The funding is payable as SpaceX meets specific milestones during development and testing, and most of the money has already been paid out.

The first launch of the Orbital Sciences Taurus 2 rocket is scheduled for late February or early March after delays in constructing and testing the booster's new launch pad in Virginia pushed the flight into next year.

In the long run, NASA is counting on both commercial cargo providers to regularly deliver supplies to the space station, but the final space shuttle mission in July stocked the complex with enough food and equipment to continue operations until late 2012 without SpaceX or Orbital Sciences.

The upcoming Dragon flight will test a host of new technologies and spacecraft systems that weren't demonstrated on the capsule's initial orbital mission in December 2010.

SpaceX added two solar array wings to generate electricity and a redundant active thermal control loop to reject heat into space and project the spacecraft from extreme temperatures.

The Dragon's first flight lasted three hours. It exercised the craft's control, electronics, propulsion and re-entry systems, but it didn't demonstrate the Dragon's complex suite of rendezvous sensors required to reach the space station.

Other new systems on the upcoming flight include the hatch, a bay door housing the craft's grapple fixture, and a claw that provides electrical and data connections between the capsule and its trunk, or service module, according to SpaceX.

The spaceship passed a suite of environmental testing before it shipped to Florida.