Space Exploration Technologies (SpaceX) is modifying its Dragon capsule to afford more payload capacity for NASA cargo runs to and from the International Space Station (ISS). But the improvements will push a planned December ISS mission into 2014, in which the company's crowded launch manifest is pending the delayed debut of the revamped SpaceX Falcon 9 rocket.

President Gwynne Shotwell says NASA needs SpaceX to make the Dragon enhancements in order to increase the reusable cargo vessel's cold-storage capacity for transporting research samples between Earth and the ISS.

“We're developing a major upgrade to Dragon to triple the amount of science that we carry up and back,” Shotwell said Sept. 10 at the World Satellite Business Week conference here, adding that the capsule's December mission is now scheduled for February.

Under the terms of SpaceX's $1.6 billion Commercial Resupply Services (CRS) contract with NASA, the company is supposed to deliver 20,000 kg (44,000 lb.) of food, supplies and science materials to the ISS by Dec. 31, 2015. Dragon's advertised payload capacity is for more than 3,300 kg of pressurized and unpressurized cargo to the space station and up to 2,500 kg on the return trip.

Since the December 2008 CRS contract was signed, however, Dragon has conducted just three trips to the ISS, delivering a combined 1,595 kg of pressurized cargo and returning a total of 2,120 kg to Earth.

NASA spokesman Joshua Byerly says no new requirements have been added to the SpaceX CRS contract, suggesting the upgrades are expected to fulfill a long-standing requirement to meet ISS cargo needs. But he says the work is taking longer than initially planned.

“The December launch date was chosen in cooperation with SpaceX and assumed the enhancements being implemented by SpaceX,” Byerly explains. “It is simply taking longer to get all the modifications completed, which is not unreasonable, given the nature of the enhancements.”

In the meantime, SpaceX is still sorting out technical troubles with a new version of its Falcon 9 rocket.

More than a year behind schedule, the Falcon 9 v1.1 is a significant departure from the baseline Falcon 9 that has launched four times since its first flight in December 2010. The changes include a complete redesign of the vehicle's Merlin 1 engine, known as the Merlin 1D, and a new octagonal configuration for the rocket's nine first-stage motors. Other enhancements include considerably longer fuel tanks and a wider payload fairing. All the upgrades are aimed at lofting more mass—including crew—to the ISS, while affording entry to the commercial launch market. Falcon 9 has more than $1 billion in commercial-launch backlog to execute in the coming years.

Previously slated to debut Sept. 15 from SpaceX's new launch pad at Vandenberg AFB, Calif., the company shifted the Falcon 9 v1.1 mission to the end of September following a recent static-fire test. SpaceX founder, CEO and Chief Technology Officer Elon Musk stated on Twitter Sept. 13 that during the 2-sec. test, the rocket's nine engines achieved full thrust, but that “some anomalies” need to be investigated. Two days later, he tweeted plans to conduct a second static-fire test before launching Sept. 29-30.

For its first flight, the new Falcon 9 is expected to deliver a small Canadian science satellite to an elliptical polar orbit. If successful, this will clear the way for SpaceX to conduct its first commercial mission to geostationary transfer orbit, launching the SES-8 satellite for SES, the world's second-largest satellite fleet operator by revenue. SES-8 was expected to launch from Cape Canaveral in the first quarter of this year. SES says it is waiting to deliver the Orbital Sciences Corp.-built spacecraft to Vandenberg until the first Falcon 9 v1.1 mission is successfully lofted.

In addition to SES-8, Shotwell says SpaceX is planning to put the Orbital-built Thaicom 6 communications satellite into orbit by year-end before launching at “a cadence of almost one a month in 2014.” For now, the company is producing four Merlin 1D engines per week, but plans to increase the rate to five per week starting in January, she says. This pace is necessary to keep up with SpaceX's busy launch manifest, which indicates 12 Falcon 9 v1.1 missions next year, including the one to the ISS in February.

“Our production is now ahead of our launch,” Shotwell adds. “We have to get these vehicles to the launch site and fly them, but production should not be an issue going forward.”