From the 2010 debut of its Falcon 9 medium-lift rocket to the inaugural flight of a more powerful variant this past September, Space Exploration Technologies Corp. (SpaceX) has always risen to the big occasion. Another high-profile test awaits in the form of the company’s first attempt to launch a satellite to geostationary transfer orbit, currently scheduled for late November.

That mission, carrying the SES-8 commercial telecommunications satellite, is bound to be another nail-biter, especially since it will require a restart of the Falcon 9 v1.1’s upper stage. SpaceX was unable to demonstrate that capability following deployment of Canada’s Cassiope satellite on the first Falcon 9 v1.1 mission for reasons the company has yet to publicly explain.

But assuming the SES-8 launch is successful, SpaceX faces a bigger challenge over the year that follows: demonstrating that it can build and launch rockets as fast as it has been able to sell them. Currently the company has a backlog of 40 missions including SES-8, 30 of which are scheduled to take place before the end of 2015.

To date, SpaceX has yet to conduct more than two space launches in any single year, meaning its manifest is constantly shifting to the right. In 2011, for example, the company launched just one of seven planned missions; in 2012, the corresponding numbers were one and five.  

SpaceX began 2013 with seven launches on its manifest; SES-8 will be the third, and it appears likely that at least one of the remaining missions will be pushed into 2014, a year in which 12 missions are already scheduled. What’s more, half of the missions on the 2014 manifest are for commercial customers, who typically are far less tolerant of delays than government customers.

Also on tap for 2014 is the inaugural launch of the Falcon Heavy, a demonstration mission that is key to SpaceX’s plan to wrest a large share of U.S. military business from United Launch Alliance.

If SpaceX is at all worried about its ability to deliver, it doesn’t show. SpaceX President and Chief Operating Officer Gwynne Shotwell recently said the company is churning out Falcon 9 fairings at a rate of seven per year and four Merlin 1C engines — each Falcon 9 has 10 such engines — per week, increasing to five by January.  Employment at the company is up to about 3,800.

There have been at least some indications of nervousness among SpaceX’s customers. Iridium Communications, for example, last year moved the initial launch of satellites for its next-generation constellation from Falcon 9 to Russia’s Dnepr rocket. All but two of the 72 Iridium Next satellites remain manifested on the Falcon 9, with launches slated for 2015 and 2016.

By and large, commercial customers, eager to have a new low-cost competitor in the launch services market, are sticking with the Falcon 9. SpaceX also might be benefiting from the fact that the manifests of its main competitors are also fairly full over the next year or so.

While holding onto hard-won business is obviously a good thing for SpaceX, it also ratchets up the pressure on the company to make a significant dent in its backlog starting next year. If that doesn’t happen, SpaceX will have a different sort of problem on its hands.