According to the United States Government Accountability Office, NASA lacks the funding for future uses of its new Space Launch System (SLS) - soon to be the most powerful rocket in the world when development is complete. Its first test flight is scheduled for 2017, but it may not be achieved.

The space agency is $400 million short of being able to launch its $12 billion rocket system in December of 2017. Despite making good progress on the rocket program design, federal auditors say that NASA might not be able to carry out the SLS's first test launch, which would delay any future plans they have for the rocket. NASA receives their annual budget from the federal government, so it's likely they'll have to ask them for more funding, or alter plans for the SLS.

The Government Accountability Office (GAO) says it will cost a total of $12 billion through the system's first test launch and billions more to develop similarly capable space vehicles. Just last week, NASA engineers installed an RS-25 engine on the A-1 Test Stand to begin developmental tests that will work toward developing the SLS core stage, which will be powered by four of those engines. This series of engine tests will collect data on the performance of its new advanced engine controller as well as other modifications.

Despite the progress of the tests and the planning for the 2017 test launch, NASA needs to figure out a way to mend this issue in order to continue with their tentative schedule.

"NASA is waiting for additional policy direction on future missions, but the agency is approaching a crossroads wherein it is confronted with defining a developmental path forward to the more capable variants of SLS," the report states, via this Space Reporter article. "[The space agency] has not developed an executable business case based on matching the program's cost and schedule resources with the requirement to develop the vehicle and conduct the first flight test in December 2017 at the required confidence level of 70 percent."

The GAO conducted the audit to ensure the SLS program was affordable and sustainable for the long term. Additionally, back in May the GAO asked NASA to address concerns about the program's cost estimates, but NASA's response did not fully address the issue, which ultimately led to the audit. NASA was allocated a $16.6 billion budget for 2014, for which the SLS received $1.77 billion. As the space agency to figures out how to deal with the fiscal situation, the fate of the SLS remains in limbo.

You can read more about the GAO audit of NASA in this government report.