Space Launch System
NASA artist's illustration of the Space Launch System (SLS) leaving the Cape Canaveral launch pad.
While the report's overall conclusions are largely positive about NASA's steady progress on meeting GAO's earlier expectations, the report says things are getting very tricky for SLS in the current tight-money Washington environment.
Here are four specific challenges facing SLS and the thousands of federal and contractor employees working on the rocket in Alabama and nationwide. These are the questions SLS supporters will likely face from the program's critics in the months ahead.
1. Funding issues: "Funding remains a top program risk," GAO says. NASA plans to spend almost $7 billion to develop SLS between now and its first scheduled flight in 2017. But NASA is asking for flat appropriations from Congress each year across the period, and the GAO says lower-tier managers are worried that flat funding may not be enough.
2. Schedule issues: NASA's schedule to develop the core stage "is aggressive," GAO says. The core is the only totally new part of the rocket, but it's the critical part. If it doesn't get done, SLS doesn't exist. Designs and hardware for the core aren't complete yet, GAO says, and neither is the production facility. NASA has also squeezed the development schedule, making early decisions about long-range issues like materials and tools, and GAO says that increases the risk of having to redo something late in the game.
3. Existing hardware issues: NASA has challenges with the leftover shuttle engines and shuttle-era solid rocket boosters it plans to use and with a key propulsion subsystem. One of its proposed solutions isn't certified for human spaceflight, because astronauts can't control it, so NASA wrote a new requirement that the system in question have an "off" switch. GAO says the full extent these challenges won't be known for at least another year.
4. Contract issues: More than two years after being established as a program, GAO says SLS contains "many" indefinite contracts. Unanticipated costs are a real risk. And the cost baselines "do not include the likely full costs of the SLS program."