"- The SLS estimate is based on the funding required to develop and operate the initial 70-metric ton variant through first flight in 2017 but not the costs for its second flight in 2021. NASA is now incurring some costs related to the second flight, but it is not currently tracking those costs for life cycle cost estimating purposes. Furthermore, the estimate does not include costs to incrementally design, develop, and produce future 105- and 130-metric ton SLS variants which NASA expects to use for decades. NASA is now funding concept development and analysis related to these capabilities.
- The Orion estimate does not include costs for production, operations, or sustainment of additional crew capsules, despite plans to use and possibly enhance this capsule after 2021. It also does not include $4.7 billion in prior costs incurred during the approximately 4 years when Orion was being developed as part of NASA's now-defunct Constellation program.
- The ground systems estimate excludes costs to develop or operate the ground systems infrastructure beyond 2017, although NASA intends to modify ground architecture to accommodate all SLS variants."