The National Aeronautics and Space Administration Authorization Act of 2010 directed NASA to, among other things, develop a space launch system as a follow-on to the Space Shuttle and as a key component in expanding human presence beyond low-Earth orbit. In 2011, NASA formally established the SLS program in response to this direction, and the Congress has provided continued support for the program. For example, the Congress has appropriated additional funding for SLS in each of the past 3 fiscal years above the level requested by the program. The cumulative additional funding totals about $610 million more than requested for SLS for fiscal years 2013, 2014, and 2015. NASA plans to develop three SLS launch vehicle capabilities, complemented by Orion, to transport humans and cargo into space. The first version of the SLS is a 70-metric ton launch vehicle known as Block I.the first in 2018 and the second in 2021/22. The vehicle is scheduled to fly an uncrewed Orion some 70,000 kilometers beyond the moon during NASA has committed to conduct two test flights of the Block I vehicle— the first test flight, known as EM-1, and to fly a second mission—EM-2— beyond the moon to further test performance with a crewed Orion vehicle. After 2021, NASA intends to build 105- and 130-metric ton launch vehicles, known respectively as Block IA/B and Block II, which it expects to use as the backbone of manned spaceflight for decades. NASA anticipates using the Block IA/B vehicles for destinations such as near- Earth asteroids and Lagrange points and the Block II vehicles for eventual Mars missions.infrastructure and systems needed to support processing and launch of Orion and SLS at Kennedy Space Center. See figure 1. The JCL is a quantitative probability analysis that requires the project to combine its cost, schedule, and risks into a complete quantitative picture to help assess whether the project will be successfully completed within cost and on schedule. NASA introduced the analysis in 2009, and it is among the agency’s initiatives to reduce acquisition management risk. The move to probabilistic estimating marks a major departure from NASA’s prior practice of establishing a point estimate and adding a percentage on top of that point estimate to provide for contingencies. NASA’s procedural requirements state that Mission Directorates should plan and budget programs and projects with an estimated life-cycle cost greater than $250 million based on a 70 percent JCL, or at a different level as approved by the Decision Authority, and any JCL approved at less than 70 percent must be justified and documented. NASA Procedural Requirements (NPR) 7120.5E, NASA Space Flight Program and Project Management Requirements, paras. 2.4.4 and 2.4.4.1 (Aug. 14, 2012) (hereinafter cited as NPR 7120.5E (Aug. 14, 2012)). 2018 as schedule reserve and the $1.3 billion difference between the $8.4 billion goal and the $9.7 billion baseline as funding for that schedule reserve. Unlike cost reserves, however, that funding largely corresponds to those 11 months and cannot be used separately from schedule to address problems as they arise. In December 2014, we testified that the ground systems and Orion programs will likely not be ready to support EM-1 before November 2018 even if SLS is able to meet its earlier internal goal. During this testimony, NASA witnesses stated that the SLS program would not be able to meet its internal goal of December 2017 and that the program would likely slip the internal goal to summer 2018. See table 1 for more specifics on estimated launch dates. NASA generally followed best practices in preparing the SLS cost and schedule baseline estimates for the limited portion of the program life cycle covered, that is, through launch readiness for the first test flight of SLS. We found that the SLS program cost and schedule estimates for this limited portion of development substantially met three of four cost characteristics—comprehensive, well documented, and accurate—and both schedule characteristics—comprehensive and well constructed— that GAO considers best practices for preparing a reliable estimate. However, because the cost estimate only partially met best practice criteria for credibility, the fourth cost characteristic, the estimates could not be deemed fully reliable. See figure 2. While the cost and schedule estimates were prepared largely in accordance with best practices, they only represent costs for the first flight of SLS, EM-1, as opposed to the program’s full life cycle. In May 2014, we recommended that NASA establish a separate cost and schedule baseline for missions beyond EM-1 and report this information via its annual budget submission. Additionally, we recommended that NASA establish life-cycle cost and schedule baselines for each upgraded block of the SLS. NASA partially concurred with our recommendations, citing that actions it plans to take to track costs and actions already in place, such as establishing a block upgrade approach for SLS, met the intent of our recommendations. To this point, however, NASA has not put forth any estimates or baselines projecting the costs of future blocks of the SLS. Comprehensive: The SLS cost estimate substantially met the criteria for being comprehensive through launch readiness for EM-1 but did not include any costs beyond the first flight. To develop the estimate, officials used a detailed work breakdown structure—the structure used to define in detail the work necessary to accomplish program objectives—that is traceable to the cost of each work element and the contract statement of work and documented ground rules and assumptions. To fully meet the criteria for being comprehensive, however, the estimate should define in detail all costs through the expected life of a program. The estimate satisfied NASA’s cost estimating approach for Human Exploration programs by including life-cycle costs through launch readiness for EM-1, but did not include any costs for deployment and operation and maintenance of SLS beyond the first flight. These costs will likely far exceed the costs of development through the first flight. For example, in October 2009, the Review of U.S. Human Spaceflight Plans Committee reported that the fixed costs of the facilities and infrastructure associated with the Shuttle program were about $1.5 billion a year. Given that NASA hopes to operate the SLS for decades, it is reasonable to expect that the deployment and operation and maintenance costs—which should be included in a reliable estimate of life-cycle costs—alone for the SLS will outweigh the agency’s current estimated cost of $9.7 billion. NASA has stated that cost estimates do not need to cover the program from “cradle to grave.” Rather, NASA’s position is that the program’s estimate is only meaningful up to the time that the SLS is delivered for its first launch, because the agency is taking what it calls a capability approach. Therefore, NASA has only estimated costs of the program to the point at which the capability will be achieved. Furthermore, NASA has yet to determine the number of launches, their missions, or the operating lifetime for the program, which according to agency officials makes it difficult to estimate the total costs of the program. Nevertheless, Office of Management and Budget guidance and GAO’s Cost Assessment Guide indicate that life-cycle cost estimates should encompass the full life cycle of a program. Well Documented: The SLS cost estimate substantially met the criteria for being well documented; however, some explanations to support the estimate were missing. A well-documented cost estimate includes thorough documentation and is traceable to information sources. We found that the SLS cost estimate documentation discusses, and is consistent with, the program’s technical baseline and provides evidence that the cost estimate was reviewed by management. The estimate also included explanations for how the estimates for the underlying components were created through an assessment of likely costs for each part of the system supplemented with an engineering review. In some instances, however, explanations of how historical data were normalized, that is, adjusted to support the estimate, were missing. For example, the cost estimate does not explain how historical costs for the space shuttle main engine were normalized to support the estimate. The purpose of data normalization is to make a given data set consistent with and comparable to other data used in the estimate so that they can be used for comparison analysis or as a basis for projecting future costs. Insufficient documentation of how the historical data were adjusted can hinder understanding and proper use of the estimate. Accurate: The SLS cost estimate substantially met the criteria for being accurate, but the continued accuracy of the estimate is in question because officials have no plans to periodically update the estimate. Accurate cost estimates are based on assessments of most likely costs, adjusted properly for inflation, and contain few, if any, minor mistakes. In addition, a cost estimate should be updated regularly to reflect significant changes in the program. The SLS cost estimate meets most of these characteristics as it is based on an assessment of likely costs, is adjusted properly for inflation, and contains few if any mistakes. Contrary to best practices, however, NASA does not periodically update the estimate based on actuals, which limits its use as a management tool for monitoring progress and planning future work. The program prepared its cost estimate and JCL in calendar year 2013. GAO’s cost estimating best practices call for estimates to be continually updated through the life of the project, ideally every month as actual costs are reported in earned value management reports. Best practices also call for a risk analysis and risk simulation exercise—like the JCL analysis—to be conducted periodically through the life of the program, as risks can materialize or change throughout the life of a program. Unless properly updated on a regular basis, the cost estimate cannot provide decisionmakers with accurate information to assess the current status of the project. Agency officials have indicated that the SLS program has no plans to update the cost and schedule estimates underlying the JCL or the JCL itself, which calls into question the continued accuracy of the estimates.