Historically, the United States has been a world leader in aerospace endeavors in both the government and commercial sectors. A key factor in aerospace leadership is continuous development of advanced technology, which is critical to U.S. ambitions in space, including a human mission to Mars. To continue to achieve progress, NASA is currently executing a series of aeronautics and space technology programs using a roadmapping process to identify technology needs and improve the management of its technology development portfolio. NASA created a set of 14 draft technology roadmaps in 2010 to guide the development of space technologies. In 2015, NASA issued a revised set of roadmaps. A significant new aspect of the update has been the effort to assess the relevance of the technologies by listing the enabling and enhancing technologies for specific design reference missions (DRMs) from the Human Exploration and Operations Mission Directorate and the Science Mission Directorate. NASA Space Technology Roadmaps and Priorities Revisited prioritizes new technologies in the 2015 roadmaps and recommends a methodology for conducting independent reviews of future updates to NASA's space technology roadmaps, which are expected to occur every 4 years.

NASA's Office of the Chief Technologist (OCT) has begun to rebuild the advanced space technology program in the agency with plans laid out in 14 draft technology roadmaps. It has been years since NASA has had a vigorous, broad-based program in advanced space technology development and its technology base has been largely depleted. However, success in executing future NASA space missions will depend on advanced technology developments that should already be underway. Reaching out to involve the external technical community, the National Research Council (NRC) considered the 14 draft technology roadmaps prepared by OCT and ranked the top technical challenges and highest priority technologies that NASA should emphasize in the next 5 years. This report provides specific guidance and recommendations on how the effectiveness of the technology development program managed by OCT can be enhanced in the face of scarce resources.

The United States has publicly funded its human spaceflight program on a continuous basis for more than a half-century, through three wars and a half-dozen recessions, from the early Mercury and Gemini suborbital and Earth orbital missions, to the lunar landings, and thence to the first reusable winged crewed spaceplane that the United States operated for three decades. Today the United States is the major partner in a massive orbital facility - the International Space Station - that is becoming the focal point for the first tentative steps in commercial cargo and crewed orbital space flights. And yet, the long-term future of human spaceflight beyond this project is unclear. Pronouncements by multiple presidents of bold new ventures by Americans to the Moon, to Mars, and to an asteroid in its native orbit, have not been matched by the same commitment that accompanied President Kennedy\'s now fabled 1961 speech-namely, the substantial increase in NASA funding needed to make it happen. Are we still committed to advancing human spaceflight? What should a long-term goal be, and what does the United States need to do to achieve it? Pathways to Exploration explores the case for advancing this endeavor, drawing on the history of rationales for human spaceflight, examining the attitudes of stakeholders and the public, and carefully assessing the technical and fiscal realities. This report recommends maintaining the long-term focus on Mars as the horizon goal for human space exploration. With this goal in mind, the report considers funding levels necessary to maintain a robust tempo of execution, current research and exploration projects and the time/resources needed to continue them, and international cooperation that could contribute to the achievement of spaceflight to Mars. According to Pathways to Exploration, a successful U.S. program would require sustained national commitment and a budget that increases by more than the rate of inflation. In reviving a U.S. human exploration program capable of answering the enduring questions about humanity's destiny beyond our tiny blue planet, the nation will need to grapple with the attitudinal and fiscal realities of the nation today while staying true to a small but crucial set of fundamental principles for the conduct of exploration of the endless frontier. The recommendations of Pathways to Exploration provide a clear map toward a human spaceflight program that inspires students and citizens by furthering human exploration and discovery, while taking into account the long-term commitment necessary to achieve this goal.

Historically, the United States has been a world leader in aerospace endeavors in both the government and commercial sectors. A key factor in aerospace leadership is continuous development of advanced technology, which is critical to U.S. ambitions in space, including a human mission to Mars. To continue to achieve progress, NASA is currently executing a series of aeronautics and space technology programs using a roadmapping process to identify technology needs and improve the management of its technology development portfolio. NASA created a set of 14 draft technology roadmaps in 2010 to guide the development of space technologies. In 2015, NASA issued a revised set of roadmaps. A significant new aspect of the update has been the effort to assess the relevance of the technologies by listing the enabling and enhancing technologies for specific design reference missions (DRMs) from the Human Exploration and Operations Mission Directorate and the Science Mission Directorate. NASA Space Technology Roadmaps and Priorities Revisited prioritizes new technologies in the 2015 roadmaps and recommends a methodology for conducting independent reviews of future updates to NASA's space technology roadmaps, which are expected to occur every 4 years.