Book excerpt: edicine to outline the ethics principles and practices that should guide the agency's decision making for future long duration or exploration missions that fail to meet existing health standards. Health Standards for Long Duration and Exploration Spaceflight identifies an ethics framework, which builds on the work of NASA and others, and presents a set of recommendations for ethically assessing and responding to the challenges associated with health standards for long duration and exploration spaceflight. As technologies improve and longer and more distant spaceflight becomes feasible, NASA and its international and commercial partners will continue to face complex decisions about risk acceptability. This report provides a roadmap for ethically assessing and responding to the challenges associated with NASA's health standards for long duration and exploration missions. Establishing and maintaining a firmly grounded ethics framework for this inherently risky activity is essential to gui