National Aeronautics and Space Administration (NASA). This NASA Procedural Requirements. Effective Date: March 12, 2008. Expiration Date: March 12, 2013. 175 p. This NASA Procedural Requirements (NPR) provides the basis for the NASA Safety Program and serves as a general framework to structure more specific and detailed requirements for NASA Headquarters, Programs, and Centers. This document does not stand alone and is to be used in conjunction with the references listed in paragraph P.4.