The NASA project life cycle is divided into 10 stages or blocks of technical work to be performed in order to complete a project. Each progressive stage marks a significant shift in the type of work required to refine the system. Between stages, control gates review the results of the previous stage to determine whether engineers can advance to the next stage of the life cycle.
Failure to involve specialty engineers from a range of disciplines, such as human factors, logistics, safety, reliability and maintainability, during the early stages of the project's life cycle can result in the project passing prematurely through control gates. In these instances, design concepts are later discovered to be impossible to build, test or operate. Thus, the life cycle flow process leverages concurrent engineering or the simultaneous contemplation of downstream processes by integrated product development teams.
Throughout the life cycle flow process, verification requires compliance with project specifications and can be ascertained by analysis and demonstration. Validation hinges on proof that the system not only functions, but serves its purpose.