The National Aeronautics and Space Administration (NASA) is responsible for developing much of the nation?s future space technology. Cost estimates for new programs are required early in the planning process so that decisions can be made accurately. Because of the long lead times required to develop space hardware, the cost estimates are frequently required 10-15 years before the program delivers hardware. The system design in conceptual phases of a program is usually only vaguely defined and the technology used is often state of the art or beyond. These factors combine to make cost estimating for conceptual programs very challenging. This paper describes an effort to develop parametric cost estimating methods for space systems in the conceptual design phase.