Development of the risk oriented program optimization tool (ROPOT) for orbital space plane design concepts

The preliminary design phase of any program is the key to its eventual successful development. The more advanced a design, the more this tends to be true. For this reason, the preliminary design phase is particularly important in the design of aerospace systems. Errors in preliminary design tend to be fundamental and tend to cause programs to be abandoned, or to be changed fundamentally, and at great cost later in the design development. In order to facilitate the identification of attractive design regimes, the NASA Ames Research Center initiated a project, supporting the 2^nd generation reusable launch vehicle (RLV) Program, to develop an advanced suite of conceptual design tools. The tool, called risk oriented program optimization tool (ROPOT) was developed for evaluation of reusable space transportation system (RSTS) conceptual analysis. The ROPOT tool is a modular "lego-block" approach that is built on risk drivers from the space shuttle. This paper illustrates how this tool was adapted and applied to the decision-making about future space transportation system architectures, including new orbital space plane designs that are to be launched on the new evolved expendable launch vehicles. ROPOT has been further developed to provide the capability to explore crew survival capabilities of the vehicles throughout the mission, and develop insights and concerning the key trades involving performance, cost, crew safety and developmental risk. The tool demonstrated the ability to capture the key trades necessary to make informed decisions concerning alternative vehicle concepts, clearly identify strengths and weaknesses of design alternatives, and identify the most fruitful areas for achieving overall benefits. The results of this effort demonstrate the ability of ROPOT to be easily adapted to evaluate a broad range of vehicle types ranging from fully-reusable advanced concepts of the 2^nd generation program, to near term expendable vehicles.