Single Shaft Turbopump Expands Capabilities of Upper Stage Liquid Propulsion

Abstract

The world's first liquid oxygen-liquid hydrogen closed expander cycle engine, the RL10, was created over 44 years ago by Pratt & Whitney Rocketdyne and has been a successful mainstay for the upper stages of US launch vehicles ever since. Continuous improvements over the years have increased the thrust of this engine to over 140%. Recent component development activity includes the cooperative design, manufacture, and test of a single shaft turbopump to replace the geared RL10 turbopumps. In combination with a liquid oxygen boost pump and a combustion chamber being developed by PWR, the single shaft turbopump can increase the RL10 thrust to 35,000 pounds while maintaining reliability, fail-safe operation, and ease of multiple restarts of the expander cycle design. The requirements for the single shaft turbopump are based on Pratt & Whitney Rocketdyne system expertise and US engine development experience, while the actual pump design and its features were based on KBKhA's more than 60 years experience in designing single shaft turbopump. This paper will review various turbopump development approaches and potential opportunities to support engines in the RL10 thrust class. The advantages of both the current geared and the single shaft turbopump configurations will be discussed. This paper will review various configurations for the single shaft turbopump including the alternate positioning of the turbine and pumps as well as various configurations for individual turbine and pump elements. The single shaft turbopump was designed for multiple thrust levels. The development methodology for a pump capable of operating at multiple thrust levels will be discussed. Some of the conceptual designs which were evaluated will be reviewed. KBKhAs approach to developing turbomachinery also addresses rotordynamics methodologies, assembly, maintainability, and off nominal operating conditions. KBKhA's integrated element, subcomponent, component, and turbopump assembly development approach will be discussed. This integrated approach continues through assembly and test of the integrated single shaft turbopump assembly using liquid hydrogen and liquid oxygen. Representative results from tests at each level will be reviewed as well as the plans for testing in the US. The test results will be reviewed to provide an understanding of KBKhA's component development approach. Finally, the potential application of the single shaft turbopumps to increase the thrust of RL10 engines at various thrust levels will be reviewed.