A transient model of the RL10A-3-3A rocket engine (1995)

RL10A-3-3A rocket engines have served as the main tm3Pulsion system for Centaur upper stage vehicles since the early 1980's.This hydrogen/oxygen expander cycle engine continues to play a major role in the American launch industry.The Space Propulsion Technology Division at the NASA Lewis Research Center has created a computer model of the RL10 engine, based on detailed component analyses and available test data.This RL10 engine model can imxlict the perfcmnanoe of the engine over a wide range of operating conditions.The model may also be used to predict the effects of any proposed design changes and anticipated failure scenarios.In this paper, the results of the component analyses are discussed.Simulation results from the new system model are compared with engine test and flight data, including the start and shut-down transient clmtaoeristics.1.0 The RL10A rocket engine is an important component of the United States space infraslntctme.Two RL10 engines form the main propulsion system for the Centaur upper stage vehicle, which boosts commercial, scientific, and military payloads from a high altitude into Earth orbit and beyond (planetary missions).The Centaur upper stage is used on both Atlas and Titan launch vehicles.The initial RL10A-1 was developed in the 1960's by Pratt & Whitney (P&W), under contract to NASA.The RL10A-3-3A, RL10A-4, and RL10A-4-1 engines used today incorporate component improvements but have the same basic configuration as that of the original RL10A-I engine.RL10's have been highly reliable servants of America's space program for over 30 years.The RLIOA-3-3A engine is represented schematically in Figure 1.The Space Propulsion Technology Division (SPTD) at the NASA Lewis Research Center began developing a computer model of the RL10 in 1991.This model was intended for government use in engine system research, _-analysis and flight failure investigations.The first version of the model was created using data provided by Pratt & Whitney, and the ROCket Engine Transient Simulator (ROCETS) I system analysis program.This model could accurately p_llct the steady-state performance of the RL10A-3-3A, but the predicted lime required for the engine to reach a specified thrust during engine start (time-to-accelerate) showed significant differences with test data 2. It is believed that these discrepancies were due to errors in exuapolating the available component perfmmance data to cover engine-start conditions, as well as errors in the physical models used for heat umsfer and two-phase flow.Analysis of each RL10 engine component was undertaken in order to verify the origin of the dam lXovided by P&W, and to improve the accuracy of the models at far off-design conditions.These analyses were also used to benchmark our ability to acowalely model new rocket engine designs forwhich test data are not yet available; the RLIO engine system provided test data to validate the available component and system modeling tools.In this paper, the RLIOA-3-3A rocket engine and its various components me described briefly.The analysis n:mlts for each component are then discussed, including comparisons with existing component test data.The new engine system model, which includes the results of selected component analyses, is described and pn_dictions of me model_ mmparedto gn_-test and flight data.For a more detailed discussion of the modeling work summariz_ here, the reader is referred m