Numerical simulation of multistage rocket interstage thermal separation and research on parameter uncertainty

DOI:	10.11809/bqzbgcxb2023.12.011
Keywords:	multi stage rockets; interstage separation; numerical simulation; uncertainty analysis; chaotic polynomial expansion
Abstract:	As the main method of interstage separation of rockets, thermal separation not only improves the reliability of the separation process, but also has problems such as the coupling of interstage regional jet and external incoming flow, and the influence of environmental parameter uncertainty is unknown. In this paper, taking the thermal separation process between a certain type of two stage rocket stage as the research object, combined with computational fluid dynamics, statistics and other research methods, this paper carries out the simulation of the thermal separation process between rocket stages by solving the RANS equation and the rigid body motion equation, and discusses the causes of the three stages of separation load change. The uncertainty of the three environmental input parameters of different flight speed, flight altitude and flight angle of attack is investigated, and the uncertainty analysis model of the separation process is constructed based on the chaotic polynomial expansion method (PCE), and the influence degree of each input parameter is quantified by combining the Sobol sensitivity analysis method. The results show that the three environmental parameters mainly affect the separation process by influencing the aerodynamics of the second substage, changing the flow field and inhibiting the development of Mach disk. The uncertain bands of axial velocity of the first and second sub stages obtained by PCE method show different change modes, and their peaks reach 50.1% and 29.2%, respectively, indicating that the second substage has strong anti interference ability. The axial and radial motion parameters have the strongest sensitivity to flight speed, and the sensitivity indexes reach 0.36 and 0.30, respectively. The quantitative characteristics of uncertainty obtained in this study provide a good means for predicting the attitude of thermal separation process, exploring the key influencing factors of separation, and further optimizing the design.
Issue:	Vol. 44 No. 12 (2023)
Published:	2023-12-28
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