This paper presents the applications of three nondestructive testing techniques，i．e．
visual examination，radiographic inspection，and leak detection in attitude control engines．The
focus of the paper is on leak detection technology．According to structural features of the engine，
performance requirements of different systems and various joint seal forms for general assembly，
different leak detection methods such as immersion method，soap bubble method and simple accu—
mulative envelope method by helium mass spectrometry are used in assembly testing．Based on the
comparative analysis of the three mentioned leak detection methods，it is concluded that different
leak detection methods should be adopted to satisfy performance requirements of different systems．