## 1 Introduction  
Aerospace pyrotechnic devices are mostly used in some key tasks, such as the separation of rocket stages, satellite attitude adjustments, and the deployment of solar panels [1]. As these tasks are quite particular and important, and the pyrotechnic devices are one-shot and irreparable products, their reliability requirements are extremely high. For such high requirements, it is too expensive to perform large sampling consecutive go/no go tests [2]; therefore, small-sample methods are now used both at home and abroad to evaluate the reliability of aerospace pyrotechnic devices.  
Many scholars have conducted research studies on small-sample evaluation methods of pyrotechnic devices [3, 4]. [PERSON] [5] presented a figure of statistical presentation of small-sample predictions of the risk of failure, from which we can predict the mechanical functional reliability of pyrotechnic devices. [PERSON] et al. [6] proposed the maximum entropy test method based on the basic principles of information theory, which was tested at a critical operating point, greatly increasing the information contained in a single sample, and thereby reducing the test sample size for reliability evaluation. [PERSON] et al. [7] proposed a reliability evaluation method of pyrotechnic devices based on the principle of test information entropy equivalence. [PERSON] et al. [8] carried out a small-samplereliability prediction method and drew an evaluation chart but did not apply the theory to actual engineering. [PERSON] et al. [PERSON] et al. (2018) conducted a Monte Carlo simulation to predict the reliability of a pin puller. These methods have played very good roles in the reliability evaluation of small-sample methods, but further research is still needed.  
Regarding the performance parameters of the pyrotechnic device, most of the previous research work has assumed that the constraint to realize the function of the pyrotechnic device was only the instantaneous resistance. However, many aerospace pyrotechnic devices need a work process to achieve their functions, and the essence of their functional reliability is the reliability of completing the work process. Therefore, taking energy as the performance parameter for the reliability evaluation is more direct and accurate.  
With regard to the energy measurement of pyrotechnic devices, [PERSON] et al. [PERSON] et al. (2018) introduced some functional performance tests and determinations of functional margins. [PERSON] et al. [PERSON] et al. (2018) developed an analytical model to understand the physics and predict the functional performance of a pin puller. Based on [PERSON]'s work, combined with the characteristics of Chinese pyrotechnic devices, some improvements and supplements of energy measurement tests are proposed in this approach.  
This paper is organized as follows: the basic theory of reliability evaluation is derived in Section 2. A total of four energy measuring devices are introduced in Section 3. In Section 4, the energy measuring results of every device are presented. In Section 5, some analyses and discussion of energy results are presented, while the reliability evaluation is also employed in this section. Conclusions are summarized in Section 6.