Satellite Environment Engineering and Simulation Experiments (Part 2)

Author: Jin Xunshu / et al.
Editor-in-Chief: Ke Shouquan
Publisher:
Publish Date: 1996-02-01
Features:
Introduction This book summarizes the basic concepts and engineering applications of space environment engineering. It is divided into two volumes: Volume 1 is on Space Environment Engineering, and Volume 2 is on Dynamics Environment Engineering. Volume 1 focuses on vacuum technology, cryogenic technology, solar irradiation technology in satellite space environment testing; space simulator design; thermal control testing methods, etc. Volume 2 focuses on satellite environmental vibration, shock, acoustic testing methods and testing technology; structural modal analysis and testing, etc. This book is of great reference value for leaders and engineering technicians engaged in aerospace engineering and quality assurance, and can also be used as a selected textbook for aerospace majors in universities.
Excerpt:
a. Resonance frequencies coupling caused by ground transportation, rocket engine operation, and resonance frequency coupling of launch vehicle structure and liquid propulsion system;
b. Transient vibration caused by sudden loads such as rocket engine ignition, shutdown, and stage separation, which are transmitted to the satellite through the vehicle structure and gradually attenuate, hence called transient vibration.
(3) Shock
During flight, satellites and launch vehicles need to separate, jettison fairings, stage separation, and unlock, release, and deploy various extendable components, requiring the use of various types of pyrotechnic devices. These devices generate extremely short-duration shock loads when operating, generally referred to as explosive shock environments. Additionally, satellites may experience impact-like shock loads during ground transportation and hoisting. Some recoverable satellite re-entry components also undergo such shocks when returning to Earth.
(4) Acceleration
During powered flight, satellites gain acceleration due to the thrust of rocket engines. This acceleration changes slowly and is approximately steady-state, combined with the low-frequency portion of the vibration environment response acceleration, to form the satellite's acceleration environment. The aforementioned dynamic environments can cause structural damage to satellites and their components. For example, electronic components may be damaged, leading to equipment failure due to circuit breaks or short circuits, loose connectors, or broken brackets. The main and secondary structures of the satellite may also be damaged or broken. The occurrence of these failures may affect the completion of the mission or even lead to the entire mission failure. According to foreign statistics [1], 30% to 60% of failures that occur after satellites are launched are caused by dynamic environments. Therefore, the impact of dynamic environments on the reliability of satellite operations cannot be ignored. It should also be noted that the aforementioned dynamic environments often coexist. For example, during powered flight, satellites are subjected to both acceleration and noise and vibration environments. The simultaneous action of these environments may produce synergistic effects, intensifying their impact. Therefore, if necessary, the combined effects of these environments should be considered.
To ensure that satellites and their subsystems and components can operate normally under potential dynamic environments, in addition to meticulous design and manufacturing and assembly, sufficient dynamic environment testing is essential. The main purpose of dynamic environment testing is:
1) To verify the correctness of the satellite structure design and assess whether the satellite structure can withstand potential dynamic environments.
2) To expose potential defects hidden during material, component selection, and manufacturing and assembly, thereby minimizing early failure rates and improving operational reliability.
3) To study the impact of dynamic environments on new materials and structures, and to investigate the effectiveness of various vibration (shock) isolation and vibration (shock) damping measures.
Satellite dynamic environment testing is closely linked to the satellite development process. At different stages of satellite development, the test items, objectives, and conditions may vary.
13.2 Design of Satellite Dynamic Environment Testing
For any satellite model, an environmental test plan must be formulated in the early stages of development, specifying the test items, objectives and requirements, test conditions, and methods and equipment to be conducted at each development stage. When preparing the test plan, the basis for compilation should be considered from the following three aspects:
1) Based on the general principles of environmental testing and the characteristics of satellite development, determine the environmental test items and requirements for each stage of satellite development to better leverage the role of environmental testing. Different products have different development processes and stages, hence different environmental testing principles. Through years of practice, a set of theories and practices suitable for satellite characteristics have been summarized and reflected in relevant satellite environmental testing standards. These standards, such as the U.S. military standard MIL-STD-1540 "Test Requirements for Spacecraft" [2] and the Chinese military standard GJB1027-90 "Environmental Test Requirements for Satellites" [3], are of great significance in guiding the formulation of environmental test plans, determining test items and requirements, and more effectively leveraging the role of environmental testing.