2023 年度修士論文“Optimization of cushioning material for low impact shock tests for Lean satellites”
Student Number: 203D5007
Name: Ei Phyu Phyu
Supervisor: Professor Mengu Cho

Increasing number of small satellites especially CubeSats are launched on dedicated launch vehicles inlarge number, being separated from the launch vehicle in different phase of a rocket launch. The satellites
need to withstand and be successfully launched from the launch vehicle and survive the shock environmentof very high frequencies, very short duration, and high accelerations generated by various separation eventsusing pyro devices during launch. CubeSats are not separated with shock. The shock experienced during
the separation events at other places of launch vehicles, such fairing separation, main satellite separation,etc. that use pyro devices which may be explosive that led to very high accelerations (order of 104m/s2) atvery short duration (~10msec). Micro components or sensors are located at or near the source of this
explosive release of energy (pyro shock) may fail, jeopardizing the entire mission. Pyrotechnic shock
environments are difficult to replicate in the laboratory but there is a need to accurately simulate the shock
generated during the satellite separation in a laboratory test prior to satellite launch.
Generally, there are various types of shock machine which are a large mechanical shock machine,
medium-weight shock machine, light-weight shock machine, free-fall drop shock machine, a Hopkinson
bar, and an air gun shock machine. These are used in an industrial and laboratory environment. All types ofshock machine are used for recreating accurate and repeatable shock level. The mechanism of shock
generation on the air gun shock machine is elaborated in our laboratory. A projectile energized bycompressed air impacts a shock table. The measured shock response is affected by the impact force, thematerial between the impacting surfaces, and the dynamics of the shock table. Simultaneous measurementof shock response on the corresponding x, y, and z axes require thicker plates as the interface jig. The shock
response measured from the accelerometers attaching on the interface can satisfy the target shockspecification simultaneously along three axes. The measured SRS was characterized by establishingstatistical and probabilistic normal to tolerance limits. The SRS analysis from the acquired accelerometerdata was done using a software designated in the LabVIEWTM environment. The magnitude of shock
response increases with the impact pressure (velocity) and generally reduces when a soft material likenatural rubber is placed between the impacting surfaces.
Launching the great numbers of satellite from the various launchers increase the use of testing equipmentin the laboratory. While the testing in the laboratory needs the use of enormous amount of damper and allthese used dampers cannot be used again after using one time of shock environment simulation. The purposeof this research is to reduce the use of the number of dampers, to get the replicable results of SRS by using
one damper in multiple tests, and to be cost effective in the laboratory environment in the future. And then,improving the reliability and reusability of the dampers used in shock simulation on an air gun shockmachine by reducing the number of dampers usage on each test which required to generate a required andrepeatable shock response for the launching environment. Improving the reusability of launcher parts byrocket company such as recapturing and reusing of fairing and first rocket stage of their launcher, and theyalso tend to use the other types of releasing mechanism such as separation with low acceleration shockmechanism.

Master Thesis“Optimization of cushioning material for low impact shock tests for Lean satellites”
Department of Graduate School of Engineering
Kyushu Institute of Technology
4 February 2023
Supervised byProfessor Mengu ChoElectrical Space System Engineering Course
Student Number: 203D5007

Name: Ei Phyu Phyu

Table of contents
Abstract
List of Acronyms and Symbols
List of Figures
List of Tables
Chapter 1 Introduction
1.1 Research Background
1.2 Research Status
1.3 Research Purpose
Chapter 2 Method of Shock Testing
2.1 Shock Testing Machines
2.1.1 Shock Testing on Air Gun Shock Machine
2.2 Method and Tools
2.2.1 Summary of Method
2.2.2 Laboratory Tools
2.3 Data Acquisition
2.4 SRS Analysis
Chapter 3 Research Purpose (for the case of experiment)
3.1 Testing without dampers
3.1.1 Low Impact Pressure without absorbers
3.1.2 High Impact Pressure without absorbers
3.2 Testing with various dampers
3.2.1 High Impact Pressure with a thick Natural Rubber as an absorber
3.2.2 High Impact Pressure using Felt as an absorber
3.2.3 High Impact Pressure using NLPF (Nano lignin) as an absorber
3.2.4 High Impact Pressure using the combination of Fabric Sheet and Aluminum Sheet as an absorber
3.2.5 High Impact Pressure using Mat as an absorber
Chapter 4 Comparison of SRS using different dampers
4.1 Experiment result figures
4.2 Analyzing the result for experiment
Chapter 5 Discussion
Chapter 6 Conclusion
6.1 Conclusion
6.2 Recommendation for future work
Chapter 7 References
Chapter 8 Appendix"If you would like the full text, please contact cho.mengu801@mail.kyutech.jp"