| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 99 === The purpose of this thesis is to demonstrate the design approach for the mechanical structure of reentry capsule for Sounding Rocket VIII Mission (Abbreviated as SR08) in Taiwan, and to verify the feasibility of the design numerically and experimentally. The major goal of Sounding Rocket VIII Mission is to continue the plan of the reentry capsule for Sounding Rocket VI Mission (Abbreviated as SR06) with additional new tasks. There are three new main tasks developed in this mission, i.e. a tri-band antenna (UHF, GPS, and S-Band) for the signal communication, a rescue antenna designed in a gas column, and a cold gas propulsion payload. The mission of the additional payload of cold gas propulsion will be conducted at the altitude about 100 km after the reentry capsule separated from the rocket. The nitrogen gas thruster will control the attitude of the reentry capsule. Simultaneously all the measurement data of the attitude and other sensors will be recorded, and some of them will be also broadcasted to the ground station by the tri-band antenna. In comparison with the SR06 Mission, the weight of the reentry capsule of SR08 is increased and the density is correspondingly larger then that of sea water. Consequently an additional gas balloon is essential for the reentry capsule that it is capable of floating on the sea water for rescue.
The main points of structural design for reentry capsule include the connection between the payload and the capsule structure, a separation mechanism for parachute chamber, an anti-vibration mechanism for the payload, tri-band antenna widows, debug and power connection widows, a balloon and the corresponding inflation mechanism, a chamber for the cold gas propulsion system. In order to fulfill the mission requirements, some of the design are quiet different than the reentry capsule of the SR06 mission, such as anti-vibration mechanism where conical silicone cushion pads are utilized to reduce the vibration in three axes. Another design consideration is the antenna for rescue, that is pasted on a gas column. In order to simplify the design, the gas column and the balloon are integrated as a whole one, and the gas column will be inflated uprightly as the balloon inflating. The design for the chamber for cold gas propulsion system includes here the arrangement of components of the system, and the interface design between the nuzzles and chamber structure.
An FEM software, COSMOSWorks, is utilized in the study to verify the structural design. The analysis results show that the main structures of the reentry capsule can support the external loads while in mission.
A vibration experiment is also conducted on a vibration testing machine to verify the performance of of the developed anti-vibration mechanism. In the experiment, the cushion pads with different compression ratio, thickness and hardness are considered and compared for the performance of vibration reduction. From the experimental results it is found that the pad will be the best if the thickness is 4 mm, the hardness is Shore A 70° and the compression ratio is 10％.
Up to now the design and manufacturing of the reentry capsule have been completed. The functions of the design must be validated by the further environment tests and field tests to ensure that the reentry capsule can be operated under the mission environment.
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