Development Of Multi-point Measurement System Of Shape Gap For The Heat-resistant Bottom

The research on manned spacecraft began in our country in 1990 s. It is a process with high enthalpy, low heat flow density, low pressure, long heating time and et al. for the reentry of the spacecraft. In the reentry process, the heat-resistant bottom of spacecraft gathers extremely high heat. In order to prevent heat from spreading into the cabin of the spacecraft, the heat-resistant bottom should be dropped off when the spacecraft gets close to the ground. Therefore, the heat-resistant bottom and the metal bottom of the spacecraft should be separate when designed and a small gap appears. The size of this gap is very small and varies across the two bottoms, so a support cushion needs to be manufactured copulated. The cushion installing test is to measure the gas between the heat-resistant bottom and the metal bottom, which is an important measurement in the assembling of spacecraft. Because the surface of the heat-resistant bottom and the metal bottom are all sphere, the gap forms an airtight space, so it is impossible to perform direct measurement to the gap of the two bottoms, therefore a special method is needed to measure the airtight space.In this thesis, a new type of fast multi-point shape gap measurement method is proposed. Firstly, we analyze of the structure of heat-resistant bottom and sealed bottom, then, a gap measure device is designed using a linear displacement sensor. In the device, a slider is designed to slide on the resistive sensor chip, and the magnitude of the voltage is changed accordingly, we use the changing voltage to measure the shape gap. A signal acquisition board acquires the voltage signals and converts them into digital signals and transmits to the control pane, the control pane calculates the size of the gap. In order to ensure accuracy, this measurement system is required to be calibrated regularly before use, and a special calibration system is developed according to this requirement.Using the multi-point shape gap measurement system, and calibration system developed in this paper, a series of tests have been carried out to the size of shape gap of simulate bottom and real bottom. The experimental results show that, the measurement accuracy and efficiency both can meet the requirement of spacecraft manufacturing.