Rarefied dynamic pressure distribution measurement near a vacuum pump

In vacuum chambers, such as those at a ground test facility, pressure is higher and the gas resident time is longer than in space because such chambers are surrounded by walls and vacuum pumps. Investigating gas flow near a vacuum pump that influences the gas flow can be useful for evaluating differences of dynamic pressure near a high-vacuum pump. A parallelepiped vacuum chamber was measured for this study using two rarefied dynamic pressure measuring devices with approximately 0.004 mPa dynamic pressure resolution. Measurement results and evaluation indicate that flow to the high vacuum pump occurs. The dynamic pressure at the measurement point near the vacuum pump is proportional to the solid angle prospected to the high vacuum pump. The vacuum chamber wall reflection influences the vacuum evacuation and flow. Results show that spacecraft devices and the system should be operated in a region with a small solid angle to the high vacuum pump to prevent any influence from vacuum evacuation. Flow measurement and evaluation near the chamber wall using this measuring device are expected to contribute to characterization of the vacuum pump performance. Moreover, more detailed evaluation of gas flows within the vacuum chamber using a more precise resolution-measuring device might be useful for research and development of vacuum test facilities.