Study on unsteady evacuation characteristics of multi-layer insulation during launch/in orbit of the cryogenic propellant tanks

Abstract

The MLI + foam is used for the thermal protection of the cryogenic propellant. However, the MLI generates unsteady evacuation when the cryogenic rocket is launched and traveled in space. The insulation performance of the MLI is determined by the evacuation level of the interstitial gas. Aiming at the unsteady evacuation of the MLI, the interlayer pressure node algorithm was developed. The transient evacuation characteristics of the interlayer pressure were predicted. The effect of layer number, slit rate, and layer density on evacuation was investigated. The evacuation and insulation performance of MLI were optimized. The results show that the innermost pressure of the 60 mm thickness (th60) MLI dropped to less than 0.5 Pa when the evacuation was conducted for more than 25 h. The pressure of the innermost layer and 10th layer is greater than 1 order of magnitude higher than that of the outermost layer. The evacuation rate of th20 is faster than that of th40 and th60. The innermost layer pressure value of the th20 is 0.168 Pa, which is 10.47 times higher than that of the outermost layer. The innermost layer pressure of the th20 is 48.3 % and 64.8 % lower than that of th40 and th60, respectively. The gas conduction decreased by 61.22 % when the opening pattern was optimized. These results can provide an important reference for the thermal protection design of cryogenic propellants.