Thermal coupon testing of Load-Bearing Multilayer Insulation

Abstract

Abstract. Advanced liquid hydrogen storage concepts being considered for long duration space travel incorporate refrigeration systems and cryocoolers to lower the heat load. Using a refrigeration loop to intercept the energy flowing through MLI to a liquid hydrogen tank at a temperature between the environment and the liquid hydrogen can lower the heat load on the propellant system by as much as 50%. However, the refrigeration loop requires structural integration into the MLI. Use of a more traditional concept of MLI underneath this refrigeration loop requires that a structural system be put in place to support the loop. Such structures, even when thermally optimized, present a relatively large parasitic heat load into the tank. Through NASA small business innovation research funding, Quest Thermal Group and Ball Aerospace have been developing a structural MLI based insulation system. These systems are designed with discrete polymeric spacers between reflective layers instead of either dacron or silk netting. The spacers (or posts) have an intrinsic structural capability that is beyond that of just supporting the internal insulation mechanical loads. This new MLI variant called Load Bearing MLI (LB-MLI) has been developed specifically for the application of supporting thermal shields within the insulation system. Test articles (coupons) of the new LB-MLI product were fabricated for thermal performance testing using liquid nitrogen at Kennedy Space Center (KSC) and using cryocooler based calorimetry at Florida State University. The test results and analysis are presented. Thermal models developed for correlation with the thermal testing results both at KSC and testing that was performed at Florida State University are also discussed.

Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

“…14 At KSC, testing was performed between 77 K and various warm boundary temperatures between 293 K and 325 K on Cryostat-100. 15 Testing showed that there was no additional penalty due to the seaming methods used in LB-MLI and that the thermal penalties due to perforations were also small enough to ignore. …”

Heat radiation reduction in cryostats with multilayer insulation technique

“…Generally, MLI systems are used in high vacuum environments, which may be a vacuum vessel or space such as planet's orbits and surfaces [7]. This is because MLI is the ideal insulation for the radiation dominated heat transfer environments such as space orbits and other high vacuum applications [20]. Furthermore, MLI systems can also be designed for soft vacuum purposes in industrial products as well as in commercial building apparatus [21].…”

Heat radiation reduction in the cryostat with multilayer insulation technique

“…Generally, MLI systems are used in high vacuum environments, which may be a vacuum vessel or space such as the Earth's orbit or the lunar surface [7]. This is because MLI is the ideal insulation for the radiation dominated heat transfer environments such as spacecraft in the low Earth orbit and the other high vacuum functions [20]. Furthermore, MLI systems can also be designed for soft vacuum purposes in industrial products as well as in commercial building apparatus [21].…”