Cryogenic fluid management (CFM) is a critical technical area that is needed for the successful development of future space exploration. A key challenge is the storability of LH2, LCH4, and LOX propellants for long durations. The storage tanks must be well insulated to prevent over-pressurization and venting, which lead to unacceptable propellant losses for long-duration missions to Mars and beyond.
There are two methods for meeting mission storage requirements that can be divided into two general types: those that use boil-off gases from the cryogen, and those that have zero boil-off. Methods that utilize boil-off for cooling include thermodynamic vent systems and vapor-cooled shields, each of which requires additional fluid mass to compensate for the boil-off losses. Methods that enable zero boil-off include actively cooled shields that use a cryocooler refrigerator and a simple, well-insulated tank. The required insulation material must outperform the current standard insulation for thermal performance and provide additional features such as durability, reliability, and cost effectiveness.
A comparison of Multi-Layer Aerogel Insulation (MLAI) with Spray-On Foam Insulation (SOFI) was done using test data from Cryostat 500 at NASA Kennedy Space Center’s Cryogenics Test Laboratory, operated by Vencore. Two MLAI test articles (G170 and G171 prototypes) tested using Cryostat 500 were compared to the SOFI BX-265 test data. Both G170 and G171 consisted of three aerogel layers separated by 0.25-mil perforated aluminized Mylar. The aerogel composites (G170 and G171) had different reinforcement materials. G170 was made using a reinforcement with a density of 0.01 g/cc and 2-mm thickness. G171 used a non-woven reinforcement and was
When analyzing the Cryostat 500 test results and normalizing the heat flux for SOFI and MLAI by unit areal weight, both MLAI prototypes outperformed SOFI by more than 90% in a vacuum environment (see figure). At atmospheric pressure, one MLAI prototype, G170, outperformed SOFI by 40%. Therefore, weight can be saved, or thermal performance improved, for the same weight as a SOFI system when using this type of MLAI system. Consequently, MLAI could serve as an improved replacement for SOFI for atmospheric and vacuum cryogenic thermal insulation.