A review of candidate multilayer insulation systems for potential use on wet-launched LH2 tankage for the Space Exploration Initiative lunar missions

Abstract

SUMMARYThe storage of cryogenic propellants such as liquid hydrogen (LH 2 ) and liquid oxygen (LO 2 ) for the future Space Exploration Initiative (SEI) will require lightweight, high performance thermal protection systems (TPS's). For the near-term lunar missions, the major weight element for most of the TPS's will be multilayer insulation (MLI) and/or the special structures/systems required to accommodate the MLI. Methods of applying MLI to LH 2 tankage to avoid condensation or freezing of condensible gases such as nitrogen or oxygen while in the atmosphere are discussed. Because relatively thick layers of MLI will be required for storage times of a month or more, the transient performance from ground-hold to space-hold of the systems will become important in optimizing the TPS's for many of the missions. The ground-hold performance of several candidate systems are given as well as a qualitative assessment of the transient performance effects.

A Revolutionary Lunar Space Transportation System Architecture Using Extraterrestrial LOX-Augmented NTR Propulsion

“…This insulation thickness exceeds the "ground holdthermal protection requirements for "wet-launched-LH2 tanks which need a minimum of 1.5 inches of helium-purged insulation 19 • The installed density of the "2 inch MLI system-is -2.62 kg/m 2 , and the resulting LH2 boiloff rate in LEO is -1.31 kg/m21 month (based on an estimated heat flux of -0.22 W/m2 at a LEO sink temperature of -240 1<). In lunar orbit, where the sink temperature and heat flux are estimated to be -272 K and 0.32 W/m 2 , respectively, the lH2 boiloff rate increased by -46% to 1.91 kg/m 2 /month.…”

Vehicle and mission design options for the human exploration of Mars/Phobos using 'bimodal' NTR and LANTR propulsion

“…This insulation thickness exceeds the "ground hold" thermal protection requirements for "wet-launched" LH2 tanks which need a minimum of -1.5 inches of helium-purged insulation. 21 The installed density of the 80 layer MLI system is -1.44 kg / m 2, and the resulting LH2 boiloff rate in LEO is -3.11 x 10-2 kg/m2/day (based on an estimated heat flux of -0.161 W / m2 at a LEO sink temperature of -230 K). The corresponding boiloff rate for LOX is shown in Table 3.…”