Using numerical simulation to assess reliability and survivability of long-duration habitation modules at Lunar Gateway

The duration of operation and exposure of the Lunar Gateway, which is a planned hub for NASA and partner agency surface operations on the Moon's surface, necessitates the evaluation of the habitable modules for reliable and survivable operation with crews on board. As the Gateway is anticipated to have a large volume and will operate well outside of Earth orbit, mass of the modules will push the current launch capabilities and dry mass will very much be at a premium. Furthermore, as the waypoint is relatively large compared to previous deep space systems and expected to continuously operating for many years, the opportunity for impact of a millimeter sized meteor or larger is not easily waived off. As a consequence of the opposing concerns of low mass and high ballistic resilience, the modules of Gateway are being evaluated against meteoroid impacts, which are expected to be at speeds greater than 20 km/s. As terrestrial facilities that deliver well characterized projectiles fall well short of this speed, numerical simulations are being used to aid in the design process of the various modules. To this end, NASA Hypervelocity Impact Technology group is using the Sandia National Laboratory Non-linear, Structural-Dynamics code, CTH, to model Gateway shield performance beyond the testable range. This paper discusses a simple shield used extensively over the Gateway modules evaluated against rocky and volatile meteoroids to improve confidence in the modeling of shield resistance to spallation or perforation for Lunar Gateway reliability assessments. Assessments are also required to evaluate temporarily manageable conditions for survivability assessments, so these perforation observations are extended to hole size for larger meteoroids. These performance observations are consolidated to a ballistic limit equation, which combined with environment models, yield quantifiable risk estimates for design engineers and program managers.