July 7, 2019
Extra-vehicular activity (EVA) suits are critical to human survival when outside the safety of a spacecraft. The inner most layer of an EVA suit is the liquid cooling and ventilation garment (LCVG), which collects heat generated by the body via direct skin contact with water cooling tubes. The current design provides relatively equal cooling over the entire skin surface from the neck to the ankles. The collected heat is dissipated by sublimation to vacuum through the Portable Life Support System (PLSS). The NASA LCVG has seen minimal changes since it was first designed for human spaceflight during Apollo. However, a well-known effect of microgravity is the cephalic shift of body fluids, and subsequent decrease in whole body fluid volume. In Earth’s gravity, blood tends to pool in the legs, with leg muscles acting as pumps to assist in venous return to the heart. The cardiovascular system provides heat redistribution from the core and working muscles to the skin where heat is lost through convection and radiation. While effects of the fluid shift on the cardiovascular system have been extensively studied, little research has been performed on the effects of the fluid shift on body heat rejection, and how such changes might impact cooling strategies during EVA. We hypothesize that the fluid reduction and redistribution in microgravity, which is reflected in decreased leg surface area, volume, and “color”, could lead to reduced heat rejection in the lower extremities. The authors will present preliminary research results on changes in human leg skin temperature (IR cameras) and surface area (photogrammetric scanning), as a function of a microgravity analog: a head down tilt table. It is anticipated that this data will help inform a possible redesign of the LCVG in order to optimize cooling locations, to reduce the length of water tubes, to reduce PLSS sublimation losses, and to reduce total mass. As NASA and other space agencies plan future exploration missions (e.g. Cis-lunar, Moon, and Mars) the need for an LCVG design for its operational environment, micro and partial gravity, will be critical to mission success.
Heinimann, Lexi. Skin Temperature Changes in a Microgravity Analog: Informing the Next Generation EVA Liquid Cooled Ventilation Garment (LCVG). Poster presented at: 49th International Conference for Environmental Systems (ICES) held in Boston, Massachusetts.; 2019 Jul 7 – 11;