Space Suit Portable Life Support System Test Bed (PLSS 1.0) Development and Testing

Abstract

A multi-year effort has been carried out at NASA Johnson Space Center to develop an advanced extravehicular activity (EVA) Portable Life Support System (PLSS) design intended to further the current state of the art by increasing operational flexibility, reducing consumables, and increasing robustness. Previous efforts have focused on modeling and analyzing the advanced PLSS architecture, as well as developing key enabling technologies. Like the current International Space Station Extravehicular Mobility Unit PLSS, the advanced PLSS comprises three subsystems required to sustain the crew during EVA, including the Thermal, Ventilation, and Oxygen Subsystems. This effort has culminated in the construction and operation of PLSS 1.0, a test bed that simulates full functionality of the advanced PLSS design. PLSS 1.0 integrates commercial off-the-shelf hardware with prototype technology development components, including the primary and secondary oxygen regulators, Ventilation Subsystem fan, Rapid Cycle Amine swingbed carbon dioxide and water vapor removal device, and Spacesuit Water Membrane Evaporator heat rejection device. The overall PLSS 1.0 test objective was to demonstrate the capability of the Advanced PLSS to provide key life support functions including suit pressure regulation, carbon dioxide and water vapor removal, thermal control, and contingency purge operations. Supplying oxygen was not one of the specific life support functions because the PLSS 1.0 test was not oxygen rated. Nitrogen was used for the working gas. Additional test objectives were to confirm PLSS technology development components performance within an integrated test bed, indentify unexpected system-level interactions, and map the PLSS 1.0 performance with respect to key variables such as crewmember metabolic rate and suit pressure. Successful PLSS 1.0 testing completed 168 test points over 44 days of testing and produced a large database of test results that characterize system-level and component performance. With the exception of several minor anomalies, the PLSS 1.0 test rig performed as expected; furthermore, many system responses trended in accordance with pre-test predictions. Nomenclature BPV= backpressure valve Btu = British thermal unit CO 2 = carbon dioxide COTS = commercial off-the-shelf DACS = data acquisition and control system

Development Status of V-SUIT - The Virtual Space Suit simulation software

“…9 the simulation results were compared to the actual test results for a number of steady state and transient test points. The parameters that were changed for the different test points are: metabolic rate of the human model, the switching criterion of the RCA and the minimum allowed RCA half-cycle time.…”

“…This makes the lack of ullage gas loss a good candidate for the explanation of lower flow rates in the simulation data for low metabolic rates and high flow rates for higher metabolic rates compared to the test data. 9. The most obvious aspect of both graphs is the high noise in the CO2 partial pressure curve.…”

“…As a result the simulated fan pressure rise had to be 8500 Pa to maintain the desired flow rate, rather than the 672 Pa published in Ref. 9.…”

Prototype Vent Gas Heat Exchanger for Exploration EVA - Performance & Manufacturing Characteristics

“…While the PLSS on NASA's Extravehicular Mobility Unit (EMU) has successfully served our astronauts for over thirty years, the requirements necessary for missions to the moon, Mars or an asteroid preclude its use. In order to meet the need for a new PLSS, NASA Johnson Space Center (JSC) began incremental development of PLSS technologies in 2011 with their PLSS 1.0 breadboard test bed (1) . Results and lessons learned from PLSS 1.0 were used to design PLSS 2.0, which incorporates higher fidelity components in a packaged volume similar to what is anticipated for a new flight PLSS.…”