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Technical Paper

Testing of an Amine-Based Pressure-Swing System for Carbon Dioxide and Humidity Control

In a crewed spacecraft environment, atmospheric carbon dioxide (CO2) and moisture control are crucial. Hamilton Sundstrand has developed a stable and efficient amine-based CO2 and water vapor sorbent, SA9T, that is well suited for use in a spacecraft environment. The sorbent is efficiently packaged in pressure-swing regenerable beds that are thermally linked to improve removal efficiency and minimize vehicle thermal loads. Flows are all controlled with a single spool valve. This technology has been baselined for the new Orion spacecraft. However, more data was needed on the operational characteristics of the package in a simulated spacecraft environment. A unit was therefore tested with simulated metabolic loads in a closed chamber at Johnson Space Center during the last third of 2006. Tests were run at a variety of cabin temperatures and with a range of operating conditions varying cycle time, vacuum pressure, air flow rate, and crew activity levels.
Technical Paper

The Design and Testing of a Fully Redundant Regenerative CO2 Removal System (RCRS) for the Shuttle Orbiter

Research into increased capacity solid amine sorbents has found a candidate (SA9T) that will provide enough increase in cyclic carbon dioxide removal capacity to produce a fully redundant Regenerative Carbon Dioxide Removal System (RCRS). This system will eliminate the need for large quantities of backup LiOH, thus gaining critical storage space on board the shuttle orbiter. This new sorbent has shown an ability to package two fully redundant (four) sorbent beds together with their respective valves, fans and plumbing to create two operationally independent systems. The increase in CO2 removal capacity of the new sorbent will allow these two systems to fit within the envelope presently used by the RCRS. This paper reports on the sub-scale amine testing performed in support of the development effort. In addition, this paper will provide a preliminary design schematic of a fully redundant RCRS.
Technical Paper

Development and Chamber Testing of Laser-Based Gas Sensors

Recent advances in semiconductor lasers and nonlinear optical materials permit construction of compact sensors that can measure trace air contaminants with high precision in real time, without sampling. A portable prototype sensor was built and tested in laboratory and field environments. This spectroscopic instrument measures carbon monoxide (CO) at concentrations between 0.1 and 10 ppm in air with 0.001 ppm precision, and 10-second response time. It uses 4.6-μm difference-frequency generation in periodically-poled lithium niobate (PPLN), pumped by two compact solid-state lasers. The sensor was used to measure the CO concentration profiles in chamber air during the Lunar-Mars Life Support Test Project (LMLSTP) Phase IIA test at NASA JSC. It is proposed to modify the instrument to measure several gases simultaneously, including formaldehyde. Projected use of fiber-coupled diode lasers and waveguide PPLN will permit development of a commercially viable, field-ready instrument.
Technical Paper

Orbiter Upgrade Activities for a Fail Safe Regenerative CO2 Removal System

Carbon dioxide removal on the Shuttle is performed either by flowing cabin ventilation air through single use LiOH beds or by using the Regenerable CO2 Removal System (RCRS) (Ref 1,2,3). The RCRS was designed for single string mechanical operation with redundancy only on electrical components. It therefore can become disabled by a number of possible single point failures such as fan failure, actuator failure or a large internal leak through the beds. Because of these possible failures, LiOH must be flown on all RCRS missions to provide contingency CO2 removal. These LiOH canisters occupy valuable stowage space onboard the shuttle orbiter. The development of a new sorbent material called HS-X with significantly more CO2 removal capacity per unit volume has made much smaller sorbent bed sizes possible. With significantly smaller beds each of the single point failures can be addressed and a fully redundant RCRS can be built to fit within the existing RCRS envelope.
Technical Paper

Sabatier CO2 Reduction System Design Status

Carbon dioxide reduction in a closed loop life support system recovers water from otherwise waste carbon dioxide and hydrogen. Incorporation of a carbon dioxide reduction assembly (CRA) into the International Space Station life support system frees up thousands of pounds of payload capacity in the supporting Space Shuttle that would otherwise be required to transport water. Achievement of this water recovery goal requires coordination of the CRA design to work within the existing framework of the interface systems that are either already on orbit or well advanced in their development; namely, the Oxygen Generator Assembly (OGA), Carbon Dioxide Removal Assembly (CDRA) and Water Processor Assembly (WPA). The Oxygen Generation System (OGS) rack is in its final design phase and is scarred to accept later installation of the CRA.
Technical Paper

Process Upsets Involving Trace Contaminant Control Systems

Paradoxically, trace contaminant control systems that suffer unexpected upsets and malfunctions can release hazardous gaseous contaminants into a spacecraft cabin atmosphere causing potentially serious toxicological problems. Trace contaminant control systems designed for spaceflight typically employ a combination of adsorption beds and catalytic oxidation reactors to remove organic and inorganic trace contaminants from the cabin atmosphere. Interestingly, the same design features and attributes which make these systems so effective for purifying a spacecraft’s atmosphere can also make them susceptible to system upsets. Cabin conditions can be contributing causes of phenomena such as adsorbent “rollover” and catalyst poisoning can alter a system’s performance and in some instances release contamination into the cabin. Evidence of these phenomena has been observed both in flight and during ground-based tests.
Technical Paper

Mir Leak Detection Using Fluorescent Tracer Gases

On June 25, 1997 a docking mishap of a Progress supply ship caused the Progress vehicle to crash into an array of solar panels and puncture the hull of the Spektr module. The puncture was small enough to allow the crew to seal off the Spektr module and repressurize the rest of the station. The Progress vehicle struck the Spektr module several times and the exact location, size, and number of punctures in the Spektr hull was unknown. Russian cosmonauts donned space suits and went inside the Spektr module to repair some electrical power cables and look for the location of the hull breach, they could not identify the exact location of the hole (or holes). The Spektr module was pressurized with Mir cabin air twice during the STS-86 fly around in an attempt to detect leakage (in the form of ice particles) from the module. Seven particles were observed within a 36 second time span, but tracking the path of the individual particles did not pinpoint a specific leak location.
Technical Paper

A Regenerable Sorbent Bed for Trace Contaminant Removal

The Regenerable Trace Contaminant Control System (RTCCS) is a system designed to meet all of the size, weight, power use, contaminant removal rate, and operational requirements of the International Space Station (ISS) Trace Contaminant Control Subassembly (TCCS) without the need to replace an approximately 80 lb charcoal bed every 90 days. It is designed to remove every class of contaminants found in spacecraft cabin air, including alcohols, aldehydes, aromatics, ethers, esters, chlorocarbons, halocarbons, fluorosilanes, hydrocarbons, ketones, silicones, sulfides, and inorganics, and it is designed to operate continuously with minimal maintenance or periodic replacement major components. The RTCCS is comprised primarily of a pre-sorbent bed, regenerable bed, catalyst bed subassembly, post sorbent bed, blower, and associated valves and instruments.