Browsing by Author "Niederwieser, Tobias"
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Item AEM-E – A small life support system for the transport of rodents to the ISS(44th International Conference on Environmental Systems, 2014-07-13) Niederwieser, Tobias; Gerren, Richard; Koenig, Paul; Tozer, Stuart; Stodieck, Louis; Rieger, Sebastian; Hoehn, AlexanderCurrent resupply carriers to the ISS, such as the Dragon or Cygnus capsules, do not yet support replenishment or control of atmosphere constituent altered by respiration of living cargo. In order to transport animals for scientific experiments to the ISS, an Environmental Control and Life Support System is therefore needed. The newly developed Animal Enclosure Module–Environmental Control (AEM-E) payload supplements the AEM-T animal carrier and was designed to compensate the respiration-induced changes by replenishing the consumed oxygen to the cabin atmosphere and by removing metabolically produced carbon dioxide and moisture. AEM-E takes a desiccant-based approach to remove moisture with silicon dioxide and carbon dioxide with lithium hydroxide. For the oxygen supply, a novel gaseous oxygen replenishment system was designed. The functionality of the AEM-E was verified under worst-case load conditions in subsystem and integrated tests with simulated and actual mice in an isolated environment for up to 10 days and up to 20 mice. This paper discusses quantitative and qualitative test results of the subsystem and integrated tests. Activity- and time-dependent air composition and respiration data from the isolated environment during the integrated flight-simulation tests are presented. The system has undergone flight certification and safety assessment and is planned to be flight-ready in late 2014.Item Design and Flight-Qualification of an Oxygen Resupply System to Support the Transport of Live Rodents to the ISS(44th International Conference on Environmental Systems, 2014-07-13) Tozer, Stuart D.; Koenig, Paul; Niederwieser, Tobias; Stodieck, Louis; Hoehn, AlexanderThe transport of live rodents to the ISS aboard a pressurized commercial cargo resupply carrier, such as SpaceX Dragon or Orbital Cygnus, requires safe and reliable delivery of gaseous oxygen. This paper will present the oxygen system design for the Animal Enclosure Module – Environmental Control (AEM-E) payload, which has undergone flight certification and safety assessment and is planned to be flight-ready by early 2014. To support an animal load of 20 mice or 6 rats and a maximum mission duration of 10 days, up to 875 liters (1.26 kg) of oxygen are required. The first design challenge was to safely store this amount of oxygen within the limited volume of a middeck-locker-sized payload. The minimum risk design uses four small composite cylinders, each containing 183 liters oxygen (at ambient pressure), compressed to 20 MPa (3,000 psig). The four independent tanks provide redundancy while limiting risk from any single tank failure. Each of the four oxygen tanks is passively flow-restricted using a precision micro-orifice (25 micron diameter), reducing the risk of cabin overpressurization or exceeding safe oxygen levels – even under catastrophic failures. For a low-power and robust oxygen release mechanism, a novel oxygen-compatible wax-actuated valve was developed and certified. Using less than 4 watts each, the 20 MPa-rated valves can be opened and closed reliably. Individual electrolytic partial pressure oxygen sensors provide the control inputs to independent analog band gap controllers for each wax-actuated valve. Oxygen concentrations are controlled with a high setpoint at nominal oxygen concentrations (20.9%) and a low setpoint at 19.6%, as required for docking to the ISS. A unique analog circuit prevents activation of more than one oxygen tank at any one time, further reducing risk from system malfunctions. System qualification of the ‘Design for Minimum Risk’ oxygen resupply system will be presented, together with system validation and integrated performance test results.Item Development of a Testbed for Flow-Through Measurements of Algal Metabolism Under Altered Pressure for Bioregenerative Life Support Applications(47th International Conference on Environmental Systems, 2017-07-16) Niederwieser, Tobias; Wall, Ryan; Nabity, James; Klaus, DavidThe utilization of algae is a widespread concept for bioregenerative life support systems in human spaceflight. Algae have the potential to combine the functions of air revitalization, wastewater treatment, and food production via photosynthesis. The potential benefits of using algae include high reliability, reduced mass, and psychological benefits to the crew. Due to the fast growth rate and ease of culturing, Chlorella vulgaris is well documented in terms of optimal growth parameters, such as carbon dioxide or oxygen concentration, growth medium, temperature, as well as light cycle, spectrum, and intensity. However, the feasibility of algal photobioreactors for air revitalization, wastewater treatment, and food production under relevant spaceflight environments is not fully assessed. In particular, algal growth under NASA’s proposed exploration atmosphere of 8.2 psia and 34 % oxygen for long-duration human spaceflight missions has not been characterized. Therefore, a flow-through photobioreactor that is capable of maintaining specified growth conditions for Chlorella vulgaris and controlling the pressure in the reactor between 56.5 and 101.3 kPa (8.2 and 14.7 psia) was developed and is presented in this paper. The sizing process of the small scale photobioreactor for gaining accurate oxygen and carbon dioxide measurements is described. Additionally, challenges, such as leak rates, measurement resolution, and water temperature alternating the solubility of carbon dioxide and oxygen, are discussed. In conclusion, the adaptations to more typical state-of-the-art, environmentally-open reactor designs, necessary to meet the minimal leak rate requirements for measuring the gas exchanges, are summarized. Preliminary metabolic measurements from the algal photobioreactor testbed are presented. Future characterization studies, using this testbed design, can lead to a better understanding of algal performance and more accurate system analysis for future life support system designs.Item Dynamic Simulation of Performance and Mass, Power, and Volume prediction of an Algal Life Support System(49th International Conference on Environmental Systems, 2019-07-07) Ruck, Thomas; Niederwieser, Tobias; Pütz, DanielThe use of state-of-the-art physicochemical life support systems will be a limiting factor on future long-duration human spaceflight missions due to the lack of frequent resupply capability. Cultivation of algae in a photobioreactor is a promising bioregenerative alternative for combined air revitalization, waste water treatment, and food supplement production. In order to correctly size a membrane-based, flat-panel photobioreactor for a biological life support system, a dynamic simulation model was developed that predicts algal growth under varying environmental influences. The model is integrated into the dynamic life support simulation tool V-HAB, which has been under development at the Technical University of Munich since 2006. With the newly developed algae model and previously developed Common Cabin Air Assembly (CCAA) and Carbon Dioxide Removal Assembly (CDRA) models, VHAB is used to simulate the interactions between a photobioreactor and a crew of 5 astronauts in a spacecraft cabin. The influence of an algal photobioreactor on fluctuating carbon dioxide and oxygen levels due to human activity in a spacecraft cabin and the related energy consumption are determined. Mass, power, and volume estimations for the simulated life support system architecture are made in this paper and a path forward is presented to outline the future work required to achieve the integration of a photobioreactor into a spacecraft cabin and improve the model validity.Item Implementation of Lithium Hydroxide as a Dual CO2/H2O Scrubber for a Rodent Research Life Support System(48th International Conference on Environmental Systems, 2018-07-08) Anthony, Jonathan; Hoehn, Alexander; Niederwieser, Tobias; Stodieck, Louis; Tozer, StuartAEM-E (Animal Enclosure Module – Environmental Control) was developed as a middeck locker payload to provide life support for rodent research in space. The AEM-E design has recently been upgraded to double its original rated capacity, now supporting 40 mice or 12 rats over a 10-day mission while maintaining its original single-locker form factor. A key enabling design modification in achieving this considerable performance increase was to combine the relative humidity (rH) and carbon dioxide (CO2) scrubber systems using a single lithium hydroxide (LiOH) scrubbing architecture. LiOH is a well-known CO2 scrubbing material with life support applications dating back to the first manned space missions. LiOH reacts with cabin atmospheres via hydration (reversibly producing LiOH·H2O) and carbonation (irreversibly producing Li2CO3). Despite a rich background of research relating to LiOH carbonation, relatively little research has been reported on LiOH hydration with most studies only focusing on its role as a catalyzing reaction for carbonation. Compared to other desiccants such as silicon dioxide (SiO2), LiOH offers superior volume and mass efficiency. Based on this, LiOH was selected as the primary humidity and CO2 scrubbing material for the updated AEM-E design, which we believe to be the first reported spacecraft life support application of LiOH where humidity control is a primary function. This paper discusses the empirical formulation of a dual CO2/H2O absorption model for LiOH and its integration into a multi-scenario mission simulation alongside other AEM E components and rodent metabolic models. Underactuated single-input multiple-output (SIMO) control is a key implementation challenge of dual CO2/rH control with LiOH and requires a specific metabolic envelope of CO2 and H2O output rates to function acceptably. However, based on the work presented herein, the dual control scheme is expected to satisfy AEM-E’s operational requirements.Item SABL – An EXPRESS locker-sized incubator for performing biological experiments onboard the ISS(45th International Conference on Environmental Systems, 2015-07-12) Niederwieser, Tobias; Anthony, Jonathan; Darnell, Asa; King, Geoffrey; Koenig, Paul; Stodieck, Louis; Wright, Jim; Gahbler, Philipp; Hoehn, AlexanderThe Space Automated Bioproduct Lab (SABL) is an EXPRESS locker-sized incubator developed by BioServe Space Technologies for use on the International Space Station (ISS). SABL provides a 41.9 x 27.9 x 19.4 cm (16.6” x 11.1” x 7.8”, DxWxH) sized science research module (SRM) volume, which can be temperature-controlled from -5 to +43 °C. SABL improves over the Commercial Generic Bioprocessing Apparatus (CGBA) in several aspects including higher thermal ramp rate, lower thermal gradients, enhanced experiment control, software adaptability, and crew interaction. SABL is designed to accommodate a variety of existing legacy life sciences hardware that was previously used with CGBA, enabling SABL to function as a flexible lab for biological experiments in microgravity. This paper focuses on the thermal design of the payload as well as on the verification testing of the engineering unit. The design process for SABL focused on minimizing thermal gradients within the SRM volume, improving thermal ramp rates between temperature set points, and eliminating the usage of forward facing cabin air exhaust systems that produce unacceptable acoustic noise. Temperature control of the SRM is accomplished using a total of four thermoelectric coolers (TECs) mounted to the top and bottom surfaces of the SRM. SABL utilizes the EXPRESS Moderate Temperature Loop (MTL) as a thermal sink for the TECs and avionics. Thermal feedback control and safety monitoring is implemented using a suite of sensors that interface to an NI sbRIO-9636 data acquisition and control computer. Performance of the engineering unit was characterized to verify thermal models of operation, cooling/heating times, and robustness against uneven internal heat loads and off-nominal operation. After starting development in 2011, the first two SABL units are manifested to launch to the ISS onboard SpaceX CRS-8 in the fall of 2015.