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In the paper at hand a model-based development approach for a diagnostic system for a multifunctional fuel cell system architecture will be presented. The approach consists primarily of four parts. The first part is a description of general steps needed to build an accurate component-based model of the system using a state of the art model-based diagnostic reasoning tool. As a first result there will be a static simulation model for nominal system behavior. The second part of the approach deals with the identification of safety critical failure conditions (SCFC) at a system level, e.g. low Power. The SCFCs are then mapped into the model. This means that categorized physical quantities and monitoring executives are chosen, that are appropriate for representing the specific SCFCs, e.g. low voltage at outlet of DC-DC converter module. According to step two there will be conflicts, meaning discrepancies between the simulated nominal and the mapped behavior.

Every coin has two sides and so does aerospace safety. The attractive face of the coin has the major concerns to which most everyone pays rapt attention, but on the reverse side are the so-called “little things or problems” which often times are relegated to the bottom of the incoming file. Experience has shown that “little things” individually or synergistically, no matter how apparently insignificant when first viewed, can be the cause of major adverse events. History tells us that more often than not such small problems are resolved as time and money permit. This results from a syndrome I call “The High Cost of Attending to Nits.” This paper examines some of these nits that have been the cause of substantial dollar and schedule losses, which could have been avoided were timely and proper attention given them. Emphasis is on the Space flight and ground elements and will provide the designer, test engineers and others with a useful set of lessons learned.

Recent NASA-funded studies of Allied-Signal metal-oxide-based absorbents demonstrated that these absorbents offer a unique capability to remove both metabolic carbon dioxide (CO2) and water (H2O) vapor from breathing air; previously, metal oxides were considered only for the removal of CO2. The concurrent removal of CO2 and H2O vapor can simplify the astronaut portable life support system (PLSS) by combining the CO2 and humidity control functions into one component. A further benefit is that the removal processes are reversible, permitting a regenerative component. Thus, a metal oxide absorbent offers many advantages over the current system, which is nonregenerative and uses separate processes for CO2 and H2O vapor removal. These advantages include lower complexity, lower maintenance, and longer life. The use of metal oxide absorbents for removal of both CO2 and H2O vapor in the PLSS is the focus of an ongoing NASA program.

In the frame of ESA's Basic Technology Research Programme an integrated Fan-Pump-Separator (FPS) unit, for the European EVA Space Suit System, was developed up to breadboard level. The development was carried out by TECHNOFAN (F) as subcontractor to DORNIER (D) under contract of the European Space Agency. Concept Trade-offs and design definition confirmed the advantages in power, mass and volume of integrating all three functions into a single unit. The unit is driven by one common brushless DC motor. The performance requirements for the three basic functions (oxygen circulation, coolant water circulation and water separation) were derived from the system layout of the life support system for the European EVA Space Suit. The separate functional units were comprehensively tested in preliminary development tests. Final assembly of the functional units led to an integrated breadboard, which was successfully tested.

The Water Recovery and Management (WRM) system on Space Station Freedom (SSF) is modeled using SINDA '85/FLUINT to determine its hydraulic operation characteristics, and to verify the design flow and pressure drop parameters. The WRM system consists of the Potable Use water, Waste water, and Fuel Cell loops, as well as the Fluid Management System and experiments, which are not included in this model. This system will be the first closed loop water regeneration system used in space flight. The water is driven in each loop by storage tanks pressurized with cabin air, and is routed through the system to the desired destination. The model considers the flow of water from the storage tanks to the use points and back, as determined by each individual flow diagram for the Permanently Manned Configuration (PMC) phase of SSF.

Separators for gas drying are used for Fuel Cell Power Plants (FCPP) and for Environmental Control and Life Support Systems (ECLS). A new separator type is the Membrane Separator (MS), which enables smaller weight and geometries and needs less energy than conventional known mechanical separator techniques for space applications. This paper describes different membrane separation principles in accordance to their application on FCPP and ECLS. The development and test of a MS module with inorganic porous membranes for the Hermes FCPP are described in detail. The successful results of the tests are illustrated. Further activities like module optimization and investigations about ECLS application are presented.

A successful CELSS (Controlled Ecological Life Support System) design must accommodate the potential mismatch between the crew's relatively constant CO2 production and the widely varying crop CO2 consumption over the plant growth cycle. Any additional changes in material flows, processor characteristics or other system characteristics may have deleterious effects which propagate throughout the CELSS. Important transient conditions which the system design and planting regimen must allow for are described, including: Crop startup. Crop failures. Changes in number of humans supported. A general-purpose life support system simulator was used to evaluate several CELSS design and operation approaches. The simulator was used to investigate CO2 generation and removal interactions occurring between the CELSS food production subsystem and the rest of the system. These interactions were selected because they are major drivers of the system design and operation.

The Space Exploration Initiative will contain many avenues for both space and terrestrial technology development and applications. In addition, the development of architecture independent technology will provide the first meaningful milestones as the overall program matures. A factor in SEI technology will be the utilization of various earth based analogs as functional testbeds for hardware, software and operations development and verification. The most interesting of these proposed analogs involves the Antarctic programs managed by the National Science Foundation (NSF). The driver for Antarctic Planetary Analog is an increased awareness of potential impacts from the continued science and exploration operations to this unique environment.

The development of a pilot production, automated laser balancing system and the results of metallurgical evaluations of laser machined materials are presented in this paper. The automated laser balancing system is designed to low speed balance, small gas turbine engine components, such as AGT1500 compressors, turbines and shafts in a single load and spin-up cycle. A high power pulsed Nd:YAG laser is used to remove material from components while they rotate at speeds to 2,000 RPM for increased balance precision and efficiency. Metallurgical examinations of laser affected zones in turbine engine materials such as 17-22A(s), IN718, AM355, Waspaloy and IN713LC as well as material fatigue testing are presently being conducted to assess the effects of the laser material removal process on both material and component fatigue life. This paper, however, presents a summary of only the 17-22A(s) results.

Directed Energy weapon (DEW) systems are being developed for both ground and airborne applications. Typically, they consist of microwave or laser powered guns. Both the microwave application and the diode based laser applications require significant amount of power. This power ranges from several hundred kilowatts (kW) for microwave applications to Megawatts (MW) for laser applications. The laser application requires that the full power be available for short duration, typically 5 seconds, which could be repeated several times with short pauses in between. The control of a generator, which delivers Megawatt of the intermittent power greatly differs from the of normal steady state generator control. It poses significant challenges. Application of power (and for this matter its removal) is a transient phenomenon that takes time and its effects ripple through the whole system.

Manufacturing design processes for complex systems, like advanced fighter aircraft, require a special emphasis on human interactions to technical fabrication and assembly functions. The role of the human is being refined as manufacturing processes become more sophisticated. The infusion of human performance requirements into manufacturing design is a sensible approach to achieving efficient, cost-effective manufacturing processes. We will discuss the early input of ergonomics criteria and the benefits of addressing the human interaction in the manufacturing design process.

The Mini Pressurized Logistic Module (MPLM) of the International Space Station (ISSA) is foreseen for the transport of service equipment, experiment racks and service racks to the station. For the orbital operational phase it needs an Environmental Control and Life Support System (ECLSS) to make it commissionable for the astronauts. Because of its short mission time and the usage as a transport vehicle it has no completely autonomous ECLSS functionality. The Temperature and Humidity Control (THC) is supported by the Space Station via an Inter Module Ventilation Interface (IMV l/F). The MPLM ECLS has the requirement to suck revitalized air through the IMV l/F and mix it up with the recirculated air in order to provide a comfortable atmosphere in the MPLM habitable area. The fulfillment of the hydraulic and thermal requirements is verified by test and analysis. With this paper we provide the hydraulic analysis performed with ECOSIM, an ESA approved software tool.

The least expensive life support for brief human missions is direct supply of all water and oxygen from Earth without any recycling. The currently most advanced human life support system was designed for the International Space Station (ISS) and will use physicochemical systems to recycle water and oxygen. This paper compares physicochemical to direct supply air and water life support systems using Equivalent Mass (EM). EM breakeven dates and EM ratios show that physicochemical systems are more cost effective for longer mission durations.

In the design process for Life Support Systems (LSS) a great multitude of concepts for and various combinations of subsystems and components exist. In order to find an optimal LSS solution, the parameters for the definition of the optimization must be determined. In the presented paper a new optimization criterion for LSS is suggested. At first the basic equivalent system mass (ESM) approach is discussed. Furthermore the basic ESM optimization concept is modified in order to represent system stability and risk analysis issues. The optimization scheme is completed by adding criteria for overall mission success, which are based on an extensive crew time analysis. All the mentioned parameters are summarized in the so-called integral reliability criterion. After the criterion introduction the paper focuses on the system modeling that is necessary to apply the previously described integral reliability criterion.

Real time knowledge of the metabolic workload of an astronaut during an Extra-Vehicular Activity (EVA) can be instrumental for space suit research, design, and operation. Three indirect calorimetry approaches were developed to determine the metabolic workload of a subject in an open-loop space suit analogue. A study was conducted to compare the data obtained from three sensors: oxygen, carbon dioxide, and heart rate. Subjects performed treadmill exercise in an enclosed helmet assembly, which simulated the contained environment of a space suit while retaining arm and leg mobility. These results were validated against a standard system used by exercise physiologists. The carbon dioxide sensor method was shown to be the most reliable and a calibrated version of it will be integrated into the MX-2 neutral buoyancy space suit analogue.

During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Last year we reported on the design and initial operational assessment tests of a novel radiator designated the Radiator And Freeze Tolerant heat eXchanger (RAFT-X).

Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is currently being investigated for removal and rejection of carbon dioxide (CO2) and heat from a Portable Life Support System (PLSS) to a Martian environment. The metabolically-produced CO2 present in the ventilation loop gas is collected using a CO2 selective adsorbent that has been cooled via a heat exchanger to near CO2 sublimation temperatures (∼195 K) with liquid CO2 (LCO2) obtained from Martian resources. Once the adsorbent is fully loaded, used, warm (∼300 K), moist ventilation loop gas is used to heat the adsorbent via another heat exchanger to reject the collected CO2 to the Martian ambient. Two beds are used to achieve continuous CO2 removal by cycling between the cold and warm conditions for adsorbent loading and regeneration, respectively.

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address carbon dioxide (CO2) and heat removal/rejection in a Mars Portable Life Support System (PLSS). The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (∼195 K) removes metabolically-produced CO2 in the ventilation loop. Once fully loaded, the adsorbent is then warmed (∼300 K) externally by the ventilation loop, rejecting the captured CO2 to Mars ambient. Two beds are used to provide a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the ventilation loop. To investigate the feasibility of the technology, a series of model calibration experiments were conducted which lead to the selection and partial characterization of an appropriate adsorbent.

The National Aeronautics and Space Administration's (NASA) planned future missions set stringent demands on the design of the Portable Life Support System (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility for Extravehicular Activity (EVA) duration and objectives. Use of regenerable systems that reduce weight and volume of the space suit life support system is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The carbon dioxide and humidity control unit in the existing PLSS design is relatively large, since it has to remove and store eight hours worth of carbon dioxide (CO2). If the sorbent regeneration can be carried out during the EVA with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced.

Carbon dioxide (CO2) removal technology development for portable life support systems (PLSS) has traditionally concentrated in the areas of solid and liquid chemical sorbents and semi-permeable membranes. Most of these systems are too heavy in gravity environments, require prohibitive amounts of consumables for operation on long term planetary missions, or are inoperable on the surface of Mars due to the presence of a CO2 atmosphere. This paper describes the effort performed to mature an innovative CO2 removal technology that meets NASA's planetary mission needs while adhering to the important guiding principles of simplicity, reliability, and operability. A breadboard cryogenic carbon dioxide scrubber for an ejector-based cryogenic PLSS was developed, designed, and tested. The scrubber freezes CO2 and other trace contaminants out of expired ventilation loop gas using cooling available from a liquid oxygen (LOX) based PLSS.