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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.

Current AF-NASA architecture level studies project future need for a heavy-lift, unmanned launch vehicle with low Earth orbit (LEO) payload delivery capability. To achieve this capability, vehicle concepts considered range from fully expendable to fully recoverable. Expendables entail high operations costs; recoverables, high development costs and, in the minds of many, high technical/cost risk. A concept that has been extensively studied is the partially reusable Shuttle-Derived Vehicle (SDV), seen as a potential candidate offering two to three times more cost-effectiveness than Titan or Shuttle ($/lb payload), and based on available hardware elements and current technology upgrades. The SDV is currently considered a viable candidate launch vehicle in ongoing systems studies.

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.

A summary of an ESA/ESTEC sponsored technology research programme is given aiming at the development of a CO2 partial pressure sensor suitable for monitoring the PP CO2 inside the oxygen ventilation loop of the EVA life support module. At first, a trade-off of candidate sensor concepts is presented. As result, the infrared optical sensor concept has been selected. In the frame of a discussion on basic facts of IR absorption the rationale for the selected configuration of the IR sensor is given. A breadboard model of the PP CO2 sensor together with a test set-up has been established. The sensor was subjected to a test programme consisting of two separate test periods. The main results are given. Finally, the findings are discussed in the light of the development of future flight hardware.

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.

This paper describes an analytical model of the Four-Bed Molecular Sieve (4BMS) proposed for the Space Station Freedom. The model was developed using modified components of the G189A Computer Program. Requirements and inlet conditions are specified for normal (four-man) and emergency (eight-man) operation. The G189A Generalized ECLSS Simulation routines for adsorption/desorption in a molecular sieve bed and for a vacuum pump have been modified to add new capabilities. The mass transfer and thermal differential equations, which are solved through numerical difference equations for the nodal networks for mass and thermal transfer within the beds, are presented. The bed adsorption/desorption routine has been modified to allow coadsorption of oxygen, nitrogen, carbon dioxide and water using ideal solution theory to adjust the pure constituent isotherms to account for coadsorption.

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.

Honeywell is currently working on several projects utilizing high-reactance permanent magnet machines (HRPMM) to develop advanced, high-performance power generation systems (HPPGS). These power generation systems (PGS), offer greatly increased safety and reduced operating costs compared to previous hardware. The approach utilizes an HRPMM that presents reduced short-circuit currents with simplified power topology and specifically developed control algorithms. These architectures offer inherent fail-safe features in that the maximum possible short-circuit current is not significantly higher than the normal operating current. Control approaches are discussed. Methodologies for system optimization to achieve top performance and robust operation are included. These power generators support implementation of on-shaft integration with the plant.

This paper addresses the challenges inherent in meeting the new power quality requirements needed on today's more electric aircraft. Technologies that generate low total distortion and minimize individual current harmonics are discussed. This paper describes several different converter topologies that are capable of meeting the power quality requirements in aerospace applications. Various multi-phase passive and active practical approaches to improving power quality are considered, analyzed and rated. The advantages and disadvantages of each are discussed. Performance results from demonstration hardware are provided, including power quality, regulation, efficiency, and reliability.

Aircraft power demands continue to increase with the increase in electrical subsystems. These subsystems directly affect the behavior of the power and propulsion systems and can no longer be neglected or assumed linear in system analyses. The complex models designed to integrate new capabilities have a high computational cost. This paper investigates the possibility of using a hardware-in-the-loop (HIL) analysis with real time integration. A representative electrical power system is removed from a turbine engine model simulation and replaced with the appropriate hardware attached to a 350 horsepower drive stand. In order to update the model to proper operating conditions, variables are passed between the hardware and the computer model. Using this method, a significant reduction in runtime is seen, and the turbine engine model is usable in a real time environment. Scaling is also investigated for simulations to be performed that exceed the operating parameters of the drive stand.

The interdependency between propulsion, power, and thermal subsystems on military aircraft such as the F-35 Joint Strike Fighter (JSF) and F-22 Raptor continues to increase as advanced war-fighting capabilities including solid-state radars, electronic attack, electric actuation, and Directed Energy Weaponry (DEW) expand to meet Air Force needs. Novel analysis and testing methodologies are required to predict these interdependencies and address adverse interactions prior to costly hardware prototyping. As a result, the Air Force Research Laboratory (AFRL) has established a dynamic hardware-in-the-loop (HIL) test-bed wherein transient simulations can be integrated through advanced real-time simulation with prototype hardware for integrated system studies and analysis. This paper details a test-bed configuration where a dynamic simulation of an aircraft turbine engine is utilized to control a dual-head electric drive stand.

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.

A discussion on the development of a Telescoping, Vaned, Exhaust Nozzle (TEVEN) is presented. This nozzle was challenged to meet the thrust vectoring requirements of an Advanced Short Takeoff and Vertical Landing (ASTOVL) aircraft. The nozzle underwent a development process from concepts to detail design using computational flow analyses and from subscale performance verification tests to full-scale hardware design. The LiftFan™ nozzle is capable of providing a pitch vector range of about 80 degrees from up to 20 degrees forward to 60 degrees aft. In addition, a set of post exit yaw doors provide ± 10 degrees yaw while maintaining a relatively high performance at all operating conditions. Further, the nozzle is axially compact, to be stowable in very short length (L/D < 0.3), while efficiently converging the upstream nozzle flow from an annular cross section to a “D” shape at the nozzle exit.