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All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Design and Development Comparison of Rapid Cycle Amine 1.0, 2.0, and 3.0

The development of the Rapid Cycle Amine (RCA) swing-bed technology for carbon dioxide (CO2) removal has been in progress since favorable results were published in 1996. Shortly thereafter, a prototype was designed, developed, and tested successfully and delivered to Johnson Space Center in 1999. An improved prototype was delivered to NASA in 2006 and was notated as RCA 1.0 and sized for the extravehicular activity (EVA). The new RCA swing-bed technology is a regenerative system which employs two alternating solid-amine sorbent beds to remove CO2 and water. The two- bed design employs a chemisorption process whereby the beds alternate between adsorbtion and desorbsion. This process provides for an efficient operation of the RCA so that while one bed is in adsorb (uptake) mode, the other is in the desorb (regeneration) mode. The RCA has now progressed through several iterations of technology readiness levels. Test articles have now been designed, developed, and tested for the advanced space suit portable life support system (PLSS) including RCA 1.0, RCA 2.0, and RCA 3.0. The RCA 3.0 was the most recent RCA fabrication and was delivered to NASA-JSC in June 2015. The RCA 1.0 test article was designed with a pneumatically actuated linear motion spool valve. The RCA 2.0 and 3.0 test articles were designed with a valve assembly which allows for switching between uptake and regeneration modes while minimizing gas volume losses to the vacuum source. RCA 2.0 and 3.0 also include an embedded controller design to control RCA operation and provide the capability of interfacing with various sensors and other ventilation loop components. The RCA technology is low power, small, and has fulfilled all test requirements levied upon the technology during development testing thus far. This paper will provide an overreview of the design and development of RCA 1.0, 2.0 and 3.0 including detail differences between the design specifications of each.

Chullen, Cinda↗
NASA NTRS2016

Design and Development Comparison of Rapid Cycle Amine 1.0, 2.0, and 3.0

The development of the Rapid Cycle Amine (RCA) swing-bed technology for carbon dioxide (CO2) removal has been in progress since favorable results were published in 1996. Shortly thereafter, a prototype was designed, developed, and tested successfully and delivered to Johnson Space Center in 1999. An improved prototype (RCA 1.0) was delivered to NASA in 2006 and sized for the extravehicular activity (EVA). The RCA swing-bed technology is a regenerative system which employs two alternating solid-amine sorbent beds to remove CO2 and water. The two-bed design employs a chemisorption process whereby the beds alternate between adsorption and desorption. This process provides for an efficient RCA operation that enables one bed to be in adsorb (uptake) mode, while the other is in the desorb (regeneration) mode. The RCA has progressed through several iterations of technology readiness levels. Test articles have now been designed, developed, and tested for the advanced space suit portable life support system (PLSS) including RCA 1.0, RCA 2.0, and RCA 3.0. The RCA 3.0 was the most recent RCA fabrication and was delivered to NASA-JSC in June 2015. The RCA 1.0 test article was designed with a pneumatically actuated linear motion spool valve. The RCA 2.0 and 3.0 test articles were designed with a valve assembly which allows for switching between uptake and regeneration modes while minimizing gas volume losses to the vacuum source. RCA 2.0 and 3.0 also include an embedded controller design to control RCA operation and provide the capability of interfacing with various sensors and other ventilation loop components. The RCA technology is low power, small, and has fulfilled all test requirements levied upon the technology during development testing thus far. This paper will provide an overview of the design and development of RCA 1.0, 2.0 and 3.0 including detail differences between the design specifications of each. Nomenclature.

Chullen, Cinda↗
DOE OSTI2024

SISGR: The regulation of carbon fixation in plant and green algae: Rubisco activase and the origin of heat inactivation of CO 2 assimilation

Rubisco activase (Rca) is a critical AAA+ ATPase protein complex that remodels and promotes the Rubisco enzyme, a key player in photosynthetic performance and carbon fixation. The assembly and function of the Rca protein complex are regulated by a range of factors, including subunit concentration, nucleotide-binding states, thermal conditions, metal-ion coordination, and post-translational modifications, such as phosphorylation. Despite its importance in photosynthesis, the detailed molecular mechanisms underlying the regulation of plant Rca and how it activates Rubisco remain elusive. This project aims to bridge this knowledge gap by integrating sophisticated enzymology tools with single-molecule methods and high-resolution electron microscopy to elucidate the structure and function of plant Rca. Through these multiple approaches, we have systematically investigated how the activity of plant Rca is impacted by various factors, such as phosphorylation and metal-ion coordination. The Rca complex assembly/disassembly dynamics were captured using anti-Brownian electrokinetic (ABEL) trap-based measurements, providing unprecedented insight into its structural flexibility and diverse assembly states. Furthermore, the structural analysis of Rca through electron crystallography and single-particle cryogenic electron microscopy (cryo-EM) reveals novel assembly states of the spinach Rca, providing insight into the mechanistic action for Rubisco remodeling. By combining cutting-edge tools and approaches, this work uncovers critical aspects of Rca’s regulation and assembly, paving the way for a deeper understanding of its role in photosynthetic efficiency and the potential for enhancing carbon fixation in crops.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRSDate not supplied

Rapid Cycle Amine 4.0 System Development

Carbon dioxide (CO2) and humidity control is a key function of the spacesuit Portable Life Support Subsystem (PLSS). The latest spacesuit design utilizes a pressure swing bed containing a solid amine sorbent to scrub CO2 and humidity produced by the crewmember from the ventilation loop. The solid amine sorbent removes CO2 and humidity from the ventilation loop through a chemisorption mechanism. Simultaneously, CO2 and humidity are desorbed to vacuum via the two-bed pressure swing system during operation. This continuous regeneration allows for longer Extravehicular Activity (EVA) times while minimizing maintenance, consumables, and power usage. This concept has been in development for over 20 years, during which many prototypes and design iterations have been fabricated and evaluated. This paper discusses the recent Rapid Cycle Amine (RCA) design, development, and testing that has been done to advance the technology. The most recent fabrication is the RCA 3.0. It was delivered to NASA Johnson Space Center in 2015 and has since been tested at the component level and at the integrated PLSS level. The purpose of the component level testing was to understand CO2 removal capacity, end-of-life performance, and establish a baseline performance prior to integrated testing. The RCA 3.0 was integrated into the Exploration Extravehicular Mobility Unit (xEMU) PLSS for a comprehensive Design Verification Test (DVT) series. The integrated testing provided the benefit of characterizing the impact performance degradation has on the system. Many of the RCA requirements were developed through analysis, based on the limitations of the PLSS and, in some cases, assumptions about the system and flow behavior. Integrated testing was an opportunity to validate those requirements and assumptions. While the RCA 3.0 was being tested, the next design iteration, RCA 4.0, was under development. The RCA 4.0 preliminary design phase began in late-2019 and shortly after the Preliminary Design Review, the critical design phase began in 2021. The design work has concluded with the completion of a Pre-Manufacturing Review in 2022. This paper provides an overview of the RCA 4.0 system design, summarizes the results of integrated RCA 3.0 testing, and discusses the pertinence of driving requirements such as mass, volume, and power consumption.

Kelsey Bloom↗
NASA NTRS2011

Maintaining Adequate CO2 Washout for an Advanced EMU via a New Rapid Cycle Amine Technology

Over the past several years, NASA has realized tremendous progress in Extravehicular Activity (EVA) technology development. This has been evidenced by the progressive development of a new Rapic Cycle Amine (RCA) system for the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support Subsystem (PLSS). The PLSS is responsible for the life support of the crew member in the spacesuit. The RCA technology is responsible for carbon dioxide (CO2) and humidity control. Another aspect of the RCA is that it is on-back vacuum-regenerable, efficient, and reliable. The RCA also simplifies the PLSS schematic by eliminating the need for a condensing heat exchanger for humidity control in the current EMU. As development progresses on the RCA, it is important that the sizing be optimized so that the demand on the PLSS battery is minimized. As well, maintaining the CO2 washout at adequate levels during an EVA is an absolute requirement of the RCA and associated ventilation system. Testing has been underway in-house at NASA Johnson Space Center and analysis has been initiated to evaluate whether the technology provides exemplary performance in ensuring that the CO2 is removed sufficiently enough and the ventilation flow is adequate enough to maintain CO2 1 Project Engineer, Space Suit and Crew Survival Systems Branch, Crew and Thermal Systems Division, 2101 NASA Parkway, Houston, TX 77058/EC5. washout in the AEMU spacesuit helmet of the crew member during an EVA. This paper will review the recent developments of the RCA unit, the testing results performed in-house with a spacesuit simulator, and the associated analytical work along with insights from the medical aspect on the testing.

Chullen, Cinda↗
NASA NTRS2012

Maintaining Adequate CO2 Washout for an Advanced EMU via a New Rapid Cycle Amine Technology

Over the past several years, NASA has realized tremendous progress in Extravehicular Activity (EVA) technology development. This has been evidenced by the progressive development of a new Rapid Cycle Amine (RCA) system for the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support Subsystem (PLSS). The PLSS is responsible for the life support of the crew member in the spacesuit. The RCA technology is responsible for carbon dioxide (CO2) and humidity control. Another aspect of the RCA is that it is on-back vacuum-regenerable, efficient, and reliable. The RCA also simplifies the PLSS schematic by eliminating the need for a condensing heat exchanger for humidity control in the current EMU. As development progresses on the RCA, it is important that the sizing be optimized so that the demand on the PLSS battery is minimized. As well, maintaining the CO2 washout at adequate levels during an EVA is an absolute requirement of the RCA and associated ventilation system. Testing has been underway in-house at NASA Johnson Space Center and analysis has been initiated to evaluate whether the technology provides exemplary performance in ensuring that the CO2 is removed sufficiently and the ventilation flow is adequate for maintaining CO2 washout in the AEMU spacesuit helmet of the crew member during an EVA. This paper will review the recent developments of the RCA unit, testing planned in-house with a spacesuit simulator, and the associated analytical work along with insights from the medical aspect on the testing. 1

Chullen, Cinda↗
NASA NTRS2010

Testing and Results of Vacuum Swing Adsorption Units for Spacesuit Carbon Dioxide and Humidity Control

A principal concern for extravehicular activity (EVA) space suits is the capability to control carbon dioxide (CO2) and humidity (H2O) for the crewmember. The release of CO2 in a confined or unventilated area is dangerous for human health and leads to asphyxiation; therefore, CO2 and H2O become leading factors in the design and development of the spacesuit. An amine-based CO2 and H2O vapor sorbent for use in pressure-swing re-generable beds has been developed by Hamilton Sundstrand. The application of solid-amine materials with vacuum swing adsorption technology has shown the capacity to concurrently manage CO2 and H2O levels through a fully regenerative cycle eliminating mission constraints imposed with non-regenerative technologies. Two prototype solid amine-based systems, known as rapid cycle amine (RCA), were designed to continuously remove CO2 and H2O vapor from a flowing ventilation stream through the use of a two-bed amine based, vacuum-swing adsorption system. The Engineering and Science Contract Group (ESCG) RCA is the first RCA unit implementing radial flow paths, whereas the Hamilton Sundstrand RCA was designed with linear flow paths. Testing was performed in a sea-level pressure environment and a reduced-pressure environment with simulated human metabolic loads in a closed-loop configuration. This paper presents the experimental results of laboratory testing for a full-size and a sub-scale test article. The testing described here characterized and evaluated the performance of each RCA unit at the required Portable Life Support Subsystem (PLSS) operating conditions. The test points simulated a range of crewmember metabolic rates. The experimental results demonstrate the ability of each RCA unit to sufficiently remove CO2 and H2O from a closed loop ambient or subambient atmosphere.

McMillin, Summer↗
NASA NTRS2011

Testing and Results of Vacuum Swing Adsorption Units for Spacesuit Carbon Dioxide and Humidity Control

A principal concern for extravehicular activity (EVA) spacesuits is the capability to control carbon dioxide (CO2) and humidity (H2O) for the crewmember. The release of CO2 in a confined or unventilated area is dangerous for human health and leads to asphyxiation; therefore, CO2 and H2O control become leading factors in the design and development of the spacesuit. An amine-based CO2 and H2O vapor sorbent for use in pressure-swing regenerable beds has been developed by Hamilton Sundstrand. The application of solidamine materials with vacuum swing adsorption technology has shown the capacity to concurrently manage CO2 and H2O levels through a fully regenerative cycle eliminating mission constraints imposed with nonregenerative technologies. Two prototype solid amine-based systems, known as rapid cycle amine (RCA), were designed to continuously remove CO2 and H2O vapor from a flowing ventilation stream through the use of a two-bed amine based, vacuum-swing adsorption system. The Engineering and Science Contract Group (ESCG) RCA implements radial flow paths, whereas the Hamilton Sundstrand RCA was designed with linear flow paths. Testing was performed in a sea-level pressure environment and a reduced-pressure environment with simulated human metabolic loads in a closed-loop configuration. This paper presents the experimental results of laboratory testing for a full-size and a sub-scale test article. The testing described here characterized and evaluated the performance of each RCA unit at the required Portable Life Support Subsystem (PLSS) operating conditions. The test points simulated a range of crewmember metabolic rates. The experimental results demonstrated the ability of each RCA unit to sufficiently remove CO2 and H2O from a closed loop ambient or sub-ambient atmosphere.

McMillin, Summer D.↗
NASA NTRSDate not supplied

Evaluation of Long-Term Storage Stability and Operational Efficiency of Rapid Cycle Amine Adsorbents

With the recent incorporation of Mars Extravehicular Activity (EVA) into the 2025 NASA roadmap, Rapid Cycle Amine (RCA) technology advancement within the Exploration Extravehicular Mobility Unit (xEMU) applies to both the upcoming Lunar Artemis missions and future human exploration of Mars. The incorporation of commercial spacesuit vendors to service NASA’s crewed-space programs since 2021 has increased the demand for regenerable, RCA-based carbon dioxide (CO2) and humidity control adsorbents. The regenerable RCA subunit is the most advanced, long-term solution for CO2 removal and humidity control, enabling both lunar and Martian EVAs. The adsorbent selected for use within the RCA unit must exhibit sufficient storage stability and operational efficiency for prolonged missions. As XploSafe worked to simultaneously develop both a recirculating sub-atmospheric test rig and adsorbents for the RCA system within the xEMU, several novel adsorbents were evaluated for long-term storage stability in support of future extended-duration missions. The chosen materials were periodically evaluated by nuclear magnetic resonance (NMR) spectroscopy, thermal desorption-coupled with gas chromatography/mass spectrometry (TD-GC/MS), and CO2 adsorption to assess long-term storage efficacy across various environmental storage conditions. NMR spectroscopy was utilized by extracting the active CO2 adsorbing chemical from the solid support with deuterated solvent and comparing the spectra over time for degradation and change. The solid adsorbents were also analyzed via TD-GC/MS to reveal any potential off-gassing chemicals over time. Additionally, XploSafe’s breakthrough test rig was utilized to dose the solid adsorbents with a 585 BTU/h metabolic rate flow-equivalent CO2 stream and monitored for 0–99% CO2 breakthrough. The performance metrics from the breakthrough analysis were compared over the storage study duration for CO2 removal and humidity control. Xplo-SA9T was evaluated for 24 months, whereas two additional adsorbent variants, MMPA-Sorbent and LPEI-Sorbent, were each evaluated for 12 months.

John R Tidwell↗
NASA NTRS1991

Investigation of long term stability in metal hydrides

It is apparent from the literature and the results of this study that cyclic degradation of AB(5) type metal hydrides varies widely according to the details of how the specimens are cycled. The Rapid Cycle Apparatus (RCA) used produced less degradation in 5000 to 10000 cycles than earlier work with a Slow Cycle Apparatus (SCA) produced in 1500 cycles. Evidence is presented that the 453 K (356 F) Thermal Aging (TA) time spent in the saturated condition causes hydride degradation. But increasing the cooling (saturation) period in the RCA did not greatly increase the rate of degradation. It appears that TA type degradation is secondary at low temperatures to another degradation mechanism. If rapid cycles are less damaging than slow cycles when the saturation time is equal, the rate of hydriding/dehydriding may be an important factor. The peak temperatures in the RCA were about 30 C lower than the SCA. The difference in peak cycle temperatures (125 C in the SCA, 95 C in RCA) cannot explain the differences in degradation. TA type degradation is similar to cyclic degradation in that nickel peaks and line broadening are observed in X ray diffraction patterns after either form of degradation.

Marmaro, Roger W.↗
NASA NTRS2010

Reactive Collision Avoidance Algorithm

The reactive collision avoidance (RCA) algorithm allows a spacecraft to find a fuel-optimal trajectory for avoiding an arbitrary number of colliding spacecraft in real time while accounting for acceleration limits. In addition to spacecraft, the technology can be used for vehicles that can accelerate in any direction, such as helicopters and submersibles. In contrast to existing, passive algorithms that simultaneously design trajectories for a cluster of vehicles working to achieve a common goal, RCA is implemented onboard spacecraft only when an imminent collision is detected, and then plans a collision avoidance maneuver for only that host vehicle, thus preventing a collision in an off-nominal situation for which passive algorithms cannot. An example scenario for such a situation might be when a spacecraft in the cluster is approaching another one, but enters safe mode and begins to drift. Functionally, the RCA detects colliding spacecraft, plans an evasion trajectory by solving the Evasion Trajectory Problem (ETP), and then recovers after the collision is avoided. A direct optimization approach was used to develop the algorithm so it can run in real time. In this innovation, a parameterized class of avoidance trajectories is specified, and then the optimal trajectory is found by searching over the parameters. The class of trajectories is selected as bang-off-bang as motivated by optimal control theory. That is, an avoiding spacecraft first applies full acceleration in a constant direction, then coasts, and finally applies full acceleration to stop. The parameter optimization problem can be solved offline and stored as a look-up table of values. Using a look-up table allows the algorithm to run in real time. Given a colliding spacecraft, the properties of the collision geometry serve as indices of the look-up table that gives the optimal trajectory. For multiple colliding spacecraft, the set of trajectories that avoid all spacecraft is rapidly searched on-line. The optimal avoidance trajectory is implemented as a receding-horizon model predictive control law. Therefore, at each time step, the optimal avoidance trajectory is found and the first time step of its acceleration is applied. At the next time step of the control computer, the problem is re-solved and the new first time step is again applied. This continual updating allows the RCA algorithm to adapt to a colliding spacecraft that is making erratic course changes.

Scharf, Daniel↗
NASA NTRS2012

Performance Characterization and Simulation of Amine-Based Vacuum Swing Sorption Units for Spacesuit Carbon Dioxide and Humidity Control

Controlling carbon dioxide (CO2) and water (H2O) vapor concentrations in a space suit is critical to ensuring an astronauts safety, comfort, and capability to perform extra-vehicular activity (EVA) tasks. Historically, this has been accomplished using lithium hydroxide (LiOH) and metal oxide (MetOx) canisters. Lithium hydroxide is a consumable material that requires priming with water before it becomes effective at removing carbon dioxide. MetOx is regenerable through a power-intensive thermal cycle but is significantly heavier on a volume basis than LiOH. As an alternative, amine-based vacuum swing beds are under aggressive development for EVA applications. The vacuum swing units control atmospheric concentrations of both CO2 and H2O through fully-regenerative process. The current concept, referred to as the rapid cycle amine (RCA), has resulted in numerous laboratory prototypes. Performance of these prototypes have been assessed experimentally and documented in previous reports. To support developmental e orts, a first principles model has also been established for the vacuum swing sorption technology. For the first time in several decades, a major re-design of Portable Life Support System (PLSS) for the extra-vehicular mobility unit (EMU) is underway. NASA at Johnson Space Center built and tested an integrated PLSS test bed of all subsystems under a variety of simulated EVA conditions of which the RCA prototype played a significant role. The efforts documented herein summarize RCA test performance and simulation results for single and variable metabolic rate experiments in an integrated context. In addition, a variety of off-nominal tests were performed to assess the capability of the RCA to function under challenging circumstances. Tests included high water production experiments, degraded vacuum regeneration, and deliberate valve/power failure and recovery.

Swickrath, Michael J.↗
DOE OSTI2025

Root cause analysis of a molten salt pump in FLUSTFA

The primary salt pump installed in the high-temperature FLUoride Salt Test Facility (FLUSTFA) was successfully operated for some time, but later ceased operation. To understand what occurred, a Root Cause Analysis (RCA) was performed. Steps taken to try to get the pump operational include adjusting the shaft position, increasing the heating power of the tape heaters on the pump volute, and manually rotating the pump shaft. While removing the insulation, corrosion was noted on the outside of the pump volute, and decolorization of the insulation and tape heaters was observed. Significant corrosion products were also observed in the pump itself and the piping connected to the pump. The nitrogen cover gas was maintained from before salt was introduced into the loop until the pump was dismounted and continues to be maintained even after the pump was removed. After considering probable scenarios, causes were assigned and corrective actions were developed to prevent those causes. Then, the RCA was presented to an advisory committee for review, the “Review Committee,” consisting of experts in large molten salt systems: Brandon Haugh, David Holcomb, Kevin Robb, and Vicente Rojas. As a result, the advisory committee provided comprehensive feedback, which have been incorporated into a revised RCA. Findings have then been summarized and reported in this publication.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Non-invasive ventral cervical magnetoneurography as a proxy of in vivo lipopolysaccharide-induced inflammation

Maintenance of autonomic homeostasis is continuously calibrated by sensory fibers of the vagus nerve and sympathetic chain that convey compound action potentials (CAPs) to the central nervous system. Lipopolysaccharide (LPS) intravenous challenge reliably elicits a robust inflammatory response that can resemble systemic inflammation and acute endotoxemia. Here, we administered LPS intravenously in nine healthy subjects while recording ventral cervical magnetoneurography (vcMNG)-derived CAPs at the rostral Right Nodose Ganglion (RNG) and the caudal Right Carotid Artery (RCA) with optically pumped magnetometers (OPM). We observed vcMNG RNG and RCA neural firing rates that tracked changes in TNF-α levels in the systemic circulation. Further, endotype subgroups based on high and low IL-6 responders segregate RNG CAP frequency (at 30-120 min) and based on high and low IL-10 response discriminate RCA CAP frequency (at 0-30 min). These vcMNG tools may enhance understanding and management of the neuroimmune axis that can guide personalized treatment based on an individual’s distinct endophenotype.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1986

Line-of-sight performance improvement with reaction-wheel isolation

Design techniques used to isolate and damp vibrations from the reaction control wheels assembly (RCA) from the structural dynamics of the Hubble Space Telescope are described. The four RCAs can generate sufficient torque for large maneuvers and precision control during fine pointing. The RCAs are to operate continuously during observations and thereby pose the potential of inducing jitter. The image stability must be constrained to less than 0.007 arcsec rms per 24 hr and pointing accuracy must be 0.01 arcsec for 100 hr. Vibration-producing characteristics of the RCAs are identified, and test results are provided from measurements of the magnitudes of the associated disturbances. Design features and test results for the vibration isolators employed with the RCAs to effect viscous damping of RCA axial perturbations are presented. The dampers are expected to reduce jitter effects of RCA operation by a half.

Rodden, J. J.↗
NASA NTRS1992

Rain compensation algorithm for ACTS mobile terminal

The initial advanced communication technology satellite (ACTS) mobile terminal (AMT) demonstrations will involve two-way communications between the high-bit-rate link evaluation terminal (HBR-LET), which is a fixed terminal (FT), and a van-housed mobile terminal (MT). The HBR-LET has the capability of adjusting its transmitted uplink power over an approximately 10-dB range to compensate for forward uplink rain attenuation. However, because of size and weight limitations, the MT cannot use power control as a rain compensation technique. Consequently, the AMT rain compensation algorithm (RCA) is based on a formula for varying the transmitted data rate in either direction to maintain link performance within acceptable limits. The objective of the AMT RCA is to ensure reliable operation in both the forward and return directions despite the possibility of uplink or downlink fading due to rain events in the vicinity of the FT or MT. In particular, the RCA must maintain at least a 3-dB link margin at the highest possible transmission rate (AMT can operate at 9.6, 4.8, or 2.4 kb/s) permitted by the prevailing channel conditions. The 3-dB minimum link margin is a system design safety factor to accommodate conceivable implementation losses.

Levitt, Barry K.↗
NASA NTRS1987

Using the MCPLXS Generator for Technology Transfer

The objective of this paper is to acquaint you with some of the approaches we are taking at Langley to incorporate escalations (or de-escalations) of technology when modeling futuristic systems. Since we have a short turnaround between the time we receive enough descriptive information to start estimating the project and when the estimate is needed (the "we-want-it-yesterday syndrome"), creativity is often necessary. There is not much time available for tool development. It is expedient to use existing tools in an adaptive manner to model the situation at hand. Specifically, this paper describes the use of the RCA PRICE MCPLXS Generator to incorporate technology transfer and technology escalation in estimates for advanced space systems such as Shuttle II and NASA advanced technology vehicles. It is assumed that the reader is familiar with the RCA PRICE family of models as well as the RCA PRICE utility programs such as SCPLX, PARAM, PARASYN, and the MCPLXS Generator.

Moore, Arlene A.↗
NASA NTRS2007

Systems Modeling to Implement Integrated System Health Management Capability

ISHM capability includes: detection of anomalies, diagnosis of causes of anomalies, prediction of future anomalies, and user interfaces that enable integrated awareness (past, present, and future) by users. This is achieved by focused management of data, information and knowledge (DIaK) that will likely be distributed across networks. Management of DIaK implies storage, sharing (timely availability), maintaining, evolving, and processing. Processing of DIaK encapsulates strategies, methodologies, algorithms, etc. focused on achieving high ISHM Functional Capability Level (FCL). High FCL means a high degree of success in detecting anomalies, diagnosing causes, predicting future anomalies, and enabling health integrated awareness by the user. A model that enables ISHM capability, and hence, DIaK management, is denominated the ISHM Model of the System (IMS). We describe aspects of the IMS that focus on processing of DIaK. Strategies, methodologies, and algorithms require proper context. We describe an approach to define and use contexts, implementation in an object-oriented software environment (G2), and validation using actual test data from a methane thruster test program at NASA SSC. Context is linked to existence of relationships among elements of a system. For example, the context to use a strategy to detect leak is to identify closed subsystems (e.g. bounded by closed valves and by tanks) that include pressure sensors, and check if the pressure is changing. We call these subsystems Pressurizable Subsystems. If pressure changes are detected, then all members of the closed subsystem become suspect of leakage. In this case, the context is defined by identifying a subsystem that is suitable for applying a strategy. Contexts are defined in many ways. Often, a context is defined by relationships of function (e.g. liquid flow, maintaining pressure, etc.), form (e.g. part of the same component, connected to other components, etc.), or space (e.g. physically close, touching the same common element, etc.). The context might be defined dynamically (if conditions for the context appear and disappear dynamically) or statically. Although this approach is akin to case-based reasoning, we are implementing it using a software environment that embodies tools to define and manage relationships (of any nature) among objects in a very intuitive manner. Context for higher level inferences (that use detected anomalies or events), primarily for diagnosis and prognosis, are related to causal relationships. This is useful to develop root-cause analysis trees showing an event linked to its possible causes and effects. The innovation pertaining to RCA trees encompasses use of previously defined subsystems as well as individual elements in the tree. This approach allows more powerful implementations of RCA capability in object-oriented environments. For example, if a pressurizable subsystem is leaking, its root-cause representation within an RCA tree will show that the cause is that all elements of that subsystem are suspect of leak. Such a tree would apply to all instances of leak-events detected and all elements in all pressurizable subsystems in the system. Example subsystems in our environment to build IMS include: Pressurizable Subsystem, Fluid-Fill Subsystem, Flow-Thru-Valve Subsystem, and Fluid Supply Subsystem. The software environment for IMS is designed to potentially allow definition of any relationship suitable to create a context to achieve ISHM capability.

Figueroa, Jorge F.↗