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At least 703 records · Page 39

Design for pressure regulating components

The design development for Pressure Regulating Components included a regulator component trade-off study with analog computer performance verification to arrive at a final optimized regulator configuration for the Space Storable Propulsion Module, under development for a Jupiter Orbiter mission. This application requires the pressure regulator to be capable of long-term fluorine exposure. In addition, individual but basically identical (for purposes of commonality) units are required for separate oxidizer and fuel pressurization. The need for dual units requires improvement in the regulation accuracy over present designs. An advanced regulator concept was prepared featuring redundant bellows, all metallic/ceramic construction, friction-free guidance of moving parts, gas damping, and the elimination of coil springs normally used for reference forces. The activities included testing of actual size seat/poppet components to determine actual discharge coefficients and flow forces. The resulting data was inserted into the computer model of the regulator. Computer simulation of the propulsion module performance over two mission profiles indicated satisfactory minimization of propellant residual requirements imposed by regulator performance uncertainties.

Wichmann, H.↗

Enterprise Mission Integration for Artemis Lunar Missions

Mission integration is an iterative process by which a specific mission is formulated, refined, planned, and executed within the established vehicle(s), architecture, and ground systems design. Mission integration includes the people, vehicle(s) and ground hardware/software, products, processes, analyses, schedules, facilities, Certification of Flight Readiness, etc. The Artemis Mission Integration Task Team (MITT) developed a series of products and processes to support the complex mission integration across various Programs within the Artemis Mission Campaign (Orion, Space Launch Systems, Exploration Ground Systems, Gateway, Human Landing System, and Extravehicular Activity and Human Surface Mobility). The Moon to Mars (M2M) Program is referred to as ‘the enterprise’ as it includes both the M2M organization and the Programs supporting the Artemis Mission Campaign. Artemis Mission Integration has five phases: mission capability, mission definition, mission preparation, mission execution, and post-mission assessment. This paper focuses on one of the enterprise-level mission checkpoints as a kick-off to the Mission Preparation phase, the Mission Integration Review (MIR), which occurs 18-24 months prior to launch. The MIR helps to confirm the defined mission technical baseline is within the existing analyzed design envelope. Details are provided on the identification of dependencies, issues, or gaps for mission-specific objectives and requirements, as well as the definition of the analysis, training, mission execution products, facilities, and detailed supporting operations requirements. The MIR was held for both Artemis I and II and this paper aims to share with the aerospace community its value as we prepare for upcoming Artemis Missions.

Mary Anne Plaza↗

Evaluating Extravehicular Activity Access Options for a Lunar Surface Habitat

NASA’s upcoming return to the moon includes a plan for longer duration lunar missions that prioritize science and surface exploration. The current Artemis Base Camp reference proposes a Surface Habitat (SH) that will support 2 to 4 crewmembers with adequate capability for living and working for 30 days or more. An important aspect of the SH’s design will be its ability to support a high frequency of Extravehicular Activities (EVAs) for scientific purposes. There are multiple airlock designs that can support EVA access from inside the SH out to the lunar surface. This paper explores three unique options for EVA access: a traditional airlock, a suitlock, and a suitport-airlock. A traditional airlock is accessed by use of a hatch, crewmembers don and doff their EVA suits inside the airlock, and it must be depressurized and repressurized for every EVA. A suitlock is also depressurized and repressurized for every EVA but the suits are donned through a suitport attached to the airlock bulkhead. A suitport-airlock is accessed through suitports that are attached to the airlock bulkhead as well, but the suitport-airlock stays in vacuum, and it does not have to be depressurized and repressurized for each EVA. This study also evaluated the use of an Airlock Airsave System in the cases of a traditional airlock and suitlock. This system captures a fraction of the airlock gas instead of venting all of the gas pre-EVA. The captured gas is then used to partially repressurize the airlock post-EVA. In this study, each option is evaluated based on seven different areas of analysis. The metrics include overhead time for EVAs, dust mitigation, consumables for resupply mass, systems mass, system power, safety and mission assurances, and programmatic considerations. The EVA access options are evaluated and compared under each area of analysis. While the baseline case assumes the SH is at 8.2 psia, the authors also investigate the impact of a 10.2 psia habitat as an alternative in this analysis. Following the conclusion of the analysis, the authors recommend the usage of a Suitport-Airlock for Lunar SH missions and detail the reasoning behind the recommendation.

EVA↗

Performance of Cassini Reaction Wheel Friction Compensation Scheme During Spin Rate Zero-Crossing and Drag Spikes

Cassini uses reaction wheels to achieve the spacecraft pointing stability that is needed during imaging operations of several science instruments. The Cassini flight software makes inflight estimates of reaction wheel bearing drag torque and the reaction wheel controller uses these estimates to achieve a high level of spacecraft pointing stability. However, the Cassini drag torque estimator was designed to accurately track the bearing drag torque only in the steady state. When the physical drag torque changes abruptly (for example, during a reaction wheel spin rate reversal or when wheel bearings experienced drag spikes), the drag estimator will not be able to track the physical drag closely. This will lead to a degradation in the spacecraft pointing stability performance. For Cassini, this was not a problem because of the significant performance margin in pointing stability. However, for missions that have very challenging pointing stability requirements and that must perform well in the presence of frequent wheel rate reversals, alternative drag-compensating control schemes must be considered. To this end, alternative drag torque compensating control schemes (such as the adaptive model reference control scheme) are briefly reviewed in this paper. Selected design features used in these friction compensation schemes may be incorporated in reaction wheel controller design to improve the robustness of spacecraft pointing stability performance with regard to a wide range of reaction wheel drag torque anomalous behavior.

Lee, Allan Y↗

Commonality of flight control systems for support of European telecommunications missions

This paper is concerned with the presentation of mission-independent software systems that provide a common software platform to ground data systems for mission operations. The objectives of such common software platforms are to reduce the cost of the development of mission-dedicated software systems and to increase the level of reliability of the ground data systems for mission operations. In accordance with this objective, the Multi-Satellite Support System (MSSS) was developed at the European Space Operations Center (ESOC). Between 1975 and 1992, the MSSS provided support to 16 European Space Agency (ESA) missions, among them very demanding science missions such as GEOS, EXOSAT, and Giotto. The successful support of these missions proved the validity of the MSSS concept with its extended mission-independent platform. This paper describes the MSSS concept and focuses on the wide use of MSSS as a flight control system for geosynchronous telecommunications satellites. Reference is made to more than 15 telecommunications missions that are operated from Western Europe using flight control systems with an underlying MSSS concept, demonstrating the benefits of a commonly used software platform. Finally, the paper outlines the design of the new generation of flight control systems, which is being developed at ESOC for this decade, following a period of more than 15 years of MSSS support.

Debatin, Kurt↗

Navigational demands of low-level helicopter flight

The present study was designed to assess the verbal references to map, terrain, direction, and position, that navigators and pilots communicate during a simulated low-level flight. Two-person crews were asked to communicate normally while negotiating six short flight missions that varied widely in regard to map-terrain characteristics. Half of the crews performed the exercises with fixed, north-up maps and the other half used movable maps that were adjusted to maintain a track-up correspondence to the flight route. An analysis was performed to compare differences in crew communication patterns between map orientations, characteristics, and navigation tasks. The results showed differences in the frequency of communication across categories for map characteristics but not for map orientations or tasks. A difference in the proportion of communications between pilot and navigator occurred when crew were lost. Pilots communicated more than navigators when crews were lost and the reverse was true when crews were not lost. The results support and extend findings from a distance error performance analysis performed on the same flight missions.

Delzell, Susanne↗

Flight Dynamics Analysis Branch End of Fiscal Year 2004 Report

This report summarizes the major activities and accomplishments carried out by the Flight Dynamics Analysis Branch (FDAB), Code 595, in support of flight projects and technology development initiatives in Fiscal Year (FY) 2004. The report is intended to serve as a summary of the type of support carried out by the FDAB, as well as a concise reference of key accomplishments and mission experience derived from the various mission support roles. The primary focus of the FDAB is to provide expertise in the disciplines of flight dynamics including spacecraft navigation (autonomous and ground based); spacecraft trajectory design and maneuver planning; attitude analysis; attitude determination and sensor calibration; and attitude control subsystem (ACS) analysis and design. The FDAB currently provides support for missions and technology development projects involving NASA, other government agencies, academia, and private industry.

DeLion, Anne↗

Cassini tour navigation strategy

The Cassini-Huygens spacecraft was launched on October 15, 1997 as a joint NASA/ESA mission to explore Saturn. After a 7 year cruise the spacecraft will enter orbit around Saturn on 1 July 2004 for a 4 year investigation of the Saturnian system. The Cassini Navigation Team is responsible for designing the reference trajectory and conducting operations to realize this design. This paper describes the strategy for achieving project requirements, the characteristics of the Cassini navigation challenge, and the underlying assumptions.

Saturn↗

Flight Dynamics Analysis Branch End of Fiscal Year 2005 Report

This report summarizes the major activities and accomplishments carried out by the Flight Dynamics Analysis Branch (FDAB), Code 595, in support of flight projects and technology development initiatives in Fiscal Year (FY) 2005. The report is intended to serve as a summary of the type of support carried out by the FDAB, as well as a concise reference of key accomplishments and mission experience derived from the various mission support roles. The primary focus of the FDAB is to provide expertise in the disciplines of flight dynamics including spacecraft navigation (autonomous and ground based), spacecraft trajectory design and maneuver planning, attitude analysis, attitude determination and sensor calibration, and attitude control subsystem (ACS) analysis and design. The FDAB currently provides support for missions and technology development projects involving NASA, other government agencies, academia, and private industry.

Source record↗

Flight Dynamics Analysis Branch 2005 Technical Highlights

This report summarizes the major activities and accomplishments carried out by the Flight Dynamics Analysis Branch (FDAB), Code 595, in support of flight projects and technology development initiatives in Fiscal Year (FY) 2005. The report is intended to serve as a summary of the type of support carried out by the FDAB, as well as a concise reference of key accomplishments and mission experience derived from the various mission support roles. The primary focus of the FDAB is to provide expertise in the disciplines of flight dynamics including spacecraft navigation (autonomous and ground based); spacecraft trajectory design and maneuver planning; attitude analysis; attitude determination and sensor calibration; and attitude control subsystem (ACS) analysis and design. The FDAB currently provides support for missions and technology development projects involving NASA, other government agencies, academia, and private industry.

Source record↗

Enabling Mission Flexibility to Battery Driven Deep Space Endeavors With Generalized Battery-Health-Monitoring Using Physics-Based and Data-Driven Reduced-Order Models

The needs and requirements for an electrochemical energy storage for deep space exploration is well explored. It is often understood that different mission sites and environmental conditions require different battery chemistries or technologies. Additionally, various engineering solutions are deployed to overcome specific chemical challenges. One often overlooked need is the “health” monitoring of an electrochemical storage system. The term generalized health monitoring, as envisioned in this work, refers to the monitoring of various aspects such as electrode health, electrolyte health, reaction pathway health, cooling system health, sensor health, and BMS health [1]. Generalized health monitoring allows mission leads, engineers, and scientists to incorporate flexibility in mission designs, make on-the-fly mission changes, and extend the duration of science missions. Moreover, it enables automation and data-driven decision-making without compromising safety and performance. Recently, our group developed a hierarchy of thermal reduced-order models (TROM) by combining a physics-based modeling approach and data-driven model reduction techniques applied to flight data [2]. The resulting TROMs were found to be not only accurate but also identifiable from the flight data. Consequently, the coefficient of variance of the model parameters is small over the course of hundreds of flights, allowing for monitoring the parameter evolution trajectories as the battery ages and degrades. These parameters constitute the metrics of the generalized health of a battery. Monitoring their evolution allows such models to be used for anomaly detection and prognostics, improving early detection of abnormal behavior and thus enabling timely maintenance, longer battery life, and enhanced battery safety. For this presentation, the practicality of the thermal model will be validated on a pack of 14cells under various topology configurations such as 1S14P, 2P7S, 7S2P, and 1P14S. It is well known that manufacturing and non-uniform aging lead to variability in the performance of a cell, which is exacerbated by cell balancing during active load. Additionally, in extreme scenarios, the paramount objective is to complete the mission, regardless of the stresses on the battery. Topology-induced balancing issues further stress the battery. The goal of this study is to determine if the noise (identifiability) in the reduced-order thermal model parameters is sensitive to topology, cell spacing, cooling strategy, and manufacturing or age variability. The variability in cells is considered by assuming a multimodal distribution for microscopic parameters of a cell (such as porosity, tortuosity, reaction kinetics, volumetric thermal conductivity, and volumetric heat capacity). The compounded effect of manufacturing variability, topological selection, cooling strategies, and cell balancing ages each cell in a battery differently. The study aims to clarify whether the challenge in extracting maximum information depends on the minimum number of sensors or models used for data extraction.

Automation↗

Feasibility of Power Ramp Testing in the Advanced Test Reactor

For decades, the Halden Boiling Water Reactor (HBWR) in Norway was an international resource for assessing nuclear fuels and materials behavior and its unexpected shutdown in 2018 represented a significant loss in experimental capability for prototypical irradiation testing. In the aftermath of the closure, a study was performed to assess capability gaps related to the Accident Tolerant Fuels (ATF) program. It was concluded that the primary capability gaps left by the closure of the HBWR were the loss of prototypic in-pile Light Water Reactor (LWR) loops that provide operational transient testing and in-pile Loss-of-Coolant Accident (LOCA) testing capabilities. The study also concluded that the Advanced Test Reactor (ATR) and Transient Reactor Test Facility (TREAT) likely have the necessary key capabilities to absorb the breadth of the HBWR mission gaps related to the ATF program, but additional investments in experimental infrastructure were needed. One such investment is the design and installation of additional pressurized water loops in the medium-I positions of the ATR, hereafter referred to as I-Loops, to support power ramp testing and testing in Boiling Water Reactor (BWR) conditions. This paper gives an overview of the planned ATR I-Loops and assesses the feasibility of performing power ramp testing inside such a loop.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Motor Qualification for Long-Duration Mars Missions

Qualification of motors for deep space under extreme thermal environments to be encountered during the Mars Science Laboratory (MSL) mission is required to verify the reliability and validate mission assurance requirements. The motor assembly must survive all ground operations, plus the nominal 670 Martian-day (or sol) mission that includes summer and winter seasons of the Mars environment. The motor assembly was tested and characterized under extreme temperature conditions with reference to hardware requirements. The motor assembly has been proved to be remarkably robust and displayed no sign of degradation due to the 3 X (three times per JPL design principles) thermal environmental exposure to the punishing Mars surface operations cycles. The motor characteristics obtained before, during, and post-test comparisons for the surface operations cycles are within measurement error of one another. The motors withstood/survived 2,010 extreme temperature cycles with a Delta T of 190 C deep temperature cycles, representing three times the expected thermal cycling exposure during the MSL surface operations. The qualification test hardware elements (A200 motor assembly, encoders, and resolver) have not shown any signs of degradation due to the PQV (Package Qualification and Verification) testing. The test hardware has demonstrated sufficient life to survive the deep thermal cycles associated with MSL mission surface operations for three lives.

Ramesham, Rajeshuni↗

A Statistical Study of Solar Particle Events in Flux and Dose

The high-energy protons from solar energetic particle (SEP) events present a hazard to space systems: damage to science instruments/electronics/materials or to astronauts. A reliable estimate of the high-energy proton environment is critical to assure mission success. Important characteristics of an SEP event are fluence, peak flux, energy spectrum, time to reach the peak flux, time to reach peak dose, and properties of the cumulative dose profile after an event starts. All of these characteristics are important to understand in order to design space missions properly for both robotic and human missions. Because of the unpredictable and sporadic nature of SEP events, statistical models are often used to represent the SEP parameters described above. In a study by Jun et al. (2007), the statistics of event fluences, durations, and time intervals between events were investigated using the then available historical SEP dataset obtained from the instruments onboard the IMP-8 spacecraft. Since then, a more comprehensive SEP dataset based off of IMP-8 and GOES called Reference Data Set Version 2.0 (RDSv2.0) has become available covering the SEP events up to Year 2015 under a framework of the European Space Agency's (ESA's) Solar Energetic Particle Environment Modelling (SEPEM) project (Jiggens et al., 2018). The main objectives of this statistical study of SEP events are two-fold: First, the statistics of peak fluxes, event fluences, durations, and time intervals will be re-visited by using RDSv2.0; Second, the statistical analyses of flux and dose timing will be performed using the same dataset RDSv2.0. The results of this study will address the statistical properties of all key parameters for designing a spacecraft or a human mission where the SEP environment is an important consideration.

Whitman, K.↗

CONTAMINATION CONTROL FOR ULTRA-SENSITIVE LIFE DETECTION SCIENCE MISSIONS

"This study report summarizes technological developments in science-required contamination control for cost-capped, life-detection missions in the Solar System. Technology advances focus on developing implementable strategies to restrict contamination of the spacecraft and instruments by the launch vehicle hardware. Secondary bake out operations during cruise further reduce molecular contaminants down to femtomolar levels in the sample path. The study validated a full-spacecraft, deployable barrier design as an effective strategy to isolate the spacecraft from the pre-launch processing and launch environment (e.g., fairing acoustic materials). It accommodates late mounting of RTGs and other required prelaunch activities. A new, high-fidelity physics, contamination-transport model for particles (including cells and their parts) and science-relevant molecules (e.g., possible biomolecules) was developed to validate the barrier concept. Importantly, this model takes into account the physics of extremely clean surfaces achieved by the best traditional contamination engineering. The ability to deal with very low levels of particulate and molecular contamination makes this model unique among standard contamination modeling approaches. Modeling also demonstrated that a high-temperature bake out during interplanetary cruise of the sample collector that comprises the largest surface area in the sample path for an Enceladus orbiter reference mission, was extremely effective. This study included the evaluation of other details necessary for an effective contamination control strategy for life detection missions including feasibility of achieving parts per trillion level cleanliness for semi-volatile hydrocarbons in nitrogen purge gas, identification of launch vehicle services required for the baseline contamination control, and defining additional contamination control measures to be taken during launch operations. Key results of the study are: • New spacecraft barrier design that accommodates RTGs is readily cleanable and repairable. Deployment of a 1/3 scale model was successfully demonstrated. • The barrier reduces particle contamination (likely biological) from fairing to spacecraft by 1e-2 to 1e-3. • On-cruise bake-out of critical surfaces significantly reduced molecular contamination (by as much as 1e-12). Subsequently, the probability of a surface contamination particle being transported to an instrument by an ice particle is less than 5.1e-5 (for microbes specifically, 4.39e-10). The report concludes that a full-spacecraft barrier designed specifically for life-detection missions that require stringent control of particulate and molecular contaminates is an effective means of mitigating risks of false positive and negative results for life signature investigations. Further, secondary cleaning steps for critical sections of the sample path can be highly effective at reducing molecular contaminants to low femtomolar levels."

Contamination↗

Contamination Control for Ultra-Sensitive Life-Detection Missions

"This study report summarizes technological developments in science-required contamination control for cost-capped, life-detection missions in the Solar System. Technology advances focus on developing implementable strategies to restrict contamination of the spacecraft and instruments by the launch vehicle hardware. Secondary bake out operations during cruise further reduce molecular contaminants down to femtomolar levels in the sample path. The study validated a full-spacecraft, deployable barrier design as an effective strategy to isolate the spacecraft from the pre-launch processing and launch environment (e.g., fairing acoustic materials). It accommodates late mounting of RTGs and other required prelaunch activities. A new, high-fidelity physics, contamination-transport model for particles (including cells and their parts) and science-relevant molecules (e.g., possible biomolecules) was developed to validate the barrier concept. Importantly, this model takes into account the physics of extremely clean surfaces achieved by the best traditional contamination engineering. The ability to deal with very low levels of particulate and molecular contamination makes this model unique among standard contamination modeling approaches. Modeling also demonstrated that a high-temperature bake out during interplanetary cruise of the sample collector that comprises the largest surface area in the sample path for an Enceladus orbiter reference mission, was extremely effective. This study included the evaluation of other details necessary for an effective contamination control strategy for life detection missions including feasibility of achieving parts per trillion level cleanliness for semi-volatile hydrocarbons in nitrogen purge gas, identification of launch vehicle services required for the baseline contamination control, and defining additional contamination control measures to be taken during launch operations. Key results of the study are: • New spacecraft barrier design that accommodates RTGs is readily cleanable and repairable. Deployment of a 1/3 scale model was successfully demonstrated. • The barrier reduces particle contamination (likely biological) from fairing to spacecraft by 1e-2 to 1e-3. • On-cruise bake-out of critical surfaces significantly reduced molecular contamination (by as much as 1e-12). Subsequently, the probability of a surface contamination particle being transported to an instrument by an ice particle is less than 5.1e-5 (for microbes specifically, 4.39e-10). The report concludes that a full-spacecraft barrier designed specifically for life-detection missions that require stringent control of particulate and molecular contaminates is an effective means of mitigating risks of false positive and negative results for life signature investigations. Further, secondary cleaning steps for critical sections of the sample path can be highly effective at reducing molecular contaminants to low femtomolar levels."

contamination, life detection, barrier, modeling↗

Root Source Analysis/ValuStream[Trade Mark] - A Methodology for Identifying and Managing Risks

Root Source Analysis (RoSA) is a systems engineering methodology that has been developed at NASA over the past five years. It is designed to reduce costs, schedule, and technical risks by systematically examining critical assumptions and the state of the knowledge needed to bring to fruition the products that satisfy mission-driven requirements, as defined for each element of the Work (or Product) Breakdown Structure (WBS or PBS). This methodology is sometimes referred to as the ValuStream method, as inherent in the process is the linking and prioritizing of uncertainties arising from knowledge shortfalls directly to the customer's mission driven requirements. RoSA and ValuStream are synonymous terms. RoSA is not simply an alternate or improved method for identifying risks. It represents a paradigm shift. The emphasis is placed on identifying very specific knowledge shortfalls and assumptions that are the root sources of the risk (the why), rather than on assessing the WBS product(s) themselves (the what). In so doing RoSA looks forward to anticipate, identify, and prioritize knowledge shortfalls and assumptions that are likely to create significant uncertainties/ risks (as compared to Root Cause Analysis, which is most often used to look back to discover what was not known, or was assumed, that caused the failure). Experience indicates that RoSA, with its primary focus on assumptions and the state of the underlying knowledge needed to define, design, build, verify, and operate the products, can identify critical risks that historically have been missed by the usual approaches (i.e., design review process and classical risk identification methods). Further, the methodology answers four critical questions for decision makers and risk managers: 1. What s been included? 2. What's been left out? 3. How has it been validated? 4. Has the real source of the uncertainty/ risk been identified, i.e., is the perceived problem the real problem? Users of the RoSA methodology have characterized it as a true bottoms up risk assessment.

Brown, Richard Lee↗

Development of small radioisotope heaters.

A design study was conducted to (1) determine potential applications of small (1 to 50 watt) radioisotope heaters in manned spacecraft thermal control and life support systems and (2) develop designs for an optimum group of heaters to fulfill a maximum number of applications with mission times from 14 days to 5 years. Thirty-seven potential application areas were identified requiring up to 300 heaters ranging in size from less than 1 to over 100 watts. Safety and design criteria were selected and reference heater designs developed. Optimization analysis indicated that two heater sizes, 10- and 50-w, and two fuels, promethia and plutonia, would most efficiently meet the majority of identified applications.

Smith, T. H.↗