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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Protecting Crew and Surface Systems with a Long-Duration Lunar Safe Haven

NASA’s Artemis program will send astronauts to the lunar surface for extended mission durations throughout the 2030s, with a focus on sustainability and extensibility for Mars exploration, as described in NASA’s “Artemis Plan”. However, NASA must place more emphasis on protecting both the crew and the exploration surface systems if they hope to achieve long-duration sustainability on the lunar surface. It is now reasonably achievable with excavation, construction, and autonomy technologies to achieve a significant level of protection that architectures have been unable to achieve to date. The Lunar Safe Haven (LSH) was proposed to protect astronauts, electronics, and other surface exploration systems from the hazards of the lunar environment, including radiation, micrometeoroid strikes, lunar dust, thermal vacuum, etc. During the study, Level Zero Requirements were developed for the LSH, and a decision analysis framework was baselined to evaluate concepts. The LSH Study also performed a comprehensive trade study, during which it identified numerous alternatives for establishing and maintaining a safe haven shelter on the lunar surface. This paper reviews the products developed during the study and presents the final recommendations.

radiation shielding↗
NASA NTRSDate not supplied

Venous Gas Embolism: Review to Quantify a Safe Volume of Air in Intravenous Fluids Bags for Spaceflight Applications

INTRODUCTION: The ability to create intravenous fluids (IVF) in-situ from the potable water supply of a spaceflight vehicle or habitat is a desired capability for an exploration medical system. In order to define an acceptable volume of air in IVF bags, an understanding of the volume of venous gas embolism as it relates to negative outcomes is needed. The purpose of this study is to review the literature to determine if there is a known volume of gas that contributes to mortality and/or morbidity that could be used to define requirements for rapid IVF infusion in microgravity. METHODS: A literature review was conducted of the PubMed database using the syntax: (Venous) AND (Gas OR Air) AND (Embolism) AND (Morbidity) AND (Mortality) AND (Volume) as well as manual review of references from relevant articles. 151 articles were screened excluding partial text and pediatric articles. Studies were reviewed for identification of volume of venous gas embolism associated with morbidity and/or mortality, which identified 27 articles. RESULTS: Reviewed literature included animal studies, case reports, and review articles. A high variation of proposed volumes contributing to mortality was reported. The limited human data values ranged from 20 ml to 200 ml of infused air with mortality estimated to be 48 – 80%. No studies evaluated human morbidity in any capacity. DISCUSSION: The lack of consensus on the safe volume of infused air has potential ramifications for IVF use in spaceflight as current technologies to create IVF from potable water may introduce air in IVF bags. While current microgravity infusion protocols call for the use of inline air removal filters, commercially available options have flow rate limitations that preclude rapid infusion in a resuscitation scenario. Such filters may be used in parallel to increase flow rate, but the time required to set up such a system may exclude its use during a medical emergency. Additionally, these consumable filters drive up the overall mass and volume of the medical system. Identification of a safe volume of air in IVF would allow for guidelines for the in-situ production of IVF in future spaceflight vehicles/habitats.

Christopher R Woodard↗
NASA NTRS2021

Autonomous Safe Landing Site Detection for a FutureMars Science Helicopter

Future Mars Rotorcrafts require advanced navigation capabilities to enable all terrain access for science investigations with long distance flights that are executed fully autonomously. A critical component is the ability to safely land in hazardous terrain as part of a mission, or triggered by an emergency situation. In this paper, we present an advanced navigation system for continuous on-board terrain reconstruction for the purpose of hazard-free landing site detection for the autonomous navigation of a Mars Science Helicopter - a JPL research concept that investigates the feasibility of flying a multi-kilogram science payload at various Mars science locations, with flight ranges of multiple kilometers per flight. Our approach builds on a visionbased perception system that incorporates an on-board visualinertial state estimator augmented by a laser altimeter (range- VIO), and a structure-from-motion 3D reconstruction approach that uses a single, downward-looking camera to provide dense depth measurements while the vehicle is in motion. Depth measurements are accumulated in a local, robot-centric, multiresolution elevation map that is analyzed by a landing site detector to extract safe landing areas below the rotorcraft, based on a heuristic that includes slope, roughness and the presence of landing hazards. Detected landing sites are prioritized by an on-board autonomy engine that either selects suitable landing sites for immediate landing maneuvers, or can explore a terrain location as part of a mission in order to find a best landing site in a pre-planned area. We demonstrate and evaluate our approach on simulated data and data acquired with a surrogate unmanned aerial system (UAS) executing flights over relevant terrain.

Tzanetos, Teddy↗
NASA NTRS2021

Multi-Resolution Elevation Mapping and Safe Landing Site Detection with Applications to Planetary Rotorcraft

In this paper, we propose a resource-efficient approach to provide an autonomous UAV with an on-board perception method to detect safe, hazard-free landing sites during flights over complex 3D terrain. We aggregate 3D measurements acquired from a sequence of monocular images by a Structure-from-Motion approach into a local, robot-centric, multi-resolution elevation map of the overflown terrain, which fuses depth measurements according to their lateral surface resolution (pixel-footprint) in a probabilistic framework based on the concept of dynamic Level of Detail. Map aggregation only requires depth maps and the associated poses, which are obtained from an on-board Visual Odometry algorithm. An efficient landing site detection method then exploits the features of the underlying multi-resolution map to detect safe landing sites based on the slope, roughness, and quality of the reconstructed terrain surface. The evaluation of the performance of the mapping and landing site detection modules are analyzed independently and jointly in simulated and realworld experiments in order to establish the efficacy of the proposed approach.

Brockers, Roland↗
NASA NTRSDate not supplied

Lidar-Based Safe Site Relative Navigation

There has been a renewed focus in exploration of the lunar surface and maximizing scientific potential of such missions is made possible in part by minimizing the time required to set up operations; that is, reducing transit time on the surface by increasing the landing precision with respect to the intended target. Established SPLICE project precision landing requirements necessitate a navigation filter architecture and underlying models developed specifically with these needs in mind. To date, test flights to characterize SPLICE GNC system performance have not provided a means to divert from the a priori selected landing site due to hazardous conditions. With the inclusion of a new sensor, the HDL, coupled with safe landing site selection algorithms, GNC can divert from the originally planned trajectory and navigate relative to the new targeted landing site. This work presents a novel hazard relative measurement model and covariance transformation methodology that enable the navigation system to inform a safe-site relative guidance profile to meet project precision landing goals.

Navigation↗
NASA NTRS2024

Ensuring Safe Decision-Making on the Moon and Mars: Cognitive Performance Assessment for Exploration Class Mission EVA

Extravehicular activity (EVA) is one of the most dangerous and cognitively demanding actions that astronauts can execute, and the cognitive demands associated with future partial gravity EVA on the Moon and Mars are expected to be higher compared to microgravity EVA currently conducted from the International Space Station (ISS). Decrements in cognitive performance present an important risk to crew safety during exploration mission class EVA. Yet there is currently insufficient data to characterize cognitive performance prior to, during, and following EVA. Furthermore, it is still unclear which cognitive domains are most important for conducting mission critical decisions with crew safety implications. To address this gap, we conducted a cognitive task analysis (CTA) of EVA to characterize the procedures, the cognitive demands required, and the critical safety decisions associated with decrements in cognitive performance. We used the applied cognitive task analysis method as outlined by Militello and Hutton (1998) and conducted interviews with subject matter experts (SMEs) in EVA at NASA Johnson Space Center in summer 2024. Interviews focused on exploration EVA and elicited feedback from SMEs on the cognitive skills required for specific EVA tasks including cognitive strategies, critical cues, and decision-making strategies. A cognitive demands table was assembled to consolidate and synthesize the information from all interviews. The information from this cognitive task analysis will inform ongoing work to identify the key cognitive domains for safe decision-making during exploration mission class EVA on the Moon and Mars. This work will importantly provide a link between cognitive domains identified in the cognitive task analysis and operationally-relevant performance metrics collected during spaceflight and simulation EVA that can be tracked and assessed by NASA mission operations. Ultimately, this work will aid in the development and application of exploration class cognitive performance monitoring capabilities to improve safe decision-making and inform EVA planning on future spaceflight missions to the Moon and Mars.

Steven R Anderson↗
DOE OSTI2020

Regulatory Development Challenges and Opportunities for the Safe and Secure Transport of Radioactive Materials

Drafting regulations for transport safety and transport security achieve two separate objectives, which can lead to divergent outcomes. With transport safety, the principle goal is to protect the public and the environment from the effects of ionizing radiation, while in contrast, the principle goal of transport security is to protect the material from malicious actors. While many Member States may have transport safety regulations for radioactive materials, transport security regulatory development is still in its nascent stages globally. Trying to develop harmonized transport safety and transport security regulations could lead to challenges ranging from differences in terminology used in transport safety versus terminology uses in transport security, roles and responsibilities for the variety of stakeholders involved in transport, and finally, the possible role of multiple competent authorities in governing the transport of dangerous goods, which includes radioactive material. While the International Atomic Energy Agency (IAEA) is currently developing a process of a methodology for drafting transport security regulations, any process must address both safety considerations and security requirements. (As the most vulnerable part of the life cycle of radioactive materials, the need for harmonized transport safety/transport security regulations is essential.) This paper investigates the regulatory elements of the safety-security interface for nuclear and other radioactive material in transport. Examining challenges including use of terms, the role of multiple competent authorities, and practical challenges involved in the safe and secure transport of radioactive material, the paper analyzes the need for integrated regulatory development for the safe and secure transport of these materials.

Anderson, Kimberly↗
DOE OSTI2022

The Nuclear Fuel Cycle: Safe Management of Spent Nuclear Fuel

The aim for storage of spent nuclear fuel (SNF) either in wet or in dry storage systems is to ensure general safety objective s are met throughout a desired storage period. Staff at the Savannah River National Laboratory (SRNL), in collaborations with partners at other national laboratories, industry research organizations, and the University of South Carolina (UofSC), have performed materials aging testing and analyses, and have established nuclear materials aging management programs to support extended periods of safe storage of research reactor (RR) SNF and of commercial power reactor (PR) SNF pending ultimate disposal. Several example challenges include susceptibility of aluminum SNF from research reactors to corrosion in poor quality water (wet storage). In dry storage, aluminum SNF can release hydrogen via radiolysis of the hydrated oxides on the aluminum cladding. Austenitic stainless steel canisters used for dry storage are susceptible to chloride-induced stress corrosion cracking (outside-in attack) that threaten the confinement boundary provided by the canister. This paper further describes these challenges, among others, and the formulated solutions to support extended safe storage of SNF.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

TRISO Fuel for High-Temperature Passively-Safe Nuclear Reactors

The poster entitled "TRISO Fuel for High-Temperature Passively-Safe Nuclear Reactors" presents reasons why TRISO fuel is a safe nuclear fuel. The poster contains four blocks: Multiple barriers to fission product release, Thermal stability, Chemical compatibility and Safety and Performance. Each block present information on the TRISO fuel in terms of the mechanical, chemical and thermal properties. In summary the safety and performance of the TRISO fuel based on the experimental results is shown.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Safe passage of American Eels through a novel hydropower turbine

Abstract Objective Study the effects of downstream passage through a novel turbine designed for fish safety, the Restoration Hydro Turbine (RHT), on American Eels Anguilla rostrata in a recirculating turbine test facility. Methods A 55‐cm‐diameter RHT was operated under 10 m of hydraulic head and 667 revolutions/min. In total, 131 eels were passed through the turbine and 43 eels were used as experimental controls (length = 33.9–65.5 cm). High‐speed video of passage through the runner region was captured for 89% of turbine‐passed eels, and injury and behavioral effects were recorded immediately before and after passage, as well as after a 48‐h holding period. A subset of 37 eels was additionally examined with X‐ray imaging for internal injuries. Result The 48‐h survival rate for both treatment and control groups was 100%, with no major internal or external injuries present after the holding period. Conclusion This is a substantial improvement over eel survival rates through conventional Kaplan and Francis turbines, which may range from 40% to 95%, and suggests that hydropower turbines designed for safe downstream fish passage could be implemented without major impacts to eels.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

A Data-Driven Framework for Power System Event Type Identification via Safe Semi-Supervised Techniques

Herein this paper investigates the use of phasor measurement unit (PMU) data with deep learning techniques to construct real-time event identification models for transmission networks. Increasing penetration of distributed energy resources represents a great opportunity to achieve decarbonization, as well as challenges in systematic situational awareness. When high-resolution PMU data and sufficient manually recorded event labels are available, the power event identification problem is defined as a statistical classification problem that can be solved by numerous cutting-edge classifiers. However, in real grids, collecting tremendous high-quality event labels is quite expensive. Utilities frequently have a large number of event records without in-depth details (i.e., unlabeled events). To bridge this gap, we propose a novel semi-supervised learning-based method to improve the performance of event classifiers trained with a limited number of labeled events by exploiting the information from massive unlabeled events. In other words, compared to existing data-driven methods, our method requires only a small portion of labeled data to achieve a similar level of accuracy. Meanwhile, this work discusses and addresses the performance degradation caused by class distribution mismatch between the training set and the real applications. Based on the proposed safe learning mechanism, our model does not directly use all unlabeled events during model training, but selectively uses them through a comprehensive evaluation procedure. Numerical studies on a sizable PMU dataset have been used to validate the performance of the proposed method.

42 ENGINEERING↗
DOE OSTI2025

Safe Reinforcement Learning-Based Transient Stability Control for Islanded Microgrids With Topology Reconfiguration

This paper proposes a safe reinforcement learning (RL)-based transient stability emergency control (TSEC) method for islanded microgrids. RL requires extensive interaction with the environment to learn control strategies, hence, a data-driven approach is used as a substitute for time-consuming time-domain simulation calculations. Deep sigma point processes (DSPP), which is a Gaussian process model, is utilized to predict the normal distribution of transient stability of microgrids and to construct a transient stability chance constraint. Reward-constrained policy optimization (RCPO) can simultaneously achieve objective prediction, policy learning, and constraint cost coefficient update across multiple timescales. RCPO interacts with the DSPP-based microgrid environment through a multi-process parallel manner, greatly increasing the training speed. Case studies on a real islanded microgrid demonstrate that the proposed method can efficiently and quickly obtain the optimal emergency control strategy while adhering to all hard constraints.

14 SOLAR ENERGY↗
NASA NTRS2001

Passive imaging based hazard avoidance for spacecraft safe landing

In this paper, a new and fast passive sensing based hazard avoidance approach for spacecraft safe landing is suggested. This approach contains two important algorithms: a texture based landing site selection algorithm and a landing site slope estimation algorithm.

spacecraft safe landing passive imaging homography↗
NASA NTRS1995

(abstract) The Design of a Benign Fail-safe Mechanism Using a Low-melting-point Metal Alloy Coupler

Because the alpha proton X ray spectrometer (APXS) sensor head on the Mars Pathfinder rover, Sojourner, is placed on Martian soil by the deployment mechanism (ADM), the rover would be crippled if the actuator fails when the mechanism is in its deployed position, as rover ground clearance is then reduced to zero. This paper describes the unique fail-safe mounted on the ADM, especially the use of a low-temperature-melting alloy as a coupler device. The final form of the design is a low-melting-point metal pellet coupler, made from Cerrobend, in parallel with a Negator spring pack. In its solid state, the metal rigidly connects the driver (the actuator) and the driven part (the mechanism). When commanded, a strip heater wrapped around the coupler melts the metal pellet (at 60(deg)C), allowing the driven part to turn independent of the driver. The Negator spring retracts the mechanism to its fully stowed position. This concept meets all the design criteria, and provides an added benefit. When the metal hardens the coupler once again rigidly connects the actuator and the mechanism. The concept presented here can easily be applied to other applications. Anywhere release devices are needed, low-melting-point couplers can be considered. The issues to be concerned with are thermal isolation, proper setting of the parts before actuation, and possible outgassing concerns. However, when these issues are overcome, the resulting release mechanism can promise to be the most light, simple, power conserving alternative available.

low-melting-point alloys couplers Negator springs ↗
NASA NTRS2005

A novel tiered sensor fusion approach for terrain characterization and safe landing assessment

This paper presents a novel tiered sensor fusion methodology for real-time terrain safety assessment. A combination of active and passive sensors, specifically, radar, lidar, and camera, operate in three tiers according to their inherent ranges of operation. Low-level terrain features (e.g. slope, roughness) and high-level terrain features (e.g. hills, craters) are integrated using principles of reasoning under uncertainty. Three methodologies are used to infer landing safety: Fuzzy Reasoning, Probabilistic Reasoning, and Evidential Reasoning. The safe landing predictions from the three fusion engines are consolidated in a subsequent decision fusion stage aimed at combining the strengths of each fusion methodology. Results from simulated spacecraft descents are presented and discussed.

fuzzy reasoning↗
NASA NTRS2006

Passive imaging based multi-cue hazard detection spacecraft safe landing

Accurate assessment of potentially damaging ground hazards during the spacecraft EDL (Entry, Descent and Landing) phase is crucial to insure a high probability of safe landing. A lander that encounters a large rock, falls off a cliff, or tips over on a steep slope can sustain mission ending damage. Guided entry is expected to shrink landing ellipses from 100-300 km to -10 km radius for the second generation landers as early as 2009. Regardless of size and location, however, landing ellipses will almost always contain hazards such as craters, discontinuities, steep slopes, and large rocks. It is estimated that an MSL (Mars Science Laboratory)-sized lander should detect and avoid 16- 150m diameter craters, vertical drops similar to the edges of 16m or 3.75m diameter crater, for high and low altitude HAD (Hazard Detection and Avoidance) respectively. It should also be able to detect slopes 20' or steeper, and rocks 0.75m or taller. In this paper we will present a passive imaging based, multi-cue hazard detection and avoidance (HDA) system suitable for Martian and other lander missions. This is the first passively imaged HDA system that seamlessly integrates multiple algorithm-crater detection, slope estimation, rock detection and texture analysis, and multicues- crater morphology, rock distribution, to detect these hazards in real time.

hazard detection↗
NASA NTRS2005

Safe Agents in Space: Preventing and Responding to Anomalies in the Autonomous Sciencecraft Experiment

This paper describes the design of the Autonomous Sciencecraft Experiment, a software agent that has been running on-board the EO-I spacecraft since 2003. The agent recognizes science events, retargets the spacecraft to respond to the science events, and reduces data downlink to only the highest value science data. The autonomous science agent was designed using a layered architectural approach with specific redundant safeguards to reduce the risk of an agent malfUnction to the EO-I spacecraft. The agent was designed to be "safe" by first preventing anomalies, then by automatically detecting and responding to them when possible. This paper describes elements of the design that increase the safety of the agent, the anomalies that occurred during the experiment, and how the agent responded to these anomalies.

autonomous science agent↗