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NASA NTRS2019

Potential Improvements to the Nuclear Safety and Launch Approval Process for Nuclear Reactors Utilized for Space Power and Propulsion Applications

This study examines potential improvements that could be made to the nuclear safety and launch approval process for fission reactors to reduce the associated uncertainties in cost and schedule while continuing to ensure public safety and environmental protection. It concentrates on the launch approval and mission safety of fission power and propulsion applications of nuclear energy. Improvements to the launch approval process for radioisotope power systems (RPSs) are being considered elsewhere but are acknowledged throughout the report. The study considered technical, process, and organizational improvements to the launch approval processes. The study exclusively evaluated reactors that would not be started up prior to achieving a “sufficiently high orbit,” per United Nations (UN) Resolution 47/68.Potential criticality accidents were considered that could occur during a launch failure or abort or during reentry. Numerous scenarios were examined that might involve one or more Earth flybys as well as potential transportation missions that could intentionally return an active, or previously active fission reactor to Earth orbit. The Study Group was guided in its deliberations according to a number of fundamental principles. These included the paramount importance of adequate and appropriate levels of public safety and environmental protection as well as the importance of the inclusion of independent scientific, engineering, and safety reviews of the applications and proposals as a critical part of the process. Also considered was the need for the development of launch approval processes that might be different, depending upon the source of the application for launch approval, whether it be derived as a governmental launch, a commercial launch, or a hybrid/combination of the two. It is clear that all launches of nuclear reactors into space should have similar safety requirements; however, the safety review effort and the details of the analysis that are required should be commensurate with the potential hazards and the actual risk, which may differ based on the reactor design and its intended purpose. Finally, the study aimed at ensuring that whatever processes and procedures are developed should maximize the sufficiency, simplicity, and transparency of the processes. The Study Group reached five Conclusions and makes thirteen Recommendations. The Conclusions and Recommendations presented here are extensions of those presented previously in other studies. This report attempts to add specificity to the actions that need to be taken in order to move forward with successful space fission reactor programs. Without action to address the perceived and real problems in the launch approval process, designers and mission managers will be reluctant to commit the resources necessary to make space fission reactors a reality.

Camp, Allen↗

NASA NTRS2019

Assessment and Validation of Collision "Consequence" Method of Assessing Orbital Regime Risk Posed by Potential Satellite Conjunctions

Collision risk management theory requires a thorough assessment of both the likelihood and consequence of potential collision events. Satellite conjunction risk assessment has produced a highly-developed theory for assessing the likelihood of collision but neglects to account for the consequences of a given collision. While any collision may compromise the operational survival of a spacecraft, the amount of debris produced by the potential collision, and therefore the degree to which the orbital corridor may be compromised, can vary greatly among satellite conjunctions. Previous studies leveraged work on satellite collision modeling to develop a method to estimate whether a particular collision is likely to produce a relatively large or relatively small amount of resultant debris. The approximation of the number of debris pieces is dependent on a mass estimation process for the secondary objects utilizing the radar cross section of said object. This study examines the validity of the mass estimation process and establishes uncertainty bounds on the secondary object mass, which will be used to best approximate the possible consequences of a potential collision. This process is then applied to a large set of historical conjunctions to assess the frequency at which possible collisions may significantly augment the orbital debris environment in operational spacecraft.

Collision Consequence↗

NASA NTRS2016

Effect of Solar Array Plume Interactions on Hall Thruster Cathode Common Potentials

In typical implementations of spacecraft electric propulsion (EP) systems the electrical ground of the EP power processing units are resistively isolated from the main spacecraft electrical ground. Telemetry measuring the potential difference between EP power processing unit and the spacecraft electrical ground is usually referred to as the “cathode common” potential. In this paper we review flight and laboratory data on natural and EP generated plasma interactions with solar arrays, present the theory of spacecraft floating potentials, show how this theory is consistent with flight data, and extend this theory to spacecraft with high power Hall effect thrusters.

Katz, Ira↗

NASA NTRS2018

Spacecraft Contamination Control Challenges for Space Missions with Organic Compound Detection Capabilities and for Potential Sample Return

Contamination control is critical to missions with organic compound detection capabilities, and for missions targeting acquisition of samples for potential return to Earth. Significant challenges are being addressed in the design of current flight projects and conceptual mission studies at JPL. These challenges extend to both orbiting spacecraft, as well as landed missions, for future missions to Mars and Europa, and potential missions to Titan and Enceladus. Contamination control during all phases of a mission, from preliminary design through operation, is fundamental to ensure that organic compounds of terrestrial origin are controlled to ensure successful completion of science objectives. This presentation summarizes contamination control challenges specific to landed missions (which include sample acquisition, encapsulation, caching, potential sample return, and UV instruments), and orbiting missions (modeling interactions between the spacecraft, and local exospheres and plumes).

Soares, Carlos↗

NASA NTRS2020

Optimal Multi-Agent Search and Rescue Using Potential Field Theory

This paper presents an algorithm for efficient search and rescue using a multi-agent system of vehicles. The algorithm uses an artificial potential field combined with a time-varying reward function for visiting various points within the search area. The reward function is used to weight the attractiveness of these points in the potential field, and collision avoidance terms are used to repel vehicles from each other, which has the additional effect of reducing duplication of searching efforts. The algorithm generates velocity commands in real-time based on communication with the other vehicles. This framework allows vehicles to react in a dynamic environment, which is a significant advantage to simply following a-priori defined trajectories. Simulation results are presented to demonstrate the ability of the algorithm to cover the search area effectively. The algorithm is also compared to an exhaustive lawn-mower search pattern. This comparison is done via a Monte Carlo simulation with randomized target initial conditions and trajectories. The time to find the target improved by 16 and 30% in the mean and median, respectively. Additionally, this paper presents a method for analyzing the upper bound for time to find a target under the potential field guidance algorithm assuming a radially expanding search area.

John R Cooper↗

NASA NTRSDate not supplied

Electrified Aircraft Propulsion Systems: Gas Turbine Control Considerations for the Mitigation of Potential Failure Modes and Hazards

This paper provides a high-level review of the potential failure modes and hazards to which electrified aircraft propulsion (EAP) systems are susceptible, along with potential gas turbine control-based strategies to assist in the mitigation of those failures. To introduce the types of failures that an EAP system may experience, a generic EAP system is considered, consisting of gas turbine engines, mechanical drives, electric machines, power electronics and distribution systems, energy storage devices, and motor driven propulsors. The functionality provided by each of these EAP subsystems is discussed, along with their potential failure modes, and possible strategies for mitigating those failures. To further illustrate the role of gas turbine controls in mitigating EAP failure modes, an example based on a simulated EAP concept aircraft proposed by NASA is given. The effects of failures are discussed, along with turbomachinery control strategies, including reversionary control modes, and control limit logic.

Donald L Simon↗

NASA NTRS2021

Electrified Aircraft Propulsion Systems: Gas Turbine Control Considerations for the Mitigation of Potential Failure Modes and Hazards

This paper provides a high-level review of the potential failure modes and hazards to which electrified aircraft propulsion (EAP) systems are susceptible along with potential gas turbine control-based strategies to assist in the mitigation of those failures. To introduce the types of failures that an EAP system may experience, a generic EAP system is considered consisting of gas turbine engines, mechanical drives, electric machines, power electronics and distribution systems, energy storage devices, and motor driven propulsors. The functionality provided by each of these EAP subsystems is discussed along with their potential failure modes and possible strategies for mitigating those failures. To further illustrate the role of gas turbine controls in mitigating EAP failure modes, an example based on a simulated EAP concept aircraft proposed by NASA is given. The effects of failures are discussed, along with turbomachinery control strategies, including reversionary control modes, and control limit logic

Electrified Aircraft Propulsion↗

NASA NTRS2017

Spacecraft Contamination Control Challenges for Space Missions with Organic Compound Detection Capabilities and for Potential Sample Return

Spacecraft contamination control is critical to space exploration missions with organic compound detection capabilities, and also for missions targeting acquisition of samples for potential return to Earth. Significant challenges are being addressed and resolved in the design of current flight projects and conceptual mission studies at JPL. These challenges extend to both orbiting spacecraft, as well as landed missions, for future missions to Mars and Europa, and potential missions to Titan and Enceladus. Contamination control during all phases of a mission, from preliminary design through operation, is fundamental to ensure that organic compounds of terrestrial origin are controlled to ensure successful completion of science objectives. This paper examines contamination control challenges specific to landed missions (which include sample acquisition, encapsulation, caching, potential sample return, and UV instruments), and orbiting missions (modeling interactions between the spacecraft and local exospheres and plumes).

Sylvia, Margarite↗

NASA NTRS2018

An Orbiting Sample Capture and Orientation System Architecture for Potential Mars Sample Return

An orbiting sample capture and orientation system architecture for a Rendezvous and Orbiting Sample Capture System (ROCS) concept was developed to enable spacecraft based, in-orbit capture, orientation, and transfer of a Mars sample container into a containment vessel as part of a potential Mars Sample Return (MSR) campaign. An analysis of the system functions, requirements, interactions, and constraints was performed. A trade study was carried out on relevant technologies, and a set of evaluation criteria was developed to help determine the most feasible concepts for implementation. The Mars Capture and Re-orientation for the potential Next Mars Orbiter (MACARONE) concept is proposed as a promising system architecture for the ROCS Capture and Orient Module (COM). The concept uses a sliding trap door for Orbiting Sample (OS) capture, a Motorized Cups Mechanism for OS orientation, and a 2 DOF Turret Arm with a paddle for transferring the OS into a containment vessel. This approach facilitates modularity, development flexibility, test-ability in a 1G environment, analyze-ability without the need to simulate or test for 0G contact dynamics, ability to encapsulate potential dust surrounding the OS, and ability to be ejected to reduce the probability of Earth exposure to non-sterilized Mars material.

Lalla, Karan↗

NASA NTRS2018

Propulsion System Options for a Potential Sample Return Lander (SRL) for Mars

A potential Mars Sample Return (MSR) campaign would be very unique challenge and has been the focus of technology development and planning efforts at JPL for several decades. The latest mission concept study focuses on a potential Sample Return Lander (SRL). The potential SRL examined several propulsion system approaches using monopropellant and bi-propellants for the terminal descent phase. A ranking was developed based on a mathematical optimization program. This paper focuses on the evaluations conducted for these system options. Historically, monopropellant and bi-propellant propulsion systems are usually considered for this application; this study took a fresh look at both conventional State of the Art (SOA) pressure fed monopropellant and bi-propellant propulsion system and augmenting the system using small Electrically Driven Pumps (EDP) for both these propulsion systems.

Preudhomme, Michael↗

NASA NTRSDate not supplied

Anomalous and Ungrouped Carbonaceous Chondrites in the US Antarctic Meteorite Collection and their Potential Relevance to Ryugu and Bennu

With two different carbonaceous asteroid sample return missions in full swing, attention has focused on what connections can be made between the asteroid samples and the wide range of carbonaceous chondrite meteorites in worldwide collections. The US Antarctic meteorite collection contains nearly 1000 carbonaceous chondrites of various types including many in well-established groups as well as ungrouped, unusual or anomalous groups [1]. Some of the latter have been included in, or are possibly related to, recently proposed new carbonaceous chondrite classifications – CA and CY chondrites [2,3]. In addition to these, there are numerous ungrouped samples that have properties intermediate between established groups (like CM and CO; [4]), distinct from any other groups [5], or have anomalous properties that might be attributable to parent body processes such as heating, fluid interaction, or impacts [6]. Some CM anomalous or ungrouped chondrites share spectral features with Ryugu, which has a small hydration peak arguably due to hydrated minerals left after either impact heating or shock in carbonaceous chondrites [7]. PCA 91008, PCA 02012, GRO 95566, and LEW 85311 are all CMs that have experienced heating or metamorphism that may be due to impacts, solar radiation, or radiogenic decay [6]. These samples all have low H contents, C/H (bulk), and low 17O [6,8] and may hold clues to understanding the mineralogy of Ryugu, or interpretations of its spectral properties. WIS 91600, on the other hand, appears to be related to several other highly altered CM [6], and shares properties with the newly proposed CY chondrites [6]. An understanding of this grouplet will also aid in the interpretation of Bennu samples which have strong hydration features. In addition, ungrouped carbonaceous chondrites may provide valuable insights into the aqueous alteration potentially recorded in Bennu and Ryugu samples; such as the relatively moderate aqueous alteration recognized and dated at 4-5 myr after CAIs in MAC 88107 (C2-ungrouped) by [9] to the extensive aqueous alteration apparent in MIL 090292 (C1-ungrouped) [10]. Finally, LON 94101/94102 is a brecciated CM chondrite with numerous lithologies. Its appearance is similar to some of the brecciated lithologies visible at the surface of Bennu and Ryugu [11]. Although CM chondrites with multiple lithologies are common (e.g., [12]), the lithologies are often difficult to resolve at the hand specimen scale and only after some detailed e-beam characterization are the subtle lithologic differences evident (e.g., [13]). LON 94102 contains visibly distinct clasts at the hand specimen scale, relatively rare for CM breccias. The largest CM chondrites by mass from the U.S. Antarctic meteorite collection may provide insights into the extent of brecciation and heterogeneity within more typical CM chondrite-like source asteroids. For example, recent curation CT scans [14] show possible clasts within in a subsplit of ALH 83100 (CM1/2) which is the largest CM chondrite or CM chondrite pairing group in the U.S. Antarctic collection with an original mass of 3.019 kg. Similar work on additional subsplits or meteorites may aid our understanding of heterogeneity within CM chondrites from Antarctica. Initial classification of CM chondrites in U.S. Antarctic meteorite collection includes preliminary pairing when petrographically similar CM chondrites that have been previously found in the same field area. The two largest CM chondrite preliminary pairing groups by mass are the ALH 83102 (CM2) pairing group with an original mass of 2.554 kg and the EET 96005 (CM2) pairing group with an original mass of 1.125 kg. However, preliminary pairing groups assigned at classification—intrinsically— do not include stones that are petrographically distinct. Rigorous pairing group studies of CM chondrites from specific field sites are needed to investigate if there is unrecognized heterogeneity in CM chondrites from Antarctica that may represent common asteroid impactors (pre-atmospheric entry asteroids/meteoroids). Detailed pairing studies have the potential to recognize initial stones with multiple lithologies and investigate if there are stones that only sample one of those respective lithologies in the collection. These groups of heated CMs, extensively hydrated CMs, intermediate between CM and CO chondrites, and brecciated samples are all potentially relevant to Bennu and Ryugu samples, where heating, hydration, and brecciation have all come into play. These bodies might also be comprised of material intermediate to CM and CO chondrites, or at least distinct from the well-established CC groups. These small and unusual groups of carbonaceous chondrites may help to unlock new information about early solar system processes and aid in the understanding of the evolution of these carbonaceous asteroids.

meteorites↗

NASA NTRS2022

Potential impacts of projected warming scenarios on winter wheat in the UK

The goals of this study are to analyse the impacts of 1.5 and 2.0°C scenarios on UK winter wheat using a combination of Global Climate Models (GCMs), crop models, planting dates and cultivars; to evaluate the impact of increased air temperature on winter wheat phenology and potential yield; to quantify the underlying uncertainties due to the multiple sources of variability introduced by climate scenarios, crop models and agronomic management. The data used to calibrate and evaluate three crop models were obtained from a field experiment with two irrigation amounts and two wheat cultivars that have different phenology and growth habit. After calibration, the model was applied to fifty locations across the wheat-growing area of the UK to cover all the main growing regions, with most points located in the main growing areas. Four GCMs, with two cultivars and five planting dates, were simulated at the end of the century. Results of this study showed that the UK potential wheat yield will increase by 2–8% under projected climate. Farmers will need to close such a gap in the future because it will have implications in terms of food security. Future climatic conditions might increase such a gap. Adaptation measures (e.g. moving the optimal planting time), along with climate-ready varieties bred for future conditions and with precision agriculture techniques can help to reduce this gap and ensure that the future actual UK wheat production will be close to the potential.

Climate change↗

NASA NTRSDate not supplied

Evaluation of the NASA Artemis Regions of Interest for ISRU Water Mine Potential

The NASA Artemis Campaign has a stated goal to return to the Moon to maintain a sustainable presence; In-Situ Resource Utilization (ISRU) is a key part of sustainability. The regions of interest identified for the Artemis campaign are at Lunar the South Pole where water ice, a valuable resource for ISRU, has been identified. As such, a preliminary evaluation of the ISRU ice mining potential has been performed for of these regions of interest. A set of ground rules for this evaluation were developed to align with current assumptions for customer needs, hardware capabilities, an initially limited infrastructure, and lunar environments/terrain. These ground rules, and the evaluation of six regions of interest, are presented here. The site selections (ISRU and customer assets) and their associated traverses are notional and were intended only to provide a broad preliminary evaluation of the water ISRU potential of the regions. Evaluation of these regions are subject to change as decisions regarding utilization are made. Water ISRU is possible at all regions, though the degree to which each criterion are met is variable. The two regions near Shackleton ranked highest in this evaluation, while the de Gerlache region presented the most difficulties meeting the current criteria. The regions were not explicitly ranked due to the nuances associated with the high number of variables but evaluation summaries of each are presented. It should also be noted that all ISRU ‘mine’ sites in this analysis focused on smaller (few kilometer) size permanently shadowed regions (PSRs). This was necessary to meet proximity requirements between these PSRs and the highly illuminated regions needed for customers and ISRU processing. The areas identified in this study are meant to focus exploration and reconnaissance efforts needed to better evaluate the ISRU potential.

In-situ resource utilization↗

NASA NTRSDate not supplied

Evaluation of the NASA Artemis Regions of Interest for ISRU Water Mine Potential

In-situ resource utilization↗

NASA NTRSDate not supplied

A Machine Learning-Derived Atomistic Potential for Y2Si2O7

Incorporation of SiC/SiC ceramic matrix composite (CMC) hot section components into aircraft engines promises to increase efficiency and safety. However, SiC/SiC CMCs are subject to water vapor-induced oxidation and recession at the high temperatures of engine operation, and thus environmental barrier coatings (EBCs) are required to reduce this degradation and enable their widespread adoption. An understanding of EBCs failure mechanisms, including thermochemical and thermomechanical mechanisms, is essential as coating degradation leads to reduced CMC component service life. Computational modeling approaches can provide insight into EBC material properties important for coating design. However, density functional theory (DFT) is computationally expensive and atomistic potentials are lacking for materials of interest. In this work, we utilize a machine learning approach and DFT training data to parameterize atomistic potentials for two candidate EBC materials, Y2Si2O7 and Yb2Si2O7. These potentials enable near DFT-accurate calculations of thermodynamic and thermomechanical properties essential to EBC design.

Cameron J Bodenschatz↗

NASA NTRSDate not supplied

Spectroscopy of Mount Etna Lava Flows as A Proxy for Age: A Potential Analogue to Recent Volcanism on Venus

There is growing evidence of geologically recent volcanism at Venus [1–3], a question that may be resolved by forthcoming missions to our sister planet that will make spectroscopic measurements of the surface. The thick, relatively opaque atmosphere of Venus makes observation difficult, but a few key atmospheric windows in the near-infrared (NIR) around 1 μm make emission from the surface detectable [4]. At these wavelengths, the spectroscopic signature of rocks are due to its primary mineralogy and chemistry, as well as the presence of secondary weathering minerals [2, 5, 6]. If the degree of alteration can be tied to the spectroscopy of Venus analogue materials, then spectroscopy of venusian lava flows can potentially reveal their degree of weathering and thus their age, which in turn gives an estimate of the extent of recent volcanism [2, 7]. A potential Earth analogue to volcanoes on Venus is Mount Etna in Sicily, Italy [8]. This composite volcano is among the most active in the world and features mafic lava flows with definitive ages that exhibit varying degrees of alteration [9]. While Mount Etna is not a perfect analogue due to its different weathering environment, the natural age progression of altered basaltic rock can be a useful comparison. Here, we will investigate how weathering at Mount Etna affects spectroscopic measurements and if this can be used as a proxy for Venus. While planned missions to Venus such as DAVINCI, VERITAS, and EnVision will measure NIR emissivity from the surface, Kirchhoff’s Law states that e = 1 − r, where e is emissivity and r is reflectance, meaning that NIR emissivity can be estimated from reflectance measurements [10]. Given its relative ease, laboratory reflectance spectroscopy is a useful tool to efficiently test potential Venus analogue materials.

Gabriel L Eggers↗

NASA NTRS2023

Spacecraft Floating Potential Measurements for the Wind Spacecraft

Analysis of 8,804,545 electron velocity distribution functions, observed by the Wind spacecraft near 1 au between 2005 January 1 and 2022 January 1, was performed to determine the spacecraft floating potential, ∅ sc . Wind was designed to be electrostatically clean, which helps keep the magnitude of ∅ sc small (i.e., ∼5–9 eV for nearly all intervals) and the potential distribution more uniform. We observed spectral enhancements of ∅ sc at frequencies corresponding to the inverse synodic Carrington rotation period with at least three harmonics. The two-dimensional histogram of ∅ sc versus time also shows at least two strong peaks, with a potential third, much weaker peak. These peaks vary in time, with the intensity correlated with solar maximum. Thus, the spectral peaks and histogram peaks are likely due to macroscopic phenomena like coronal mass ejections (solar cycle dependence) and stream interaction regions (Carrington rotation dependence). The values of ∅ sc are summarized herein and the resulting data set is discussed.

Lynn B Wilson III↗

NASA NTRSDate not supplied

The Scientific Significance of Potential Samples From the Jezero Crater Rim

The Mars 2020 Perseverance rover has been exploring Jezero crater, Mars to characterize the geology,assess the potential for rocks to represent ancient habitable environments and/or preserve biosignatures, and collect a suite of scientifically compelling samples for return to Earth (Farleyet al.,2020).Thus far, Perseverance has collected samples that represent the diversity of igneous materials encountered on the crater floor and a suite of aqueously deposited sedimentary rocks from the fanand margin units(Simon et al., 2023; Bosak et al., 2024). When the rover ascendsthe crater rimit will encounter rocktypesthat are not included in the current sample cache. These include rocks fromthe Noachian whose mineralogical, geochemical, and geochronological recordswould greatly expand our understanding of early Mars. Some of the exposures are understood to come from subsurface aquifers that may represent the most ancient potentially habitablesubsurfaceenvironmentson Mars(Ehlmann et al., 2024). Samples ofthese rocks will add uniquescientific value tothe sample cache and to the Mars sample returnprogramby addressing outstanding questions in Mars science including potential habitability and how the climate and the interior of the planet evolved through time.

Mars 2020↗