A Polynomial-time Algorithm for Solving Certain Classes of Rank Minimization Problem
We present a non-interior point based, polynomial-time, algorithm for solving certain classes of rank minimization problem.
Rank↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A New Class Of Opto-Electronic Oscillators (OEO) for Microwave Signal Generation and Processing
A new class of oscillators based on photonic devices is presented. These opto-electronic oscillators (OEO's) generate microwave oscillation by converting continuous energy from a light source using a feedback circuit which includes a delay element, and electro-optic switch, and a photodetector. Different configurations of OEO's are presented, each of which may be applied to a particular application requiring ultra-high performance, or low cost and small size.
oscillators↗
Heavy-Ion Test Results of Several Commercial Components for Use in a JPL Class D Interplanetary Mission Payload
This paper presents recent heavy ion single-event effects test results for commercial off the shelf devices. Data was taken in CY17 for device evaluation for use in a Class D NASA interplanetary mission payload.
Allen, Gregory R.↗
A New Class of Flares from Accreting Supermassive Black Holes
Accreting supermassive black holes (SMBHs) can exhibit variable emission across the electromagnetic spectrum and over a broad range of timescales. The variability of active galactic nuclei (AGNs) in the ultraviolet and optical is usually at the few tens of per cent level over timescales of hours to weeks1. Recently, rare, more dramatic changes to the emission from accreting SMBHs have been observed, including tidal disruption events2,3,4,5, ‘changing look’ AGNs6,7,8,9 and other extreme variability objects10,11. The physics behind the ‘re-ignition’, enhancement and ‘shut-down’ of accretion onto SMBHs is not entirely understood. Here we present a rapid increase in ultraviolet–optical emission in the centre of a nearby galaxy, marking the onset of sudden increased accretion onto a SMBH. The optical spectrum of this flare, dubbed AT 2017bgt, exhibits a mix of emission features. Some are typical of luminous, unobscured AGNs, but others are likely driven by Bowen fluorescence—robustly linked here with high-velocity gas in the vicinity of the accreting SMBH. The spectral features and increased ultraviolet flux show little evolution over a period of at least 14 months. This disfavours the tidal disruption of a star as their origin, and instead suggests a longer-term event of intensified accretion. Together with two other recently reported events with similar properties, we define a new class of SMBH-related flares. This has important implications for the classification of different types of enhanced accretion onto SMBHs.
Benny Trakhtenbrot↗
Heat Shields for Aerogravity Assist Vehicles Whose Deceleration at Titan Saves Mass for Future Flagship Class Exploration of Enceladus
A mission of great Astrobiological interest is one that would search for life signatures associated with the oceans and geysers of Enceladus [1]. Spilker et al., [2] have shown in a 2009 paper that use of an Aerogravity Assist (AGA) maneuver with a blunt body in Titan’s atmosphere could enable a Flagship Class Mission to Enceladus within reasonable cost ($3 B) and mission duration (14 years). This paper will summarize the 2023 Decadal Survey (DS) Whitepaper by Arnold, et al. [3] that estimated heat shield masses for an AGA vehicle whose deceleration in Titan’s atmosphere saves mass for future missions to explore Enceladus. This study focused on Titan AGA for an Enceladus lander corresponding to mission “E” in the Spilker, et al. paper [2]. The analysis is the first reported for heat shield requirements for an AGA aeroshell that accounts for the convective and radiation heating arising from flight in Titan’s atmosphere.
James O. Arnold↗
The Effect of Anode Configuration on the Plasma Plume of a 25-A class Hollow Cathode
The effect of anode configuration on the plasma plume properties of a 25-A class hollow cathode are experimentally characterized. At a nominal operating condition of 20.8 A and 14.7 sccm of xenon, the cathode was operated with two axially-segmented anodes of different diameters at varying distance from the cathode. A fast, reciprocating motion stage was used to rapidly insert an ion saturation probe and an emissive probe on cathode centerline, and from those measurements, spatial profiles of plasma density, plasma potential, and electron temperature were calculated. For both anode diameters, maximum plasma potential and electron temperature increased with increasing anode distance. However, the 64-mm diameter anode was found to be significantly more sensitive to position, with measurements indicating that parameters changed continuously with position instead of an instantaneous mode change at a certain critical distance. The 254-mm diameter, in contrast, showed much more similar plasma property profiles across the range of anode positions tested and much smaller changes per unit increase in distance. These results are discussed in the context of assessing anode design for component-level cathode tests.
Space propulsion↗
The Effect of Anode Configuration on the Plasma Plume of a 25-A class Hollow Cathode
The effect of anode configuration on the plasma plume properties of a 25-A class hollow cathode are experimentally characterized. At a nominal operating condition of 20.8 A and 14.7 sccm of xenon, the cathode was operated with two axially-segmented anodes of different diameters at varying distance from the cathode. A fast, reciprocating motion stage was used to rapidly insert an ion saturation probe and an emissive probe on cathode centerline, and from those measurements, spatial profiles of plasma density, plasma potential, and electron temperature were calculated. For both anode diameters, maximum plasma potential and electron temperature increased with increasing anode distance. However, the 64-mm diameter anode was found to be significantly more sensitive to position, with measurements indicating that parameters changed continuously with position instead of an instantaneous mode change at a certain critical distance. The 254-mm diameter, in contrast, showed much more similar plasma property profiles across the range of anode positions tested and much smaller changes per unit increase in distance. These results are discussed in the context of assessing anode design for component-level cathode tests.
space propulsion↗
Characterization of the Eugene Stansbery-Meter Class Autonomous Telescope on Ascension Island
In a focused effort to meet full operational capability for NASA’s Eugene Stansbery-Meter Class Autonomous Telescope (ES-MCAT), a thorough system characterization analysis was completed. NASA’s Orbital Debris Program Office (ODPO) utilizes ES-MCAT as the primary sensor for characterizing the geosynchronous Earth orbit (GEO) environment to acquire photometric data of small, faint debris objects in or near GEO. ES-MCAT is located on Ascension Island in the middle of the Atlantic Ocean at nearly 8° South latitude and 14° West longitude. This location provides dark skies suited for faint object observations but is also continuously subject to a harsh environment exposed to volcanic ash and salt spray. To better assess the overall system performance of the optical instrument, a historical assessment of the system’s performance was conducted. This analysis investigated all systematic and optical operational data to determine the overall performance parameters for ES-MCAT. A complete optical system throughput calculation was performed to determine the optimal filter for observing orbital debris in GEO orbits. The responses of each optical component to the solar spectrum, with atmospheric absorption, were multiplied and integrated to give ES-MCAT’s total system response for various filters. With the highest flux values, the Sloan Digital Sky Survey (SDSS) r′ and g′ were determined to be the optimal filters for ES-MCAT observations. Further analysis with known GEO debris objects enabled the selection of the r′ filter for characterization of the GEO debris population. A detailed overview of the optical system throughput, data reduction, photometric and astrometric data, and other system characteristics that define ES-MCAT are discussed.
Corbin L Cruz↗
Intent Modeling and Conflict Probability Calculation for Operations in Upper Class E Airspace
This work presents a probabilistic operational intent model for vehicles operating in upper Class E airspace. A hybrid method is developed to calculate the intent conflict probability leveraging and extending past works on probabilistic conflict computation. Simulation results verify that the probabilistic intent model can accurately encompass the uncertain positions of each vehicle type, that are a result of wind prediction errors and vehicle performance. A comparison with past methods showed that the proposed hybrid method captures the intent conflict probability with better accuracy, especially for a larger look-ahead horizon, and computational time is reasonable for real-time applications. An example is presented to illustrate the use of the intent conflict probability in strategic planning applications.
Air traffic management↗
Intent Modeling and Conflict Probability Calculation for Operations in Upper Class E Airspace
This work presents a probabilistic operational intent model for vehicles operating in upper Class E airspace. A hybrid method is developed to calculate the intent conflict probability leveraging and extending past works on probabilistic conflict computation. Simulation results verify that the probabilistic intent model can accurately encompass the uncertain positions of each vehicle type, that are a result of wind prediction errors and vehicle performance. A comparison with past methods showed that the proposed hybrid method captures the intent conflict probability with better accuracy, especially for a larger look-ahead horizon, and computational time is reasonable for real-time applications. An example is presented to illustrate the use of the intent conflict probability in strategic planning applications.
Air traffic management, operational intent, confli↗
An Astro-Animation Class: Optimizing Artistic, Educational and Outreach Outcomes
The authors investigate how teaching art and astronomy together has the potential to inspire new art forms, enhance scientific public outreach, and promote art and science education. The authors teach an astro-animation class at the Maryland Institute College of Art in partnership with NASA scientists. The animations explore science in creative ways. Astrophysicists, educators, students, and the general public were surveyed to evaluate the experiences, and benefits from this project. The responses were very positive -the program is an effective way to stimulate art students to learn science, share an artist’s viewpoint beyond the classroom, and engage with the public.
Animation↗
Science Objectives for Flagship-Class Mission Concepts for the Search for Evidence of Life at Enceladus
Cassini revealed that Saturn's Moon Enceladus hosts a subsurface ocean that meets the accepted criteria for habitability with bio-essential elements and compounds, liquid water, and energy sources available in the environment. Whether these conditions are sufficiently abundant and collocated to support life remains unknown and cannot be determined from Cassini data. However, thanks to the plume of oceanic material emanating from Enceladus’ south pole, a new mission to Enceladus could search for evidence of life without having to descend through kilometers of ice. In this article, we outline the science motivations for such a successor to Cassini, choosing the primary science goal to be determining whether Enceladus is inhabited and assuming a resource level equivalent to NASA's Flagship-class missions. We selected a set of potential biosignature measurements that are complementary and orthogonal to build a robust case for any life detection result. This result would be further informed by quantifications of the habitability of the environment through geochemical and geophysical investigations into the ocean and ice shell crust. This study demonstrates that Enceladus’ plume offers an unparalleled opportunity for in situ exploration of an Ocean World and that the planetary science and astrobiology community is well equipped to take full advantage of it in the coming decades.
Enceladus↗
Upper Class E Traffic Management (ETM) and ATM-X
This is a slide set to be used as part of a panel presentation at the Association for Unmanned Vehicle Systems International's XPONENTIAL event. The contents present the organization of the work in Upper Class E Traffic Management (ETM) within the Project structure, the background and need for the work, ongoing efforts, and next steps.
Upper E↗
Conflict Resolution Strategies for Balloon-Airship Encounters in Upper Class E Air Traffic Management (ETM)
This paper examines strategic conflict resolution strategies for pair-wise high-altitude balloon, airship encounters. By strategic is meant that the conflict is identified (detected) at the time of flight plan submission or flight plan alteration through a service, such as an ETM Service Supplier (ESS). We investigate optimal control solutions for two classes of problems: non-cooperative, where the balloon must alter its ascent trajectory in order to avoid the airship and cooperative, where both vehicles make maneuvers through a negotiation protocol.
airship balloon negotiation optimal control↗
Conflict Resolution Strategies for Balloon-Airship Encounters in Upper Class E Air Traffic Management (ETM)
This paper examines strategic conflict resolution strategies for pair-wise high-altitude balloon, airship encounters. By strategic is meant that the conflict is identified (detected) at the time of flight plan submission or flight plan alteration through a service, such as an ETM Service Supplier (ESS). We investigate optimal control solutions for two classes of problems: non-cooperative, where the balloon must alter its ascent trajectory in order to avoid the airship and cooperative, where both vehicles make maneuvers through a negotiation protocol.
airship balloon negotiation optimal control↗
Emitter Surface Temperature Measurements of a 25-A Class Hollow Cathode
The axial emitter surface temperature profile is experimentally characterized for a 25-A class hollow cathode operating across a range of operating conditions. Profiles were measured using aratio pyrometry diagnostic featuring a fiber optic inserted into the emitter region using a fast motion stage. Emitter temperature is found to increase with increasing discharge current, decreasing flow rate, and increasing magnetic field strength. Across a range of 10 –29 A, the maximum emitter temperature increased 176 ºC, an order of magnitude more than the changes measured for flow rate or magnetic fields strength. Profiles were generally self-similar across all operating conditions, and the difference between maximum and minimum emitter temperature never surpassed 10%, indicating that this cathode design results in satisfactory emitter utilization across its operating envelope
space propulsion↗
Strategy for Developing Technologies for Megawatt-class Nuclear Electric Propulsion Systems
A strategy for maturing the technologies required for a megawatt-class nuclear electric propulsion (NEP) system is presented. The effort is responsive to recent non-advocate reviews stating high-power NEP technologies were relatively immature and significant maturation was required before contemplating the use of NEP on a flight mission. The maturation strategy presented accomplishes this through hardware test and evaluation at the sizes, scales, and conditions expected during high-power NEP missions. The development effort is accompanied by modeling of such a system to demonstrate thorough understanding and verification of the performance, lifetime, and failure modes. The proposed effort uses a building-block approach, maturing technologies for a 1 MWe block under the assumption that a future high-power NEP mission will have requirements that can be met either through straightforward scaling of this building block to the levels required or through the use of multiple blocks to meet the overall power needs. The plan is outlined for maturation to technology readiness level 5, characterized by test and evaluation using brassboard-fidelity hardware in a relevant environment and by demonstration of agreement between test data and analytical predictions.
Kurt A. Polzin↗
Component-level Performance and Mass Sensitivity Analysis of NEP MW-class Power System
Nuclear electric propulsion (NEP) is a promising option towards enabling missions to Mars and is an area of interest for NASA’s Space Nuclear Propulsion project. This project is currently investigating technology development opportunities for an NEP vehicle. Physics-based modeling can be used in the early stages of technology development to gain understanding of the effects of technology and performance assumptions on the system performance and mass. This information can then inform technology maturation planning for near term development. By using a Brayton power conversion model and vehicle mass model for megawatt class NEP applications, a sensitivity analysis is performed to assess the impact of individual components’ performance on the power conversion system performance and system mass. A Monte Carlo simulation is also used to determine the variability in system mass based on uncertainty within the modeling parameters. The sensitivity analysis shows a high sensitivity to power conversion inlet temperature, compressor inlet temperature, and recuperator performance. A Monte Carlo analysis suggests a range of -10% to +15% for a 90% confidence interval on system mass based on the uncertainties in the model inputs.
Nuclear electric propulsion↗