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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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At least 361 records · Page 20
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NASA NTRS2022

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↗
NASA NTRSDate not supplied

The Meteoroid Environment Encountered By the James Webb Space Telescope

All spacecraft run the risk of being damaged by meteoroids at a rate proportional to the spacecraft's surface area. The exceptionally large James Webb Space Telescope (JWST) has endured 20 impacts on its primary mirror in its first year of operation. While most of the impacts experienced were commensurate with pre-launch predictions, one particularly large impact in May 2022 prompted the program to take a fresh look at the meteoroid environment in order to determine whether potentially unaccounted-for meteoroid risks can be mitigated. In this talk, we present a directional model of the meteoroid environment encountered by the spacecraft and compare it with the observed impact rate. Because of JWST’s ability to measure nanometer-size changes to the primary mirror surface, our results indicate that meteoroids carrying as little as 1 Joule of kinetic energy can produce measurable effects. We also find that the impact rate is highest when JWST faces in the direction of orbital motion about the Sun. By implementing a "meteoroid avoidance zone" that discourages observations within 75° of the ram direction, we estimate that JWST has reduced the impact rate by more than half.

Althea Moorhead↗
NASA NTRSDate not supplied

The Cloud: Obstacles and Barrier Encountered By Users

Increasing exposure to and adoption of the Earthdata Cloud yields new concerns from users include: financial resource allotment, steep learning curves, institutional support, and cloud-readiness of data. We present common concerns expressed by early cloud adopters, and encourage conference-goers to relay their own or users's experiences. We also encourage brainstorming for how open science principles can help solve some of the barriers and obstacles users encounter with the cloud.

Alexis Hunzinger↗
NASA NTRSDate not supplied

Orbit Determination For Lucy's First Asteroid Encounter: The Dinkinesh (1999VD57) Flyby

Lucy, NASA’s 13th Discovery program mission, launched on October 16, 2021, is enroute to explore the Jupiter-Trojan asteroids situated at the L4 and L5 Lagrange points. Along this trajectory, Lucy will conduct flybys of two main belt asteroids and perform three Earth fly-bys. This paper delves into the Orbit Determination (OD) process during the Dinkinesh flyby, marking Lucy’s inaugural encounter with an asteroid. The Dinkinesh flyby achieved a significant milestone, flawlessly completing the engineering systems checkout. The discussion herein encompasses the OD strategy, setup, and computed OD solutions during operations. The paper further explores the impact of solar conjunction on the OD solutions and decisions and sheds light on the discovery of Selam, a contact binary orbiting Dinkinesh. Preliminary reconstructed trajectories for both Lucy and Dinkinesh, and an initial state of Selam, are presented. The close approach radial distance of Lucy from Dinkinesh was 430.63 km±0.02km in formal uncertainty.

Jeroen L. Geeraert↗
NASA NTRS2015

Characteristics of a Well Clear Definition and Alerting Criteria for Encounters Between UAS and Manned Aircraft in Class E Airspace

Unmanned aircraft systems (UAS) will be required to equip with a detect-and-avoid (DAA) system in order to satisfy the federal aviation regulations to remain well clear of other aircraft. For a DAA system to satisfy the requirement to stay well clear of other airborne traffic, a quantitative definition of well clear needs to be defined and evaluated. This study investigates the implications of UAS using proposed well clear definitions as a separation standard for conducting operations in the National Airspace System (NAS). The first analysis considers three well clear definitions and presents the relative state conditions of intruder aircraft as they encroach upon the well clear boundary. The second analysis focuses on the definition of the alerting criteria needed to inform the UAS operator of a potential loss of well clear. All analyses are conducted in a NAS-wide fast-time simulation environment using UAS aircraft models, proposed UAS missions, and historical air defense radar data to populate the background traffic operating under visual flight rules. The results presented in this study inform the safety case, requirements development, and the operational environment for DAA minimum operational performance standards.

Safety↗
NASA NTRS1962

SOME TYPICAL SHELL STABILITY PROBLEMS ENCOUNTERED IN THE DESIGN OF BALLISTIC MISSILES

Investigations carried out at STL on three current problems involving instability of thin shells in applications to aerospace vehicles are discussed. The first concerns the experimental determination of the buckling behavior of longitudinally stiffened pressurized cylinders; the second, the analytic prediction and experimental confirmation of the buckling behavior of multi-layer cylinders and the third involves the behavior of cylinders under combined axial load and lateral pressure. In each case the background of the application is reviewed, followed by a short description of the work. It is indicated that the longitudinally stiffened cylinder shows considerable promise in taking maximum advantage of the strengthening effect of internal pressure, that the use of an external low modulus layer as an insulator can have a significant effect on the buckling capability of a shell, and that the assumption of a linear interaction for pressure and axial load is unnecessarily conservative.

SHELL STABILITY↗