Search

Comet Interceptor (Comet-I) was selected in June 2019 as the first ESA F-Class mission and aims to explore a pristine comet, which will visit the inner Solar System for the first time. Comet-I will hitch a ride to a Sun-Earth L2 quasi-halo orbit, as a co-passenger in ESA's M4 ARIEL's launch. At the time of writing, this is scheduled for 2029. It will then remain there awaiting the right departure conditions to leave definitively and intercept a newly discovered comet. Comet-I will be the first mission to be designed and launched without an already identified target. Given the latter, the Comet-I Target Identification Working Group is tasked with the continuous follow-up of newly discovered comets, to analyse their characteristics as virtual targets for Comet-I. The goal of the paper is to inform the decision-making process that will eventually be necessary to commit Comet-I spacecraft to its final target. Within this context, this paper presents a trajectory optimization process based on Primer Vector theory that considers intercept trajectories with multiple revolutions and multiple deep space manoeuvres (DSM). The process is applied to 21 long period comets, which were discovered since July 1, 2020 and whose characteristics are of interest for the Comet-I mission. In fact, one of the latest of these recently discovered comets, C/2023H2, is the most accessible virtual target discovered at the time of writing, with delta-V intercept costs well within Comet-I capabilities. A complete launch window analysis is thus presented for C/2023H2, which accounts not only for the most optimal delta-V intercept transfer, but also considers all launch options that satisfy all Comet-I's current boundary conditions and flyby constraints. A systematic launch window analysis is made possible by a grid search approach on which departure and fly-by dates are fixed and the remaining design variables, including the times for manoeuvres and their Δ v impulse vector, are optimized via Primer Vector theory. This allows to understand the latest possible departure date, but also the sensitivity to departure and arrival dates of key encounter characteristics such as relative fly-by speed, the solar aspect angle and the Earth distance. • A Primer Vector Theory-based trajectory optimization tool is shown, tailored for ESA's Comet Interceptor (Comet-I). • The method supports trajectories with multiple revolutions around the Sun and multiple impulses. • The method allows rapid grid search over the search space, finding the lowest cost trajectory and other notable solutions. • A novel analysis of the launch window is presented, contributing to the decision-making process of Comet-I. • A multi-manoeuvre strategy benefits Comet-I's trajectory design, lowering the delta-V cost and improving mission flexibility. [ABSTRACT FROM AUTHOR]

• A new viscoelastic model is derived and studied. • A single element model exhibits solid-like viscoelastic behavior. • A two-element model (a distribute-springpot and a dashpot in series) is more suitable for viscoelastic fluids. • The new model provides a better fit to bread dough and blood viscoelastic behavior when compared to classical models. In this work, our focus is on investigating the significance of the weighting function (c (α)) in the Generalised Distributed-Order Maxwell (GDOM) model. The GDOM model comprises a distributed springpot and a dashpot in series, rendering it more intricate than the Fractional Viscoelastic Fluid - FVF model (consisting of only one springpot and one dashpot in series). However, the GDOM model remains simple enough to facilitate a better comprehension of its behaviour in various flow scenarios, such as relaxation, creep compliance, steady shear viscosity, and small amplitude oscillatory shear. To validate our findings, we conduct fitting analyses using experimental data, which affirm that the single-element model demonstrates solid-like viscoelastic behaviour at low frequencies, while the GDOM model exhibits fluid-like viscoelastic behaviour, accurately capturing the rubbery plateau and transition region observed in polymer systems. [ABSTRACT FROM AUTHOR]

This paper describes the process of use cases prioritizing by ranking their usefulness to improve water losses, control and water-energy efficiency in networks, to provide new services to the consumer, to improve billing systems and pricing schemes, to improve leak detection and water-energy efficiency and to develop better services to consumers. Results showed that priority use cases were to obtain water consumption data, understand water consumption and assist consumers to increase water use efficiency (consumer domain) and to obtain water and related energy consumption data, understand water consumption and get support to increase operational efficiency (water utility domain). [ABSTRACT FROM AUTHOR]