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An Algorithm to Engineer Autonomous Ballistic Capture at Mars
Full text linkCurrent deep-space missions heavily count on ground-based operations. Although reliable, ground slots will saturate soon, so hampering the current momentum in space exploration. EXTREMA, a project awarded an ERC Consolidator Grant in 2019, enables self-driving spacecraft, challenging the current paradigm and aiming, among others, at autonomously engineering ballistic capture. This work presents an autonomous ballistic capture algorithm suitable for spacecraft with limited control authority and onboard resources. The algorithm is applied to construct BC corridors at Mars, time-varying manifolds supporting capture that can be targeted far away from the planet. The algorithm envisaged a novel methodology to generate families of ballistic capture orbits characterized by succeeding capture epochs. The families are built by correcting in sequence the initial conditions of ballistic capture orbits provided that they are enough regular. New orbits are obtained solving a well-posed three-point boundary value problem exhibiting 8 boundary conditions. The conditions are linearized, and the problem is solved for a finite set of variables with the multiple shooting technique. The computationally demanding problem of finding ballistic capture orbits through stable sets manipulation is unburdened by just solving a linear system, making the algorithm compatible with CubeSats onboard resources. An overview of the autonomous BC algorithm and the details of the correction procedure are provided. The methodology is applied to generate families of orbits belonging to capture sets C−11 and C−16 starting from the same baseline capture orbit. In both cases, the method constructs sequences of initial conditions spanning more than 100 days. The algorithm performance is assessed and its limitations are discussed. Results are inspected against the solar gravity gradient field to get insight about how the methodology acts when it corrects a reference solution into a new capture orbit
Characterization of Ballistic Capture Corridors Aiming at Autonomous Ballistic Capture at Mars
Full text linkExterior Earth Moon Transfers Design Using the Theory of Functional Connections and Homotopy
Full text linkCost-effective access to the lunar environment can be achieved by leveraging the weak stability boundary of the Earth–Moon–Sun system. Upcoming missions to our natural satellite are foreseen to exploit these long-duration transfers. By combining the recent Theory of Functional Connection and a homotopy continuation process, this paper proposes a novel method to design low-energy transfers to the Moon. Planar patched transfer legs within the Earth–Moon and the Sun–Earth systems are refined into higher-fidelity models. Eventually, the full Earth–Moon transfer conforms to the dynamics of the planar Earth–Moon Sun-perturbed, bi-circular restricted four-body problem. This method eliminates the need to numerically propagate the dynamic equations during the continuation and final convergence to the full trajectory. A grid search is implemented to generate a wide range of exterior Earth–Moon transfers. This work illustrates that the Theory of Functional Connections can effectively represent two-impulses, long-duration, low-energy transfers modeled in chaotic dynamic environments. Furthermore, its synergy with a homotopic continuation approach is demonstrated
Low-energy Earth–Moon transfers via Theory of Functional Connections and homotopy
Full text linkNumerous missions leverage the weak stability boundary in the Earth–Moon–Sun system to achieve a safe and cost-effective access to the lunar environment. These transfers are envisaged to play a significant role in upcoming missions. This paper proposes a novel method to design low-energy transfers by combining the recent Theory of Functional Connections with a homotopic continuation approach. Planar patched transfer legs within the Earth–Moon and Sun–Earth systems are continued into higher-fidelity models. Eventually, the full Earth–Moon transfer is adjusted to conform to the dynamics of the planar Earth–Moon Sun-perturbed, bi-circular restricted four-body problem. The novelty lies in the avoidance of any propagation during the continuation process and final convergence. This formulation is beneficial when an extensive grid search is performed, automatically generating over 2000 low-energy transfers. Subsequently, these are optimized through a standard direct transcription and multiple shooting algorithm. This work illustrates that two-impulse low-energy transfers modeled in chaotic dynamic environments can be effectively formulated in Theory of Functional Connections, hence simplifying their overall design process. Moreover, its synergy with a homotopic continuation approach is demonstrated
Selection of the Propulsion System for the LUMIO Mission: an Intricate Trade-Off Between Cost, Reliability and Performance
Full text linkThe Lunar Meteoroid Impact Observer (LUMIO), one of the two winning concepts of the SysNova Lunar CubeSats for Exploration call by ESA, is a mission designed to observe, quantify, and characterize the meteoroid impacts on the Lunar far side by detecting the flashes generated by the impact. While Earth-based Lunar observations are restricted by weather, geometric and illumination conditions, a Lunar-based observation campaign can improve the detection rate and, when observing the Lunar far side, complement in both space and time the observations taken from Earth. The mission, which has successfully completed its Phase A in March 2021, is based on a 12U CubeSat that carries the LUMIO-Cam, a custom-designed optical instrument capable of detecting light flashes in the visible spectrum. The spacecraft is placed on a halo orbit about the Earth–Moon L2 point, where permanent full-disk observation of the Lunar far side can be performed with excellent quality, given the absence of background noise due to the Earth. The propulsion system is one of the most crucial design choices for the LUMIO spacecraft. It accomplishes various functions: orbital transfer from the initial Lunar orbit to the final halo orbit around L2, station keeping, reaction wheel desaturation, end of life disposal manoeuvres. The total required Delta-V budget for orbital transfer and station keeping is 201.8 m/s, plus an additional total impulse for reaction control tasks ranging from 110 Ns to 170 Ns, depending on the type of reaction control system that is selected. This paper presents a detailed summary of the phase A selection and design of the LUMIO propulsion system, based on the full list of requirements generated by the mission analysis. The main challenges of this process and the way they have been tackled are presented and discussed, including: use of two separate systems as opposed to an integrate one for main propulsion and reaction control tasks; availability of sufficiently reliable European propulsion options, to reduce the general mission costs; feasibility of replacing a chemical/cold gas system with electric propulsion; possible need for custom changes to the design of the selected COTS option (e.g. due to tank sizing).Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Space Systems Egineerin
ELAPSE: a FlatSat Software and Processing Unit for Deep-Space Autonomous GNC Systems Testing
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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