1,720,984 research outputs found
Combined Chemical–Electric Propulsion for a Stand-Alone Mars CubeSat
Full text linkStand-alone interplanetary CubeSats require primary propulsion systems for orbit maneuvering and precise trajectory control. The current work focuses on the design and performance characterization of the combined chemical–electric propulsion systems that shall enable a stand-alone 16U CubeSat mission on a hybrid high-thrust– low-thrust trajectory from a supersynchronous geostationary transfer orbit to a circular orbit about Mars. The highthrust chemical propulsion is used to escape Earth and to initiate stabilization at Mars. The low-thrust electric propulsion is used in heliocentric transfer, ballistic capture, and circularization. For chemical propulsion, design and performance characteristics of a monopropellant thruster and feed system using ADN-based FLP-106 propellant are presented. For electric propulsion, a performance model of an iodine-propelled inductively coupled miniature radiofrequency ion thruster is implemented to calculate the variation of thrust, specific impulse, and efficiency with input power. A power-constrained low-thrust trajectory optimization using the thruster performance model is pursued to calculate the transfer time, ΔV, and the required propellant mass for fuel-optimal and time-optimal transfers. Overall, the combined chemical–electric systems yield a feasible propulsion solution for stand-alone CubeSat missions to Mars that balances propellant mass and transfer time
Assessing control robustness of CubeSat propulsion systems for minor body proximity operations
Full text linkExploration of minor celestial bodies is attracting increasing attention due to the scientific insights and engineering advancements it can provide. Concurrently, miniaturized platforms such as CubeSats are becoming increasingly popular because of their reduced development, qualification, and launch costs. This enables riskier operations, making them ideal for proximity operations around minor bodies. This work introduces a 6-DoF guidance and control simulation framework for proximity operations along hyperbolic trajectories near minor bodies. An optimization algorithm was designed coupling attitude dynamics with trajectory design, while directly considering performance and technological limitations of CubeSat propulsion systems. This is to evaluate the feasibility of using miniaturized propulsion systems in a minor body environment. The analysis examines various propulsion technologies, orbital distances, and minor bodies to assess the feasibility of flying hyperbolic arcs. Key performance metrics, including observation time, firing time, propellant consumption, and pointing accuracy, are considered
Experimental Characterization of Thermal Cavitation Effects on Space Rocket Axial Inducers
No full textThe paper shows the results of an experimental campaign conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A., aimed at characterizing the cavitation thermal effects on two tapered-hub, variable-pitch inducers, designated as DAPAMITO. The semi-empirical method proposed by Ruggeri and Moore for scaling the thermal cavitation effects has been successfully applied and, consequently, a further validation of this method has been provided. The influence of the temperature on the intensity of the performance degradation associated with the attached cavitation instability has been identified as a new typology of cavitation thermal effects. In this case, the inhibition of the bubble growth due to thermal effects can be detected by the reduction of the performance degradation usually associated with this type of instability
Review of State-of-the-Art Green Monopropellants: For Propulsion Systems Analysts and Designers
No full textCurrent research trends have advanced the use of “green propellants” on a wide scale for
spacecraft in various space missions; mainly for environmental sustainability and safety concerns.
Small satellites, particularly micro and nanosatellites, evolved from passive planetary-orbiting to
being able to perform active orbital operations that may require high-thrust impulsive capabilities.
Thus, onboard primary and auxiliary propulsion systems capable of performing such orbital operations
are required. Novelty in primary propulsion systems design calls for specific attention to
miniaturization, which can be achieved, along the above-mentioned orbital transfer capabilities, by
utilizing green monopropellants due to their relative high performance together with simplicity, and
better storability when compared to gaseous and bi-propellants, especially for miniaturized systems.
Owing to the ongoing rapid research activities in the green-propulsion field, it was necessary to
extensively study and collect various data of green monopropellants properties and performance that
would further assist analysts and designers in the research and development of liquid propulsion systems.
This review traces the history and origins of green monopropellants and after intensive study
of physicochemical properties of such propellants it was possible to classify green monopropellants
to three main classes: Energetic Ionic Liquids (EILs), Liquid NOx Monopropellants, and Hydrogen
Peroxide Aqueous Solutions (HPAS). Further, the tabulated data and performance comparisons will
provide substantial assistance in using analysis tools—such as: Rocket Propulsion Analysis (RPA)
and NASA CEA—for engineers and scientists dealing with chemical propulsion systems analysis and
design. Some applications of green monopropellants were discussed through different propulsion
systems configurations such as: multi-mode, dual mode, and combined chemical–electric propulsion.
Although the in-space demonstrated EILs (i.e., AF-M315E and LMP-103S) are widely proposed and
utilized in many space applications, the investigation transpired that NOx fuel blends possess the
highest performance, while HPAS yield the lowest performance even compared to hydrazine
Composite structures with embedded fiber optic sensors: A smart propellant tank for future spacecraft applications
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Continuous Spectrum of the Rotordynamic Forces on a Four Bladed Inducer
No full textThe paper illustrates the results of an experimental campaign conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A., aimed at characterizing the rotordynamic forces acting on a whirling four-bladed, tapered-hub, variable-pitch inducer, designated as DAPAMITO4. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. A novel experimental technique, consisting in measuring the continuous spectra of the forces as functions of the whirl ratio, has been developed and validated. This technique gives the possibility of extracting valuable information from the experiments by clearly identifying the qualitative and quantitative behavior of the forces, and is therefore useful to catch the unlikely foreseeable complexity of the rotordynamic forces and their consequences on the stability of axial inducers
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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