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SITAEL is active in the field of electric propulsion and is involved in the development of different thruster technologies—mainly Hall thrusters (HTs)—of power levels ranging from 100 W up to 20 kW. Low-power HTs are the most effective choice to perform orbit transfer, drag compensation, and de-orbiting maneuvers for small satellites. This paper is dedicated to the activities regarding HC1, the hollow cathode conceived for the 100-W-class Hall thruster under development at SITAEL. Successful test campaigns were performed and are described, with emphasis on the improvements in the cathode design after an extensive research and development phase. The results are presented and discussed, along with future developments of the ongoing activities.
Daniela Pedrini; Cosimo Ducci; Ugo Cesari; Tommaso Misuri; Mariano Andrenucci. SITAEL HC1 Low-Current Hollow Cathode. Aerospace 2020, 7, 96 .
AMA StyleDaniela Pedrini, Cosimo Ducci, Ugo Cesari, Tommaso Misuri, Mariano Andrenucci. SITAEL HC1 Low-Current Hollow Cathode. Aerospace. 2020; 7 (7):96.
Chicago/Turabian StyleDaniela Pedrini; Cosimo Ducci; Ugo Cesari; Tommaso Misuri; Mariano Andrenucci. 2020. "SITAEL HC1 Low-Current Hollow Cathode." Aerospace 7, no. 7: 96.
There are a number of pressing problems mankind is facing today that could, at least in part, be resolved by space systems. These include capabilities for fast and far-reaching telecommunication, surveying of resources and climate, and sustaining global information networks, to name but a few. Not surprisingly, increasing efforts are now devoted to building a strong near-Earth satellite infrastructure, with plans to extend the sphere of active life to orbital space and, later, to the Moon and Mars if not further. The realization of these aspirations demands novel and more efficient means of propulsion. At present, it is not only the heavy launch systems that are fully reliant on thermodynamic principles for propulsion. Satellites and spacecraft still widely use gas-based thrusters or chemical engines as their primary means of propulsion. Nonetheless, similar to other transportation systems where the use of electrical platforms has expanded rapidly, space propulsion technologies are also experiencing a shift toward electric thrusters that do not feature the many limitations intrinsic to the thermodynamic systems. Most importantly, electric and plasma thrusters have a theoretical capacity to deliver virtually any impulse, the latter being ultimately limited by the speed of light. Rapid progress in the field driven by consolidated efforts from industry and academia has brought all-electric space systems closer to reality, yet there are still obstacles that need addressing before we can take full advantage of this promising family of propulsion technologies. In this paper, we briefly outline the most recent successes in the development of plasma-based space propulsion systems and present our view of future trends, opportunities, and challenges in this rapidly growing field.
I. Levchenko; S. Xu; S. Mazouffre; D. Lev; D. Pedrini; D. Goebel; L. Garrigues; F. Taccogna; K. Bazaka. Perspectives, frontiers, and new horizons for plasma-based space electric propulsion. Physics of Plasmas 2020, 27, 020601 .
AMA StyleI. Levchenko, S. Xu, S. Mazouffre, D. Lev, D. Pedrini, D. Goebel, L. Garrigues, F. Taccogna, K. Bazaka. Perspectives, frontiers, and new horizons for plasma-based space electric propulsion. Physics of Plasmas. 2020; 27 (2):020601.
Chicago/Turabian StyleI. Levchenko; S. Xu; S. Mazouffre; D. Lev; D. Pedrini; D. Goebel; L. Garrigues; F. Taccogna; K. Bazaka. 2020. "Perspectives, frontiers, and new horizons for plasma-based space electric propulsion." Physics of Plasmas 27, no. 2: 020601.
Giulia Becatti; Manuel Martín Saravia; Daniela Pedrini; Fabrizio Paganucci; Tommaso Andreussi; Mariano Andrenucci. Low-frequency cathode plume oscillations in a 5-30A LaB6 cathode. AIAA Propulsion and Energy 2019 Forum 2019, 1 .
AMA StyleGiulia Becatti, Manuel Martín Saravia, Daniela Pedrini, Fabrizio Paganucci, Tommaso Andreussi, Mariano Andrenucci. Low-frequency cathode plume oscillations in a 5-30A LaB6 cathode. AIAA Propulsion and Energy 2019 Forum. 2019; ():1.
Chicago/Turabian StyleGiulia Becatti; Manuel Martín Saravia; Daniela Pedrini; Fabrizio Paganucci; Tommaso Andreussi; Mariano Andrenucci. 2019. "Low-frequency cathode plume oscillations in a 5-30A LaB6 cathode." AIAA Propulsion and Energy 2019 Forum , no. : 1.
Low-power Hall effect thrusters (HETs) belong to a class of electric thrusters with an operating power lower than 500 W. The application of this class of HETs is suited for small satellites for telecommunications and Earth observation missions. Sitael is active in this field, through the development of two HETs, HT100, and HT400, belonging to a power class of 100 and 400 W, respectively. HT100 is a permanent-magnet thruster operating in the 100- to 250-W range, providing thrust between 4 and 13 mN, and specific impulse between 900 and 1400 s. HT400 operates in the 350- to 750-W range, providing thrust between 20 and 45 mN, and specific impulse between 1300 and 1700 s. Two cathodes have been developed and tested, referred to as HC1 and HC3, conceived for HT100 and HT400, respectively. Both cathodes are based on Sitael heritage in theoretical modeling and experimental activities for the development of such devices, and rely on lanthanum hexaboride emitters. HC1 is a cathode designed to provide a discharge current in the 0.3-1 A range, operating in steady-state conditions at mass flow rates between 0.08 and 0.5 mg/s of xenon. HC3 was designed for the range 1-3 A of discharge current, with 0.08-0.5 mg/s of mass flow rate. Both HC1 and HC3 have an expected lifetime higher than 10⁴ h, based on the rate of material evaporation from the emitter surface, computed with the aid of a theoretical model developed to guide the cathode design. Experiments were carried out, including preliminary characterization campaigns, of each of the two cathodes and HET-cathode coupling tests. The collected data are presented and discussed with reference to the model predictions, showing a good agreement between theoretical and experimental results.
Daniela Pedrini; Cosimo Ducci; Tommaso Misuri; Fabrizio Paganucci; Mariano Andrenucci. Sitael Hollow Cathodes for Low-Power Hall Effect Thrusters. IEEE Transactions on Plasma Science 2017, 46, 296 -303.
AMA StyleDaniela Pedrini, Cosimo Ducci, Tommaso Misuri, Fabrizio Paganucci, Mariano Andrenucci. Sitael Hollow Cathodes for Low-Power Hall Effect Thrusters. IEEE Transactions on Plasma Science. 2017; 46 (2):296-303.
Chicago/Turabian StyleDaniela Pedrini; Cosimo Ducci; Tommaso Misuri; Fabrizio Paganucci; Mariano Andrenucci. 2017. "Sitael Hollow Cathodes for Low-Power Hall Effect Thrusters." IEEE Transactions on Plasma Science 46, no. 2: 296-303.
Hollow cathodes are electron sources used for the gas ionization and the beam neutralization in both ion and Hall effect thrusters (HETs). A reduction of power and propellant consumption from the cathode is particularly needed in small satellite applications, where power and mass budgets are inherently limited. Concurrently, the interest in high-power HETs is increasingly fostered for a number of space applications, including final positioning and station-keeping of Geostationary Earth Orbit (GEO) satellites, spacecraft transfers from Low Earth Orbit (LEO) to GEO, and deep-space exploration missions. As such, several hollow cathodes have been developed and tested at Sitael, each conceived for a specific power class of thrusters. A numerical model was used during the cathode design to define the geometry, in accordance with the thruster unit specifications in terms of discharge current, mass flow rate, and lifetime. Lanthanum hexaboride (LaB6) hollow cathodes were successfully developed for HETs with discharge power ranging from 100 W to 20 kW. Experimental campaigns were carried out in both stand-alone and coupled configurations, to verify the operation of the cathodes and validate the numerical model. The comparison between experimental and theoretical results are presented, offering a sound framework to drive the design of future hollow cathodes.
Daniela Pedrini; Tommaso Misuri; Fabrizio Paganucci; Mariano Andrenucci. Development of Hollow Cathodes for Space Electric Propulsion at Sitael. Aerospace 2017, 4, 26 .
AMA StyleDaniela Pedrini, Tommaso Misuri, Fabrizio Paganucci, Mariano Andrenucci. Development of Hollow Cathodes for Space Electric Propulsion at Sitael. Aerospace. 2017; 4 (2):26.
Chicago/Turabian StyleDaniela Pedrini; Tommaso Misuri; Fabrizio Paganucci; Mariano Andrenucci. 2017. "Development of Hollow Cathodes for Space Electric Propulsion at Sitael." Aerospace 4, no. 2: 26.
Thermionic hollow cathodes are currently used as sources of electrons in a variety of space applications, in particular as cathodes/neutralizers of electric thrusters (Hall effect and ion thrusters). Numerical tools are needed to guide the design of new devices before their manufacturing and testing, since multiple geometrical parameters influence the cathode performance. A reduced-order, numerical model was developed to assess the performance of orificed hollow cathodes, with a focus on the operational lifetime. The importance of the lifetime prediction is tied to its impact on the operational lifetime of the thruster to which the cathode is coupled. The cathode architecture consists of a refractory metal tube with an internal electron emitter made of lanthanum hexaboride (LaB6). The choice of LaB6 accounts for the reduced evaporation rate, the low sensitivity to poisoning and the absence of an activation procedure with respect to oxide cathodes. A LaB6 emitter is thus a valuable option for long-lasting cathodes, despite its relatively high work-function and reactivity with many refractory metals at high temperatures. The suggested reduced-order model self-consistently predicts the key parameters of the cathode operation, shedding light on the power deposition processes as well as on the main erosion mechanisms. Preliminary results showed good agreement with both the experimental data collected by Alta and data available from the literature for different operating conditions and power levels. Next developments will include further comparisons between theoretical and experimental data, considering cathodes of various size and operating conditions
Daniela Pedrini; Riccardo Albertoni; Fabrizio Paganucci; Mariano Andrenucci. Modeling of LaB6 hollow cathode performance and lifetime. Acta Astronautica 2015, 106, 170 -178.
AMA StyleDaniela Pedrini, Riccardo Albertoni, Fabrizio Paganucci, Mariano Andrenucci. Modeling of LaB6 hollow cathode performance and lifetime. Acta Astronautica. 2015; 106 ():170-178.
Chicago/Turabian StyleDaniela Pedrini; Riccardo Albertoni; Fabrizio Paganucci; Mariano Andrenucci. 2015. "Modeling of LaB6 hollow cathode performance and lifetime." Acta Astronautica 106, no. : 170-178.
A model to predict the plasma properties inside a thermionic hollow cathode as a function of operational conditions and geometry is presented. The hollow cathode features a lanthanum hexaboride (LaB6) insert, which is capable of emitting current densities as high as 105 Am-2 at temperatures of ~1900 K, along with a tantalum orifice plate located at the downstream end of the cathode tube. The model self-consistently computes the plasma parameters in both the emitter and orifice regions. A simple semiempirical relation is suggested to evaluate the plasma penetration depth in the cathode interior, which is of primary importance to establish the plasma conditions. The heat transfer mechanisms and the related temperature gradients along the cathode are evaluated with the aid of a dedicated thermal model, which is coupled to the plasma model and accounts for temperature-dependent material properties. A parametric study of the cathode performance was conducted to assess the dependence of the power consumption and operational lifetime on discharge current and mass flow rate, as well as on the geometry. The results are in good agreement with both theoretical and experimental trends found in the literature as well as with experimental data collected by Alta. Further developments will include a deeper investigation into the cathode erosion phenomena, along with a broader comparison with empirical data.
Daniela Pedrini; Riccardo Albertoni; Fabrizio Paganucci; Mariano Andrenucci. Theoretical Model of a Lanthanum Hexaboride Hollow Cathode. IEEE Transactions on Plasma Science 2014, 43, 209 -217.
AMA StyleDaniela Pedrini, Riccardo Albertoni, Fabrizio Paganucci, Mariano Andrenucci. Theoretical Model of a Lanthanum Hexaboride Hollow Cathode. IEEE Transactions on Plasma Science. 2014; 43 (1):209-217.
Chicago/Turabian StyleDaniela Pedrini; Riccardo Albertoni; Fabrizio Paganucci; Mariano Andrenucci. 2014. "Theoretical Model of a Lanthanum Hexaboride Hollow Cathode." IEEE Transactions on Plasma Science 43, no. 1: 209-217.
A reduced-order numerical model describing the plasma in an orificed hollow cathode is presented as a quick tool for the design of thermionic cathodes. A time-independent, volume-averaged model is developed to determine plasma properties, wall temperatures, and cathode lifetime without requiring experimental data as input. A system of particle and energy balance equations is numerically solved without invoking a Saha-type equilibrium under the hypothesis of a direct-impact ionization process. Further, a lumped-parameter thermal model is coupled with the plasma model to estimate the temperature profile along the cathode axis and the emitter lifetime. The obtained results capture most of the characteristic features of this class of hollow cathodes as compared with the available experimental data. In addition, the model gives insight into the most important power deposition processes affecting the emitter and orifice regions. The effect of the geometry on both plasma parameters and cathode performance is discussed to suggest design guidelines for the development of state-of-the-art hollow cathodes.
Riccardo Albertoni; Daniela Pedrini; Fabrizio Paganucci; Mariano Andrenucci. A Reduced-Order Model for Thermionic Hollow Cathodes. IEEE Transactions on Plasma Science 2013, 41, 1731 -1745.
AMA StyleRiccardo Albertoni, Daniela Pedrini, Fabrizio Paganucci, Mariano Andrenucci. A Reduced-Order Model for Thermionic Hollow Cathodes. IEEE Transactions on Plasma Science. 2013; 41 (7):1731-1745.
Chicago/Turabian StyleRiccardo Albertoni; Daniela Pedrini; Fabrizio Paganucci; Mariano Andrenucci. 2013. "A Reduced-Order Model for Thermionic Hollow Cathodes." IEEE Transactions on Plasma Science 41, no. 7: 1731-1745.