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Author: Carl Pigeon Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
To enable more advanced commercial microsatellite missions, a low power electric propulsion system was designed by the University of Toronto Space Flight Laboratory. A prototype cylindrical Hall thruster was first developed using electromagnets. The thruster's performance was evaluated over a range of 20-300 W. At the nominal 200 W operation, 6.2 mN of thrust with a specific impulse of 1139 s was measured with xenon propellant. Significant erosion of the thruster's discharge chamber wall was observed which limited its lifetime to 100 hours. Subsequently, a flight representative version of the thruster was developed. Permanent magnets were used to reduce the size, mass, and power consumption. Changes to the design were implemented to improve lifetime. Performance characterization and literature suggest that a reduction in performance is expected with the use of permanent magnets. Lastly, thermal vacuum and vibration tests were performed to bring the thruster to Technology Readiness Level 6.
Author: Carl Pigeon Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
To enable more advanced commercial microsatellite missions, a low power electric propulsion system was designed by the University of Toronto Space Flight Laboratory. A prototype cylindrical Hall thruster was first developed using electromagnets. The thruster's performance was evaluated over a range of 20-300 W. At the nominal 200 W operation, 6.2 mN of thrust with a specific impulse of 1139 s was measured with xenon propellant. Significant erosion of the thruster's discharge chamber wall was observed which limited its lifetime to 100 hours. Subsequently, a flight representative version of the thruster was developed. Permanent magnets were used to reduce the size, mass, and power consumption. Changes to the design were implemented to improve lifetime. Performance characterization and literature suggest that a reduction in performance is expected with the use of permanent magnets. Lastly, thermal vacuum and vibration tests were performed to bring the thruster to Technology Readiness Level 6.
Author: Kean How Cheah Publisher: Elsevier ISBN: 0128190388 Category : Technology & Engineering Languages : en Pages : 330
Book Description
Space Micropropulsion for Nanosatellites: Progress, Challenges and Future features the latest developments and progress, the challenges faced by different researchers, and insights on future micropropulsion systems. Nanosatellites, in particular cubesats, are an effective test bed for new technologies in outer space. However, most of the nanosatellites have no propulsion system, which subsequently limits their maneuverability in space. Explains why nanosatellite requirements need unique micro-technologies to help develop a compliant propulsion system Features an overview of nanosatellites and the global nanosatellite market Covers chemical and electric micropropulsion and the latest developments
Author: Ryan Conversano Publisher: ISBN: Category : Languages : en Pages : 240
Book Description
This dissertation presents an investigation of the applicability of magnetic shielding to low-power Hall thrusters as a means to significantly improve operational lifetime. The key life-limiting factors of conventional Hall thrusters, including ion-bombardment sputter erosion of the discharge channel and high-energy electron power deposition to the channel walls, have been investigated extensively for a wide range of thruster scales. As thruster power is reduced to the "miniature" (i.e. sub-500 W) power regime, the increased surface-to-volume ratio of the discharge channel and decreased thruster component sizes promotes increased plasma-wall interactions and susceptibility to overheating, thereby reducing thruster operational lifetime and performance. Although methods for compensating for these issues have been investigated, unshielded miniature Hall thrusters are generally limited to sub-45% anode efficiencies and maximum lifetimes on the order of 1,000 h. A magnetically shielded magnetic field topology aims to maintain a low electron temperature along the channel surfaces and a plasma potential near that of the discharge voltage along the entire surface of the discharge channel along its axial length. These features result in a reduction of the kinetic energy of ions that impact the channel surfaces to near to or below the sputtering threshold, thus preventing significant ion-bombardment erosion of the discharge channel. Improved confinement of high-energy electrons is another byproduct of the field structure, aiding in the reduction of electron power deposition to the channel. Magnetic shielding has been shown to dramatically reduce plasma-wall interactions on 4 - 6 kW Hall thrusters, resulting in significant increases in projected operational lifetimes with minimal effects to thruster performance. In an effort to explore the scalability of magnetic shielding to low-power devices, two magnetically shielded miniature Hall thrusters were designed, fabricated and tested. The performance of the first thruster, called the MaSMi 40, was characterized at an operating condition of 275 V and 325 W. A peak thrust of approximately 13 mN with a specific impulse of approximately 1,100 s at an anode efficiency of approximately 22% were measured at the nominal operating point. Observations of the near exit plasma discharge during operation, and the discharge channel after operation, suggested that the outer channel wall of the thruster was well shielded from ion bombardment while the inner channel wall appeared to be weakly shielded. Further analysis concluded that the MaSMi-40 generated a partially-magnetically shielded field topology. However, the shortcomings of the MaSMi-40's magnetic circuit design were investigated in detail and are now well understood. The second design iteration in the development of a low-power magnetically shielded Hall thruster was the MaSMi-60. Magnetic field measurements confirmed that a symmetric and fully shielded magnetic field topology was generated by this device across a wide range of possible operating conditions. At operating powers of 160 W to nearly 750 W, the key performance metrics of the MaSMi-60 included a measured thrust ranging from approximately 8 mN to over 33 mN with anode specific impulses of up to approximately 1370 s at anode efficiencies of over 28%. Downstream plume measurements identified the primary factors contributing to the low anode efficiency. Visual observations of the discharge plasma and channel walls during and after thruster operation offered strong evidence of magnetic shielding. Erosion rates of the channel were approximated using carbon backsputter measurements; the results suggested a 10x - 100x decrease in wall erosion compared to unshielded Hall thrusters, corresponding to an equal increase in discharge channel lifetime compared to conventional miniature unshielded Hall thrusters. The physics and behaviors of the MaSMi-60's plasma discharge upstream of and in the near-field of the thruster exit plane were investigated using Hall2De, the 2-D axisymmetric code developed at the Jet Propulsion Laboratory for the simulation of the partially ionized plasma in Hall thrusters. Simulations of the MaSMi-60 suggested that the thruster achieved the plasma properties required for effective magnetic shielding, including low electron temperatures and a near-constant plasma potential along the channel walls. This was the final piece of evidence suggesting that magnetic shielding was attained at the miniature scale. The experimentally measured performance of the MaSMi-60 was captured by the Hall2De model, offering physical explanations for the low measured anode efficiency and leading to suggestions for improving the performance in future design iterations.
Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
Busek Co. Inc. completed delivery of flight-qualified colloid thrusters for NASA's ST7 mission in May 2008. This effort has led to development of variants of the technology suitable for small satellite applications. Colloid thrusters operate by electrostatically accelerating charged droplets of an electrically conductive ionic liquid, and are capable of providing a high degree of throttling and variable Isp. Life tests of the ST7 thrusters have demonstrated over 3000 hours of continuous operation with no deterioration in performance. A further benefit is that the colloid thrusters do not present high pressure and fire safety hazards common to many other propulsion systems- the propellant is nonreactive and is typically stored at less than 20psig. The thrusters presented have a target maximum thrust of 1 milliNewton with 0.1-1.0 milliNewton throttling. They are designed to operate in the Isp range of 400-1000s, consume a maximum of 15W (including power supply losses), and be self-contained in a 10cm x 10cm x 20cm package requiring only power and thrust command inputs. The package contains sufficient propellant for 500 hours operation at maximum thrust, yielding total impulse of 1800 seconds capable of imparting almost 200 m/s delta V to a 10kg satellite.
Author: Publisher: ISBN: Category : Languages : en Pages : 15
Book Description
Three different types of sub kilowatt class Hail thrusters tor on-board propulsion of small to mid size satellites are being developed at Busek. This paper describes their performance focusing on plasma behavior outside of the thrusters end contrasts the typical Hail thruster plasma with that encountered in MHD generators end accelerators researched in the past and familiar to the plasmadynamic community. A simple performance predicting analytical model. applicable to all sizes of thrusters also is presented. It adequately matches the measured thrust and specific impulse expressed in terms of primary electron loss parameter, and an overall voltage loss which includes the loss in the plasma bridge between the external cathode and the thruster. The external plasma plume was surveyed using a Faraday cup and an emissive probe to measure the beam current and the plasma potential. These measurements. together with the model support our visual observation that the plume. of a well performing thruster. forms at its center a highly conductive jet with sharply defined cone shaped boundaries. These boundaries were tentatively identified as an ion acoustic shock. The preliminary data and analysis indicate that the plasma downstream of the ion acoustic shock is at least partially responsible for the widely reported correlation between increasing test tank pressure and an increase in performance of Hall thrusters.
Author: Carl Pigeon
Author: Carl Pigeon
Author: Kean How Cheah
Author: Vadim Khayms
Author: Ryan Conversano
Author: Y. Raitses
Author: 
Author: Y. Raitses
Author: 
Author: Michael Matthew Micci
Author: A. I. Smirnov