Structural Analysis of Pyrolytic Graphite Optics for the HiPEP Ion Thruster

Meckel, Nicole; Polaha, Jonathan; Juhlin, Nils

doi:10.2514/6.2004-3629

Cited by 7 publications

(6 citation statements)

References 7 publications

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“…The hot gap change in the edge region is not tested for the camera is obscured by the arched shape of the grids. Errors between simulation results and test results are considered mainly from the structural equivalent model [12]. Non-aperture equivalent structure by homogenization method can approximately reflect the real structural characteristics, especially for elastic modulus of the triple grids.…”

Section: Test Results and Discussionmentioning

confidence: 99%

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Thermal Deformation Analysis and Measurement of the Triple Grid for a 30cm Diameter Ion Thruster

SUN

GENG

CHEN

et al. 2022

Preprint

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Critical ion thruster component that affects operation and service life is the grids assembly, and the hot gap variation of the grids directly determines the erosion process of the grids. In order to obtain the hot gap variation of the triple grid for a 30cm diameter ion thruster under 5kW work condition, finite element analysis is used to calculate the distribution of temperature and thermal deformation, then a deflection measurement experiment is carried out to verify the simulations. The results show that the temperature change of the screen grid is the fastest for the lowest heat capacity and the highest deposition energy among the three grids. The hot gap between the center area of the screen grid and the accelerator grid is decreased from 0.95 mm to 0.45 mm in the first 5 minutes. Meanwhile, the central gap is decreased from 0.85 mm to 0.42 mm between the accelerator grid and the decelerator grid after the thruster works about 2000s. The thermal deformation of the decelerator grid presents a “trapezoid” shape. On the contrary, that of the accelerator grid presents a “parabolic” shape. The results of simulation and measurement of temperature in the edge of the screen grid are 338 ℃ and 321 ℃ , respectively. The thermal displacement test results show that the hot gap in the center area between the screen grid and the accelerator grid, the accelerator grid and the decelerator grid are decreased from 0.95 mm to 0.48 mm, and 0.85 mm to 0.46 mm, respectively. The simulation results are consistent with test results, and the errors are considered mainly come from the structural equivalent model and which is calculated to be less than 10%.

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Section: Test Results and Discussionmentioning

confidence: 99%

“…The grids has thin wall, multi-holes and shell structure features, and it is hard to model as a real structure [12]. Therefore, the model needs to be simplified to complete mesh generation.…”

Section: Fem Modelmentioning

confidence: 99%

Thermal Deformation Analysis and Measurement of the Triple Grid for a 30cm Diameter Ion Thruster

SUN

GENG

CHEN

et al. 2022

Preprint

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“…n i p  is the primary electron generation rate, which includes univalent ionization and bivalent ionization with the same generation rate [12], n i s  is the secondary electron generation rate by ionization collision, n tem p  is the thermal electron generation rate when a small portion of primary electrons change to secondary electrons for the reduction of the energy during the thermalization process [13] and n ex p  is the electron generation rate of the excitation collision. The primary electron generation rate n i p  can be expressed as equation 4 as equation (4), which only changes the density of the different particle types. where n a is the neutral density, and v ea e s á ñ is the collision reaction coefficient, which is given by Mikellides et al [14].…”

Section: Ion Density In the Upstream Of The Gridsmentioning

confidence: 99%

“…Thermal expansion can cause hot gap change of the grids as the edge of the grids are fixed to the main structure of the thruster. If metallic material is used in the grid manufacture, the hot gap change would be significant, caused by the thermal expansion effect, which would further cause a series of disadvantage factors such as contact breakdown, ion beam focus performance degrades and CEX ion sputtering frequency increase [4]. The cumulative numbers of NSTAR ion thruster breakdown times between the screen grid and the accelerator grid [5] are shown in figure 1(c).…”

Section: Introductionmentioning

confidence: 99%

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

Sun¹,

Jia²,

Huang³

et al. 2018

Plasma Sci. Technol.

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In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process, a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 kW operation mode. Meanwhile, the fluid simulation method and particle-in-cell-Monte Carlo collision (PIC-MCC) method are adopted to simulate the ion extraction process according to the previous test results. The numerical calculation results are verified by the ion thruster performance test. The results show that after about 1.2 h operation, the hot gap between the screen grid and the accelerator grid reduce to 0.25-0.3 mm, while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium, and the hot gap is almost unchanged. In addition, the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value. Fluid simulation results show that the plasma density of the screen grid is in the range 6×10 17-6×10 18 m 13 and displays a parabolic characteristic, while the electron temperature gradually increases along the axial direction. The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant. Meanwhile, the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap. The ion beam current has optimal perveance status without thermal deformation, and the intercepted current of the accelerator grid and the decelerator grid are 3.65 mA and 6.26 mA, respectively. Furthermore, under the effect of thermal deformation, the ion beam current has over-perveance status, and the intercepted current of the accelerator grid and the decelerator grid are 10.46 mA and 18.24 mA, respectively. Performance test results indicate that the breakdown times increase obviously. The intercepted current of the accelerator grid and the decelerator grid increases to 13 mA and 16.5 mA, respectively, due to the change in the hot gap after 1.5 h operation. The numerical calculation results are well consistent with performance test results, and the error comes mainly from the test uncertainty of the hot gap.

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“…6 Specific aspects of the HiPEP program are described more thoroughly elsewhere. 6,7,9,10,11,12,13,14,15 This year the JIMO-HiPEP team explored various plasma production options including DC hollow cathode and AC microwave discharge options. 7 Both were used with the HiPEP thruster, demonstrating the applicability of either discharge approach to the rectangular concept.…”

Section: High Power Electric Propulsion System (Hipep)mentioning

confidence: 99%

Electric Propulsion Technology Development for the Jupiter Icy Moon Orbiter Project

Oleson

2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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During 2004, the Jupiter Icy Moons Orbiter project, a part of NASA's Project Prometheus, continued efforts to develop electric propulsion technologies. These technologies addressed the challenges of propelling a spacecraft to several moons of Jupiter. Specific challenges include high power, high specific impulse, long lived ion thrusters, high power/high voltage power processors, accurate feed systems, and large propellant storage systems. Critical component work included high voltage insulators and isolators as well as ensuring that the thruster materials and components could operate in the substantial Jupiter radiation environment. A review of these developments along with future plans is discussed.

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Structural Analysis of Pyrolytic Graphite Optics for the HiPEP Ion Thruster

Cited by 7 publications

References 7 publications

Thermal Deformation Analysis and Measurement of the Triple Grid for a 30cm Diameter Ion Thruster

Thermal Deformation Analysis and Measurement of the Triple Grid for a 30cm Diameter Ion Thruster

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

Electric Propulsion Technology Development for the Jupiter Icy Moon Orbiter Project

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