Plume Control of a Cusped Field Thruster
The cusped field thruster uses several permanent ring magnets of alternating polarity to create a multistage cusp magnetic topology. It has demonstrated a long lifetime because of reduced plasma losses to the discharge channel surface. However, the high beam divergence problem has not been solved in this type of thruster. The purpose of this technical note is to describe a plume control method to reduce its plume angle. The results show that the magnetic field intensity in the plume region and the shape of the last separatrix have great influence on plume divergence.
Study of channel length effect on low power HEMP Thruster
Abstract The HEMP Thruster, also known as “cusped field thruster”, becomes a candidate micro thruster of new generation space observation missions for its low complexity, potential long life over a wide range of thrust. As one of the main parameters of thruster, channel length selection is required in the downscaling of cusped field thruster. Three low power thrusters with different channel length are designed to discover the effect on performance and discharge characteristics. Due to the complexity of the ionization and acceleration process of the special cusped magnetic field, the plume is diagnosed by a Faraday probe and a retarding potential analyzer, and a Partial-In-Cell simulation is carried out to analyze the discharge mechanism. The result shows that lengthen of channel length has a diminishing positive effect on propellant utilization, but a negative effect on the total efficiency and kinetic performance at the same time. Decisive factors are discovered through the study on four internal efficiencies, with crucial physics process analyzed in the numerical simulation, which provides an important reference for the downscaling of the electric propulsion devices and similar low-temperature plasma discharge conditions.
Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 ? 1 Rib Cotton Knitted Fabrics
This study investigates the impact of yarn count and stitch length of 100% cotton knitted fabrics. 1 × 1 ribs structured fabrics were used in this research work. The stitch length 2.50 mm, 2.52 mm, 2.60 mm, 2.70 mm, 2.80 mm and 2.96 mm were used of the yarn count of 26Ne, 28Ne and 36Ne. The areal densities of the grey fabrics were in various amounts. The impacts of yarn count and stitch length were measured concerning pilling resistance, abrasion resistance, and shrinkage and tightness factor. The result showed that the fabric pilling grade decreased while number of cycle increased. Abrasion resistance decreased but length wise shrinkage increased despite the fact that the stitch length increased. The results also exposed that the tightness factor of the fabric increased with the increase of the stitch length in both dyeing and washing state and finished state compared to grey state for the yarn count 26Ne and homogeneous result not found for yarn count 28Ne and 36 Ne. Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 × 1 Rib Cotton Knitted Fabrics