Development of the linear gridless ion thruster

Abstract

The design of the Linear Gridless Ion Thruster, or LGIT, is presented in detail. The LGIT is a hybrid thruster that combines an ionization stage similar to those normally found on gridded ion engines with the acceleration mechanism of a Hall effect thruster. This thruster also features a linear geometry, which simplifies the design of the magnetic circuit while making the LGIT particularly well suited to future work on clustering and, perhaps, thrust vectoring by varying the magnetic fields in the acceleration zone. Initial testing with the thruster operating in a single-stage, unoptimized mode resulted in a specific impulse of 1400 seconds and an anode efficiency of 12%. The low efficiency is believed to be due in large part to operating the thruster in a single-stage mode, rather than the two-stage mode for which it was designed, and to setting the acceleration stage magnets to less than half their design value.

Magnetoplasmadynamic two-stage micro-cathode arc thruster for CubeSats

“…with high thrust or with high I sp ). Some examples of two-stage propulsion systems are the P5-2 (5 kW) thruster [10], Helicon Hall Effect Thruster (600-1200 W) [11], Linear Gridless Ion Thruster (2 kW) [12], VASIMR engine (200 kW) [13], D-80 Thruster with Anode Layer (TAL, 3 kW) [14] and the VHITAL thruster (25-36 kW) [15]. The issue with the above thrusters is that they operate at high power of hundreds to thousands of Watts, at power levels that are unfeasible for most small satellites, which provide only 0.1-100 W. However, it should be noted that Hall thrusters with gaseous propellants, operating at lower power levels (50-200 W), are being actively developed worldwide.…”

Operation of an Annular Helicon Plasma Source

“…Ion number density, electron temperature, and electron energy distribution function measurements are taken at several axial and radial locations inside the device at each operating condition with a ratio-frequency-compensated Langmuir probe. The annular helicon plasma source is characterized over a range of applied radio frequencies (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), magnetic field strengths (0-400 G), and radio frequency forward-power settings (100-1400 W) for both argon and xenon propellants. The peak ion number density measured in the annular helicon is 2:6 10 17 m 3 for argon and 2:4 10 17 m 3 for xenon at 1000 W of radio frequency power.…”

“…Therefore, a method to improve the efficiency of the HET in a highthrust-to-power operating condition is to replace the dc electron bombardment ionization stage with a more efficient helicon ionization source [3]. Two-stage HETs, which have separate ionization and acceleration stages, have been investigated in the past, but a helicon source has never been used as the ionization stage [1,[4][5][6][7][8][9][10][11][12][13][14][15]. For a helicon source to serve as the ionization stage of a two-stage HET, it must produce steady-state plasma with an ion number density and electron temperature appropriate for the acceleration stage.…”