Determining Vacuum-Arc Thruster Performance Using a Cathode-Spot Model

Numerical simulation of hydrogen arcjet thruster with coupled sheath model

“…The sheath thickness (not including the pre-sheath) is on the scale of Debye length [12], and therefore, for the present study, the sheath thickness is taken as Debye length l = ( ) d . D The electric field E c thus observed is of the order of -10 V m 9 1 equivalent to the field observed by Messaad et al [16] and Lun et al [17].…”

“…A simplified sheath model, inspired by previous work of Fujita et al [14], Lu et al [12], Messaad et al [16], and Lun et al [17], is considered in this study. The model presented in the literature [12,14,16] assumes the net heat flux to the cathode to be zero.…”

“…2 ) of pure tungsten is considered for this study [40]. Substitution of the above equations (18)-( 20) into (17) gives us the expression for the current density at the cathode sheath. The number density of ion (n d ) and electron temperature (T ed ) at the sheath edge are taken from the simulation and are values of the finite volume cell immediately next to the cathode tip.…”

“…The model estimated the temperature and electric field strength at the cathode surface, electrons emitted and total current density, cathode spot radius, different kinds of power densities heating and cooling the cathode, and the plasma electron density. Lun et al [17] developed a model for the vacuum-arc cathode-spot and plasma region to predict the performance of vacuum-arc thrusters operating roughly in the arc current range of 80-300 A. Lun et al [17] reported the conventional-based cathode-spot model with many simplifying assumptions predicted spot radius, surface temperature, electric field, current densities, plasma densities, and energy fluxes. The most recent research conducted in the area has been done by Wang and his co-workers, where the plasma flow feature [18] and species diffusion [19] in a low-power nitrogen-hydrogen arcjet and plasma characteristics of a nitrogen arc [20] were studied by simulation of non-equilibrium arcjets to better understand the arcjet physics.…”

Optimization of discharge triggering in micro-cathode vacuum arc thruster for CubeSats

“…The study of physical factors (such as the value of the anode-cathode gap, the arcing pulse energy, the presence of a magnetic field, and the choice of cathode material and electrode geometry [10,13,15,16,25]), which greatly affect the process of re-deposition of the film and thus thruster performance and lifetime, seems to be highly relevant. The currently widespread VAT geometries are coaxial, tubular and planar [26,27]; in the authors' opinion, a planar geometry is the most attractive from the point of view of studying triggering features, due to the following considerations. A planar geometry is machinable, convenient and practical for experiments: it allows one to easily vary the inter-electrode gap and thus to investigate the effect of the value of this gap, as well as one specific component of the magnetic field (say, that parallel to the surface of the inter-electrode film), on the thruster lifetime.…”