2. Physical model

member of EPTs, pulsed plasma thruster (PPT) has a broad prospect on small satellites for its small, compact, and low mass [3–5]. PPT has been studied decades on its performance and lifetime, and has been successfully applied to a number of satellites [6–8]. However, the

Early in the year 2000, Horisawa et al. proposed a laser-assisted plasma thruster (LS-PPT), in which a laser-induced plasma was induced through laser beam irradiation onto a solid target and accelerated by electrical means [9–16]. Compared with the conventional PPT, the LS-PPT combines the laser ablation with electromagnetic acceleration means, which can significantly enhance the thrust performance. However, the phenomenon of "late ablation" is still inevitable in the LS-PPT, which significantly reduces the thrust efficiency of the thruster. In order to overcome the shortage of "late ablation," a novel laser ablation plasma thruster (LA-PPT) is proposed [17]. The LA-PPT separates the laser ablation from electromagnetic acceleration through a ceramic tube. As shown in Figure 1, the LA-PPT consists of a pair of rectangular electrodes, a ceramic tube and an insulator. The propellant is placed inside the ceramic tube. Because of the unique structure of this thruster, almost all types of solid matter can be applied as the propellant, such as metals, polymers and so on. Because laser-ablation plasma can has a directed initial velocity of tens of kilometers per second, which will be further accelerated by electrical means, a significant specific impulse can be expected [9]. Hence the LA-PPT is a promising candidate for small satellites propulsion, and the physical mechanisms of the thruster should be further investigated. The working process of the LA-PPT can be divided into two stages: laser-induced ablation and plasma-induced discharge. The ablation plasma expansion and ionization in the ceramic tube is the combination of the two stages, and it is crucial to understand the working process of the LA-PPT. However, the ablation plasma expansion and ionization is difficult to be experimentally investigated, especially when it occurs in a ceramic tube. Therefore, we utilize numerical method

problem of low efficiency and ignition failure still restricts the development of PPT.

190 Plasma Science and Technology - Basic Fundamentals and Modern Applications

to investigate the ablation plasma expansion and ionization in the ceramic tube.

Figure 1. (a) Front and (b) right view of the laser ablation plasma thruster.

By using the numerical method to simulate the ablation plasma expansion and ionization in the ceramic tube, the relevant physics of propellant ablation needs to be implemented. The heating process within a propellant material during the irradiation of the laser pulse can be calculated by taking into account temperature-dependent material properties, melting, phase transition, dielectric transition, phase explosion, and the reflection of the laser beam at the surface of the propellant [18]. In addition, the ablation plasma absorbs part of laser
