Innovative EP systems that address these specific segments are essential for market participants looking to capitalize on growing opportunities in the rapidly evolving space industry. In the context of \"new space business\", HPTs based on multi-mode MEICP reactors offer a novel solution to the challenges associated with LEO/VLEO missions, as illustrated in Figure 1.  
Its compact form-factor, combined with high specific impulse capabilities, enhances its potential for in-space commercialization and exploration initiatives. Furthermore, the thruster's extensive thrust throttleability allows for effective adaptation to atmospheric density fluctuations, optimizing propulsion metrics in varying operational environments. Helicon-heated plasmas offer multiple benefits for space propulsion applications, including the ability to maintain stable high-density plasmas (ranging from \(10^{12}\) to \(\div 10^{13}\) cm\({}^{-3}\)), high ionization efficiency, operation at low magnetic fields, independent control of ion and electron, energies and low-pressure operation [30]. A Helicon Plasma Thruster based on a compact MEICP reactor operates at frequencies near the hybrid resonance, which lies between the ion and cyclotron frequencies, with low external magnetic fields (50-1200 G) [28]. This capability is sustained across a wide operational range, accommodating different scales, working gasses, and RF antenna designs. The primary challenges associated with wave-heated discharges, particularly in MEICS, involve optimizing plasma generation sources to establish a competitive EP system. Achieving optimal propulsion efficiency requires a comprehensive assessment of key parameters that influence plasma power absorption, such as RF supply power, magnetic field strength, neutral pressure, and antenna configuration. Effective RF power transfer and deposition are essential for generating highly ionized, dense plasmas even in low magnetic field conditions. In addition, it is crucial to ensure that all subsystems and components remain simple, lightweight, and robust. The HPT must also exhibit a wide range of thrust throttleability to adapt to various mission profiles. Finally, extending the operational lifespan in LEO and VLEO environments is of utmost importance. Due to several inherent challenges, including robustness, RF antenna design, wave coupling efficiency, wave propagation, and wave absorption, MEICP reactors utilizing helicon waves are among the most complex heating systems to miniaturize effectively. Figure 1: Block diagram of a HPT based on MEICP reactor and inhomogeneous magnetic field. This article presents findings from an experimental testing campaign conducted on a compact HPT breadboard model specifically designed for spacecraft operation in LEO and VLEO environments. The study focuses on operational regimes characterized by low magnetic fields (<400 G) and a moderate power envelope (<600 W) in a pulsed wave mode (PWM) operation. To address the deep-throttling requirements and multiple thrust vectoring capabilities of a fully electrodeless plasma thruster, this research aims to validate the multi-mode operation of an MEICP reactor complemented by a magnetic nozzle (MN) acceleration scheme. This paper is structured as follows: Section 2 provides a survey of various power absorption mechanisms present in a HPT, particularly one featuring a compact MEICP reactor. It also discusses a critical element of multi-mode operation, the Helicon to Whistler (H-W) transition, which significantly influences the thruster's overall performance metrics. Section 3 ensures a detailed description of the HPT breadboard architecture and an overview of its design point. Section 4 addresses the test setup and the experimental testing campaign of the HPT in a PWM. Section 5 presents the measurement results obtained from the HPT tests, drawing conclusions based on the data. The results provide critical insights into the thruster's performance, validating its design and highlighting areas for potential improvement.