The transition from old space to new space along with increasing commercialization has a major impact on space flight, in general, and on electric propulsion (EP) by ion thrusters, in particular Ion thrusters are nowadays used as primary propulsion systems in space This article describes how these changes related to new space affect various aspects that are important for the development of EP systems Starting with a historical overview of the development of space flight and of the technology of EP systems, a number of important missions with EP and the underlying technologies are presented The focus of our discussion is the technology of the radio frequency ion thruster as a prominent member of the gridded ion engine family Based on this discussion, we give an overview of important research topics such as the search for alternative propellants, the development of reliable neutralizer concepts based on novel insert materials, as well as promising neutralizer-free propulsion concepts In addition, aspects of thruster modeling and requirements for test facilities are discussed Furthermore, we address aspects of space electronics with regard to the development of highly efficient electronic components as well as aspects of electromagnetic compatibility and radiation hardness This article concludes with a presentation of the interaction of EP systems with the spacecraft

Ion thrusters for electric propulsion: Scientific issues developing a niche technology into a game changer.

System analysis and test-bed for an atmosphere-breathing electric propulsion system using an inductive plasma thruster

The research challenges for electric propulsion technologies are examined in the context of s-curve development cycles It is shown that the need for research is driven both by the application as well as relative maturity of the technology For flight qualified systems such as moderately-powered Hall thrusters and gridded ion thrusters, there are open questions related to testing fidelity and predictive modeling For less developed technologies like large-scale electrospray arrays and pulsed inductive thrusters, the challenges include scalability and realizing theoretical performance Strategies are discussed to address the challenges of both mature and developed technologies With the aid of targeted numerical and experimental facility effects studies, the application of data-driven analyses, and the development of advanced power systems, many of these hurdles can be overcome in the near future

https://www.mdpi.com/2226-4310/7/9/120/pdf

Future directions for electric propulsion research

In a pulsed plasma thruster discharge, the propellant utilization efficiency is commonly seen as the weak point for its thrust performance, and for its low thrust efficiency respectively. However, the value depends strongly on operational settings and the design of the pulsed plasma thruster itself. To access this efficiency to understand further the influence of parameters, a method combining experimental and modeling efforts is proposed within this paper. By using various optical methods, including high-speed camera imaging, emission spectroscopy, and Mach–Zehnder interferometry, the plasma bulk velocity for different energy configurations of the SPPT-68 ADD SIMP-LEX is derived. Together with the total ablated mass and an improved slug model, the ratio of mass accelerated in the discharge process is computed and, thus, the propellant utilization efficiency is derived. Velocities in the range of 25 to 55  km/s were measured, leading to propellant utilization efficiencies of about 40 to 60% depending on t...

Propellant Utilization Efficiency in a Pulsed Plasma Thruster

Model-based systems engineering is a relatively new discipline. As a result, many system designers are not familiar with the main concepts of model-based systems engineering and how it can beneficially impact systems design. The paper presents an overview of architecture frameworks and modeling languages for model-based systems engineering as well as indicates future trends.Copyright © 2011 by ASME

Overview of Architecture Frameworks and Modeling Languages for Model-Based Systems Engineering

More than 25 years of experience have been gained in the field of electric propulsion at IRS. Recent developments within the field of electric propulsion are summarized and foremost results are highlighted. The various types of electric propulsion systems are not considered as to be competitive. Here, system analysis shows that optimum parameter such as the required exhaust velocity or specific impulse result taking into account both the mission profile and system related sizes such as the power conditioner efficiency, the thrust efficiency and the specific mass of the corresponding power unit. Correspondingly, ion thrusters, Hall thrusters, thermal arcjets, or magnetoplasmadynamics (MPD) thrusters are preferable depending on the mission. Among the described electric propulsion systems are recent developments in the field of applied field MPD but also from high power hybrid thrusters. In addition, new concepts such as the hybrid systems TIHTUS and CETEP are analysed.

Activities in Electric Propulsion Development at IRS

central product model. The approach has been applied to the design phase of the Perseus satellite which is part of the Stuttgart Small Satellite Program. This paper presents the UML lightweight extensions necessary to represent geometric features authored in CATIA and control system features authored in Matlab/Simulink in a common UML model. Next to the unied description of product data, the use of UML to represent design processes was investigated. An iterative design sequence consisting of several CATIA- and Matlab/Simulink-specic evaluations was formulated as an executable UML activity diagram. This study shows that the UML, which is already widespread for sofware design, has the potential to become the future unifying product modeling language which can close the gap between the traditional distinct mechanical, electronic and software-related disciplines.

An Executable Unied Product Model Based on UML to Support Satellite Design

This paper presents first steps for the development of a thermal arcjet system for a science mission to the moon. A first approach for a propulsion feed system as well as results accomplished during tests with a laboratory model of the thermal arcjet ARTUR- 2 are introduced. The tests were done at different power levels from 0.9 up to 1.SkW at mass flows between 10 and 15 mg/s hydrogen. The cathode gap was kept constant at 0.8 mm during all tests. The constrictor diameter is 0.6 mm. The highest effective exceeded exhaust velocity was 8 km/s at a thrust efficiency of 32%.

1 kW Ammonia Arcjet System Development for a Science Mission to the Moon

Previous investigation of the propellant feed system for the thermal arcjet thruster of the lunar mission Bw1 concluded in the necessity that the pressure regulator of the propellant feed system needs to be modified to reach a higher pressure level inside the propellant feed system. The mass flow rate showed fluctuations of 15%, which are not acceptable for stable arcjet operation. To sustain a high temperature behind the vaporizer the propellant feed system is insulated by use of space blankets wrapped around the pipings. A new vaporizer concept is developed increasing the heat transfer into the ammonia by use of stainless steel srub inside the vaporizer. The necessary heating power for complete vaporization is calculated to be 50W. The results of the tests with the modificated propellant feed system show that first the fluctuations of the mass flow rate disappear by use of the modified pressure regulator. Secondly, the higher pressure level is reached but the mass flow is to high. Consequently, the diameter of the flow aperture has to be decreased.

Dagmar Bock

Papers

Activities in Electric Propulsion Development at IRS

An Executable Unied Product Model Based on UML to Support Satellite Design

1 kW Ammonia Arcjet System Development for a Science Mission to the Moon

An Advanced Ammonia Propellant Feed System for the Thermal Arcjet TALOS

Experimental Investigations on Thermal Arcjet Thruster Development for a Science Mission to the Moon