*† ‡ § ¶ The objectives of the NASA’s Evolutionary Xenon Thruster (NEXT) program are to develop a next generation ion propulsion system to Technology Readiness Level 6 and to transfer the NASA technology to industry partners to facilitate the manufacturing of future flight systems. A primary focus of the program is to minimize first user cost of the system through a flexible system design approach, manufacturing process development, and element and system validation. The NEXT program has made significant progress towards these goals in the last 18 months. With the fabrication and qualification-level testing of engineering and prototype model hardware, a substantial level of technical and production readiness has been demonstrated. This paper describes the development and validation status of each of five system elements, summarizes performance and interface characteristics for each element, and details Aerojet’s readiness to manufacture the flight system.

NEXT Ion Propulsion System Production Readiness

Purpose




This paper aims to provide an overview of current and historical arcjet development. The reviewed arcjets are considered with respect to both design and thruster relevant parameters. Correspondingly, the paper enables the identification of adequate design criteria and of the probable thruster parameters.




Design/methodology/approach




The approach consists of a database for thruster relevant parameters in conjunction with relevant operational requirements (such as type of propellant) and specific design criteria (such as e.g. propellant injection systems).




Findings




The synopsis of both operational parameter and respectively assigned design allows for the derivation of development approaches for arcjets under given high level requirements such as power regime.




Research limitations/implications




The paper is a general review. However, its strength is in the synthesis of the arcjet classification, the functional evidence of design criteria and the application scenario.




Practical implications




Not only basic but also specific design criteria are analyzed and evaluated leading to a recommendation feature of the paper with respect to the overall design of adequate arcjets.




Social implications




Within the scope of the Clean Space initiative, new applications and scenarios from the operation of arcjets arise enabling EOL phases of spacecraft that fulfill respective levels of debris mitigation and, in addition, the requirements concerning the adequately adapted re-entry of spacecrafts that are at end of life.




Originality/value




The paper is a general review. However, its strength is in the synthesis of the arcjet classification, the functional evidence of design criteria and the application scenario.

Overview of thermal arcjet thruster development

The U.S. Air Force Research Laboratory’ s Electric Propulsion Space Experiment was launched and successfully operated on the Advanced Research and Global Observation Satellite, demonstrating the compatibility and readiness of high-power electric propulsion. This e ight was the culmination of an Air Force technology program to demonstrate the applicability of high-power electric propulsion for satellite applications. A brief history of the program is presented, followed by a description of the e ight operations, which successfully demonstrated the critical system components, the arcjet, power processor, and propellant feed system, verifying the interoperability of high-power electric propulsion with satellite operations. The two anomalies experienced during on-orbit operations, and their proposed causes, are also described.

Review of the Electric Propulsion Space Experiment (ESEX) Program

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.

An Advanced Ammonia Propellant Feed System for the Thermal Arcjet TALOS

A New Manner for Energy Reintroduction in AJAX

The Electric Propulsion Space Experiment (ESEX) flew in 1999 on the Air Force Space Test Program Advanced Research and Global Observation Satellite. ESEX was initiated to address potential in-space operational issues associated with the use of high-power electric propulsion. Potential issues included plume deposition, electromagnetic interference, and thermal radiation. Because of physical constraints of even the largest test facilities, that is, vacuum chamber size, these phenomena are best measured in space. The propulsion component for the ESEX demonstration, a 26-kW ammonia arcjet propulsion subsystem, including thruster, power processing, and propellant feed, was developed and flight qualified on the Air Force Research Laboratory'Arcjet Advanced Technology Transition Demonstration program. Each of the propulsion system elements, the principal design challenges, and the program of risk reduction and qualification testing that provided preflight verification of the arcjet propulsion subsystem are described.

C. E. Vaughan

Papers

Development and Flight Qualification of a 26-Kilowatt Arcjet Propulsion Subsystem