Closed drift thrusters are reviewed. The publications on these thrusters constitute a large body of information. This article can therefore include only the most prominent theoretical and experimental features of closed drift thrusters. In some regards, this article is also an attempted synthesis of the differing views of these thrusters found in literature, as well as in our own work. In a closed drift thruster, the electric field that accelerates the ions is established by an electron current that passes through and is impeded by a magnetic field. The precessing electrons in this magnetic field follow a closed drift path giving this thruster its name. Closed drift thrusters are divided into magnetic layer and anode layer types, based both on the geometrical and material differences in the discharge channels of the two types, and on the different physical processes that take place within the discharge plasma. Considered as a whole, the publications on closed drift thrusters constitute an impressive body of information that, for the most part, was generated in Russia independently of US research on electric thrusters.

https://iopscience.iop.org/article/10.1088/0963-0252/8/1/021/pdf

Physics of closed drift thrusters

The historical background and characteristics of the experimental flights of ion propulsion systems and the major ground-based technology demonstrations are reviewed. The results of the first successful ion engine flight in 1964, Space Electric Rocket Test (SERT) I, which demonstrated ion beam neutralization, are discussed along with the extended operation of SERT II starting in 1970. These results together with the technologies employed on the early cesium engine flights, the applications technology satellite series, and the ground-test demonstrations, have provided the evolutionary path for the development of xenon ion thruster component technologies, control systems, and power circuit implementations. In the 1997-1999 period, the communication satellite flights using ion engine systems and the Deep Space 1 flight confirmed that these auxiliary and primary propulsion systems have advanced to a high level of flight readiness.

/pdf/ion-propulsion-development-projects-in-us-space-electric-32ahsse4ql.pdf

Ion Propulsion Development Projects in US: Space Electric Rocket Test I to Deep Space 1

The SERT II spacecraft, containing two 15-cm-diam mercury electron bombardment ion thrusters, was launched February 3, 1970. One thruster operated for 5 months of the 6month mission goal. The over-all thruster efficiency 0.68 remained constant; the specific impulse was about 4200 sec; and the thrust was 28 mN (6.3 mlb) for a thruster input power of 850 w. A second flight thruster operated 3 months in space. Both thrusters failed due to sudden shorts between high voltages which have since been determined as resulting from the neutralizer location. This paper compares the thrusters performance with corresponding preflight ground testing. The thrust in flight, determined by three different methods, is presented. In addition, the SERT II spacecraft and mission are described.

SERT II - Mission, thruster performance, and in-flight thrust measurements

The current interest in ion thrusters for near-Earth and deep-space missions has occurred because of long-term development efforts yielding an understanding of the physical phenomena involved in thruster operation and hardware that is suited to a wide range of missions. Features of state-of-the-art thrusters are described in terms of the various physical processes that occur within them. Tradeoffs that must be considered to arrive at thruster designs suited to commercialization are discussed.

/pdf/ion-thruster-development-trends-and-status-in-the-united-2u5pd1wbjy.pdf

Ion Thruster Development Trends and Status in the United States

Electric thrusters offer the promise of a substantial improvement in performance over that of conventional chemical rockets currently used in space propulsion applications. There are three basically different ways in which electrical power and propellant inputs might be combined to produce thrust: (1) propellant can be heated electrically and then expanded through a nozzle; (2) electromagnetic body forces can be applied to accelerate a plasma to the desired exhaust velocity; or (3) electrostatic body forces can be applied to accelerate charged particles. Electric thrusters are classified in accordance with the mechanism by which they induce thrust as electrothermal, electromagnetic, and electrostatic. The characteristics of plasmas in electric thrusters along these lines are considered. >

R. J. Cybulski

Papers

Results from sert i ion rocket flight test

Results from SERT I ion rocket flight test.