Ion thrusters are designed to provide continuous operation for intervals of weeks to years. The lifetime of electrostatic ion thrusters is limited by several processes.
|Electrostatic Propulsion Systems - An Analysis of Current Propulsion Systems||The first was SERT-1launched July 20,which successfully proved that the technology operated as predicted in space. The second test, SERT-II, launched on February 3,  verified the operation of two mercury ion engines for thousands of running hours.|
Lifetime[ edit ] Ion thrusters' low thrust requires continuous operation for a long time to achieve the necessary change in velocity delta-v for a particular mission. Ion thrusters are designed to provide continuous operation for intervals of weeks to years. The lifetime of electrostatic ion thrusters is limited by several processes.
In electrostatic gridded designs, charge-exchange ions produced by the beam ions with the neutral gas flow can be accelerated towards the negatively biased accelerator grid and cause grid erosion. End-of-life is reached when either the grid structure fails or the holes in the grid become large enough that ion extraction is substantially affected; e.
Grid erosion cannot be avoided and is the major lifetime-limiting factor. Thorough grid design and material selection enable lifetimes of 20, hours or more. Post-test examination indicated the engine Electrostatic ion thrusters not approaching failure.
The total impulse generated would require over 10, kilograms of conventional rocket propellant for a similar application. The Advanced Electric Propulsion System AEPS is expected to accumulate about 5, hr and the design aims to achieve a flight model that offers a half-life of at least 23, hours  and a full life of about 50, hours.
Propellants[ edit ] Ionization energy represents a large percentage of the energy needed to run ion drives. In addition, the propellant should not erode the thruster to any great degree to permit long life; and should not contaminate the vehicle.
However, xenon is globally in short supply and expensive. Older designs used mercurybut this is toxic and expensive, tended to contaminate the vehicle with the metal and was difficult to feed accurately.
A modern commercial prototype may be using mercury successfully. However, in current tests the most practical propellant is argonwhich is relatively abundant and inexpensive. Note that peak vehicle efficiency occurs at about 1.
Ion thruster efficiency is the kinetic energy of the exhaust jet emitted per second divided by the electrical power into the device. Overall system energy efficiency is determined by the propulsive efficiencywhich depends on vehicle speed and exhaust speed. Some thrusters can vary exhaust speed in operation, but all can be designed with different exhaust speeds.
At the lower end of specific impulse, Isp, the overall efficiency drops, because ionization takes up a larger percentage energy and at the high end propulsive efficiency is reduced. Optimal efficiencies and exhaust velocities for any given mission can be calculated to give minimum overall cost.
Missions[ edit ] Ion thrusters have many in-space propulsion applications. The best applications make use of the long mission interval when significant thrust is not needed. Examples of this include orbit transfers, attitude adjustments, drag compensation for low Earth orbitsfine adjustments for scientific missions and cargo transport between propellant depotse.
Ion thrusters can also be used for interplanetary and deep-space missions where acceleration rates are not crucial. Continuous thrust over a long interval can reach high velocities while consuming far less fuel than traditional chemical rockets.
Among electric thrusters, ion thrusters have received the most serious commercial and academic consideration. Ion thrusters are seen as the best solution for these missions, as they require high change in velocity but do not require rapid acceleration.
These were electrostatic ion thrusters using mercury and cesium as the reaction mass. SERT-II, launched on February 3,  verified the operation of two mercury ion engines for thousands of running hours. Two geostationary satellites ESA's Artemis in —03  and the US military's AEHF-1 in —12  used the ion thruster to change orbit after the chemical-propellant engine failed.
Boeing  began using ion thrusters for station-keeping in and planned in —14 to offer a variant on their platform, with no chemical engine and ion thrusters for orbit raising; this permits a significantly lower launch mass for a given satellite capability.
AEHF-2 used a chemical engine to raise perigee to 10, miles and proceeded to geosynchronous orbit using electric propulsion.
It used ion propulsion throughout its twenty-month mission to combat the air-drag it experienced in its low orbit altitude of kilometres before intentionally deorbiting on November 11, It was space-tested in the highly successful space probe Deep Space 1launched in This was the first use of electric propulsion as the interplanetary propulsion system on a science mission.
Hayabusa[ edit ] The Japanese space agency's Hayabusa launched in and successfully rendezvoused with the asteroid Itokawa and remained in close proximity for months to collect samples and information.Fundamentals of Electric Propulsion: Ion and Hall Thrusters March The research described in this publication was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under.
A typical three-grid system in electrostatic ion thrusters extracts ions from the source and simultaneously accelerates them.
Space Travel Aided by Plasma Thrusters: Past, Present and Future Space Travel Aided by Plasma Thrusters: Past, Present and Future; Reliability of UAVs and Drones; UAS Threats, Solutions, and the Collaboration.
Electrostatic thrusters (“ion engines”) are the best developed type of electric propulsion de vice, dating in conception to the ’s, and having been demonstrated in space in on a suborbital ﬂight of the SERT I spacecraft.
Hall thrusters are electrostatic ion accelerators in which the grid system (which serves in classical ion engines to anchor the negative charges used to accelerate the ions) is replaced with a relatively strong magnetic ﬁeld perpendicular to the ﬂow.
An ion thruster is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions with electricity. The term refers strictly to gridded electrostatic ion thrusters, but may more loosely be applied to all elect.
1 Electric Propulsion-1 Copyright © , by Jerry M. Seitzman. All rights reserved. AE Rocket Propulsion Electrostatic Propulsion.