Scientists are currently working with a new process of propulsion for rockets used in space travel called Ion Propulsion.

• A rocket moves in accordance with Sir Isaac Newton’s third law of motion, which says that for every action there is an equal and opposite reaction. Burning gases are ejected forcibly from an exhaust nozzle of a rocket. The opposing reaction to this exhaust blast, and not the exhaust blast itself, moves the rocket forward. The greater the speed of the exhaust blast, the greater the reaction against the forward end of the rocket and the greater its speed.

• With the launch of Deep Space 1 in October of 1998, many people thought that the ion propulsion engine is a new technology.

• That is not true, the ion propulsion engine that is some times called the solar-electric propulsion engine has been four decades in the making.
• The ion engine works on the principles of low thrust for long periods of time.
• The research and development changes included anything from the number of thrusters onboard to the gas they used to power the spacecraft.

• Ion thrusters rely on the same simple equation as any other rocket engine.

• Since the exhaust blast need not push against anything at the rear, a rocket can operate even better in empty space, or a vacuum, than in the atmosphere, where the exhaust blast is slowed down by the air.
• The experimental solar powered ion propulsion engine is the first non-chemical propulsion system to be used as the primary means of propelling a spacecraft.
• It uses a chemical rocket to get it out of the earth’s atmosphere then the Ion Propulsion will take over which is slow at first but can increase to 10 times faster than a chemical rocket.
• Initially the ion thruster will take a whole day to accelerate the craft by 30 feet per second, after a few months of operation that tiny force will speed the craft up to 10,000 miles per hour. (9)
• The ion propulsion thruster pushes its exhaust about 10 times faster than a chemical rocket and when the large solar ray is taken into account, you can fly a spaceship on an interplanetary cruise with much less fuel then the conventional chemical rocket.

• The result, it will be less expensive and use less fuel to get the rocket off the ground in the first place, since you won’t have to carry the additional fuel that a totally chemical-dependent rocket would need given the same specifications. (9)
• The ion engine, which is sometimes called the electrostatic engine, is the electric system that obtains the highest degree of conversion of electric power into thrust, high exhaust velocity, and the longest operational lifetime.
• This engine works on the principle of the ionization of the propellant gas through the use of direct electron bombardment or radio frequency fields to increase the temperature of the gas and cause the desired thrust.
• The gas used to propel this type of engine is either the gas Ar (Argon) or Xe (Xenon), or the vaporized form of Hg (Mercury) or Cs (Cesium).
• This stored gas enters the ionization chamber to increase its temperature up to the thrust temperature.
• The increase in temperature is done through the ionization of the gas.
• It passes through two acceleration grids which bombard it with positive ions from the power source.
• Before reaching the nozzle the accelerated mass of ionized gas is injected with electrons.
• Thrust is obtained, and the exhaust beam is electrically neutral behind the thruster nozzle. (10)

• The force (F) it produces equals the mass (M) of propellant moved times its acceleration (A).
• Thus F = MA. Since chemical rockets accelerate their exhaust to about 6,000 miles an hour, increasing the velocity of exhaust may liberate spacecraft from this dead-end physical equation: getting more thrust requires more propellant, yet accelerating that propellant takes evermore propellant.
• Instead of increasing F by adding mass, the thruster does the same thing by increasing A, which allows you to reduce M.
• Aside from the extreme rapidity of the beam, the biggest novelty of an ion thruster is its source of energy.
• Chemical rockets store energy in the chemicals, but ion thrusters get power from solar cells, which make the electricity for the electrostatic field that moves the ions.
• That limits the thruster to 2400 watts produced by those photovoltaic cells.
• Thus solar-powered ion thrusters are usable in the inner solar system, where sunlight is abundant. (11)
• Hughes Space and Communication Company is current using Xenon ion propulsion for satellites.

• The world's first satellite to carry ion propulsion is 10 times more efficient than other currently used systems.
• By the end of 1998, 5 on-orbit satellites were using the XIPS (Xenon Ion Propulsion System).
• Four decades of research went into XIPS.
• It’s available in two different power models.
• The following benefits have been realized; increased efficiency allows for a reduction in propellant mass of up to 90%, reduced cost for launch, an increase in payload, no noted interference on broadcasting and telemetry operations, it is less corrosive to satellite components than are conventional propulsion systems and is safe to the environment.
• Xenon has been found to offer the highest thrust of all the inert, non-reactive gases and is non-corrosive and non-explosive. (12)

• NASA scientists tested the new ion propulsion system.
• Over the course of the mission, the ion propulsion system increased the speed of Deep Space 1 by 10,000 miles per hour. (1)
• The spacecraft carries 181 pounds of xenon, the same gas used in flash bulbs, as fuel.
• It would take 1,810 pounds of chemical propellant to achieve the same velocity. Xenon is released into the chamber ringed by magnets. (The magnets enhance the efficiency of the ionization process.)
• Electrons are emitted from a cathode ray tube, similar to the tube that operates a television set.
• The electrons from the cathode hit the xenon atoms and knock an electron off them, imparting a net positive charge to the atoms and turning them into ions.
• At the rear of the chamber a pair of electrically charged metal grids, one positive and one negative, generate an electrostatic pull on the ions.
• The ions are yanked past the grids at a speed of more than 62,000 miles per hour, right out of the back of the engine and into space.
• To prevent the xenon atoms from being attracted back into the engine chamber, an electrode at the rear of the engine emits free electrons that rejoin many of the positive xenon ions, rendering their charge neutral again.

• With the launch of Deep Space 1 in October of 1998, many people thought that the ion propulsion engine is a new technology.

• That is not true, the ion propulsion engine that is some times called the solar-electric propulsion engine has been four decades in the making.
• The research and development changes included anything from the number of thrusters onboard to the gas they used to power the spacecraft.
• In 1959, a NASA engineer by the name of Dr. Harold Kaufman built and tested the first ion propulsion engine at NASA Glenn.
• By the 1960’s, NASA adopted the engine to their new spaceflight test program called (SERT) which is short for Space Electric Rocket Test.
• In 1964, in the Wallops Islands, VA, two-ion engines built by NASA were launched on the Scout rocket named SERT 1.
• SERT 1 contained onboard two ion thrusters; one of which did not work at all and the other only worked for 31 minutes. (2)
• The ion engines onboard SERT 1 contained one mercury fueled engine and one cesium fueled engine. Mercury and cesium was the fuel of choice for the early ion engine endeavors. NASA followed up with SERT 2 in 1970. Both engines were powered by mercury. One of the engines lasted for more than five months and the other engine for three months. (2)
• One of the problems that faced NASA is that the fuel they were using, mercury and cesium, was hard to work with. The mercury was in a liquid state and the cesium in a solid state. To solve the problem, both of the fuels had to be heated up in order to uses them.
• The atoms from the mercury and the cesium would eventually cool and condense on the exterior of the spacecraft.
• Many smaller mission’s to develop the ion engine existed such as Meteor-10 in 1971, ATS-6 in 1974, IAPS/P80-1 1980, ETS-3 in 1982, and RITA/EURECA-1 in 1992.
• All of these missions worked off the old fuel source of mercury and cesium but engineers just could not make the fuel work.
• Cesium had to be put aside due to its corrosive properties, and mercury was rejected due to its impacts on the environment.
• At the Hughes Research Laboratories in California, beginning in the 1960’s a new fuel source was under development to replace the mercury and cesium.
• Xenon fuel is the new fuel of choice for the current spacecrafts.
• Xenon by comparison is four times heavier than air. (2)
• The first xenon ion propulsion engine developed by Hughes was launched in 1979.
• The engine was aboard the Air Force Geophysics Laboratory’s Spacecraft Charging at High Altitude (SCATHA) satellite.
• This mission was an experimental mission for the new fuel.
• In 1984 Hughes, after many years of research found that xenon fuel offered the highest thrust of all the inert, nonreactive gases.
• With xenon being an inert gas, it is neither explosive nor corrosive which was good for the life of the satellites, and the safety for the personal involved with loading the xenon gases on the spacecraft.
• Hughes then in 1992 focused its effort on the XIPS technology, making it the technology of future satellites.
• XIPS which stands for xenon ion propulsion system, was four decades of vigorous research and development which now is the latest in propulsion technology.
• Hughes has currently developed two models of its ion propulsion technology engine, the HS 601HP thruster, and HS 702 thruster.
• The HS 601HP (the HP stands for high power) is 13 centimeters in diameter, has 2568 seconds ISP (impulse rate), and 18 mN (millinewtons) of thrust. (3)
• The HS 702 thruster is 25 centimeters in diameter, has 3800 seconds ISP and 165 mN of thrust. (3)
• This design allows for a reduction in fuel up to 90% from previous models. (3)
• Less fuel allows for lower cost for launch, and an increase in payload.
• The HS 601HP operates for around five hours a day, while the 702 ion thruster generally operates for only thirty minutes a day during normal operations. (3)
• The XIPS thrusters are made up of a propellant supply system, a (PPU) power processing unit and the thruster itself which will be broken down even further later in this paper.
• In the testing of the XIPS thrusters, five vacuum chambers measuring nine feet in diameter are needed. (3)
• The flight unit testing uses three of the five chambers and the other two are used for on going life testing.
• The two chambers used in the life test have logged 8,000 hours on the ion propulsion thruster unit that was built in 1995. (3)
• The second chamber has logged 4,000 plus hours on its thruster that was built in 1996. (3)
• Hughes Research Laboratories started the design work, but now the duties have been handed over to the Hughes Electron Dynamics department.
• The world's first commercial satellite to use the new propulsion system was PAS-5.
• The ion propulsion system on the PAS-5 is 10 times more efficient then systems that uses chemical propulsion.
• PAS-5 was launched in 1997; the spacecraft contained four thrusters.
• Hughes had five satellites in orbit, using the XIPS by the end of 1998.
• One of the downfalls of the ion propulsion engine is that it is not good for quick speed changes.
• Hughes Electron Dynamics was awarded a contract for $9.2 million in 1995 to design and construct the NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) which was to be used for the Deep Space 1 (DS1) project. (5)
• The ion engine would be used as the spacecraft’s primary means of propulsion.
• DS1 is made up of an ion thruster, PPU, and a digital control and interface unit.
• The most ground breaking thing about the mission is that it was the first to use solar electric ion propulsion and it will be the first spacecraft to use the onboard autonomous system for navigation.
• The mission was launched from Cape Canaveral on October 24, 1998.
• The mission, which cost a total of $152 million, was to test and validate 12 new technologies in space. (4)
• It was the first of NASA’s New Millennium Program, focusing on technology rather than on science.
• The ion propulsion engine itself was one of the technologies that were being researched on this mission.
• With the success of the ion propulsion, the concept will be adapted to future NASA space missions.
• Deep Space 1 carries 81.5 kilograms of xenon fuel, this provided approximately 20 months of continuous thrusting. (6)
• The mission was scheduled to end on September 18, 1999, but with the success of the mission, the date has been pushed off to sometime in October depending on how things go.
• DS1 was scheduled to fly by and gather information about an asteroid, Mars and possibly even a comet.
• The asteroid that DS1 was going to try to observe is Asteroid 1992 KD.
• By the use of the autonomous navigation system DS1 will determine where the asteroid may be heading.
• The way it does this is by the software that was loaded on DS1 onboard computer system (RAD 6000).
• The orbits of 250 asteroids and the positions of 250,000 stars have been studied and stored on the computer. (7)
• As DS1 moves in space, its onboard camera called MICAS (Miniature Integrated Camera Spectrometer) takes pictures of the celestial surroundings.
• From the pictures NASA can determine the positions much the same as sailors use the stars to get around on the sea.
• Engineer’s working on this project hope to even be able to measure the effect of solar wind on things like asteroids.
• NASA may decide to extend the mission, this could allow the study of the Comet Wilson-Harrington and Comet Borelly.
• DS1 would fly by Wilson-Harrington in January of 2001 and Borelly in September of that same year.
• The ion engine is a superior choice for long duration missions.
• Some disadvantages of the ion propulsion engine, are electricity and time.
• Atoms in an ion thruster are charged by electricity and used as a propellant.
• In order to perform this procedure large amounts of electricity (around 2000 watts plus) are need to be generated.
• The DS1 for example got its electricity from solar arrays which the further you are out in space the less intense the rays become.
• Another disadvantage of the ion propulsion engine is the time it takes to thrust.
• The thrust produced by xenon fuel is 0.02 pounds compared to chemical propulsion, which produces 50 to 500 pounds of thrust. (5)
• The ion engine works on the principles of low thrust for long periods of time.
• The ion engine can reach speeds up to 70,000 miles per hour, compared to that of a chemically propelled engine which maxis out at 10,000 miles per hour. (5)