Asp ii ion propulsion

ION PROPULSION SYSTEM

Definition

• Ion propulsion is a technology that involves ionizing a gas

to propel a craft. Instead of a spacecraft being propelled

with standard chemicals, the gas xenon is given an

electrical charge, or ionized.

• It is then electrically accelerated to a speed of about 30

km/second.

• When xenon ions are emitted with the help of ion

thrusters at high speed as exhaust from a spacecraft, they

push the spacecraft in the opposite direction.

ION :

• An ion is simply an atom or molecule that is electrically

charged

IONIZATION :

• It is a process of converting an atom or molecule into

ions.

• It can done by either adding or removing electrons then

they become cation (+ve) or anion (-ve) respectively

ION THRUSTER :

• An ion thruster is form of electric propulsion used for

spacecraft propulsion that creates trust by accelerating

ions

PARTS OF IPS(Ion Propulsion system) :

• Ion propulsion system consists of the following five

parts :

1. Power source

2. Power processing unit

3. Propellant management system

4. The control computer

5. Ion thruster

1.Power source :

• power source can be any source of electrical power, but

solar and nuclear are the primary options.

• A solar electric propulsion system (SEP) uses sunlight

and solar cells for power generation.

• A nuclear electric propulsion system (NEP) uses a

nuclear heat source coupled to an electric generator.

2.Power processing unit (PPU):

• The PPU converts the electrical power generated by the

power source into the power required for each

component of the ion thruster.

• It generates the voltages required by the ion optics and

discharge chamber and the high currents required for the

hollow cathodes.

3.Propellent management system:

• The PMS controls the propellant flow from the propellant

tank to the thruster and hollow cathodes.

• Modern PMS units have evolved to a level of

sophisticated design that no longer requires moving

parts.

4.The computer control :

• The control computer controls and monitors system

performance

5. Ion Thrusters :

• then processes the propellant and power to perform

work.

• They are of two types:

1)Electrostatic

2)Electromagnetic

Ion propulsion process:• The fuel used my modern ion engines is xenon gas

which is four times heavier than air

• When the ion engine is running, electrons are emitted

from a hollow cathode tube called as discharge cathode.

• These electrons enter a magnet-ringed chamber, where

they strike the xenon atoms.

• These electrons hits the electrons of xenon atom as it

consists of 54 electrons .

• This results in the formation of ions in discharge

chamber

• High-strength magnets are placed along the discharge

chamber walls so that as electrons approach the walls,

they are redirected into the discharge chamber by the

magnetic field

• At the rear of the chamber, a pair of metal grids is

charged positively and negatively, respectively, with

up to 1,280 volts of electricity

• The force of this electric charge exerts a strong

electrostatic pull on the xenon ions

• The xenon ions shoot out the back of the engine at high

speeds which propels the spacecraft in opposite

direction and produces thrust force .

• The force of this electric charge exerts a strong

electrostatic pull on the xenon ions

• The xenon ions shoot out the back of the engine at high

speeds which propels the spacecraft in opposite

direction and produces thrust force .

1)Electrostatic ion thruster:

• This type of thruster commonly use xenon gas which has

no charge and it is ionized by bombarding with energetic

electrons.

• These electrons are provided from hot cathode filament

and accelerated into electric field of cathode fall to anode.

• the electrons can be accelerated by the oscillating electric

field induced by an alternating magnetic field of a

coil which results in a self-sustaining discharge and omits

any cathode

• The positive ions are extracted after bombarding of

electrons with xenon atoms, and these ions are

accelerated by electrostatic forces

• The electric fields used for acceleration are generated by

electrodes positioned at the end of the thruster ,such set

of electrodes are called as ion optics or grids.

• Some ion thrusters use a two-electrode system, where

the upstream electrode(screen grid) is charged highly

positive, and the downstream electrode(accelerator grid)

is charged highly negative.

• Since the ions are generated in a region of high positive

and the accelerator grid's potential is negative, the ions

are attracted toward the accelerator grid and are focused

out of the discharge chamber through the apertures,

creating thousands of ion jets.

• The stream of all the ion jets together is called the ion

beam

• The thrust force is the force that exists between the

upstream ions and the accelerator grid.

• The exhaust velocity of the ions in the beam is based on

the voltage applied to the optics.

• Because the ion thruster expels a large amount of

positive ions, an equal amount of negative charge must

be expelled to keep the total charge of the exhaust beam

neutral.

• A second hollow cathode called the neutralizer is

located on the downstream of the thruster and expels the

needed electrons.

• A second hallow cathode tube called the neutralizer is

located on the downstream of the thruster and expels the

needed electrons.

• thus how an electrostatic thruster produces thrust with

the help of ions and propells the spacecraft

Amount of thrust :

• At full throttle, the ion engine will consume 2,500 watts of

electrical power, and put out 1/50th of a pound of thrust

• Ion thrusters are capable of propelling a spacecraft up to

90,000 meters per second (over 200,000mph)

• thrusters can deliver up to 0.5 Newtons (0.1 pounds) of

thrust

APPLICATIONS :• Ion thrusters have many applications for in-space

propulsion

• The best applications of the ion thrusters make use of

the long lifetime when significant thrust is not needed.

• This type of propulsive device can also be used for

interplanetary and deep space missions where time is

not crucial

• Used to spiral at lower altitudes on vesta

• Helps Spacecraft Cruise Solar System on the Cheap

Propellant:• Many current designs use xenon gas due to its low

ionization energy, reasonably high atomic number, inert

nature, and low erosion

• Ion thrusters use inert gas for propellant, eliminating the

risk of explosions

• The usual propellant is xenon, but other gases such as

krypton and argon may be used.

ADVANTAGES:

• on propulsion could be used for a manned mission to

Mars

• Ion propulsion makes efficient use of the onboard fuel by

accelerating it to a velocity ten times that of chemical

rockets

• The ion propulsion system, although highly efficient, is

very gentle in its thrust

• Less expensive launch vehicle is required when

compared to chemical propulsion .

• Less amount of propellant carrying tanks which reduces

weight of spacecraft

• With xenon, it is possible to reduce propellant mass

onboard a spacecraft by up to 90 percent.

• The advantages of having less onboard propellant

include a lighter spacecraft, and, since launch costs are

set based on spacecraft weight, reduced launch cost..

• Additional velocity can be obtained

• Greater life time when compared to other propulsive

devices

• Continuous thrust over a very long time can build up a

larger velocity than traditional chemical rockets

• High specific impulse , high efficiency

Disadvantages:

• Unlike a chemical propulsion system ion propulsion

produces gentle amount of thrust but for a long duration

• Ion propulsion system is mostly applicable only for deep

space missions

• Cost of propellant used is very expensive

• Complex power coditioning ,high voltages

• Single propellant

• Low thrust per unit area

conclusion

• the propellant chose should not cause erosion of the

thruster to any great degree to permit long life; and

should not contaminate the vehicle.

• More efficient than the chemical propulsion

• In 1998, Deep Space 1 became the first spacecraft to

use ion propulsion to reach destinations in the solar

system

If any queries please ask

By:

R.Sagar reddy