Asp ii ion propulsion
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Transcript of Asp ii ion propulsion
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ION PROPULSION SYSTEM
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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.
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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
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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
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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.
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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.
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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.
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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
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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
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• 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 .
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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
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• 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.
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• 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
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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
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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
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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.
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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.
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• 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
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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
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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
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If any queries please ask
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By:
R.Sagar reddy