AE-1351

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AE-1351

• PROPULSION-II

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UNIT-1

• AIRCRAFT GAS TURBINES

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Gas Turbine

• In an aircraft gas turbine the output of the
  turbine is used to turn the compressor (which may
  also have an associated fan or propeller). The
  hot air flow leaving the turbine is than
  accelerated into the atmosphere  through an
  exhaust nozzle (Fig. la) to provide thrust or
  propulsion power

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• FUNCTION OF TURBINE
• A portion of the kinetic energy of the expanding
  gases is extracted by the turbine section, and
  this energy is transformed into shaft horsepower
  which is used to drive the compressor and
  accessories.

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• TYPES OF TURBINES
• AXIAL FLOW TURBINE
• RADIAL FLOW TURBINE

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AXIAL FLOW TURBINE
It consists of two main elements A set of
stationary vanes followed by a turbine rotor.
Axial-flow turbines may be of the single-rotor or
multiple-rotor type. A stage consists of two
main components a turbine nozzle and a turbine
rotor or wheel.
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RADIAL FLOW TURBINE
The radial flow turbine is similar in design and
construction to the centrifugal-flow compressor .
Advantages -ruggedness and simplicity -relatively
inexpensive and easy to manufacture when
compared to the axial-flow turbine.
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BLADE TYPES

• IMPULSE TYPE
• REACTION TYPE

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Single-rotor, Single-stage Turbine
Multiple-rotor, Multiple-stage Turbine
Multirotor - Multistage Turbine.  
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TURBINE BLADE COOLING

• Current turbine inlet temperatures in gas turbine
  engines are beyond the melting point of the
  turbine blade material.
• To prevent the blades from melting, turbine blade
  cooling methods are applied to the first turbine
  stages. Since
• convectively cooled flow fields and temperature
  fields are coupled and interact strongly, it is
  necessary to understand
• the flow physics in order to accurately predict
  how cooling will behave. In case of the rotating
  turbine blades, the effects
• of rotation also influence the flow. Centrifugal
  forces as well as the Coriolis force have to be
  included in the analysis.
• The present research project is an experimental
  and computational investigation of the flow
  through internal turbine
• blade cooling passages. In the first phase, the
  flow in a straight, stationary cooling channel is
  observed. Pressure
• measurements as well as hot-wire and PIV
  measurements are used to determine efficacy of
  different turbulator
• geometries. In the phase 2, the flow in a
  rotating cooling channel with an 180 bend will
  be investigated using PIV.

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Advantages of the gas turbine

• It is capable of producing large amounts of
  useful power for a relatively small size and
  weight
• Since motion of all its major components involve
  pure rotation (i.e. no reciprocating motion as in
  a piston engine), its mechanical life is long and
  the corresponding maintenance cost is relatively
  low.
• Although the gas turbine must be started by some
  external means (a small external motor or other
  source, such as another gas turbine), it can be
  brought up to full-load (peak output) conditions
  in minutes as contrasted to a steam turbine plant
  whose start up time is measured in hours.
• A wide variety of fuels can be utilized. Natural
  gas is commonly used in land-based gas turbines
  while light distillate (kerosene-like) oils power
  aircraft gas turbines. Diesel oil or specially
  treated residual oils can also be used, as well
  as combustible gases derived from blast furnaces,
  refineries and the gasification of solid fuels
  such as coal, wood chips and bagasse.

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Difference between impulse and reaction turbine
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UNIT-II

• RAMJET PROPULSION

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• A ramjet, sometimes referred to as a stovepipe
  jet, or an athodyd, is a form of jet engine that
  contains no major moving parts. Unlike most other
  airbreathing jet engines, ramjets have no rotary
  compressor at the inlet, instead, the forward
  motion of the engine itself 'rams' the air
  through the engine. Ramjets therefore require
  forward motion through the air to produce thrust.
• Ramjets require considerable forward speed to
  operate well, and as a class work most
  efficiently at speeds around Mach 3, and this
  type of jet can operate up to speeds of at least
  Mach 5.
• Ramjets can be particularly useful in
  applications requiring a small and simple engine
  for high speed use such as missiles. They have
  also been used successfully, though not
  efficiently, as tip jets on helicopter rotors.
• Ramjets are frequently confused with pulsejets,
  which use an intermittent combustion, but ramjets
  employ a continuous combustion process, and are a
  quite distinct type of jet engine

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RAMJET ENGINE PARTS
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RAMJET ENGINE THRUST
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Axial turbine blade vortex balding

• A turbine blade for a turbine engine having one
  or more cavities in a trailing edge of the
  turbine blade for forming one or more vortices in
  inner aspects of the trailing edge.
• In at least one embodiment, the turbine blade may
  include one or more elongated cavities in the
  trailing edge of the blade formed by one or more
  ribs placed in a cooling chamber of the turbine
  blade.
• The elongated cavity in the trailing edge may
  have one or more orifices in the rib on the
  upstream side of the cavity. The orifice may be
  positioned relative to a vortex forming surface
  so that as a gas is passed through one or more
  orifices into the elongated cavity, one or more
  vortices are formed in the cavity. The gas may be
  expelled from the cavity and the blade through
  one or more orifices in an inner wall forming the
  pressure side of the turbine blade

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INLETS

• SUBSONIC INLETS
• For aircraft that cannot go faster than the speed
  of sound, like large airliners, a simple,
  straight, short inlet works quite well. On a
  typical subsonic inlet, the surface of the inlet
  from outside to inside is a continuous smooth
  curve with some thickness from inside to outside.
  The most upstream portion of the inlet is called
  the highlight, or the inlet lip. A subsonic
  aircraft has an inlet with a relatively thick
  lip.
• SUPERSONIC INLETS
• An inlet for a supersonic aircraft, on the other
  hand, has a relatively sharp lip. The inlet lip
  is sharpened to minimize the performance losses
  from shock waves that occur during supersonic
  flight. For a supersonic aircraft, the inlet must
  slow the flow down to subsonic speeds before the
  air reaches the compressor. Some supersonic
  inlets, like the one at the upper right, use a
  central cone to shock the flow down to subsonic
  speeds. Other inlets, like the one shown at the
  lower left, use flat hinged plates to generate
  the compression shocks, with the resulting inlet
  geometry having a rectangular cross section. This
  variable geometry inlet is used on the F-14 and
  F-15 fighter aircraft. More exotic inlet shapes
  are used on some aircraft for a variety of
  reasons. The inlets of the Mach 3 SR-71 aircraft
  are specially designed to allow cruising flight
  at high speed. The inlets of the SR-71 actually
  produce thrust during flight.
• HYPERSONIC INLETS
• Inlets for hypersonic aircraft present the
  ultimate design challenge. For ramjet-powered
  aircraft, the inlet must bring the high speed
  external flow down to subsonic conditions in the
  burner. High stagnation temperatures are present
  in this speed regime and variable geometry may
  not be an option for the inlet designer because
  of possible flow leaks through the hinges. For
  scramjet-powered aircraft, the heat environment
  is even worse because the flight Mach number is
  higher than that for a ramjet-powered aircraft.
  Scramjet inlets are highly integrated with the
  fuselage of the aircraft. On the X-43A, the inlet
  includes the entire lower surface of the aircraft
  forward of the cowl lip. Thick, hot boundary
  layers are usually present on the compression
  surfaces of hypersonic inlets. The flow exiting a
  scramjet inlet must remain supersonic.

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INLET EFFICIENCY

• An inlet must operate efficiently over the entire
  flight envelope of the aircraft. At very low
  aircraft speeds, or when just sitting on the
  runway, free stream air is pulled into the engine
  by the compressor. In England, inlets are called
  intakes, which is a more accurate description of
  their function at low aircraft speeds. At high
  speeds, a good inlet will allow the aircraft to
  maneuver to high angles of attack and sideslip
  without disrupting flow to the compressor.
  Because the inlet is so important to overall
  aircraft operation, it is usually designed and
  tested by the airframe company, not the engine
  manufacturer. But because inlet operation is so
  important to engine performance, all engine
  manufacturers also employ inlet aerodynamicists.
  The amount of disruption of the flow is
  characterized by a numerical inlet distortion
  index. Different airframes use different indices,
  but all of the indices are based on ratios of the
  local variation of pressure to the average
  pressure at the compressor face.
• The ratio of the average total pressure at the
  compressor face to the free stream total pressure
  is called the total pressure recovery. Pressure
  recovery is another inlet performance index the
  higher the value, the better the inlet. For
  hypersonic inlets the value of pressure recovery
  is very low and nearly constant because of shock
  losses, so hypersonic inlets are normally
  characterized by their kinetic energy efficiency.
  If the airflow demanded by the engine is much
  less than the airflow that can be captured by the
  inlet, then the difference in airflow is spilled
  around the inlet. The airflow mis-match can
  produce spillage drag on the aircraft.

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SCRAMJET

• A scramjet (supersonic combustion ramjet) is a
  variation of a ramjet with the distinction being
  that some or all of the combustion process takes
  place supersonically. At higher speeds, it is
  necessary to combust supersonically to maximize
  the efficiency of the combustion process.
  Projections for the top speed of a scramjet
  engine (without additional oxidiser input) vary
  between Mach 12 and Mach 24 (orbital velocity).
  The X-30 research gave Mach 17 due to combustion
  rate issues. By way of contrast, the fastest
  conventional air-breathing, manned vehicles, such
  as the U.S. Air Force SR-71, achieve
  approximately Mach 3.4 and rockets from the
  Apollo Program achieved Mach 30.
• Like a ramjet, a scramjet essentially consists of
  a constricted tube through which inlet air is
  compressed by the high speed of the vehicle, a
  combustion chamber where fuel is combusted, and a
  nozzle through which the exhaust jet leaves at
  higher speed than the inlet air. Also like a
  ramjet, there are few or no moving parts. In
  particular, there is no high-speed turbine, as in
  a turbofan or turbojet engine, that is expensive
  to produce and can be a major point of failure.
• A scramjet requires supersonic airflow through
  the engine, thus, similar to a ramjet, scramjets
  have a minimum functional speed. This speed is
  uncertain due to the low number of working
  scramjets, relative youth of the field, and the
  largely classified nature of research using
  complete scramjet engines. However, it is likely
  to be at least Mach 5 for a pure scramjet, with
  higher Mach numbers (between 7 and 9) more
  likely. Thus scramjets require acceleration to
  hypersonic speed via other means. A hybrid
  ramjet/scramjet would have a lower minimum
  functional Mach number, and some sources indicate
  the NASA X-43A research vehicle is a hybrid
  design. Recent tests of prototypes have used a
  booster rocket to obtain the necessary velocity.
  Air breathing engines should have significantly
  better specific impulse while within the
  atmosphere than rocket engines.
• However, scramjets have weight and complexity
  issues that must be considered. While very short
  suborbital scramjet test flights have been
  successfully performed, perhaps significantly no
  flown scramjet has ever been successfully
  designed to survive a flight test. The viability
  of scramjet vehicles is hotly contested in
  aerospace and space vehicle circles, in part
  because many of the parameters which would
  eventually define the efficiency of such a
  vehicle remain uncertain. This has led to
  grandiose claims from both sides, which have been
  intensified by the large amount of funding
  involved in any hypersonic testing. Some notable
  aerospace gurus such as Henry Spencer and Jim
  Oberg have gone so far as calling orbital
  scramjets 'the hardest way to reach orbit', or
  even 'scamjets' due to the extreme technical
  challenges involved. Major, well funded projects,
  like the X-30 were cancelled before producing any
  working hardware

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Axial turbine blade cooling
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UNIT-III

• FUNDAMENTALS OF ROCKET PROPULSION

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INTERNAL BALLISTICS

• Internal ballistics is what happens inside a
  weapon when it is fired. The firing pin makes a
  distinct mark on the cartridge. Then explosive
  pressure causes the bullet to expand slightly to
  fill the spiral 'rifling' grooves cut in the
  bore. This makes the bullet spin as it passes
  down the barrel, but it leaves tell-tale marks on
  the bullet that are unique to that particular
  firearm. The presence of rust or spider silk
  indicates the gun has not been fired recently. At
  close range, particles from a wound may lodge
  inside the barrel. 
• External ballistics is what happens to the bullet
  and residues outside the gun, including the
  direction and velocity of the shot, as well as
  any deviation in the trajectory.
• Terminal ballistics looks at the changes in
  trajectory and speed caused by ricochet and
  penetration of objects, as well as the layered
  deposits on parts of the bullet accumulated as it
  contacts these objects. Terminal ballistics
  includes examination of the shape of wounds and
  the extent of tissue damage. If a bullet cannot
  be removed for examination, its calibre can be
  measured by CT scanning.

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NOZZLES
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ROCKET NOZZLE CLASSIFICATION

• FIXED NOZZLE
• MOVABLE NOZZLE
• SUBMERGED NOZZLE

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UNIT-IV

• CHEMICAL ROCKETS

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ADVANTAGES OF SOLID ROCKET MOTOR

• Advantages/Disadvantages
• Solid fueled rockets are relatively simple
  rockets. This is their chief advantage, but it
  also has its drawbacks.
• Once a solid rocket is ignited it will consume
  the entirety of its fuel, without any option for
  shutoff or thrust adjustment. The Saturn V moon
  rocket used nearly 8 million pounds of thrust
  that would not have been feasible with the use of
  solid propellant, requiring a high specific
  impulse liquid propellant.
• The danger involved in the premixed fuels of
  monopropellant rockets i.e. sometimes
  nitroglycerin is an ingredient.

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SOLID ROCKET MOTOR
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• A simple solid rocket motor consists of a casing,
  nozzle, grain (propellant charge), and igniter.
• The grain behaves like a solid mass, burning in a
  predictable fashion and producing exhaust gases.
  The nozzle dimensions are calculated to maintain
  a design chamber pressure, while producing thrust
  from the exhaust gases.
• Once ignited, a simple solid rocket motor cannot
  be shut off, because it contains all the
  ingredients necessary for combustion within the
  chamber that they are burned in. More advanced
  solid rocket motors can not only be throttled but
  can be extinguished and then re-ignited by
  controlling the nozzle geometry or through the
  use of vent ports. Also, pulsed rocket motors
  which burn in segments and which can be ignited
  upon command are available.
• Modern designs may also include a steerable
  nozzle for guidance, avionics, recovery hardware
  (parachutes), self-destruct mechanisms, APUs,
  controllable tactical motors, controllable divert
  and attitude control motors and thermal
  management materials

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• Thrust is the force which moves a rocket through
  the air. Thrust is generated by the rocket engine
  through the reaction of accelerating a mass of
  gas. The gas is accelerated to the the rear and
  the rocket is accelerated in the opposite
  direction. To accelerate the gas, we need some
  kind of propulsion system. We will discuss the
  details of various propulsion systems on some
  other pages. For right now, let us just think of
  the propulsion system as some machine which
  accelerates a gas.
• From Newton's second law of motion, we can define
  a force to be the change in momentum of an object
  with a change in time. Momentum is the object's
  mass times the velocity. When dealing with a gas,
  the basic thrust equation is given as
• F mdot e Ve - mdot 0 V0 (pe - p0) Ae
• Thrust F is equal to the exit mass flow rate mdot
  e times the exit velocity Ve minus the free
  stream mass flow rate mdot 0 times the free
  stream velocity V0 plus the pressure difference
  across the engine pe - p0 times the engine area
  Ae.
• For liquid or solid rocket engines, the
  propellants, fuel and oxidizer, are carried on
  board. There is no free stream air brought into
  the propulsion system, so the thrust equation
  simplifies to
• F mdot Ve (pe - p0) Ae
• where we have dropped the exit designation on the
  mass flow rate.
• Using algebra, let us divide by mdot
• F / modt Ve (pe - p0) Ae / mdot
• We define a new velocity called the equivalent
  velocity Veq to be the velocity on the right hand
  side of the above equation
• Veq Ve (pe - p0) Ae / mdot
• Then the rocket thrust equation becomes
• F mdot Veq
• The total impulse (I) of a rocket is defined as
  the average thrust times the total time of
  firing. On the slide we show the total time as
  "delta t". (delta is the Greek symbol that looks
  like a triangle)
• I F delta t
• Since the thrust may change with time, we can
  also define an integral equation for the total
  impulse. Using the symbol (Sdt) for the integral,
  we have
• I S F dt
• Substituting the equation for thrust given above
  
• I S (mdot Veq) dt

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• A bipropellant rocket engine is a rocket engine
  that uses two propellants (very often liquid
  propellants) which are kept separately prior to
  reacting to form a hot gas to be used for
  propulsion.
• In contrast, most solid rockets have single solid
  propellant, and hybrid rockets use a solid
  propellant lining the combustion chamber that
  reacts with an injected fluid. Because liquid
  bipropellant systems permit precise mixture
  control, they are often more efficient than solid
  or hybrid rockets, but are normally more complex
  and expensive, particularly when turbopumps are
  used to pump the propellants into the chamber to
  save weight

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Liquid propellant

• Thousands of combinations of fuels and oxidizers
  have been tried over the years. Some of the more
  common and practical ones are
• liquid oxygen (LOX, O2) and liquid hydrogen (LH2,
  H2) - Space Shuttle main engines, Ariane 5 main
  stage and the Ariane 5 ECA second stage, the
  first stage of the Delta IV, the upper stages of
  the Saturn V, Saturn IB, and Saturn I as well as
  Centaur rocket stage
• liquid oxygen (LOX) and kerosene or RP-1 - Saturn
  V, Zenit rocket, R-7 Semyorka family of Soviet
  boosters which includes Soyuz, Delta, Saturn I,
  and Saturn IB first stages, Titan I and Atlas
  rockets
• liquid oxygen (LOX) and alcohol (ethanol, C2H5OH)
  - early liquid fueled rockets, like German (World
  War II) A-4, aka V-2, and Redstone
• liquid oxygen (LOX) and gasoline - Robert
  Goddard's first liquid-fuel rocket
• T-Stoff (80 hydrogen peroxide, H2O2 as the
  oxidizer) and C-Stoff (methanol, CH3OH, and
  hydrazine hydrate, N2H4n(H2O as the fuel) -
  Walter Werke HWK 109-509 engine used on
  Messerschmitt Me 163B Komet a rocket fighterplane
  of (World War II)
• nitric acid (HNO3) and kerosene - Soviet Scud-A,
  aka SS-1
• inhibited red fuming nitric acid (IRFNA, HNO3
  N2O4) and unsymmetric dimethyl hydrazine (UDMH,
  (CH3)2N2H2) Soviet Scud-B,-C,-D, aka SS-1-c,-d,-e
  
• nitric acid 73 with dinitrogen tetroxide 27
  (AK27) and kerosene/gasoline mixture - various
  Russian (USSR) cold-war ballistic missiles, Iran
  Shahab-5, North Korea Taepodong-2
• hydrogen peroxide and kerosene - UK (1970s) Black
  Arrow, USA Development (or study)
• hydrazine (N2H4) and red fuming nitric acid -
  Nike Ajax Antiaircraft Rocket
• Aerozine 50 and dinitrogen tetroxide - Titans
  24, Apollo lunar module, Apollo service module,
  interplanatary probes (Such as Voyager 1 and
  Voyager 2)
• Unsymmetric dimethylhydrazine (UDMH) and
  dinitrogen tetroxide - Proton rocket and various
  Soviet rockets
• monomethylhydrazine (MMH, (CH3)HN2H2) and
  dinitrogen tetroxide - Space Shuttle Orbital
  maneuvering system (OMS) engines
• Robert Goddard and his rocket
• One of the most efficient mixtures, oxygen and
  hydrogen, suffers from the extremely low
  temperatures required for storing hydrogen and
  oxygen as liquids (around 20 K or -253 C)) and
  low fuel density (70 kg/m³), necessitating large
  and heavy tanks. The use of lightweight foam to
  insulate the cryogenic tanks caused problems for
  the Space Shuttle Columbia's STS-107 mission, as
  a piece broke loose, damaged its wing and caused
  it to break up and be destroyed on reentry.
• For storable ICBMs and interplanetary spacecraft,
  storing cryogenic propellants over extended
  periods is awkward and expensive. Because of
  this, mixtures of hydrazine and its derivatives
  in combination with nitrogen oxides are generally
  used for such rockets. Hydrazine has its own
  disadvantages, being a very caustic and volatile
  chemical as well as being toxic. Consequently,
  hybrid rockets have recently been the vehicle of
  choice for low-budget private and academic
  developments in aerospace technology

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UNIT-V

• ADVANTAGES OF PROPULSION TECHNIQUES

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• Chemical rocket engines, like those on the space
  shuttle, work by burning two gases to create
  heat, which causes the gases to expand and exit
  the engine through a nozzle. In so doing they
  create the thrust that lifts the shuttle into
  orbit. Smaller chemical engines are used to
  change orbits or to keep satellites in a
  particular orbit.
• For getting to very distant parts of the solar
  system chemical engines have the drawback in that
  it takes an enormous amount of fuel to deliver
  the payload. Consider the Saturn V rocket that
  put men on the moon 5,000,000 pounds of it's
  total take off weight of 6,000,000 pounds was
  fuel.
• Electric rocket engines use less fuel than
  chemical engines and therefore hold the potential
  for accomplishing missions that are impossible
  for chemical systems. To understand how, we have
  to understand a number called specific impulse.

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• A resistojet simply uses electricity passing
  through a resistive conductor, something like the
  wires in your toaster, to heat a gas as it passes
  over the conductor. As the conductor heats up the
  gas is heated, expands, exits through a nozzle
  and creates thrust.
• In real resistojets the conductor is a coiled
  tube through which the propellant flows. This is
  done to get maximum heat transfer from the
  conductor to the propellant.

diagram of a resistojet
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• An arcjet is simply a resistojet where instead of
  passing the gas through a heating coil it's
  passed through an electric arc.
• diagram of an arcjet
• Because arcs can achieve temperatures of 15,00
  degrees C. this means the propellant gets heated
  to much higher temperatures (typically 3,000
  degrees C.) than in resistojets and in so doing
  achieve higher specific impulses, anywhere from
  800 sec for ammonia to 2,000 seconds for
  hydrogen. Arcjets tend to be higher power
  devices, typically 1 to 2 kilowatts, and used for
  higher thrust applications, like station keeping
  of large satellites. Several are currently in
  orbit.

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• Ion engines
• Rub a balloon against your hair or shirt and then
  hold it near your arm, the hairs on your arm will
  feel tingly and be attracted to the balloon.
  Bring the balloon near the carpet and bits of
  lint will be pulled to it. What's happening is
  that electrons have been deposited onto or
  removed from the balloon depending on what it was
  rubbed against, giving it an electrostatic
  charge, which creates an electrostatic field. A
  similar field can be used to produce thrust in a
  rocket engine called an ion thruster.
• ion engine diagram
• As propellant enters the ionization chamber (the
  small ns on the left), electrons (small -s in the
  middle) emitted from the central hot cathode and
  attracted to the outer anode collide with them
  knocking an electron off and causing the atoms of
  the propellant to become ionized (s on the
  right). This means that they have an electric
  field around them like the balloon. As these ions
  drift between two screens at the right hand side
  of the ionization chamber, the strong electric
  field of the "" side repels them and the "-"
  side attracts them, accelerating them to very
  high velocities. The ions leave the engine and
  since the engine pushes on them to accelerate
  them, they in turn push back against the engine
  creating thrust. Ion thrusters typically use
  Xenon (A very heavy, inert gas) for propellant,
  have specific impulses in the 3,000 to 6,000
  range and efficiencies up to 60 percent. An
  average thruster is one to two feet in diameter,
  produces thrust on the order of small fractions
  of a pound and weighs some tens of pounds.

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Nuclear rocket motor
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• In a nuclear thermal rocket a working fluid,
  usually hydrogen, is heated to a high temperature
  in a nuclear reactor, and then expands through a
  rocket nozzle to create thrust.
• The nuclear reactor's energy replaces the
  chemical energy of the reactive chemicals in a
  traditional rocket engine.
• Due to the higher energy density of the nuclear
  fuel compared to chemical ones, about 107 times,
  the resulting efficiency of the engine is at
  least twice as good as chemical engines even
  considering the weight of the reactor, and even
  higher for advanced designs.

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Risk in nuclear rocket motor

• There is an inherent possibility of atmospheric
  or orbital rocket failure which could result in a
  dispersal of radioactive material, and resulting
  fallout. Catastrophic failure, meaning the
  release of radioactive material into the
  environment, would be the result of a containment
  breach. A containment breach could be the result
  of an impact with orbital debris, material
  failure due to uncontrolled fission, material
  imperfections or fatigue and human design flaws.
  A release of radioactive material while in flight
  could disperse radioactive debris over the Earth
  in a wide and unpredictable area. The zone of
  contamination and its concentration would be
  dependent on prevailing weather conditions and
  orbital parameters at the time of re-entry.
  However given that oxide reactor elements are
  designed to withstand high temperatures (up to
  3500 K) and high pressures (up to 200 atm normal
  operating pressures) it's highly unlikely a
  reactor's fuel elements would be reduced to
  powder and spread over a wide-area. More likely
  highly radioactive fuel elements would be
  dispersed intact over a much smaller area, and
  although individually quite lethal up-close, the
  overall hazard from the elements would be
  confined to near the launch site and would be
  much lower than the many open-air nuclear weapons
  tests of the 1950s.

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Solar sail
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• The spacecraft arranges a large membrane mirror
  which reflects light from the Sun or some other
  source.
• The radiation pressure on the mirror provides a
  small amount of thrust by reflecting photons.
• Tilting the reflective sail at an angle from the
  Sun produces thrust at an angle normal to the
  sail.
• In most designs, steering would be done with
  auxiliary vanes, acting as small solar sails to
  change the attitude of the large solar sail.
• The vanes would be adjusted by electric motors.

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Limitation of solar sail

• Solar sails don't work well, if at all, in low
  Earth orbit below about 800 km altitude due to
  erosion or air drag. Above that altitude they
  give very small accelerations that take months to
  build up to useful speeds. Solar sails have to be
  physically large, and payload size is often
  small. Deploying solar sails is also highly
  challenging to date.
• Solar sails must face the sun to decelerate.
  Therefore, on trips away from the sun, they must
  arrange to loop behind the outer planet, and
  decelerate into the sunlight.
• There is a common misunderstanding that solar
  sails cannot go towards their light source. This
  is false. In particular, sails can go toward the
  sun by thrusting against their orbital motion.
  This reduces the energy of their orbit, spiraling
  the sail toward the sun

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• THANK U