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AE-1351 PROPULSION-II UNIT-1 AIRCRAFT GAS TURBINES Gas Turbine In an aircraft gas turbine the output of the turbine is used to turn the compressor (which may also ... – PowerPoint PPT presentation

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Title: AE-1351


1
AE-1351
  • PROPULSION-II

2
UNIT-1
  • AIRCRAFT GAS TURBINES

3
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

4
  • 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.

5
  • TYPES OF TURBINES
  • AXIAL FLOW TURBINE
  • RADIAL FLOW TURBINE

6
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.
7
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.
8
BLADE TYPES
  • IMPULSE TYPE
  • REACTION TYPE

9
Single-rotor, Single-stage Turbine
Multiple-rotor, Multiple-stage Turbine
Multirotor - Multistage Turbine.  
10
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.

11
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.

12
Difference between impulse and reaction turbine
13
UNIT-II
  • RAMJET PROPULSION

14
  • 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

15
RAMJET ENGINE PARTS
16
RAMJET ENGINE THRUST
17
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

18
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19
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.

20
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.

21
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

22
Axial turbine blade cooling
23
UNIT-III
  • FUNDAMENTALS OF ROCKET PROPULSION

24
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.

25
NOZZLES
26
ROCKET NOZZLE CLASSIFICATION
  • FIXED NOZZLE
  • MOVABLE NOZZLE
  • SUBMERGED NOZZLE

27
UNIT-IV
  • CHEMICAL ROCKETS

28
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.

29
SOLID ROCKET MOTOR
30
  • 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

31
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33
  • 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

34
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35
  • 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

36
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

37
UNIT-V
  • ADVANTAGES OF PROPULSION TECHNIQUES

38
  • 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.

39
  • 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
40
  • 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.

41
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42
  • 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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44
Nuclear rocket motor
45
  • 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.

46
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.

47
Solar sail
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49
  • 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.

50
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

51
  • THANK U
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