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Reusable Launch Vehicle RLV


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A   hundred     years    ago,    on    December      17,     1903,      Wilbur    and
Orville    Wright       successfully        achieved     a   piloted,         powered
flight. Though the Wright Flyer I flew only 10 ft off the
ground    for    12     seconds,      traveling      a     mere    120    ft,     the
aeronautical technology it demonstrated paved the way for
passenger air transportation. Man had finally made it to
the air. The Wright brother’s plane of 1903 led to the
development of aircrafts such as the WWII Spitfire, and
others.    In    1926    the    first       passenger    plane     flew       holiday
makers from American mainland to Havana and Bahamas. In 23
years the world had moved from a plane that flew 120 ft and
similar planes that only a chosen few could fly, to one
that can carry many passengers. Today air travel is worth
billions.        The military has produced planes for special
purposes      like    SR-71     for    high     speed      and    high    altitude
flying,    F-117      Nightbird       the    stealth     fighter,        and    other
world    class    dogfighters         like     Russian     Sukhoi       37,    French
Mirage, British Harriers, and American F22 Raptor.

                                      In October 1957, man entered the
space age. Russia sent the first satellite, the Sputnik,
and in April 1961, Yuri Gagarin became the first man on
space. In the years since Russia and United States has sent
many air force pilots and a fewer scientists, engineers and
others.    But    even    after       almost    50   years,       the    number    of
people who has been to space is close to 500.
                          The      people     are    losing       interest   in
seeing a chosen few going to space and the budgets to space
research is diminishing. The space industry now makes money
by taking satellites to space. But a major factor here is
the cost. At present to put a single kg into orbit will
cost   you    between    $10000       and    $20000.       This    is   clearly
prohibitively high and a major objective for the coming
years is to drop the cost to a fraction of today's value.
Despite the fact that the space shuttle has regularly gone
into orbit over the last two decades there is still no
tourist business. This is due to the fact that to build an
orbital hotel under present conditions will cost 100's of
billions of dollars (at least). It is clear why there has
been so little progress in orbital developments.

                                   The development of a plane which
can fly to space at lower cost, which is reusable and can
take   more   payloads,      is    very     much    required      for   further
development     of     space      industries.       The     Reusable     Launch
Vehicle, usually called Spaceplane or Hyperplane which can
take crew and payload into orbit is being developed by
various      space     agencies       and     private       companies.       The
Spaceplane would make space travel cheap and will help in
increasing    space     tourism      and    just    like    in    the   aviation
industry,     within     a     few     decades,       the    space      tourism
industries would be worth billions.
The Advantages

The rockets which take satellites and other payloads have
to   carry    the   fuel     and     oxidizer         with    them    as    it       uses
conventional       rocket    engines.          The   combined      weight       of    the
fuel and oxidizer is very large due to the fact that a lot
of energy is expended pushing the plane forwards. This is
why today's rockets launch vertically as it maximizes the
rocket's potential by allowing all the energy expended to
be focused in the direction we want to go - upwards. With
present technology it is the easiest and cheapest method of
reaching space.

                         Clearly       then      the    way     forward         is     to
utilize jet engines in some manner. The main advantages of
jet engines over rocket engines are that they do not need
to carry their own oxidizer; instead they suck in air and
use the oxygen present in the air as their oxidizer. This
will greatly remove the need to carry oxidizer, as it will
only be needed when at an altitude that the air contains
insufficient oxygen for jets to operate. At this point the
rocket engines will fire and burn the much smaller quantity
of   onboard      oxidizer.      This     will       dramatically       reduce        the
take-off weight and also the cost of the craft. Reduction
in   take-off     weight     means       the    payload      can   be    increased.
Further      to   this     the   use     of     jet    engines       will   make       a
substantial       saving    on     the    expensive       rocket        fuel.    As     a
comparison to produce the same thrust, jet (air-breathing)
engines require less than one seventh the propellants (fuel
+ oxidizer) that rockets do. For example, the space shuttle
needs     143,000      gallons    of     liquid      oxygen,       which    weighs
1,359,000 pounds (616,432 kg). Without the liquid oxygen,
the shuttle weighs a mere 165,000 pounds (74,842 kg).

                          Another      advantage       of    jet-engine       craft
is that as they rely on aerodynamic forces rather than on
rocket thrust, they have greater maneuverability, which in
turn provides better flexibility and safety, for example
missions can be aborted mid-flight if there is a problem.
This is not the case for staged vehicles, which typically
have    complex     "range     safety"       requirements      as     the   stages
detach and fall back to earth. Range safety is one of the
main reasons that the US launches from Florida, where the
rocket's flight path takes it out over open water almost
immediately. The lack of such abort modes on the Shuttle
requires    incredible       failure       avoidance      costs      and    massive

                 The   space     shuttle     used    by     NASA    is   partially
reusable. It still has to take off vertically with the help
of multistage rocket and solid boosters. The use of rockets
increases the cost of manufacturing parts for each launch
as some rocket parts are not reusable. Further more, using
rockets increases the amount of fuel and oxidizer required.
Some of the components of the rocket get added to the space
debris     and    continue       orbiting      the    earth.        This    causes
unwanted collisions with other debris or satellites. Thus
using a jet-engine craft as a reusable launch vehicle is
faster,     efficient,         and     has     increased           affordability,
flexibility and safety for ultra high-speed flights within
the atmosphere and into Earth orbit.
The Different Proposals

Today     three    main     concepts       are    being    proposed.       The
difference is in way the RLV is launched. This difference
results in differing levels of complexity in design. The
major concepts are…

Two Stage To Orbit (TSTO)

This is the easiest method; firstly a large aeroplane takes
off   carrying     a    smaller   rocket    engine    craft   (called      the
orbiter)    and    reaches    a   fairly     high    altitude.   Then      the
smaller    craft       launches   from   the     carrier   and   as   it    is
already at high altitude before firing its engines, the
need for fuel is minimized. It also means that the wings on
the orbiter can be made smaller. There is no doubt that
this option certainly creates less engineering problems.
This type of technology was around in the 1960's and was
used during the testing of the X-15.

One and a Half Stage To Orbit (OHSTO)

There are various 'One and a Half Stages' ideas that are
certainly innovative ideas and deserve mention. The most
promising is that of mid-air fuelling, taking on the fuel
and oxidizer for space once at a high altitude. These ideas
do not overcome the problems of commercially viability that
the 2-stage models suffer from; however it could be a good
temporary measure.
Single Stage To Orbit (SSTO)

It is a reusable launch vehicle (RLV) that takes off and
lands     horizontally     like    a     conventional          plane.    It     is
generally regarded that this method will be more efficient
and safer than the 2-stage model, though that is not to
belittle the 2-stage method which would be a considerable
improvement on the vertical take off craft of today. It is
also felt that while the 2-stage idea would be easier, the
1-stage would almost certainly be more commercially viable
and     would    achieve   a    higher    level        of    success     in    the
objectives of a spaceplane.

                                              What    is    required    here    is
further development of jet engines. The only possibility at
the     moment    is   ramjet     working       together       with     scramjet
(Supersonic Combustion Ramjet). The major problem is that
the scramjets are far from fully developed, offering many
difficult aerodynamic problems. These, however, offer the
only current hope of sustained hypersonic flight.

                       Even     with     the         advance    of      scramjet
development there are still many problems to be addressed
with horizontal take off of spaceplanes. This is because a
Scramjet    will    only   function      at    hypersonic       speeds    and    a
ramjet will only function at supersonic speeds. The design
will therefore require:
  1. A turbojet, once the air intake reaches to mach 1
       (supersonic speed) the ramjet would fire.
  2. The ramjet would accelerate the plane to about mach 4
       (hypersonic speed) then the scramjet would fire.
  3. The scramjet is expected to be able to reach speeds of
       mach 15, when finally the rocket engine would fire.
  4. The rocket engine would accelerate the plane to mach
       25    (escape   velocity)          and    would     be    used       in     space

While this sounds very good in theory, in practice it is
very    doubtful       whether      such        vehicles        will        have    the
efficiency to reach orbit, due to the excessive weight and
complexity of such a system. Further to this such a design
will    not    solve    the       other     problem      of      heat       build-up.
These problems have not, however, removed the interest in
this    system   and    several          proposals     are      currently          being
tested by NASA.

                                 What we are really looking for is
the    development     of    a    combined       jet   engine        that    operates
across the range, with maybe a switch to a rocket engine
for    the    last     stage       and     for     space        operations.          The
difficulties of designing a jet engine to perform at these
levels are such that it can not even be seen how it could
be done with present technology. The differences between
the    engines   are    how      they     physically       take      the     air    in.
Nanotechnology       could       solve    the    problem        by   allowing        the
engine to reshape itself in flight, whether it could be
shaped fast enough remains to be seen.

The working of a RLV can be divided into 4 stages

1. First stage – subsonic and supersonic stage:
The RLV with its payload takes off from the runway and
climbs to about 100,000 feet or 30km using conventional
jet-engines, or using a combination of conventional jet-
engine and ramjet engine, or using another plane to carry
or pull the plane to a lower height and using a booster

                          A       ramjet       operates       by      subsonic
combustion of fuel in a stream of air compressed by the
forward speed of the aircraft. It doesn’t have or use very
less    moving    parts   compared      to   a   conventional      jet-engine
with    thousands    of   moving     parts.      The    compression    of   air
before    burning    of    fuel    is   done     in    the   ramjet    by   the
addition of a diffuser at the inlet, while it is done by
the turbine in conventional jet-engine. The flow of air is

                  The plane is accelerated to a speed of mach 4
or     mach   5   and     the   flow       inside      the   engine   becomes
supersonic. Then the scramjet is powered up.
2.    Second      stage        -    Hypersonic         stage:             When     the
spaceplane is at an altitude of about 100,000 ft and at a
velocity of about mach 4, the scramjets are fired.

Scramjets are basically ramjets. They introduce fuel and
mix it with oxygen obtained from the air which compressed
for   combustion.        The   air    is     naturally     compressed       by     the
forward speed of the vehicle and the shape of the inlet,
similar to what turbines or pistons do in slower-moving
airplanes      and       cars.      Rather      than       using     a     rotating
compressor,       like    a      turbojet     engine       does,    the     forward
velocity and aerodynamics compress the air into the engine.
Hydrogen fuel is then injected into the air stream, and the
expanding hot gases from combustion accelerate the exhaust
air   to   create      tremendous       thrust.      While    the     concept       is
simple,     proving      the       concept    has    not     been     simple.       At
operational      speeds,       flow   through       the    scramjet       engine    is
supersonic - or faster than the speed of sound. At that
speed, ignition and combustion take place in a matter of
milliseconds. This is one reason it has taken researchers
decades to demonstrate scramjet technologies, first in wind
tunnels    and    computer         simulations,      and    only     recently      in
experimental flight tests.
                 The   Scramjet       engine      takes     the     RLV    to    even
greater heights and to speeds of up to Mach 15. This is the
fastest speed an air breathing plane can go using current
technologies. At Mach 15, the RLV is at a great height that
there isn’t enough oxygen to sustain the scramjet engine.
At this point the rocket engine fires up.
3. Third stage - Space stage:                          When the rocket engine
fires by mixing oxygen from the onboard storage tanks into
the     scramjet      engine,    thereby         replacing         the        supersonic
airflow. The rocket engine is capable of accelerating the
RLV to speeds of about Mach 25, which is the escape

velocity. It takes the RLV into orbit. The rocket engine
takes the RLV to the payload release site and the required
operations are done. Once this is over it enters its last
stage – the re-entry stage.

4. Fourth stage – Re-entry stage:                                       Once the RLV
finishes       its    mission       in    space,       It    performs           de-orbit
operations, including firing its thrusters to slow itself
down,    thereby      dropping      to    a    lower     orbit      and       eventually
entering the upper layers of the atmosphere. As the vehicle
encounters denser air, the temperature of the ceramic skin
builds to over 1,000 degrees C, and is also cooled by using
any remaining liquid hydrogen fuel. It is here that the
structure of the plane undergoes heavy thermal stress. If
the heat shields do not protect the plane, it would simply
burn    off    to     the   ground,       just    like       the        space    shuttle
Columbia. It enters a radio silence zone as due to the
heat, radio contact is lost. Once it reaches dense air, it
can    use    its    aerodynamics        to    glide     down      to     the    landing
strip.    It    can    also   use    any       remaining         fuel    to     fire   the
ramjet    or    conventional        jet       (depends      on    the     design)      and
change its course. Once on the landing strip it engages it
slows down using a series of parachutes and engages the

The construction of a true RLV that can take a payload to
space is still in the design stage. It will sure have lot
of designs taken from the space shuttle. Here are the main
construction details.

Body:     The       body    of     a     RLV    has    to    withstand      very       high
stresses including thermal stresses during re-entry. The
plane expands due to the high heat of nearly 1500˚C or
more.     It    also       has    to     cope    with       the     rapid   change       in
temperatures once in space. It changes from -250 degrees in
the shade to 250 degrees in direct sunlight. This change in
temperature between two sides of the same plane will put a
lot of stress on its body. Titanium alloys are being used,
being     very      strong        and     light.      To     cope    with    the        high
temperatures developed in parts of the wing and fuselage of
the   spacecraft       today,           reinforced      carbon-carbon          composite
material       is    being       added     to    the       leading     edges      of    the
vehicle's nose and wings to handle the higher temperatures.

                                        Researches are being conducted to
find the best materials for different parts of the plane.
One of these materials, γ-TiAl (Titanium Aluminide), has
superior        high-temperature           material          properties.       Its       low
density        provides      improved          specific       strength      and        creep
resistance in comparison to currently used titanium alloys.
However, it is inherently brittle, and long life durability
is    a    potential             problem       along        with     the    material’s
sensitivity to defects.
Wings:       The wing of the spacecraft has to be designed so
that    it   provides      enough   lift    to    fly    to   space    and   also
reduce the friction during re-entry.

Cockpit:       The cockpit is the place where the astronauts
will stay most of the time during the journey. It will have
many    windows,     which    are   special      double-paned       glass,    and
each pane alone can withstand the pressure and force of
flight and the vacuum. This doubling up ensures that if
either window were to crack, the passengers would still be

                                 The air inside the cockpit is made
breathable by a three-part system. Breathable air is added
at a constant rate by oxygen bottles. The exhaled carbon
dioxide is removed from the cabin by an absorber system,
and     humidity     is    controlled      by    an     additional     absorber
created to remove water vapor from the air. During the
entire flight, the cockpit remains comfortable, cool and

                   The     avionics   system       and    display     unit    for
navigating     has    to    be   computer       controlled    and     free   from
bugs. It should give the pilot all the necessary data to
make his choices. The avionics are very critical, and it
also needs to be very precise for the pilot to do what he
wants to do, and do it well.

Electric Power: The electrical power required for the
running of the spacecraft has to be taken from batteries.
These batteries could be charged, if needed by using solar
energy. Researches are being initiated to find better and
reliable batteries, like the lithium-based (i.e., Li metal
or Li-ion intercalation compound as negative electrode),
polymer    electrolyte       regenerative       battery    system.    Its
advantages       include    reduced   battery    weight    and    volume,
relative    to    conventional   Ni-Cd   and     Ni-H2,   which   permits
greater payloads and greater cell voltage, 3.5 volts vs.
1.2 volts, which permits use of fewer cells and results in
reduced battery system complexity.

Controls: When we're out in space, all you need to do is
release a puff of air in a direction to give you a reaction
force to push you the other way. That is called a reaction
control system. High-pressure air is stored in bottles on
the ship, and on the release of a little blast of air for
about one     second,      for example, with      the right wing tip
pointing up. And that is enough when you're in space to
push that wingtip down. It effectively rolls the aircraft,
and that are the controls when it is out in space.

Fuels: Many challenges have been overcome recently by the
discovery and synthesis of propellants that can have higher
performance      than   traditional    O2/H2,    and   aircraft    fuels.
These propellants include high-density monopropellants for
sounding rockets and upper stages, and onboard propulsion
for small spacecraft. Higher energy fuels, such as N4, N6,
BH4, and others, have a longer range development time and
would be more applicable to future launch vehicles.
Reusable Launch Vehicles

The X-43 Hyper-X from NASA

Hyper-X,     NASA's       multi-year        hypersonic          flight       research
program, seeks to overcome one of the greatest aeronautical
research challenges - air-breathing hypersonic flight. Far
outpacing contemporary aircraft of supersonic capability,
three X-43A vehicles were built to fly at speeds of Mach 7
and 10. Ultimately, the revolutionary technologies exposed
by   the    Hyper-X        Program        promise    to        increase        payload
capacities       and    reduce     costs     for    future       air     and     space

                  MicroCraft, Inc. of Tullahoma, Tenn., is the
industry    partner       chosen     by    NASA     to    construct       the    X-43
vehicles. The contract award announcement occurred on March
24, 1997, with construction of the vehicles beginning soon
thereafter. Orbital Sciences Corporation's Launch Vehicles
Division    in    Chandler,      Ariz.      will    construct          the   Hyper-X
launch vehicles.

                          The goal of the Hyper-X program is to
flight validate key propulsion and related technologies for
air-breathing          hypersonic    aircraft.           The    first     X-43     was
scheduled to fly at Mach 7. This is far faster than any
air-breathing aircraft have ever flown. The world's fastest
air-breathing aircraft, the SR-71, cruises slightly above
Mach 3. The highest speed attained by NASA's rocket-powered
X-15 was Mach 6.7, back in 1967.

                               Hyper-X       research         began   with      conceptual
design and wind tunnel work in 1996. Three unpiloted X- 43A
research aircraft were built. Each of the 12-feet long, 5-
feet-wide lifting body vehicles was designed to fly once.
They    are       identical         in     appearance,         but    engineered       with
slight differences that simulate variable engine geometry,
generally a function of Mach number. The first and second
vehicles were designed to fly at Mach 7 and the third at
Mach 10. At these speeds, the shape of the vehicle forebody
serves the same purpose as pistons in a car, compressing
the    air        as    fuel    is        injected      for     combustion.        Gaseous
hydrogen fuels the X-43A. The first flight attempt in June
2001 failed when the booster rocket went out of control and
the booster rocket and X-43A combination—was destroyed by
ground controllers. The second attempt at Mach 7, in March
2004, was highly successful.

                                         At Mach 6.8—or almost seven times
the speed of sound—the X-43A research vehicle was traveling
nearly       5,000       mph   during        the    March      2004    flight,     easily
setting       a    world       speed       record       for    a   jet-powered         (air-
breathing) vehicle. Guinness World Records has recognized
the accomplishment

                                          The tricky part in the development
of    this    technology            is    that     as   the    air    is   in    the   tube
remains for mere milliseconds, getting such details as the
fuel-air mixture right, is still very difficult. And the
fact     that          what    is        right     is    different         at   different
velocities        makes    the       problem    more    complicated.          The    big
challenge of designing a ―variable geometry engine‖ (as the
professionals call it), which will be able to accommodate
these     differences,          has     not     yet    been     still       solved   by
engineers. So, for simplicity, the flights of the X-43A
didn’t have to accelerate under its own power. Instead, it
was carried by a booster rocket to the required speed and

                      On     16       November,       2004,        NASA's     unmanned
Hyper-X (X-43A) aircraft reached Mach 9.6. The X-43A was
boosted to an altitude of 33,223 meters (109,000 feet) by a
Pegasus      rocket       launched      from     beneath       a    B52-Bomber       jet
aircraft, which had taken off from Edwards Air Force Base
in California in the U.S. Then the booster rocket lofted it
to a height of 33,223 meters (109,000 feet). Thereafter the
booster    separated        and      the    scramjet    was        ignited.    Moments
later the scramjet fired for about 10 seconds and the craft
while flying on its own at about 7000 miles/hour (using its
own gaseous hydrogen fuel) conducted a series of high speed
maneuvers,        before     gliding          away    and     crashing      into     the
Pacific Ocean.


The   SpaceShipOne         is    a    RLV     built    by   the     company     Scaled
Composites LLC for competing in the X – Price. The Ansari X
Prize   is    a    contest       that      promised     a   cash      prize    of    $10
million to the first registered team to:

     Build a spaceship able to carry three adults (height
      up to 188 centimeters [6 feet, 2 inches] and weight up
      to 90 kilograms [198 pounds] each).
     Launch the spaceship with three soon-to-be astronauts
      to    a    height     of     100     kilometers          (62.5      miles),          the
      internationally            recognized       altitude           at       which     sub-
      orbital space begins.
     Return       the    spaceship      to     Earth        safely      --    no     broken
      bones on the astronaut, no severe damage to the ship,
     Repeat       the    flight     within      two        weeks    using      the     same
      ship, having replaced no more than 10 percent of the
      ship's       parts     (with       the     exception          of    fuel),        thus
      classifying          the     spacecraft          as     a     Reusable          Launch
      Vehicle (RLV).
     Do it all without any government funding, using only
      private financing.

             The     company       designed           and     built       another          jet
aircraft which would carry the SpaceShipOne to a height of
about 50,000 feet. This turbofan powered aircraft, called
the   White      knight     takes    off       like    a     plane    from      a     normal
airstrip, with SpaceShipOne attached to its belly. The two
ships      fly     together      under      White          Knight's       power       to     a
predetermined            altitude.       Then         White         Knight       releases
SpaceShipOne and drifts away. Once clear of White Knight,
SpaceShipOne begins its journey to sub-orbital space. The
White   Knight       was    designed       with       a     high     thrust-to-weight
ratio and powerful speed brakes. These features help to
simulate space flight maneuvers.

                              On October 4th 2004, the SpaceShipOne
flew to take the $10 million price. It was timed partially
to coincide with the 47th anniversary of the Soviet launch
of Sputnik. When the SpaceShipOne is released, it glides
for about 10 seconds while the pilot sets up the aircraft
for the rocket boost and he throws the switch, and the
hybrid   rocket      motor    in     the    SpaceShipOne      accelerates      the
aircraft.   The      hybrid    rocket       motor     has   combined    elements
from both solid and liquid rocket motors. This makes for a
unique motor capable of accelerating SpaceShipOne to twice
the speed of sound.           SpaceShipOne is propelled by a mixture
of   hydroxy-terminated             polybutadiene       (tire    rubber)       and
nitrous oxide (laughing gas). The rubber acts as the fuel
and the laughing gas as the oxidizer. The pilot immediately
commences a pullout maneuver to go straight up. The ship
continues to accelerate going straight out for a little
over a minute. It flies for about one minute, straight up
and then burn out about 150,000 feet, roughly. The motor
stop burning at that point, but now the ship is moving over
2,000 miles per hour, straight out, and so it coasts. From
there it coasts up another 150,000 feet roughly, up until
it   reaches    apogee       (the    point     at   which    SpaceShipOne      is
farthest    from      Earth).         The     pilot     feels    Zero      g    or
weightlessness for some time at the topmost point. Then it
falls    back   to    earth.        The     pilot   makes    changes    to     the
aerodynamics and the spacecraft slows down. It then glides
down to the landing strip.

                                      In     addition       to   meeting       the
altitude requirement to win the X-Prize, pilot Brian Binnie
also broke the August 22, 1963 record by Joseph A. Walker,
who flew the X-15 to an unofficial world altitude record of
354,200 feet.        Brian Binnie's SpaceShipOne flight carried
him all the way to 367,442 feet or 69.6 miles above the
Earth's surface.

The   recent     development       in    the   field      of     scramjets,
hyperplanes, and truly Reusable Launch Vehicle will result
in the development of space tourism. This advancement of
technology helps us to understand more about science and
also helps us to improve our life.
                                          In   1927,     hotel       magnate
Raymond Orteig's announced an aviation contest, a price of
$25,000 to be awarded to the first man to build and fly an
airplane non-stop from New York to Paris. As a result of the
successful     flight    of    Charles   Lindbergh's,     in   the    United

     The number of airline passengers increased by 167,623
      between 1926 and 1929.
     The number of pilot's license applications increased
      by 300 percent in 1927.
     The   number      of    licensed   aircraft      increased     by   400
     The number of airports doubled within three years.

            Once this technology will be common, people will
start their pursuit towards even better technologies. Only
time will tell if the Ansari X Prize will have a similar
effect on the burgeoning sub-orbital flight industry as the
1927 $25,000 Orteig's price did.

 1. http://www.nasa.gov/missions/research/x43-main.html

 Official site of NASA X-43 spaceplane.

 Contains    basic   information   about   the   Reusable   Launch
 Vehicles and current projects.

 Contains facts about the NASA X-43 Hyper-X plane.

 Contains motion pictures of the X-43 .

 Contains images of the X-43 spaceplane.

 For details about X-Price.

 7. http://www.lerc.nasa.gov/WWW/RT1999/intro/contents.html
 For advance papers on space research

 For information on SpaceShipOne.

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