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 brothers plane of 1903 led to the

    development of aircrafts such as the WWII Spitfire, and

    others. In 1926 the first passenger plane flew holiday

    makersfrom American mainland to Havana and Bahamas. In 23years 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.

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    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 goneinto 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.

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    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
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    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 helpof 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.

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    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.

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    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 designwill therefore require:

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    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 isthe 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.

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    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 rocket.

    A ramjet operates by subsonic

    combustion of fuel in a stream of air compressed by

    the forward speed of the aircraft. It doesnt have or

    use very less moving parts compared to a conventionaljet-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 subsonic.

    The plane is accelerated to a speed of mach 4

    or mach 5 and the flow inside the engine becomessupersonic. Then the scramjet is powered up.

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    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 isnt enough oxygen to sustain the scramjet engine.

    At this point the rocket engine fires up.

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    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.

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    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 brake.


    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 1500C or

    more. It also has to cope with the rapid change in

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    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, -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 materials

    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


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    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 andreliable 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

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    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

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    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 anyair-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

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    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 combinationwas destroyed by

    ground controllers. The second attempt at Mach 7, in March

    2004, was highly successful.

    At Mach 6.8or almost seven times

    the speed of soundthe 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 thefact 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

    didnt 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

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    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 from SCALED COMPOSITES LLC

    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

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    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

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    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 theaerodynamics 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.

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    In 1927, hotel magnate

    Raymond Orteig's announced an aviation contest, a price of

    $25,000 to beawarded 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.



    Official site of NASA X-43 spaceplane.
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    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. advance papers on space research


    For information on SpaceShipOne.