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About The Space Shuttle "Challenger".. Brief History

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    AVio_niCS
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    About The Space Shuttle "Challenger".. Brief History

    This is a brief history about the space shuttle Challenger, mainly concentrating on the final flight and the accedent analysis according to NACA.



    Abdout Challenger

    Challenger, was the second orbiter to become operational at Kennedy Space Centre, it was named after the British Naval research vessel HMS Challenger that sailed the Atlantic and Pacific oceans during the 1870's. The Space Shuttle Challenger contributed a lot to the America's scientific growth. Challenger joined NASA fleet of reusable winged spaceships in July 1982. It flew nine successful Space Shuttle missions. On the 28th of January 1986, as the Challenger was launched for its tenth flight it exploded killing a crew of seven members on board.

    Challenger started out as a high-fidelity structural test article (STA-099). The airframe was completed by Rockwell and delivered to Lockheed Plant 42 for structural testing on 04/02/78. STA-099 underwent 11 months of intensive vibration testing in a 43 ton steel rig built especially for the Space Shuttle Test Program. The rig consisted of 256 hydraulic jacks, distributed over 836 load application points. Under computer control, it was possible to simulate the expected stress levels of launch, ascent, on-orbit, re-entry and landing. Three 1 million pound-force hydraulic cylinders were used to simulate the thrust from the Space Shuttle Main Engines. Heating and thermal simulations were also done.

    STA-099 was returned to Rockwell on 7/11/79 and it's conversion into a fully rated Orbiter Vehicle was started. The forward fuselage halves had to be separated to gain access to the crew module. Additionally, the wings were modified and reinforced to incorporate the results of structural testing and two heads-up displays (HUD's) were installed in the cockpit.


    Challenger’s final flight

    Mission planned to accomplish on the tenth flight of the Challenger, 51-l were as follow:
    • Tracking and Data Relay Satellite-B
    • Spartan-Halley Satellite
    • Comet Halley Active Monitoring Program
    • Fluid dynamics experiment
    • Phase Partitioning Experiment
    • Teacher in space project
    • Shuttle student involvement program
    • Radiation monitoring experiment

    The 51-L payload crew member consisted of:
    Michael J. Smith (Pilot)
    Francis R. Scobee (Commander)
    Judith A. Resnik (Mission Specialist 1)
    Ellison S. Onizuka (Mission Specialist 2)
    Ronald E. McNair (Mission Specialist 3)
    Gregory B. Jarvis (Payload Specialist 1)
    Sharon Christa McAuliffe (Payload Specialist 2)


    CHALLENFER's Accident Analysis

    The Space Shuttle Challenger was first scheduled to launch on the January 22nd 1986, however was then postponed to the 23rd, then the 24th. The launch of the shuttle was then reset to the 25th because of bad weather. The shuttle was yet again delayed due to a technical problem that was discovered by the ground crew and also the cross winds exceeded the limits at which the shuttle would be able to take off in. The shuttle was then rescheduled for the 28th at approximately 14:38 pm, but a further two delay occurred due to the failure of a instrument that monitors the fire detection system. On January 28th 1986 at 16:53.444 pm at the Kennedy Space Centre, the Space Shuttle Challenger was given its commands to start the ignition of its main engines and the SRB’s (Solid Rocket Boosters).
    About 0.678 seconds after lift-off a puff of strong grey smoke was observed by the launch pad cameras, spurting from a field joint called an ‘O’ Ring, on the right SRB. The ‘O’ Ring is a joint on the SRB which is sealed tight with a rubber ring inside and insulation outside to prevent any of the fuel from inside the SRB to leak. However due to the cold weather and the ‘O’ Ring not being sealed tight enough, the hot gases inside were leaking out and burning the rubber, grease and insulation, causing the grey smoke puffs. The leak on the SRB was on the side of the SRB, which faces the external tank, which was about 270o – 310o around the circumference of the SRB. Eight more of these puffs of smoke were seen getting blacker in colour between 0.836 and 2.500 seconds after launch.

    As the shuttles’ upward velocity increased the last puff of smoke was seen 2.733 seconds after launch.
    At approximately 37 – 64 seconds after the launch, the Challenger shuttle first came into contact with the wind shear forces, which were enough to cause large fluctuations on the shuttle. The shuttles’ computer systems would have adjusted the shuttle to counteract these forces and was used more in this flight than any other previous flight. The shuttles’ main engines and the SRB’s at this point were operating at a reduced thrust, and the throttle for the main engine were increased to 104% while the SRB’s were increasing their thrust, when the first flicker of flame coming out of the same spot on the right SRB as the smoke was seen. The film of the shuttle launch had to be enhanced in order to see this flame at 58.788 seconds after launch.

    At 59.262 seconds after launch the flame grew into a continuous plume and could be seen without enhancement of the launch camera film. At about 60 seconds the shuttles computer noted a decrease in pressure inside the right SRB, which confirmed that there was a leak. This plume continued to grow and was being blown down the SRB by the aerodynamic slipstream and also around the circumference of the SRB onto the strut, which held the SRB to the external tank. This was confirmed when the wreckage of the space shuttle was analysed.

    64.660 seconds after launch the fiery plume changed in colour and shape meaning that the flames had burned through the external tank and were mixing with the liquid hydrogen inside, which was also backed up when the shuttles’ computer detected a depressurisation in the external tank. Within 45 milliseconds of the breach of the external tank, there was a continuous bright glow on the black tiled underside of the Challenger between the shuttle and the external tank. At about 72.20 seconds the lower strut, which held the right SRB to the external tank, was severed leaving the SRB to rotate about the top strut.

    The SRB rotated about this strut and impacted the external tank, which caused the liquid oxygen to leak out. At approximately 73 seconds after launch there was a massive, almost explosive, burning of the hydrogen from the bottom leak in the external tank and the oxygen from the leak near the top of the tank. The Challenger shuttle was totally enveloped in the explosive burn and was torn to pieces due to the very large aerodynamic forces. The shuttle was traveling at a Mach number of 1.92 and was at a high of 46,000 feet when the tragedy occurred.

    Shortly after the disaster, President Ronal Regan commissioned an investigation into the cause of the Challenger Disaster. The investigation team included former secretary of state William Rogers, astronaut Neil Armstrong and former test pilot Chuck Yeager. It was said in the final report that the NASA engineers expressed their concerns for the safety of the Challenger. However the launch, even though delay several times still when ahead.

    Thanks

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    amir eleslam
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    Thanks alot

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    Eng.Amir Eleslam

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    AVio_niCS
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    Thanks for passing by..
    a pleasure having your first reply

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  4. [4]
    fullbank
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    [FRAME="2 90"]thanks to my dear so much for all these informations and i wish you to give us more[/FRAME]

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    fullbank
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    [FRAME="2 90"]thanks you my dear i wish you to give us more and to be very good engineer [/FRAME]

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  6. [6]
    هبة محمود
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    تاريخ التسجيل: Apr 2006
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    i want to say thanks alot for you for adding this important subject
    and i want you to add more and more information about the space in general
    thank you

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