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Shuttles prepped for Frances
Workers close the payload bay doors, retract the landing gear and secure NASA's space shuttles in hangars at Kennedy Space Center to ride out Hurricane Frances. (3min 48sec file)
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Station pieces bagged
Modules and equipment awaiting launch to the International Space Station are covered with bags inside the processing facility at Kennedy Space Center as added protection from Hurricane Frances. (51sec file)
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Atlas blasts off
Lockheed Martin's last Atlas 2AS rocket blasts off from Cape Canaveral carrying a classified National Reconnaissance Office spacecraft. (3min 59sec file)
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Salute to pad 36A
The Atlas launch team in the Complex 36 Blockhouse celebrate the history of pad 36A in a post-launch toast. The Atlas 2AS rocket flight was the last to launch from the pad, which entered service in 1962. (2min 09sec file)
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Mission success
The classified NRO payload is deployed from the Centaur upper stage to successfully complete the launch. (1min 56sec file)
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Hurricane Frances
An external camera aboard the International Space Station captured this dramatic view of Hurricane Frances churning in the Atlantic Ocean. (4min 46sec file)
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Planet discovery
A team of planet-hunters announce their discovery of a new class of planets beyond our solar system at this NASA news conference on Tuesday, August 31. (52min 49sec file)
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Atlas launch preview
Preview the launch of Lockheed Martin's Atlas 2AS rocket carrying a classified National Reconnaissance Office spacecraft with this narrated animation package. (2min 22sec file)
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Space shuttle update
NASA's William Readdy, Space Operations associate administrator and Bill Parsons, space shuttle program manager, provide a status report on returning the shuttles to flight in this teleconference with reporters held on the one-year anniversary since the CAIB report was issued. (37min 35sec file)
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Helios mishap report issued by NASA officials
NASA NEWS RELEASE
Posted: September 3, 2004

The board that investigated the loss of the remotely operated Helios Prototype aircraft during a test flight last summer released its final report today.


This view of the Helios Prototype from a chase helicopter shows abnormally high wing dihedral of more than 30 feet from wingtip to the center of the aircraft that resulted after the Helios entered moderate air turbulence on its last test flight. The extreme dihedral caused aerodynamic instability that led to an uncontrollable series of pitch oscillations and overspeed conditions, resulting in structural failures and partial breakup of the aircraft. Photo: NASA
 
The board determined that the mishap resulted from the inability to predict, using available analysis methods, the aircraft's increased sensitivity to atmospheric disturbances such as turbulence, following vehicle configuration changes required for the long-duration flight demonstration.

The Helios Prototype aircraft involved in the mishap was a proof-of-concept solar electric- powered flying wing designed to operate at high altitudes for long duration flight. The failure occurred during a flight from the U.S. Navy's Pacific Missile Range Facility (PMRF) on the Hawaiian island of Kauai on June 26, 2003.

The propeller-driven aircraft had been flying under guidance of ground-based controllers from AeroVironment, Inc., of Monrovia, Calif., the plane's builder and operator, with assistance from NASA Dryden Flight Research Center personnel. The aircraft was destroyed when it sustained structural failure and fell into the Pacific Ocean. No other property damage or any injuries occurred as a result of the mishap.

The lightweight, highly flexible flying wing took off at 10:06 a.m. local time. At 10:22 and 10:24 a.m., the aircraft encountered atmospheric turbulence, typical of conditions expected by the test crew, causing abnormally high wing dihedral (upward bowing of both wingtips). Unobserved mild pitch oscillations began, but quickly diminished, according to post-test data analysis.


Wreckage of the Helios Prototype solar-electric aircraft floats in the Pacific Ocean near the Hawaiian island of Kauai shortly after the aircraft became uncontrollable and broke up during a test flight on June 26, 2003. About 75 percent of the wreckage was recovered, but the prototype fuel cell system that was to have provided power at night during the planned long-endurance flight demonstration sank in mile-deep water and could not be recovered. Photo: NASA
 
At about 10:36 a.m., the aircraft again experienced normal turbulence and transitioned into an unexpected, persistent high wing dihedral configuration. As a result, the aircraft became unstable, exhibiting growing pitch oscillations. Airspeed deviated from the normal flight speed, with the deviations rapidly increasing with every cycle of the oscillation. The aircraft's design speed was subsequently exceeded. The resulting high dynamic pressures caused the wing leading edge secondary structure on the outer wing panels to fail and the solar cells and skin on the upper surface to rip off. The remotely piloted aircraft came down within the confines of the Pacific Ocean test range, northwest of PMRF.

"The mishap underscores our need to assess carefully our assumptions as we push the boundaries of our knowledge," said Dr. Victor Lebacqz, Associate Administrator for NASA's Office of Aeronautics. "It should not, however, diminish the significant progress AeroVironment and NASA have made over the past 10 years in advancing the capabilities of this unique class of aircraft on many successful flights, including Helios' record setting flight to just under 97,000 feet altitude in August 2001. It is important that we learn from this experience, and apply the board's findings and recommendations to help ensure the payoffs of such vehicles are fully realized."

The report is available on the Web at: http://www.nasa.gov/pdf/64317main_helios.pdf