Space Shuttle Columbia disaster

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Image:TIME feb 2003.jpg The Space Shuttle Columbia disaster was the disintegration of the Space Shuttle Columbia over Texas on February 1, 2003, during reentry into the Earth's atmosphere on its 28th mission, STS-107. The entire seven-member crew died.

The loss of the Columbia was caused by damage sustained during launch when most of the left bipod foam ramp (see below) broke off the main propellant tank under the aerodynamic forces of launch and struck the orbiter's left wing leading edge. A thermal protection system (TPS) panel on the wing was damaged, which allowed the hot gasses of reentry to penetrate and weaken the wing structure, ultimately causing it to fail. The vehicle became uncontrollable and was destroyed by the extreme heat of reentry.

Some engineers suspected damage to the thermal protection, but NASA managers limited the investigation, feeling that nothing could be done even if damage was found.

U.S. manned space flights did not resume until over two years later, but the foam shedding problem continued. Despite these setbacks, the International Space Station continues to operate with a skeleton crew transported and supplied by Russian space vehicles.

There have now been two such losses of a space shuttle and crew. The first was the Challenger disaster in 1986.

Contents

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Crew

Image:Sts107crewsmall.jpg Image:Caib foam ramp.jpg Image:STS-107 launch.jpg

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Debris strike during launch

STS-107 had been delayed 18 times over the course of two years (despite its designation as the 107th mission, it was actually the 113th mission launched) from its original launch date of 11 January 2001 to its actual launch date of 16 January 2003. A well-publicized launch delay due to cracks in the shuttle's propellant distribution system occurred one month before a 19 July 2002 launch date, but the Columbia Accident Investigation Board (CAIB) determined that this delay had nothing to do with the catastrophic failure six months later.

The Left Bipod Foam Ramp is an approximately three-foot (one-meter) piece made entirely out of foam, as opposed to being a metal ramp that is merely coated with foam. As such, the foam, not normally considered to be a structural material, is required to bear some aerodynamic loads. Because of these special requirements, the casting-in-place and curing of the ramps may be performed only by a senior technician. Apparently, even the best technical servicing available could not compensate for this fatal design flaw.

Bipod Foam Ramps had fallen off on at least three previous Shuttle flights, with at least one previous Shuttle strike but no serious damage. The euphemism used by NASA management to refer to this phenomenon was "foam shedding." As with the O-ring erosions that ultimately doomed the Challenger Shuttle, NASA management seemed to grow complacent and accustomed to these phenomena when no serious consequences resulted from these earlier episodes.

Video taken during lift-off was routinely reviewed two hours after the launch and revealed nothing unusual. The following day, higher-resolution film that had been processed overnight revealed that a piece of insulation foam fell from the external fuel tank 81.9 seconds after launch and appeared to strike the shuttle's left wing, potentially damaging the thermal protection on the Space Shuttle. The exact location where the foam struck the wing could not be determined due to the low resolution of the tracking camera footage.

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Launch to Landing

In a risk-management scenario similar to the Challenger disaster, NASA management failed to recognize the relevance of engineering concerns for safety. Two examples of this were failure to honor engineer requests for imaging to inspect possible damage, and failure to respond to engineer requests about status of astronaut inspection of the left wing.

Engineering made three separate requests for Department of Defense (DOD) imaging of the shuttle in orbit to more precisely determine damage. While the images were not guaranteed to show the damage, the capability existed for imaging of sufficient resolution to provide meaningful examination. In fact the Columbia Accident Investigation Board (CAIB) recommended subsequent shuttle flights be imaged while on orbit using ground-based or space-based Department of Defense assets Template:Ref. NASA management did not honor the requests and in some cases intervened to stop DOD from assisting.

NASA's chief thermal protection system (TPS) engineer was concerned about left wing TPS damage and asked NASA management whether an astronaut would visually inspect it. NASA managers never responded.

Throughout the risk assessment process, senior NASA managers were influenced by their belief nothing could be done even if damage was detected, hence this affected their stance on investigation urgency, thoroughness and possible contingency actions. They decided to conduct a parametric "what-if" scenario study more suited to determine risk probabilities of future events, instead of inspecting and assessing the actual damage.

Much of the risk assessment hinged on damage predictions to the thermal protection system. These fall into two categories: damage to the silica tile on the wing lower surface, and damage to the reinforced carbon/carbon leading edge panels.

Boeing-developed damage prediction software was used to evaluate possible tile and reinforced carbon/carbon (RCC) damage. The software predicted severe penetration of multiple tiles by the impact, but Boeing engineers downplayed this. They believed that results showing that the software overstated damage from small projectiles meant that the same would be true of larger foam (SOFI) impacts. The program used to predict RCC damage was based on small ice impacts, not larger SOFI impacts. Under 1 of 15 predicted SOFI impact paths, the software predicted an ice impact would completely penetrate the RCC panel. Engineers downplayed this, too, believing that impacts of the less dense SOFI material would result in less damage than ice impacts. In an e-mail exchange, NASA managers questioned whether the density of the SOFI could be used as justification for reducing predicted damage. Despite engineering concerns about the energy imparted by the SOFI material, NASA managers ultimately accepted the rational to reduce predicted damage of the RCC panels from complete penetration to slight damage to the panel's thin coating.[1]

NASA managers assumed a rescue or repair was impossible, so there was no point in trying to inspect the vehicle for damage while on orbit. However the CAIB determined either a rescue mission or on-orbit repair, though risky, might have been possible had NASA verified severe damage within five days into the missionTemplate:Ref Template:Ref.

Ultimately the NASA Mission Management Team felt there was insufficient evidence to indicate that the strike was an unsafe situation, so they declared the debris strike a "turnaround" issue (not of highest importance) and denied the requests for the Department of Defense images.

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Destruction during re-entry

At 2:30 a.m. EST on February 1, 2003, the Entry Flight Control Team began duty in the Mission Control Center. The Flight Control Team was not working on any issues or problems related to the planned de-orbit and re-entry of Columbia. In particular, the team indicated no concerns about the debris impact to the left wing during ascent, and treated the re-entry like any other. The team worked through the de-orbit preparation checklist and re-entry checklist procedures. Weather forecasters, with the help of pilots in the Shuttle Training Aircraft, evaluated landing-site weather conditions at the Kennedy Space Center. At the time of the de-orbit decision, about 20 minutes before the initiation of the de-orbit burn, all weather observations and forecasts were within guidelines set by the flight rules, and all systems were normal.

Shortly after 8:00 a.m., the Mission Control Center Entry Flight Director polled the Mission Control room for a GO/NO-GO decision for the de-orbit burn, and at 8:10 a.m., the Capsule Communicator notified the crew they were GO for de-orbit burn.

As the Orbiter flew upside down and tail-first over the Indian Ocean at an altitude of 175 statute miles (282 km), Commander Husband and Pilot McCool executed the de-orbit burn at 8:15:30 a.m. using Columbia’s two Orbital Maneuvering System engines. The de-orbit maneuver was performed on the 255th orbit, and the 2-minute, 38-second burn slowed the Orbiter from 17,500 mph (7.8 km/s) to begin its re-entry into the atmosphere. During the de-orbit burn, the crew felt about 10% of the effects of gravity. There were no problems during the burn, after which Husband maneuvered Columbia into a right-side-up, forward-facing position, with the Orbiter’s nose pitched up.

Entry Interface, arbitrarily defined as the point at which the Orbiter enters the discernible atmosphere at 400,000 feet (120 km), occurred at 8:44:09 a.m. (Entry Interface plus 000 seconds, written EI+000) over the Pacific Ocean. As Columbia descended from space into the atmosphere, the heat produced by air molecules colliding with the Orbiter typically caused wing leading-edge temperatures to rise steadily, reaching an estimated 2,500 degrees Fahrenheit (1400 °C) during the next six minutes. As superheated air molecules discharged light, astronauts on the flight deck saw bright flashes envelop the Orbiter, a normal phenomenon.

At 8:48:39 a.m. (EI+270), a sensor on the left wing leading edge spar showed strains higher than those seen on previous Columbia re-entries. This was recorded only on the Modular Auxiliary Data System, and was not telemetered to flight controllers or displayed to the crew.

At 8:49:32 a.m. (EI+323), traveling at approximately Mach 24.5, Columbia executed a roll to the right, beginning a pre-planned banking turn to manage lift, and therefore limit the Orbiter’s rate of descent and heating.

At 8:50:53 a.m. (EI+404), traveling at Mach 24.1 and at approximately 243,000 feet (74 km), Columbia entered a 10-minute period of peak heating, during which the thermal stresses were at their maximum. By 8:52:00 a.m. (EI+471), nearly eight minutes after entering the atmosphere and some 300 miles (500 km) west of the California coastline, the wing leading-edge temperatures usually reached 2,650 degrees Fahrenheit (1450 °C). Columbia crossed the California coast west of Sacramento at 8:53:26 a.m. (EI+557). Traveling at Mach 23 and 231,600 feet (70.6 km), the Orbiter’s wing leading edge typically reached more than an estimated 2,800 degrees Fahrenheit (1540 °C).

Image:Columbia 02-01-03 - 0857 EST.jpg

Now crossing California, the Orbiter appeared to observers on the ground as a bright spot of light moving rapidly across the sky. Signs of debris being shed were sighted at 8:53:46 a.m. (EI+577), when the superheated air surrounding the Orbiter suddenly brightened, causing a noticeable streak in the Orbiter’s luminescent trail. Observers witnessed another four similar events during the following 23 seconds, and a bright flash just seconds after Columbia crossed from California into Nevada airspace at 8:54:25 a.m. (EI+614), when the Orbiter was traveling at Mach 22.5 and 227,400 feet (69.3 km). Witnesses observed another 18 similar events in the next four minutes as Columbia streaked over Utah, Arizona, New Mexico, and Texas.

In Mission Control, re-entry appeared normal until 8:54:24 a.m. (EI+613), when the Maintenance, Mechanical, and Crew Systems (MMACS) officer informed the Flight Director that four hydraulic sensors in the left wing were indicating “off-scale low,” a reading that falls below the minimum capability of the sensor. As the seconds passed, the Entry Team continued to discuss the four failed indicators.

At 8:55:00 a.m. (EI+651), nearly 11 minutes after Columbia had re-entered the atmosphere, wing leading-edge temperatures normally reached nearly 3,000 degrees Fahrenheit (1650 °C). At 8:55:32 a.m. (EI+683), Columbia crossed from Nevada into Utah while traveling at Mach 21.8 and 223,400 ft (68 km). Twenty seconds later, the Orbiter crossed from Utah into Arizona.

At 8:56:30 a.m. (EI+741), Columbia initiated a roll reversal, turning from right to left over Arizona. Traveling at Mach 20.9 and 219,000 feet, Columbia crossed the Arizona-New Mexico state line at 8:56:45 (EI+756), and passed just north of Albuquerque at 8:57:24 (EI+795).

Image:Columbia debris detected by radar.jpg

Around 8:58:00 a.m. (EI+831), wing leading-edge temperatures typically decreased to 2,880 degrees Fahrenheit (1580 °C). At 8:58:20 a.m. (EI+851), traveling at 209,800 feet (64 km) and Mach 19.5, Columbia crossed from New Mexico into Texas, and about this time shed a Thermal Protection System tile, which was the most westerly piece of debris that has been recovered. Searchers found the tile in a field in Littlefield, Texas, just northwest of Lubbock. At 8:59:15 a.m. (EI+906), MMACS informed the Flight Director that pressure readings had been lost on both left main landing-gear tires. The Flight Director then told the Capsule Communicator (CAPCOM) to let the crew know that Mission Control saw the messages and was evaluating the indications, and added that the Flight Control Team did not understand the crew’s last transmission.

Image:Columbia makeshift memorial.jpg

At 8:59:32 a.m. (EI+923), a broken response from the mission commander was recorded: “Roger, uh, bu - [cut off in mid-word] …” It was the last communication from the crew and the last telemetry signal received in Mission Control. Videos made by observers on the ground at 9:00:18 a.m. (EI+969) revealed that the Orbiter was disintegrating.

At about 9:05 (14:05 UTC), residents of north central Texas reported a loud boom, a small concussion wave and smoke trails and debris in the clear skies above the counties southeast of Dallas. More than 2,000 debris fields, as well as human remains, were found in sparsely populated areas southeast of Dallas from Nacogdoches in East Texas, where a lot of debris fell, to western Louisiana and the southwestern counties of Arkansas. This debris included live C. elegans worms from a science package that survived the re-entry. NASA issued warnings to the public that any debris could contain hazardous chemicals, that it should be left untouched, its location reported to local emergency services, or government authorities and that anyone in unauthorized possession of debris would be prosecuted.

Shortly after being told of reports of pieces of the shuttle being seen to break away, the NASA flight director declared a contingency (events leading to loss of the vehicle) and alerted search and rescue teams in the area. He told the ground controller to "lock the doors", which is the code phrase that a contingency is in effect, nobody can enter or leave the room, and flight controllers should preserve all the mission data for later investigationTemplate:Ref.

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Response from the President

At 14:04 EST (19:04 UTC), a somber President George W. Bush addressed the United States: "This day has brought terrible news and great sadness to our country... The Columbia is lost; there are no survivors." Despite the major setback, the President reassured Americans that the space program would continue: "The cause in which they died will continue. Our journey into space will go on." Template:Ref

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Initial investigation

NASA Space Shuttle Program Manager Ron Dittemore reported that "The first indication was loss of temperature sensors and hydraulic systems on the left wing. They were followed seconds and minutes later by several other problems, including loss of tire pressure indications on the left main gear and then indications of excessive structural heating" Template:Ref. Analysis of 31 seconds of telemetry data which had initially been filtered out because of data corruption within it showed the shuttle fighting to maintain its orientation, eventually using maximum thrust from its reaction control system jets.

The focus of the investigation centered on the foam strike from the very beginning. Incidents of debris strikes from ice and foam causing damage during take-off were already well known, and had actually damaged orbiters, most noticeably during STS-45, STS-27, and STS-87 Template:Ref. Tile damage had also been traced to ablative insulating material from the solid rocket motors in the past. The composition of the foam insulation had been changed in 1997 to exclude the use of freon, a chemical that causes ozone depletion; while NASA was exempted from legislation phasing out CFCs, the agency chose to change the foam nonetheless. This led to many statements linking the foam strike to environmental pressures. STS-107 used an older "lightweight tank" where the foam was sprayed on to the larger cylindrical surfaces using the newer no freon foam. However the bipods were manufacturered from BX-250 foam which was excluded from the EPA regulations and did use the original freon formula. The composition change did not contribute to the accident.

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Was rescue or repair possible?

Had NASA management acted in time, two possible contingency procedures were available: A rescue mission by shuttle Atlantis, and an emergency spacewalk to attempt repairs to the left wing thermal protection.

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Rescue

The CAIB determined a rescue mission, though risky, might have been possible provided NASA management took action soon enough.

Normally a rescue mission isn't possible, due to the time required to prepare a shuttle for launch, and the limited consumables (power, water, air) of an orbiting shuttle. However in this case Atlantis was well along in processing for a March 1 launch. Also Columbia carried an unusually large quantity of consumables due to an Extended Duration Orbiter (EDO) package. This would have allowed Columbia to stay in orbit until flight day 30 (February 15). NASA investigators determined that Atlantis processing could have been expedited with no skipped safety checks for a February 10 launch. Hence if nothing went wrong there was a five day overlap for a possible rescue.

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Repair

NASA investigators determined on-orbit repair by the shuttle astronauts was possible but risky, primarily due to the uncertain resiliency of the repair using available materials.

Columbia did not carry the Remote Manipulator System which would normally be used for camera inspection or transporting a spacewalking astronaut to the wing. Therefore an unusual emergency EVA would have been required. While there was no astronaut EVA training for maneuvering to the wing, astronauts are always prepared for a similarly difficult emergency EVA – to close the external tank umbilical doors located on the orbiter underside. During launch these doors are open for the propellant feed lines from the external tank to supply the main engines in the orbiter tail. If they fail to close after jettisoning the external tank, it constitutes a thermal protection breach which would destroy the orbiter upon reentry. This requires an emergency EVA to close them manually. Similar methods could have reached the shuttle left wing for inspection or repair.

For the repair, astronauts would have to use tools and small pieces of titanium, or other metal, scavenged from the crew cabin. These heavy metals would help protect the wing structure and would be held in place during re-entry by a water-filled bag that had turned into ice in the cold of space. The ice and metal would help restore wing leading edge geometry, preventing a turbulent airflow over the wing and therefore keeping heating and burn-through levels low enough for the crew to survive re-entry and bail out before landing. Because the NASA team could not verify that the repairs would survive even a modified re-entry, the rescue option had a considerably higher chance of bringing Columbia's crew back alive.

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The Columbia Accident Investigation Board

Image:Columbia debris grid.jpg Following protocols established after the loss of Challenger, an independent investigating board was created immediately following the accident. The Columbia Accident Investigation Board, or CAIB, consisted of expert military and civilian analysts who investigated the accident in great detail.

Columbia's flight data recorder was found near Hemphill, Texas on March 20, 2003. Unlike commercial jet aircraft, the space shuttles do not have flight data recorders intended for after crash analysis. Rather the vehicle data is transmitted in real time to the ground via telemetry. However since Columbia was the first shuttle, it had a special flight data OEX (Orbiter EXperiments) recorder, designed to help engineers better understand vehicle performance during the first test flights. Even after these were completed, the recorder was never removed from Columbia, and was still functioning. It records many hundreds of different parameters and contained very extensive logs of structural and other data which allowed the CAIB to reconstruct many of the events during the process leading to breakup. Investigators could often use the loss of signals from sensors on the wing to track how the damage progressed. This was correlated with analysis of debris and tests to obtain a final conclusion about the probable events.

On July 7, 2003 foam impact tests were performed by Southwest Research Institute, which used a foam block of similar size, mass and speed to that which struck Columbia, and it created a hole 41 cm by 42.5 cm (16.1 inches by 16.7 inches) in the protective RCC panel Template:Ref. The tests clearly demonstrated that a foam impact of the type Columbia sustained could seriously breach the protective RCC panels on the wing leading edge Template:Ref.

On August 26, the CAIB issued its report on the accident. The report confirmed the immediate cause of the accident was a breach in the leading edge of the left wing, caused by insulating foam shed during launch. The report also delved deeply into the underlying organizational and cultural issues that led to the accident. The report was highly critical of NASA's decision-making and risk-assessment processes. It concluded the organizational structure and processes were sufficiently flawed that compromise of safety was expected no matter who was in the key decision-making positions. An example was the position of Shuttle Program Manager, where one individual was responsible for achieving safety, timely launches and acceptable costs, which are often conflicting goals. The CAIB report found that NASA had accepted deviations from design criteria as normal when they happened on several flights and did not lead to fatal consequences. One of those was the conflict between a design specification stating the thermal protection system was not designed to withstand significant impact damage and the common occurrence of impact damage to it during flight. The board made recommendations for significant changes in processes and culture.

In late July 2003, an Associated Press poll revealed that Americans' support for the space program remained strong, despite the tragedy. Two-thirds believed the space shuttle should continue to fly and nearly three-quarters said that the space program was a good investment. On the question of sending humans to Mars, 49% thought it was a good idea, while 42% opposed it. Support slipped for sending civilians like teachers into space with 56% supporting the idea and 38% opposed.

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Miscellaneous items

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Unfounded fears of terrorism

Despite some initial fears that the addition of the first Israeli astronaut to the crew had made the Columbia a more likely target for terrorists, there is no evidence to support any theory that terrorism was involved. In any case, security surrounding the launch and landing of the space shuttle had been increased to ward off any potential terrorist attack Template:Ref. The Merritt Island launch facility, like all sensitive government areas, had increased security measures put in place in the wake of the September 11 attack. Gordon Johndroe, spokesman for the United States Department of Homeland Security, stated: "There is no information at this time that this was a terrorist incident."

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Surviving worms

A group of small (1 mm adult) C. elegans worms, living in petri dishes enclosed in aluminum canisters, survived re-entry and impact with the ground and were recovered weeks after the disasterTemplate:Ref Template:Ref. They were part of a Biological Research in Canisters (BRIC) experiment (led by Catharine Conley [2] of NASA Ames Research Center) designed to study the effect of weightlessness on physiology. Some usable data were recovered.

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Ground Search fatalities

Debris Search Pilot Jules F. Mier Jr. and Debris Search Aviation Specialist Charles Krenek died in a helicopter crash that injured three others while contributing to the ground search effort.

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Memorials

Image:Challenger-Columbia-Disasters-Plaque-Astronaut-Memorial-KSC.jpg Image:MERA-NAVcam-Patch-01-05-04-br.jpg

Image:Sts107memorial.JPG

On February 4, 2003, President George Bush and his wife Laura led a memorial service for the astronauts' families at the Lyndon B. Johnson Space Center. Two days later, Vice President Richard Cheney and his wife Lynne led official Washington in paying tribute at a similar service at Washington National Cathedral. During that service, singer Patti LaBelle sang "Way up There" Template:Ref.

On March 26 the United States House of Representatives' Science Committee approved funds for the construction of a memorial at Arlington National Cemetery for the STS-107 crew. A similar memorial was built at the cemetery for the last crew of Space Shuttle Challenger.

On August 6, 2003, NASA announced that the IAU had approved naming seven asteroids discovered in July 2001 at the Mount Palomar observatory in honor of the seven astronauts: 51823 Rickhusband, 51824 Mikeanderson, 51825 Davidbrown, 51826 Kalpanachawla, 51827 Laurelclark, 51828 Ilanramon, 51829 Williemccool Template:Ref.

A mountain peak near Kit Carson Peak and Challenger Point in the Sangre de Cristo Range was renamed Columbia Point. A dedication plaque was placed on the point in August 2003.

On October 28, 2003, the names of the astronauts were added to the Astronaut Memorial at the Kennedy Space Center Visitor Complex

On October 29, 2003, at the Florida Institute of Technology in Melbourne, Florida, just down the road from the Kennedy Space Center Visitor Complex, the Crane Creek Apartments, a complex of seven buildings, which were under construction were renamed Columbia Village. Each crew member is honored with a building named after them.

Also during 2003, the city of Amarillo, Texas renamed its airport Rick Husband Amarillo International Airport, after its native son and commander of STS-107.

On January 6, 2004, NASA announced that the landing site of the recently landed Mars rover Spirit would henceforth be known as Columbia Memorial Station. On February 2, it was also announced that NASA was naming a complex of hills east of the landers 'The Columbia Hills', after the crew of Columbia. The Spirit lander incudes a memorial plaque to the Columbia crew mounted on the back of its high gain antenna.

On January 10, 2004, Columbia Elementary school in the Brevard County School District, planted seven oak trees, with plaques for each crewmember, and dedicated eight new classrooms to the crew.

On June 13, 2004, Creighton University in Omaha, Nebraska dedicated the plaza east of the newly-constructed Hixson-Lied Science Building in Anderson's memory.

On August 25, 2005, NASA announced the renaming of the National Scientific Balloon Facility. It will be known as the Columbia Scientific Balloon Facility.

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Impact for space programs

Following the loss of Columbia, the space shuttle program was suspended. The expansion of International Space Station was also delayed, as the space shuttles were the delivery vehicle for station modules. The station was supplied and crews exchanged using Russian manned Soyuz spacecraft and unmanned Progress ships.

Less than a year later, President Bush announced the Vision for Space Exploration, calling for the retirement of the space shuttle fleet following the completion of the International Space Station and the development of the Crew Exploration Vehicle. NASA planned to return the space shuttle to service around September 2004. That date was pushed back to July 2005. On July 26, 2005, at 10:39 am EST, Space Shuttle Discovery cleared the tower, marking NASA's return to space. Overall the STS-114 flight was highly successful, but a similar piece of foam from a different portion of the tank was shed, although the debris did not strike the Orbiter. Due to this, NASA has once again grounded the shuttles until the problem can once again be solved. After delaying their re-entry by two days due to adverse weather conditions, the shuttle safely returned to Earth on 9 August 2005.

Later that same month, the external tank construction site, Michoud Assembly Facility located in New Orleans, Louisiana was damaged by Hurricane Katrina, with all work shifts cancelled up to September 26, 2005. This could potentially set back further Shuttle flights by at least two months and possibly more.

In reaction to the disaster, foreign plans, to develop and deploy next-generation manned spacecraft appear to have accelerated, as well as plans forwarded by private industry.

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See also

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References

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External links

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