On February 1, 2003, Space Shuttle Columbia disintegrated as it re-entered the atmosphere over Texas and Louisiana, killing all seven astronauts on board. It was the second of two Space Shuttle missions to end in disaster, after the loss of Challenger and crew in 1986. The mission, designated STS-107, was the 28th flight for the orbiter and the 113th flight of the Space Shuttle fleet. It was dedicated to research in various fields, mainly on board the SpaceHab module inside the shuttle's payload bay. During launch, a piece of the insulating foam broke off from the Space Shuttle external tank and struck the thermal protection system tiles on the orbiter's left wing. Similar foam shedding had occurred during previous Space Shuttle launches, causing damage that ranged from minor to near-catastrophic, but some engineers suspected that the damage to Columbia was more serious. When Columbia re-entered the atmosphere of Earth, the damage allowed hot atmospheric gases to penetrate the heat shield and destroy the internal wing structure, which caused the orbiter to become unstable and break apart. After the disaster, Space Shuttle flight operations were suspended for more than two years, as they had been after the Challenger disaster. Construction of the International Space Station (ISS) was paused until flights resumed in July 2005 with STS-114. NASA made several technical and organizational changes to subsequent missions, including the addition of an on-orbit inspection to determine how well the orbiter's thermal protection system (TPS) had endured the ascent, and continual readiness of designated rescue missions in case irreparable damage was found. Except for one mission to repair the Hubble Space Telescope, subsequent Space Shuttle missions were flown only to the ISS to allow the crew to use it as a haven if damage to the orbiter prevented safe re-entry. The remaining three orbiters were retired after the building of the ISS was completed.
Background
Space Shuttle
The Space Shuttle was a partially reusable spacecraft operated by the US National Aeronautics and Space Administration (NASA). It flew in space for the first time in April 1981, and was used to conduct in-orbit research, and deploy commercial, military, and scientific payloads. At launch, it consisted of the orbiter, which contained the crew and payload, the external tank (ET), and the two solid rocket boosters (SRBs). The orbiter was a reusable, winged vehicle that launched vertically and landed as a glider. Five operational orbiters were built during the Space Shuttle program. Columbia was the first space-rated orbiter constructed, following the atmospheric test vehicle Enterprise. The orbiter contained the crew compartment, where the crew predominantly lived and worked throughout a mission. Three Space Shuttle main engines (SSMEs) were mounted at the aft end of the orbiter and provided thrust during launch. Once in space, the crew maneuvered using the two smaller, aft-mounted Orbital Maneuvering System (OMS) engines. The orbiter was protected from heat during re-entry by the thermal protection system (TPS), a thermal soaking protective layer around the orbiter. In contrast with previous US spacecraft, which had used ablative heat shields, the reusability of the orbiter required a multi-use heat shield. During re-entry, the TPS experienced temperatures up to 3,000 °F (1,600 °C), but had to keep the orbiter vehicle's aluminum skin temperature below 350 °F (180 °C). The TPS primarily consisted of four sub-systems. The nose cone and leading edges of the wings experienced temperatures above 2,300 °F (1,300 °C), and were protected by the composite material reinforced carbon–carbon (RCC). Thicker RCC was developed and installed in 1998 to prevent damage from micrometeoroid and orbital debris. The entire underside of the orbiter vehicle, as well as the other hottest surfaces, were protected with black high-temperature reusable surface insulation. Areas on the upper parts of the orbiter vehicle were covered with white low-temperature reusable surface insulation, which provided protection at temperatures below 1,200 °F (650 °C). The payload bay doors and parts of the upper wing surfaces were covered with reusable felt surface insulation, as the temperature there remained below 700 °F (370 °C). Two solid rocket boosters (SRBs) were connected to the ET, and burned for the first two minutes of flight. The SRBs separated from the ET once they had expended their fuel and fell into the Atlantic Ocean under a parachute. NASA retrieval teams recovered the SRBs and returned them to the Kennedy Space Center (KSC), where they were disassembled and their components were reused on future flights. When the Space Shuttle launched, the orbiter and SRBs were connected to the ET, which held the fuel for the SSMEs. The ET consisted of a tank for liquid hydrogen (LH2), stored at −423 °F (−253 °C) and a smaller tank for liquid oxygen (LOX), stored at −297 °F (−183 °C). It was covered in insulating foam to keep the liquids cold and prevent ice forming on the tank's exterior. The orbiter connected to the ET via two umbilicals near its bottom and a bipod near its top section. After its fuel had been expended, the ET separated from the orbiter and reentered the atmosphere, where it would break apart during re-entry and its pieces would land in the Indian or Pacific Ocean.
Debris strike concerns
… excerpt ends here. Continue reading the full article.
