On Feb. 1, 2003, space shuttle Columbia broke up as it returned to Earth, killing the seven astronauts on board. NASA suspended space shuttle flights for more than two years as it investigated the disaster.
An investigation board determined that a large piece of foam fell from the shuttle's external tank and fatally breached the spacecraft wing. This problem with foam had been known for years, and NASA came under intense scrutiny in Congress and in the media for allowing the situation to continue.
A fatal strike
Columbia, on mission STS-107, left Earth for the last time on Jan. 16, 2003. At the time, the shuttle program was focused on building the International Space Station. However, STS-107 stood apart as it emphasized pure research.
The seven-member crew — Rick Husband, commander; Michael Anderson, payload commander; David Brown, mission specialist; Kalpana Chawla, mission specialist; Laurel Clark, mission specialist; William McCool, pilot; Ilan Ramon, payload specialist from the Israeli Space Agency — spent 24 hours a day doing science experiments in two shifts. They performed around 80 experiments in life sciences, material sciences, fluid physics and other matters.
During the crew's 16 days in space, NASA was investigating a foam strike during launch. About 82 seconds after Columbia left the ground, a piece of foam fell from a "bipod ramp" that was part of a structure that attached the external tank to the shuttle. Video from the launch appeared to show the foam striking Columbia's left wing.
Several people within NASA pushed to get pictures of the breached wing in orbit. The Department of Defense was reportedly prepared to use its orbital spy cameras to get a closer look. However, NASA officials in charge declined the offer, according to the Columbia Accident Investigation Board (CAIB) and "Comm Check," a book about the disaster.
On Feb. 1, 2003, the shuttle made its usual landing approach to the Kennedy Space Center. Just before 9 a.m. EST, however, abnormal readings showed up at Mission Control. They lost temperature readings from sensors located on the left wing. Then, tire pressure readings from the left side also vanished.
The Capcom, or spacecraft communicator, called up to Columbia to discuss the tire pressure readings. At 8:59:32 a.m., Husband called back from Columbia: "Roger," followed by a word that was cut off in mid-sentence.
At that point, Columbia was near Dallas, travelling 18 times the speed of sound and still 200,700 feet (61,170 meters) above the ground. Mission Control made several attempts to get in touch with the astronauts, with no success.
It was later found that a hole on the left wing allowed atmospheric gases to bleed into the shuttle as it went through its fiery re-entry, leading to the loss of the sensors and eventually, Columbia itself.
Searching for debris
Twelve minutes later, when Columbia should have been making its final approach to the runway, a mission controller received a phone call. The caller said a television network was showing video of the shuttle breaking up in the sky.
Shortly afterward, NASA declared a space shuttle "contingency" and sent search and rescue teams to the suspected debris sites in Texas and later, Louisiana. Later that day, NASA declared the astronauts lost.
“This is indeed a tragic day for the NASA family, for the families of the astronauts who flew on STS-107, and likewise is tragic for the nation,” stated NASA's administrator at the time, Sean O’Keefe.
The search for debris took weeks, as it was shed over a field of some 2,000 square miles (5,180 square kilometers) in east Texas alone. NASA eventually recovered 84,000 pieces, representing nearly 40 percent of Columbia. Among them were the crew remains, which were identified with DNA.
Much later, in 2008, NASA released a crew survival report detailing the Columbia crew's last few minutes. The astronauts probably survived the initial breakup of Columbia, but lost consciousness in seconds after the cabin lost pressure and then died as it disintegrated.
Report calls for more funding, emphasis on safety
In the weeks after the disaster, a dozen officials began sifting through the Columbia disaster, led by Harold W. Gehman Jr., former commander-in-chief of the U.S. Joint Forces Command. The Columbia Accident Investigation Board, or CAIB, as it was later known, later released a multi-volume report on how the shuttle was destroyed, and what led to it.
Besides the physical cause – the foam – CAIB had a damning assessment about the culture at NASA that led to the foam problem and other safety issues being minimized over the years.
"Cultural traits and organizational practices detrimental to safety were allowed to develop," the board wrote, citing "reliance on past success as a substitute for sound engineering practices" and "organizational barriers that prevented effective communication of critical safety information" among the problems found.
CAIB recommended NASA ruthlessly seek and eliminate safety problems, such as the foam, to help astronaut safety in future missions. It also called for more predictable funding and political support for the agency, and added that the shuttle must be replaced with a new transportation system.
"The shuttle is now an aging system but still developmental in character. It is in the nation's interest to replace the shuttle as soon as possible," the report stated.
Returning to flight
The shuttle's external tank was redesigned, and other safety measures implemented. In July 2005, STS-114 lifted off and tested a suite of new procedures, including one where astronauts used cameras and a robotic arm to scan the shuttle's belly for broken tiles. NASA also put more camera views on the shuttle during liftoff to better monitor foam shedding.
Due to more foam loss than expected, the next shuttle flight did not take place until July 2006. After STS-121's safe conclusion, NASA deemed the program ready to move forward and shuttles resumed flying several times a year.
"We're still going to watch and we're still going to pay attention," STS-121 commander Steve Lindsey said at the time. "We're never ever going to let our guard down."
Columbia's loss – as well as the loss of several other space-bound crews – receives a public tribute every year at NASA's Day of Remembrance. That date is marked in late January or early February because, coincidentally, the Apollo 1, Challenger and Columbia crews were all lost in that calendar week.
The crew has received several tributes to their memory over the years. On Mars, the rover Spirit's landing site was ceremonially named Columbia Memorial Station. Also, seven asteroids orbiting the sun between Mars and Jupiter now bear the crew's names.
— Elizabeth Howell, SPACE.com Contributor