Cole / AP, file
The shuttle Challenger's mission in 1986 was meant to mark a milestone in spaceflight: the first orbital voyage of an American teacher. NASA's choice for the honor was Christa McAuliffe, a social-studies teacher at Concord High School in New Hampshire. Here, McAuliffe rides past the New Hampshire State House in Concord with her daughter Caroline and son Scott, during a Lions Club parade on July 21, 1985. (Jim Cole / AP)
Jim Cole / AP, file
High-school teacher Christa McAuliffe folds her training uniform as she packs for the trip to Johnson Space Center in Houston on Sept. 8, 1985.
Terry Renna / AP, file
The space shuttle Challenger is transferred to the high bay of the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida on Dec. 17, 1985. Inside the cavernous VAB, the Challenger orbiter was mated with its solid rocket boosters and external tank in preparation for its launch a month later.
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Christa McAuliffe gets a preview of microgravity on NASA's specially equipped KC-135 "zero gravity" aircraft on Jan. 13, 1986. The plane flies in a parabolic pattern that provides short periods of weightlessness. For some people, those bouts of zero-G can induce nausea - which is why the airplane was nicknamed the "Vomit Comet."
The shuttle Challenger is delivered to its launch pad at NASA's Kennedy Space Center atop a mobile crawler-transporter.
Challenger's crew members practice the procedure for escaping from the launch pad at Kennedy Space Center using slide wire baskets. From left are Ronald McNair, Gregory Jarvis and Christa McAuliffe. Directly behind them are astronauts Judy Resnik and Ellison Onizuka. The basket system was designed to take the astronauts off the pad quickly if an emergency arose just before launch.
Challenger's crew members stand in the White Room at Launch Pad 39B after a dress rehearsal for launch. From left are Christa McAuliffe, Gregory Jarvis, Judy Resnik, commander Dick Scobee, Ronald McNair, pilot Michael Smith and Ellison Onizuka.
Steve Helber / AP, file
Challenger's crew members leave their quarters at Kennedy Space Center for the launch pad on Jan. 27, 1986. Commander Dick Scobee is at the front of the line, followed by Judy Resnick, Ronald McNair, Gregory Jarvis, Ellison Onizuka, Christa McAuliffe and pilot Michael Smith. NASA had to scrub the launch attempt on Jan. 27, due to high winds at the pad, and liftoff was rescheduled for Jan. 28.
A launch-pad camera captures a close-up view of the shuttle Challenger's liftoff on Jan. 28, 1986. From this camera position, a cloud of gray-brown smoke can be seen on the right side of the solid rocket booster, directly across from the letter "U" in "United States" on the orbiter. This was the first visible sign that a breach in the booster's joint may have occurred. Investigators determined that frigid overnight temperatures caused the booster joints' normally pliable rubber O-ring seals to become hard and non-flexible. The failure of the seals caused hot exhaust gases to blow through the joints, cutting into the external fuel tank.
A wide-angle view shows the ascent of the shuttle Challenger on Jan. 28, 1986. In the seconds after ignition, the rocket engines' hot blast began the process of destruction.
Why did the O-rings fail? On the day of the shuttle Challenger's launch, icicles draped structures at NASA's Kennedy Space Center in Florida. The unusually cold weather, beyond the tolerances for which the rubber seals were approved, most likely caused the O-ring failure.
JIM COLE / AP, file
Classmates of the son of America's first teacher-astronaut cheer as the space shuttle Challenger lifts skyward from Launch Pad 39B on Jan. 28, 1986. Their delight turned to horror as the shuttle exploded 73 seconds into flight. The boy in the white hat and glasses at center is Peter Billingsley, the star of "A Christmas Story" and a spokesman for the young astronaut program.
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The right solid rocket booster on the shuttle Challenger begins to explode, just a little more than a minute into the shuttle's ascent from NASA's Kennedy Space Center on Jan. 28, 1986.
Bruce Weaver / AP, file
An orange fireball marks the explosion of the space shuttle Challenger on Jan. 28, 1986.
At about 76 seconds, fragments of the orbiter can be seen tumbling against a background of fire, smoke and vaporized propellants from Challenger's external fuel tank. The left solid rocket booster is still shooting skyward. A reddish-brown cloud envelops the disintegrating orbiter. The color is indicative of the nitrogen tetroxide oxidizer propellant in the orbiter's reaction control system.
This picture, released by the presidential commission that investigated the Challenger tragedy, shows fragments of the orbiter flying away from the explosion on Jan. 28, 1986, 78 seconds after liftoff. The top arrow shows the orbiter's left wing. The center arrow shows the orbiter's main engine; and the bottom arrow shows the orbiter's forward fuselage. Investigators suggested that some of Challenger's crew members may have survived the explosion itself but died in the fall down to Earth.
Flight director Jay Greene studies data at his console inside Johnson Space Center's Mission Control Center in Texas, just minutes after the announcement that Challenger's ascent was not nominal.
Jim Cole / AP, file
Members of teacher-astronaut Christa McAuliffe's family react shortly after the failed liftoff of the space shuttle Challenger from NASA's Kennedy Space Center on Jan. 28, 1986. Christa's sister, Betsy, is in front, with parents Grace and Ed Corrigan behind.
Ken Williams / Concord Monitor via AP
Carina Dolcino, senior class president at Concord High School, is stunned by the news that the space shuttle carrying Christa McAuliffe, one of the school's teachers, exploded after launch on Jan. 28, 1986. Students watched the launch on television sets scattered throughout the school in Concord, N.H., and a celebration had been planned for a successful liftoff.
Craig Fujii / AP, file
President Ronald Reagan, center, is surrounded by members of his senior staff on Feb. 3, 1986, as he watches a TV replay of the Challenger shuttle explosion at the White House. From left are Larry Speakes, deputy White House press secretary; presidential assistant Dennis Thomas; special assistant Jim Kuhn; Reagan; White House communications director Patrick Buchanan; and chief of staff Donald Regan.
Toby Talbot / AP, file
Lisa Mitten of Concord, N.H., wipes tears from her eyes as her daughter Jessica reads some of the letters of sympathy that were on display at Concord High School on Feb. 1, 1986. Hundreds of Concord residents visited the school library to see the many telegrams and letters that were sent from all over the United States.
Debris from the ill-fated shuttle Challenger is unloaded from the Coast Guard cutter Dallas during February 1986.
For weeks after the accident, search and recovery teams went out to retrieve Challenger debris from the Atlantic Ocean, with the help of the U.S. Coast Guard and U.S. Navy. Vessels brought pieces of debris to the Trident Basin at Cape Canaveral Air Force Station, from which they were shipped to Kennedy Space Center for investigation. The Coast Guard cutter Dallas transported this fragment of exterior tiling.
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A piece of debris from the space shuttle Challenger is hoisted onto the deck of the Stena Workhorse off the coast of Florida during a recovery mission.
The remains of the shuttle Challenger's seven crew members are transferred from seven hearses to a MAC C-141 transport plane at the Kennedy Space Center's Shuttle Landing Facility, for transport to Dover Air Force Base, Del.
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President Ronald Reagan and his wife, Nancy, stand with the wife of astronaut Michael Smith and other family members at a memorial service for the victims of the Challenger disaster.
Scott Stewart / AP, file
Apollo 11 moonwalker Neil Armstrong, a member of the presidential panel investigating the Challenger explosion, listens to testimony before the commission in Washington on Feb. 11, 1986. Another commission member, David Acheson, listens in the background. A model of the space shuttle sits on the table.
Search and recovery teams located pieces of both the left and right sidewall of the shuttle Challenger during the months-long retrieval effort that followed the explosion on Jan. 28, 1986. Heat and fire damage scarred the right sidewall. But the left sidewall, depicted here, escaped the flames and suffered only from overload fractures and deep gouge marks. The largest intact piece formed part of the payload bay sidewall and measured approximately 30 by 12 feet.
AFP - Getty Images
Some pieces of the shuttle Challenger did not surface until long after the explosion. A tractor carries one of the shuttle's elevons after it washed ashore on Cocoa Beach, Fla., on Dec. 17, 1996, almost 11 years after the loss of Challenger and its crew.
Bill Ingalls / NASA via Getty Images
Every January, NASA recalls the Challenger explosion as well as other space tragedies on a "Day of Remembrance." Here, NASA Administrator Sean O'Keefe lays a wreath at the Space Shuttle Challenger Memorial at Arlington National Cemetery in Virginia on Jan. 28, 2003. O'Keefe also paid tribute to the three astronauts of Apollo 1 who died in a launch pad fire on Jan. 27, 1967. Sadly, seven more astronauts died just days after this picture was taken, on Feb. 1, 2003, when the shuttle Columbia broke up during re-entry.