NASA PHOTO ABOVE: Close-up view of the liftoff of the Challenger on mission STS-51L taken from camera site 39B-2/T3. From this camera position, a cloud of grey-brown smoke can be seen on the right side of the Solid Rocket Booster (highlighted). This was the first visible sign that an SRB joint breach may have occurred. On January 28, 1986 frigid overnight temperatures caused normally pliable rubber O-ring seals and putty that are designed to seal and establish joint integrity between the Solid Rocket Booster joint segments, to become hard and non- flexible. At the instant of SRB ignition, tremendous stresses and pressures occur within the SRB casing and especially at the joint attachment points. The failure of the O-rings and putty to "seat" properly at motor ignition, caused hot exhaust gases to blow by the seals and putty. During Challenger's ascent, this hot gas "blow by" ultimately cut a swath completely through the steel booster casing; and like a welder's torch, began cutting into the External Tank (ET). It is believed that the ET was compromised in several locations starting in the aft at the initial point where SRB joint failure occurred. The ET hydrogen tank is believed to have been breached first, with continuous rapid incremental failure of both the ET and SRB. A chain reaction of events occurring in milliseconds culminated in a massive explosion. The orbiter Challenger was instantly ejected by the blast and went askew into the supersonic air flow. These aerodynamic forces caused structural shattering and complete destruction of the orbiter. Though it was concluded that the G-forces experienced during orbiter ejection and break-up were survivable, impact with the ocean surface was not. Tragically, all seven crew members perished.

NASA PHOTO: On January 28, 1986, the Challenger and her seven-member crew were lost when a ruptured O-ring in the right Solid Rocket Booster caused an explosion soon after launch. Using submarines and sonar, among other equipment, to scan the ocean floor for debris, search and recovery teams located many pieces of the Shuttle. Shown here is the forward skirt of the right Solid Rocket Booster (SRB), which transfers thrust loads from the SRB to the External Tank and contains much of the SRB's electrical and instrumentation subsystem.

NASA PHOTO: STS-51L Challenger wreckage remains and boxes of debris being lowered into abandoned Minuteman Missile Silos at Complex 31 on Cape Canaveral Air Force Station.

Shuttle Challenger

The Challenger made its first flight on April 4, 1983. It was the 2nd shuttle to go into service behind the Columbia. It had flown just nine missions before exploding in a horrific explosion as the result of a leak in the right external rocket.

NASA PHOTO: Full view of Space Shuttle Orbiter Challenger in space, taken by the Space Pallet Satellite (SPAS) on June 22, 1983. A heavily cloud-covered portion of the Earth forms the backdrop for this scene of Challenger. Visible in the payload bay are the protective cradles for the Palapa-B and Telesat F communications satellites, the pallet for the NASA Office of Space and Terrestrial Applications (OSTA-2), the Remote Manipulator System (RMS) robot arm in the shape of the numeral seven and the KU- band antenna. A number of GetAway Special (GAS) canisters are also visible along the port side.

The "Challenger" Name

Challenger was named after HMS Challenger, a British corvette that was the command ship for the Challenger Expedition, a pioneering global marine research expedition undertaken from 1872 through 1876.

Challenger Test Vehicle

Although Challenger was built to serve as a test vehicle for the Space Shuttle, it was decided to convert the ship into a space-rated orbiter in early 1979. Once that process was completed, it became the main shuttle up till its destruction in 1986. It had flown 85 percent of all the shuttle missions even after Discovery and Atlantis had come online. It set several records including flying the first American woman into space, the first African-American and the first Canadian. It also had the first nighttime launch of a shuttle. It made 3 Space lab missions.

Flight STS-51-L

STS-51-L was going to be the 25th flight of the American Space Shuttle program. Part of the mission was to deploy the 2nd in a series of Tracking and Data Relay Satellites as well as carry out the first flight of the Shuttle-Pointed Tool for Astronomy and Halley's Comet Experiment Deployable in order to observe Halley's Comet.

It was christened to be the first time a civilian astronaut was to be included in the crew. Sharon Christa McAuliffe, a New Hampshire school teacher was selected from more than 11,000 applicants to participate in the NASA Teacher in Space Project. As a member of mission STS-51-L she was planning to conduct experiments and teach two lessons from Space. After her death schools and scholarships were named in her honor and in 2004 she was posthumously awarded the Congressional Space Medal of Honor.

NASA PHOTO: On January 28, 1986, the Space Shuttle Challenger and her seven-member crew were lost when a ruptured O-ring in the right Solid Rocket Booster caused an explosion soon after launch. This photograph, taken a few seconds after the accident, shows the Space Shuttle Main Engines and Solid Rocket Booster exhaust plumes entwined around a ball of gas from the External Tank. Because shuttle launches had become almost routine after fifty successful missions, those watching the shuttle launch in person and on television found the sight of the explosion especially shocking and difficult to believe until NASA confirmed the accident.