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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Space Shuttle Solid Rocket Booster | 7/9 | https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster | reference | science, encyclopedia | 2026-05-05T13:22:36.055022+00:00 | kb-cron |
The loss of Space Shuttle Challenger originated with a system failure of one of its SRBs. The cause of the accident was found by the Rogers Commission to be "a faulty design unacceptably sensitive to a number of factors" of the SRB joints compounded by unusually cold weather the morning of the flight. The field joint design was flawed, with flexure of the joints during launch compromising the seal of the large rubber O-rings and allowing them to extrude further into the joint and erode as hot exhaust gases passed through during past launches. Additionally, the O-rings were not resilient at low temperatures like those of the January 1986 morning of the accident (36 °F; 2.2 °C). A cold-compromised joint in the right SRB failed at launch and allowed hot gases from within that rocket booster to sear a hole into the adjacent main external fuel tank and also weaken the lower strut holding the SRB to the external tank. The leak in the SRB joint caused the eventually catastrophic failure of the lower strut and partial detachment of the SRB, which led to a collision between the SRB and the external tank. With the external tank being destroyed and the shuttle stack, traveling at a speed of Mach 1.92 at 46,000 feet (14 km), thrusted off-axis by the right SRB as well as the tank's collapse, Challenger disintegrated. Both SRBs survived the accident initially, until they were destroyed by the range safety officer. Prior to the disaster, a teleconference was held between Marshall Spaceflight Center, Kennedy Space Center, and Morton Thiokol to discuss the upcoming launch. Originally, Morton Thiokol held the stance that the launch temperatures were too cold for launch. However, after a period of recess, Morton Thiokol had changed their stance, and was no longer opposed to launch.
During the subsequent downtime, detailed structural analyses were performed on critical structural elements of the SRB. Analyses were primarily focused on areas where anomalies had been noted during postflight inspection of recovered hardware. One of the areas was the attachment ring where the SRBs are connected to the external tank. Areas of distress were noted in some of the fasteners where the ring attaches to the SRB motor case. This situation was attributed to the high loads encountered during water impact. To correct the situation and ensure higher strength margins during ascent, the attach ring was redesigned to encircle the motor case completely (360°). Previously, the attachment ring formed a 'C' shape and encircled the motor case just 270°. Additionally, special structural tests were performed on the aft skirt. During this test program, an anomaly occurred in a critical weld between the hold-down post and skin of the skirt. A redesign was implemented to add reinforcement brackets and fittings in the aft ring of the skirt. These two modifications added approximately 450 lb (200 kg) to the weight of each SRB. The result is called a Redesigned Solid Rocket Motor (RSRM).
== Construction and delivery == The prime contractor for the manufacture of the SRB motor segments was ATK Launch Systems (formerly Morton Thiokol Inc.) Wasatch Division based in Magna, Utah. United Space Boosters Inc. (USBI), a division of Pratt & Whitney, under United Technologies, was the original SRB prime contractor for SRB assembly, checkout and refurbishment for all non-solid-rocket-motor components and for SRB integration. They were the longest-running prime contractor for the Space Shuttle that was part of the original launch team. USBI was absorbed by United Space Alliance as the Solid Rocket Booster Element division in 1998 and the USBI division was disbanded at Pratt & Whitney the following year. At its peak, USBI had over 1500 personnel working on the Shuttle Boosters at KSC, FL and Huntsville, Alabama. Components of the SRBs were transported from Utah to the Kennedy Space Center in Florida via rail over twelve days covering 2,000 miles (3,200 km) and eight states. Each segment and its custom built rail car weighed approximately 300,000 pounds (140,000 kg). Cars carrying SRBs were separated by empty cars to distribute the load over bridges and trestles, particularly the bridge over the Indian River, the last bridge on the train's journey. Following recovery, spent segments were loaded onto those same train cars and returned to Utah for refurbishment and refueling.
=== Incident === On May 2, 2007, a freight train carrying segments of the space shuttle's solid rocket boosters derailed in Myrtlewood, Alabama, after a rail trestle collapsed. The train was carrying eight SRB segments intended for STS-120 and STS-122. Four segments dropped approximately 10 feet (3.0 m). Four other segments along with a car carrying aft exit cones (nozzles), not yet on the trestle, remained on solid ground. The segments that fell from the trestle were recovered and returned to Utah for inspection. After analyses of the forces put on the remaining four segments that had not fallen were found to be well within tolerances, those segments continued on to Florida.
== Upgrade projects not put into service ==