EST, February 1,
O-ring concerns[ edit ] Challenger being carried atop a Crawler-transporter on the way to the launch pad Each of the Space Shuttle's two Solid Rocket Boosters SRBs was constructed of seven sections, six of which were permanently joined in pairs at the factory. The factory joints were sealed with asbestos-silica insulation applied over the joint, while each field joint was sealed with two rubber O-rings.
After the destruction of Challenger, the number of O-rings per field joint was increased to three. During the Space Shuttle design processa McDonnell Douglas report in September discussed the safety record of solid rockets.
While a safe abort was possible after most types of failures, one was especially dangerous: As originally designed by Thiokol, the O-ring joints in the SRBs were supposed to close more tightly due to forces generated at ignition, but a test showed that when pressurized water was used to simulate the effects of booster combustion, the metal parts bent away from each other, opening a gap through which gases could leak.
This phenomenon, known as "joint rotation," caused a momentary drop in air pressure. This made it possible for combustion gases to erode the O-rings. In the event of widespread erosion, a flame path could develop, causing the joint to burst—which would have destroyed the booster and the shuttle.
For example, one engineer suggested that joint rotation would render the secondary O-ring useless, but Hardy did not forward these memos to Thiokol, and the field joints were accepted for flight in Even after the O-rings were redesignated as "Criticality 1"—meaning that their failure would result in the destruction of the Orbiter—no one at Marshall suggested that the shuttles be grounded until the flaw could be fixed.
In the post-flight analysis, Thiokol engineers found that the amount of blow-by was relatively small and had not impinged upon the secondary O-ring, and concluded that for future flights, the damage was an acceptable risk.
However, after the Challenger disaster, Thiokol engineer Brian Russell identified this event as the first "big red flag" regarding O-ring safety. Perhaps most concerning was the launch of STSB in Aprilflown by Challenger, in which the worst O-ring damage to date was discovered in post-flight analysis.
The primary O-ring of the left nozzle had been eroded so extensively that it had failed to seal, and for the first time hot gases had eroded the secondary O-ring.
This tang would grip the inner face of the joint and prevent it from rotating. They did not call for a halt to shuttle flights until the joints could be redesigned, but rather treated the problem as an acceptable flight risk.
For example, Lawrence Mulloy, Marshall's manager for the SRB project sinceissued and waived launch constraints for six consecutive flights. NASA decided to use Casablanca as the TAL site, but because it was not equipped for night landings, the launch had to be moved to the morning Florida time. Predictions of unacceptable weather at KSC on January 26, caused the launch to be rescheduled for First, one of the micro-switch indicators, used to verify that the hatch was safely locked, malfunctioned.
The Shuttle was never certified to operate in temperatures that low. The O-rings, as well as many other critical components, had no test data to support any expectation of a successful launch in such conditions.
Bob Ebeling in October wrote a memo—titled "Help! NASA manager Jud Lovingood responded that Thiokol could not make the recommendation without providing a safe temperature.
The company prepared for a teleconference two hours later during which it would have to justify a no-launch recommendation. Several engineers most notably Ebeling and Roger Boisjoly reiterated their concerns about the effect of low temperatures on the resilience of the rubber O-rings that sealed the joints of the SRBs, and recommended a launch postponement.
This was an important consideration, since the SRB O-rings had been designated as a "Criticality 1" component, meaning that there was no backup if both the primary and secondary O-rings failed, and their failure could destroy the Orbiter and kill its crew.
Thiokol management initially supported its engineers' recommendation to postpone the launch, but NASA staff opposed a delay. During the conference call, Hardy told Thiokol, "I am appalled.
I am appalled by your recommendation. This was unproven, and was in any case an argument that did not apply to a "Criticality 1" component. NASA claimed that it did not know of Thiokol's earlier concerns about the effects of the cold on the O-rings, and did not understand that Rockwell Internationalthe shuttle's prime contractor, additionally viewed the large amount of ice present on the pad as a constraint to launch.
For reasons that are unclear, Thiokol management disregarded its own engineers' warnings and now recommended that the launch proceed as scheduled;   NASA did not ask why. Ice had accumulated all over the launch pad, raising concerns that ice could damage the shuttle upon lift-off.
This was believed to be the result of supercooled air blowing on the joint from the liquid oxygen LOX tank vent. It was much lower than the air temperature and far below the design specifications for the O-rings. The low reading was later determined to be erroneous, the error caused by not following the temperature probe manufacturer's instructions.
Tests and adjusted calculations later confirmed that the temperature of the joint was not substantially different from the ambient temperature. The temperature on the day of the launch was far lower than had been the case with previous launches:In the sea there are countless gains, But if thou desirest safety, it will be on the shore.
— Saadi (Abū-Muḥammad Muṣliḥ al-Dīn bin Abdallāh Shīrāzī, or سعدی, The Gulistan of Saadi, The danger? Challenger, the second orbiter to become operational at Kennedy Space Center, was named after the British Naval research vessel HMS Challenger that sailed .
More Information and Timeline for UK Public Labor Strike On January 22nd, public sector workers in the United Kingdom go on strike in the largest strike to take place in the country since Comprehensive list of all manned space flights, USA and Russia. Konstantin Tsiolkovsky publishes a paper in Russia that mathematically demonstrates how to achieve liftoff with liquid fuels.
He also proposes using multistage rockets, which would be jettisoned as they spent their fuel, and guidance systems using gyroscopes and movable vanes positioned in the exhaust stream. Challenger was built to serve as a structural test article for the shuttle program.
A lighter-weight orbiter was NASA's goal during the years in which the orbiter fleet was being built, but a test article was needed to ensure that a lighter airframe could handle the stress of space flight.