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Atseventy-six seconds, fragments of Challenger could be seen against the backdrop of a largefireball, caused by the ignition of thousands of pounds of hydrogen from the externaltank. The orbiter was torn apart by the enormous aerodynamic forces, which greatlyexceeded the orbiter’s design limits. Large parts of Challenger began to tumble throughthe atmosphere and fall back toward the Atlantic Ocean. The forward fuselage and thecrew module, both of which remained largely intact, plunged into the waves a few secondslater, killing all seven astronauts on board.67This description of the sequence of events during the failure of the vehicle was gainedonly through a meticulous examination of the photographs and the recovery and detailedinspection of many Challenger parts from the ocean floor.

It also required a methodicalanalysis of the sequence of events during launch. This analysis also contributed to a moreprecise understanding of the O-ring failure that caused the loss of Challenger. Knowledgeof the structural details of the SRBs became widespread as newspapers printed detaileddrawings of the Shuttle system and the joint that held the motor segments together. The“tang-and-clevis” joint, which was supposed to hold the segments together with seventeenbolts and a rubber O-ring seal, received special attention from the media as well fromexperts, because it was this critical part of the Shuttle system that had failed.

Duringengine firing, the joint was subject to enormous pressure. NASA and Morton Thiokol hadintended to design the joint so that the O-ring would deform under pressure and fill inany small openings between the tang and clevis, preventing a “blow-by” of the hot ignitiongases during motor firing. However, as NASA’s own tests during SRB development hadshown, the O-rings would occasionally suffer damage during firing.68 During the secondShuttle flight (STS-2) and on several subsequent flights, the O-rings sustained both erosion and blow-by, indicating problems that could become worse. Of particular concern, asthe temperature of the joint fell, the O-ring material would stiffen up and prevent it fromproperly squeezing into any voids, even when under pressure.

Although several NASA officials and Morton Thiokol engineers were aware of the problem and the catastrophic failure it could cause, the two organizations failed to act to redesign the joint. Instead, theytried a number of other fixes, including tightening the joint and adding putty to the jointto assist the O-ring in sealing the joint.The open hearings of the Rogers Commission, which NASA officials opposed, gavethe public extraordinary insight into the almost overwhelming complexities of preparingand operating the Shuttle.

In one particularly dramatic moment during the hearings,commission member Richard Feynman placed a short section of the O-ring in ice water,demonstrating on live television how inflexible the material becomes with cold. His simple demonstration dramatized a major problem that NASA officials had virtually ignored.As noted in the commission’s report, “Prior to the accident, neither NASA nor Thiokolfully understood the mechanism by which the joint sealing action took place.”69The hearings and the report that resulted from it also exposed publicly a number ofcrucial management deficiencies within NASA, among which was the difficulty contractorpersonnel and mid-level NASA engineers had in conveying the seriousness of known technical problems to senior-level managers.

[II-39] The hearings also made it clear thatsenior NASA officials had subtly but inexorably shifted their attitude regarding the launch67. Report of the Presidential Commission on the Space Shuttle Challenger Accident (Washington, DC: U.S. GovernmentPrinting Office, June 6, 1986), pp.

19–39.68. Ibid., p. 120.69. Ibid., p. 148.****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 185EXPLORING THE UNKNOWN185of the Shuttle. At first, the engineers had to demonstrate that the Shuttle was safe tolaunch. The shift was that by the time of the ill-fated Challenger launch (STS 51-L), theyhad to demonstrate that it was not safe to launch. At one point in the hearings, for example, Roger M.

Boisjoly, a Morton Thiokol engineer, noted that “we were being put in aposition to prove that we should not launch rather than being put in the position andprove that we had enough data to launch.”70 Decision-making regarding the Shuttle hadbecome “a kind of Russian roulette . . . [the Shuttle] flies [with O-ring erosion] and nothing happens. Then it is suggested, therefore, that the risk is no longer so high for the nextflights. We can lower our standards a little bit because we got away with it last time. .

. . Yougot away with it, but it shouldn’t be done over and over again like that.”71Return to FlightReturning the Space Shuttle to space after the loss of Challenger was a challenging task.While the Rogers Commission investigated the technical and managerial causes of the failure, NASA had the difficult chore not only of redesigning the faulty SRBs, but also ofincreasing public confidence in its procedures. On March 24, 1986, well before thedetailed causes of the Shuttle’s failure were definitively established, the new AssociateAdministrator for Space Flight, former astronaut Richard H.

Truly, announced a strategyfor returning the Shuttle to flight status. [II-40] Among other things, his memorandumcalled for reassessing the entire program management structure and operation, and it laidout a plan for a “conservative return to operations.”Three weeks before Truly’s memo, veteran astronaut John W. Young wrote a highlycritical memorandum critiquing the management of the Shuttle program and outliningmany of the steps needed to assure safety of flight. His views were representative of manywho had been aware of the increasing acceptance of risk in Shuttle operations. [II-41]During the hiatus in flight, NASA examined every vulnerable element of Shuttle designand rethought Shuttle launch preparation and operations.

NASA instituted many newsafety procedures and replaced system components. For example, when first witnessingthe huge fireball and destruction of Challenger, many engineers immediately concludedthat one of the SSME turbopumps, which were highly susceptible to breakdown, mighthave failed. NASA used the “standdown” to go over the SSME piece by piece to improveits safety and reliability. NASA also increased its contractor staff at Kennedy Space Centerto handle the load of new procedures for safety and quality assurance and documentationpaperwork. The amount of time NASA technicians took to refurbish the orbiters afterflight, to prepare the entire Shuttle system for launch, and to follow new safety and quality procedures more than doubled.

The procedures were not only lengthened but becamemore complicated and intensive, making it increasingly doubtful that NASA could everachieve its planned yearly launch rate of twenty-four flights, even if sufficient funding forShuttle payloads and launch services became available to support such a rate.72 Mostimportant, however, NASA redesigned and tested the Shuttle’s solid rocket motors so theywould be much less likely to fail again, especially at the joints between motor segments.70. Ibid., p. 93.71. Richard Feynman, quoted in ibid., p.

148.72. Generally missing in most NASA Space Shuttle briefings of the 1980s was a sense of the connectionbetween launch rate and the overall costs for both payloads and Shuttle launch services. This was a case of radical optimism. Payload costs (on the launch vehicle) hovered between $40,000 and an astounding $650,000 perpound, depending on the amount of inexpensive elements in the payload (such as fuel) and the technical difficulties encountered in designing and building the spacecraft.

See U.S. Congress, Office of TechnologyAssessment, Affordable Spacecraft: Design and Launch Alternatives, OTA-BP-ISC-60 (Washington, DC: U.S.Government Printing Office, January 1990).****EU4 Chap 2 (161-192)1864/2/0112:45 PMPage 186DEVELOPING THE SPACE SHUTTLEThe shock of losing Challenger and its crew also forced officials within the Reaganadministration to reconsider what types of payloads the Shuttle would carry.

For example,well before the failure, some observers had complained that using the Shuttle to launchcommercial communications satellites, which could routinely be launched by ELVs, was awaste of federal resources and competed with possible commercial ELV efforts (seeChapter 3). In August 1986, the administration issued a statement on Shuttle use, followed by a formal policy statement in December. [II-42, II-43] That policy restrictedShuttle payloads to those requiring the unique capabilities of the Shuttle or needing theShuttle for national security purposes. In particular, the Shuttle would no longer be usedto launch commercial communications satellites.The costs of losing Challenger were high, not only to the crew members and their families, but also in economic terms. NASA’s Office of Space Flight estimated that the nationlost about seventy equivalent Shuttle flights over a period of ten years as a result of the lossof Challenger, as well as the loss of two Titan 34Ds and the Atlas-Centaur within a fewmonths.73 Europe’s Ariane launched many of these lost payloads.