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The heat-resistant panels separated by insulation would transfer the mechanical load while shielding the underlying structure fromatmospheric heating. This concept suffered from excessive weight and difficulties indesigning the shielding to avoid buckling or excessive deflection. NASA’s estimatesshowed that the ablative heat shields would require costly refurbishment.Therefore, NASA chose the fourth option after extensive testing, in part because theagency decided that using tiles would lead to the lowest overall cost. A ceramic heat shieldalso allowed NASA engineers to use aluminum for the Shuttle orbiter’s structure—42.

National Academy of Sciences, National Research Council, Assembly of Engineering, Second Review—Technical Status of the Space Shuttle Main Engine: Report of the Ad Hoc Committee for Review of the Space Shuttle MainEngine Development Program (Washington, DC: National Academy of Sciences, February 1979), p. 21.43. U.S. Congress, Congressional Research Service, United States Civilian Space Programs 1958–1978, reportprepared for the Subcommittee on Space Science and Applications of the Committee on Science andTechnology, U.S.

House of Representatives, 97th Cong., 1st sess. (Washington, DC: U.S. Government PrintingOffice, January 1981), p. 473.****EU4 Chap 2 (161-192)1764/2/0112:45 PMPage 176DEVELOPING THE SPACE SHUTTLEa material with which they had considerable experience. The particular ceramic materialchosen was foamed silica coated with borosilicate glass. The shield was divided into thousands of small tiles to enable the stiff material to conform to the shape of the orbiter skin.(The tiles are what give the orbiters’ lower surfaces the look of being constructed of blocks.)No one had ever used such materials over an aluminum structure, and many expertsexpressed concerns about NASA’s ability to develop an appropriate means to bond thebrittle, nonpliable ceramic tiles to an aluminum structure that would deform slightlyunder aerodynamic loads.

Fitting and attaching the tiles became a major effort, one thatwas highly labor intensive. Each tile is approximately fifteen centimeters square and isindividually cut and fitted to match its neighbor. Because every tile is slightly different insize and shape, it carries its own number and has its own documentation.44 The orbiternose cap and its wing leading edges, which experience heating of above 1,500 degreesKelvin during reentry, are protected by a high-temperature, high-cost, carbon-carbonmaterial. Other temperature-resistant materials are used on the upper parts of the orbiter.Problems with installing the tiles caused NASA to deliver the first flight-qualifiedorbiter, Columbia, to Kennedy Space Center in early 1979 before NASA technicians hadcompleted installation.

Attaching the tiles then became the critical element in schedulingthe first Shuttle launch. Originally planned for 1978, by March 1979, the schedule hadslipped at least two years.45 Work on the tiles went on twenty-four hours a day for six daysa week, as technicians struggled to install more than 30,000 individual tiles. While NASAworked on methods to speed up the process, it also continued to explore better materialsto develop a method that would make the tile stronger without adding weight.In the meantime, as Rockwell and NASA engineers began to understand the extent ofthe aerodynamic loads the orbiter’s surface would experience during the launch phase,they developed concerns that some tiles might loosen, or even fall off.

Upon reentry, theyfeared, weakened tiles might peel away, causing the underlying aluminum structure tooverheat. Thus NASA also explored various means to examine the Shuttle while in orbitto check on the tiles, and the agency began to develop a tile repair kit.46 [II-21]Shuttle development problems were so severe during the late 1970s that some withinthe Carter administration’s OMB proposed that the program be cancelled. This led to aseries of external reviews of the program during 1979.

[II-22] Even before this recommendation, OMB had been resisting NASA’s attempt to gain approval for building a fifthShuttle orbiter. NASA believed that a five-orbiter fleet would be needed to provide adequate capability to meet anticipated launch demand. [II-23, II-24] While not authorizingthe construction of a fifth orbiter (an issue NASA continued to press until the 1986Challenger accident), President Jimmy Carter was persuaded that ending the program wasnot a good move. [II-25, II-26, II-27] After extraordinary efforts, by early 1980, NASA feltit was bringing its tile problems under control and was able to project a launch date ofMarch 1981.

[II-28]Before NASA could launch Columbia, however, it had to attend to thousands of details,both large and small. In addition to the tiles, the agency had to install and test many otherShuttle orbiter subsystems. For this work, Columbia was rolled into the Orbiter ProcessingFacility at Kennedy Space Center. Because virtually everything about the Shuttle system wasdifferent from the Saturn V, launch operations crews had to learn new methods for handlingthe vehicle, its SRBs, and the external tank.

NASA altered the Vehicle Assembly Building44. Paul A. Cooper and Paul F. Holloway, “The Shuttle Tile Story,” Astronautics and Aeronautics, January1981, pp. 24–34.45. U.S. Congress, House Committee on Science and Technology, 1980 NASA Authorization Hearingsbefore a subcommittee on H.R. 1756, 96th Cong., 1st sess., February and March 1979, pt. 4, p. 1664.46. NASA, “On-Orbit Tile Repair Kit Being Produced,” Press Release 80-10, January 23, 1980.****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 177EXPLORING THE UNKNOWN177(VAB) and the Mobile Launch Platform that had been developed for Apollo to accommodate the Shuttle.47 NASA also made substantial alterations to launch pads 39A and 39B.For each Shuttle launch, the first elements of the launch system to be erected are thetwo large SRBs.

Each is about twelve feet in diameter, 149 feet long, and composed of ninemajor elements—a nose cap, a frustrum, a forward skirt, four individually cast solid rocket motor segments, a nozzle, and an aft skirt. NASA technicians begin assembly of theShuttle by attaching the aft skirt of each of the two SRBs to support posts on the MobileLaunch Platform. Then, piece by piece, technicians hoist each SRB element atop the nextone and bolt it down. The motor segments are joined to their neighbors by tang-andclevis joints and secured by steel pins located along the circumference of each joint.48 Forsafety reasons, all nonessential personnel must evacuate the VAB while the SRBs are beingassembled.

After the two SRBs are safely bolted to the Mobile Launch Platform, a cranehoists the external tank to a vertical position and mates it with the twin SRBs. Then theorbiter is transferred from the Orbiter Processing Facility to the VAB, lifted by its nosemore than 100 feet off the floor, and lowered into place and mated with the external tank.Although NASA could have made the first launch, reentry, and touchdown in an automated mode, NASA engineers felt confident enough in the safety and reliability of theSpace Shuttle system to believe that such a procedure was unnecessary.49 [II-29] In thisthey were strongly supported by the astronaut corps, which was anxious to return to space.(The last crewed flight was the Apollo-Soyuz Test Project in July 1975.) Besides, preparingthe orbiter for automated landing would have entailed additional expense and weight forthe avionics and would have injected additional uncertainty in the interpretation of theflight results.The first launch of the Space Shuttle Columbia was scheduled for April 10; it was to bepiloted by astronauts John Young and Robert Crippen.

After a delay caused by computerproblems, the launch actually took place at 7:00 a.m. on April 12, 1981 (Figure 2–5).When the countdown clock reached T–3.8 seconds, NASA started up the SSMEs, allowingthe launch directors to determine that they were firing properly. At about T+3.0 seconds,they fired up the SRBs, irrevocably committing NASA to the launch. At an altitude of400 feet, eight seconds after lifting off the pad on a column of flame and smoke, computerinstructions caused Columbia to roll over on its back and continue its upward climb overthe Atlantic Ocean.

About two minutes later, at an altitude of twenty-seven nautical miles,the SRBs, which had completed their part of the launch sequence, separated from theorbiter and fell to the ocean on orange and white parachutes. Eight minutes and fifty-twoseconds after liftoff, Columbia reached orbit and jettisoned the nearly empty external tank,which fell back through the atmosphere into the Indian Ocean. A short burn of Columbia’sorbital maneuvering system rockets circularized the orbit at 130 nautical miles.Young and Crippen orbited Earth thirty-seven times while testing the various Shuttlecomponents, such as the large cargo bay doors, which they opened and closed. One ofNASA’s major concerns was the condition of the tiles.

Upon opening the payload doors,the astronauts discovered that several tiles on the fairings for the orbital maneuvering andreaction control engines had separated during launch. Although the loss of these tiles,which were on the upper side of the orbiter, would not have prevented a safe reentry,Mission Control in Houston remained unsure about the condition of Columbia’s underside, which could not be seen from the cockpit. As the orbiter circled Earth, NASA47.

For example, because the Shuttle does not make use of the tower and gantry required by the SaturnV, these were removed.48. The tang-and-clevis joints are called “field joints” because they are assembled at the launch site (“inthe field”) rather than at the factory.49. The Soviet Union flew its Buran shuttle orbiter in an automated mode in its first and only flight inNovember 1988.****EU4 Chap 2 (161-192)1784/2/0112:45 PMPage 178DEVELOPING THE SPACE SHUTTLEFigure 2–5. The Space Shuttle is finally realized with the launch of Columbia from Launch Complex 39A on April 12, 1981,on its first orbital mission.