ENDNOTES FOR CHAPTER 2

¶The citations that contain a reference to "CAIB document" with CAB or

¶CTF followed by seven to eleven digits, such as CAB001-0010, refer to a document in the Columbia Accident Investigation Board database maintained by the Department of Justice and archived at the National Archives.

¶The primary source document for this process is NSTS 08117,

¶Requirements and Procedures for Certification and Flight Readiness.

¶CAIB document CTF017-03960413.²² before the 1986 Challenger accident NASA adopted an alternate Space For detailed discussions of the origins of the Space Shuttle, see Dennis R. Shuttle mission numbering scheme, this report uses the original STS flight Jenkins, Space Shuttle: The History of the National Space Transportation designations. System – The First 100 Missions (Cape Canaveral, FL: Specialty Press, 12 2001); T. A. Heppenheimer, The Space Shuttle Decision: NASAʼs Search President Reaganʼs quote is contained in President Ronald Reagan, for a Reusable Space Vehicle, NASA SP-4221 (Washington: Government "Remarks on the Completion of the Fourth Mission of the Space Shuttle Printing Office, 1999; also published by the Smithsonian Institution Press, Columbia," July 4, 1982, p. 870, in Public Papers of the Presidents of the 2002); and T. A. Heppenheimer, Development of the Space Shuttle, United States: Ronald Reagan (Washington: Government Printing Office, 1972-1981 (Washington: Smithsonian Institution Press, 2002). Much of 1982-1991). The emphasis noted is the Boardʼs. the discussion in this section is based on these studies. 13 "Pricing Options for the Space Shuttle," Congressional Budget OfficeShow full note

¶Statement of Daniel S. Goldin, Administrator, National Aeronautics and

¶Space Administration, before the Subcommittee on VA-HUD-Independent

¶Agencies, Committee on Appropriations, House of Representatives,

¶March 31, 1998. CAIB document CAB048-04000418.³³ President George H. W. Bush, "Remarks on the 20th Anniversary of the Apollo 11 Moon Landing," Washington, D.C., July 20, 1989.

¶Roberta L. Gross, Inspector General, NASA, to Daniel S. Goldin,

¶Administrator, NASA, "Assessment of the Triana Mission, G-99-013, Final

¶Report," September 10, 1999. See in particular footnote 3, concerning

¶Triana and the requirements of the Commercial Space Act, and Appendix

¶C, "Accounting for Shuttle Costs." CAIB document CAB048-02680269.⁴⁴ See also comments by Robert F. Thompson, Columbia Accident Shuttle Development," June 8, 1986, p. 1-7. Investigation Board Public Hearing, April 23, 2003, in Appendix G. 16 The 1971 cost-per-flight estimate was $7.7 million; $140.5 million dollars Although there is more volume of liquid hydrogen in the External Tank, liquid hydrogen is very light and its slosh effects are minimal and are generally ignored. At launch, the External Tank contains approximately 1.4 million pounds (140,000 gallons) of liquid oxygen, but only 230,000 pounds (385,000 gallons) of liquid hydrogen.⁵⁵ Heppenheimer, The Space Shuttle Decision, pp. 278-289, and Roger in 1985 when adjusted for inflation becomes $52.9 million in 1971 A. Pielke, Jr., "The Space Shuttle Program: ʻPerformance vs. Promise,ʼ" dollars or nearly seven times the 1971 estimate. "Pricing Options for the Center for Space and Geosciences Policy, University of Colorado, August Space Shuttle." 31, 1991; Logsdon, "The Space Shuttle Program: A Policy Failure?" pp. 17 See Diane Vaughan, The Challenger Launch Decision: Risky Technology, 1099-1105. Culture, and Deviance at NASA (Chicago: The University of ChicagoShow full note

¶The Performance Enhancements (PE) flight profile flown by STS-107 is a combination of flight software and trajectory design changes that were introduced in late 1997 for STS-85. These changes to the ascent flight profile allow the Shuttle to carry some 1,600 pounds of additional payload on International Space Station assembly missions. Although developed to meet the Space Station payload lift requirement, a modified PE profile has been used for all Shuttle missions since it was introduced.

Chapter 3: Accident Analysis

¶One of the central purposes of this investigation, like those for other kinds of accidents, was to identify the chain of circumstances that caused the Columbia accident. In this case the task was particularly challenging, because the breakup of the Orbiter occurred at hypersonic velocities and extremely high altitudes, and the debris was scattered over a wide area. Moreover, the initiating event preceded the accident by more than two weeks. In pursuit of the sequence of the cause, investigators developed a broad array of information sources. Evidence was derived from film and video of the launch, radar images of Columbia on orbit, and amateur video of debris shedding during the in-flight breakup. Data was obtained from sensors onboard the Orbiter – some of this data was downlinked during the flight, and some came from an on-board recorder that was recovered during the debris search. Analysis of the debris was particularly valuable to the investigation. Clues were to be found not only in the condition of the pieces, but also in their location – both where they had been on the Orbiter and where they were found on the ground. The investigation also included extensive computer modeling, impact tests, wind tunnel studies, and other analytical techniques. Each of these avenues of inquiry is described in this chapter.

¶Because it became evident that the key event in the chain leading to the accident involved both the External Tank and one of the Orbiterʼs wings, the chapter includes a study of these two structures. The understanding of the accidentʼs physical cause that emerged from this investigation is summarized in the statement at the beginning of the chapter. Included in the chapter are the findings and recommendations of the Columbia Accident Investigation Board that are based on this examination of the physical evidence.

3.1 The Physical Cause

¶The physical cause of the loss of Columbia and its crew was a breach in the Thermal Protection System on the leading edge of the left wing. The breach was initiated by a piece of insulating foam that separated from the left bipod ramp of the External Tank and struck the wing in the vicinity of the lower half of Reinforced Carbon-Carbon panel 8 at 81.9 seconds after launch. During re-entry, this breach in the Thermal

¶Protection System allowed superheated air to penetrate the leading-edge insulation and progressively melt the aluminum structure of the left wing, resulting in a weakening of the structure until increasing aerodynamic forces caused loss of control, failure of the wing, and breakup of the Orbiter.

¶Figure 3.1-1. Columbia sitting at Launch Complex 39-A. The upper circle shows the left bipod (–Y) ramp on the forward attach point, while the lower circle is around RCC panel 8-left.