10.1 Public Safety

¶Shortly after the breakup of Columbia over Texas, dramatic images of the Orbiterʼs debris surfaced: an intact spherical tank in an empty parking lot, an obliterated office rooftop, mangled metal along roadsides, charred chunks of material in fields. These images, combined with the large number of debris fragments that were recovered, compelled many to proclaim it was a "miracle" that no one on the ground had been hurt.¹¹ "And stunningly, in as much as this was tragic and horrific through a loss of seven very important lives, it is amazing that there were no other collateral damage happened as a result of it. No one else was injured. All of the claims have been very, very minor in dealing with these issues." NASA Administrator Sean OʼKeefe, testimony before the United States Senate Committee on Commerce, Science, and Transportation, May 14, 2003.Show full note

¶The Columbia accident raises some important questions about public safety. What were the chances that the general public could have been hurt by a breakup of an Orbiter? How safe are Shuttle flights compared with those of conventional aircraft? How much public risk from space flight is acceptable? Who is responsible for public safety during space flight operations?

¶Public Risk from Columbiaʼs Breakup

¶The Board commissioned a study to determine if the lack of reported injuries on the ground was a predictable outcome or simply exceptionally good fortune (see Appendix D.16). The study extrapolated from an array of data, including census figures for the debris impact area, the Orbiterʼs last reported

¶position and velocity, the impact locations (latitude and longitude), and the total weight of all recovered debris, as well as the composition and dimensions of many debris pieces.²² An intensive search of over a million acres in Texas and Louisiana recovered 83,900 pieces of Columbia debris weighing a total of 84,900 pounds. (Over 700,000 acres were searched on foot, and 1.6 million acres were searched with aircraft.) The latitude and longitude was recorded for more than 75,000 of these pieces. The majority of the recovered items were no larger than 0.5 square feet. More than 40,000 items could not be positively identified but were classified as unknown tile, metal, composite, plastic, fabric, etc. Details about the debris reconstruction and recovery effort are provided in Appendix E.5, S. Altemis, J. Cowart, W. Woodworth, "STS-107 Columbia Reconstruction Report," NSTS-60501, June 30, 2003. CAIB document CTF076- 20302182.Show full note

¶Based on the best available evidence on Columbiaʼs disintegration and ground impact, the lack of serious injuries on the ground was the expected outcome for the location and time at which the breakup occurred.³³ The precise probability is uncertain due to many factors, such as the amount of debris that burned up during re-entry, and the fraction of the population that was outdoors when the Columbia accident occurred.

¶NASA and others have developed sophisticated computer tools to predict the trajectory and survivability of spacecraft debris during re-entry.⁴⁴ "Userʼs Guide for Object Reentry Survival Analysis Tool (ORSAT), Version 5.0, Volume I-Methodology, Input Description, and Results," JSC-28742, July 1999; W. Alior, "What Can We Learn From Recovered Debris," Aerospace Corp, briefing presented to CAIB, on March 13, 2003. Such tools have been used to assess the risk of serious injuries to the public due to spacecraft re-entry, including debris impacts from launch vehicle malfunctions.⁵⁵ "Reentry Survivability Analysis of Delta IV Launch Vehicle Upper Stage," JSC-29775, June 2002. However, it is impossible to be certain about what fraction of Columbia survived to impact the ground. Some 38 percent of Columbiaʼs dry (empty) weight was recovered, but there is no way to determine how much still lies on the ground. Accounting for the inherent uncertainties associated with the amount of ground debris and the number of people outdoors,⁶⁶ Analysis of the recovered debris indicates that relatively few pieces posed a threat to people indoors. See Appendix D.16. there was about a 9- to 24-percent chance of at least one person being seriously injured by the disintegration of the Orbiter.⁷⁷ Detailed information about individual fragments, including weight in most cases, was not available for the study. Therefore, some engineering discretion was needed to develop models of individual weights, dimensions, aerodynamic characteristics, and conditions of impact. This lack of information increases uncertainty in the accuracy of the final results. The study should be revisited after the fragment data has been fully characterized.Show full note

¶Debris fell on a relatively sparsely populated area of the United States, with an average of about 85 inhabitants per square mile. Orbiter re-entry flight paths often pass over much more populated areas, including major cities that average more than 1,000 inhabitants per square mile. For example, the STS-107 re-entry profile passed over Sacramento, California, and Albuquerque, New Mexico. The Board-sponsored study concluded that, given the unlikely event of a similar Orbiter breakup over a densely populated area such as Houston, the most likely outcome would be one or two ground casualties.

¶Space Flight Risk Compared to Aircraft Operations

¶A recent study of U.S. civil aviation accidents found that between 1964 and 1999, falling aircraft debris killed an average of eight people per year.⁸⁸ K.M. Thompson, R.F. Rabouw, and R.M. Cooke, "The Risk of Groundling Fatalities from Unintentional Airplane Crashes," Risk Analysis, Vol. 21, No. 6, 2001. In comparison, the National Center for Health Statistics reports that between 1992 and 1994, an average of 65 people in the United States were killed each year by lightning strikes. The aviation accident study revealed a decreasing trend in the annual number of "groundling" fatalities, so that an average of about four fatalities per year are predicted in the near future.⁹⁹ Ibid. The probability of a U.S. resident being killed by aircraft debris is now less than one in a million over a 70-year lifetime.¹⁰¹⁰ The civil aviation study indicates that the risk to groundlings is significantly higher in the vicinity of an airport. The average annual risk of fatality within 0.2 miles of a busy (top 100) airport is about 1 in a million.

214

¶The history of U.S. space flight has a flawless public safety record. Since the 1950s, there have been hundreds of U.S. space launches without a single member of the public being injured. Comparisons between the risk to the public from space flight and aviation operations are limited by two factors: the absence of public injuries resulting from U.S. space flight operations, and the relatively small number of space flights (hundreds) compared to aircraft flights (billions).¹¹¹¹ Thompson, "The Risk of Groundling Fatalities;" Code of Federal Regulations (CFR) 14 CFR Part 415, 415, and 417, "Licensing and Safety Requirements for Launch: Proposed Rule," Federal Register Vol. 67, No. 146, July 30, 2002, p. 49495. Nonetheless, it is unlikely that U.S. space flights will produce many, if any, public injuries in the coming years based on (1) the low number of space flight operations per year, (2) the flawless public safety record of past U.S. space launches, (3) government-adopted space flight safety standards,¹²¹² Code of Federal Regulations (CFR) 14 CFR Part 415 Launch License, Federal Register Vol. 64, No. 76, April 21, 1999; Range Commanders Council Standard 321-02, "Common Risk Criteria for National Test Ranges," published by the Secretariat of the RCC U.S. Army White Sands Missile Range, NM 88002-5110, June 2002; "Mitigation of Orbital Debris," Notice of Proposed Rulemaking by the Federal Communications Commission, FCC 02-80, Federal Register Vol. 67, No. 86, Friday, May 3, 2002.Show full note and (4) the risk assessment result that, even in the unlikely event of a similar Orbiter breakup over a major city, less than two ground casualties would be expected. In short, the risk posed to people on the ground by U.S. space flight operations is small compared to the risk from civil aircraft operations.

¶The government has sought to limit public risk from space flight to levels comparable to the risk produced by aircraft. U.S. space launch range commanders have agreed that the public should face no more than a one-in-a-million chance of fatality from launch vehicle and unmanned aircraft operations.¹³¹³ Air Force launch safety standards define a Hazardous Launch Area, a controlled surface area and airspace, where individual risk of serious injury from a launch vehicle malfunction during the early phase of flight exceeds one in a million. Only personnel essential to the launch operation are permitted in this area. "Eastern and Western Range Requirements 127-1," March 1995, pp. 1-12 and Fig. 1-6. This aligns with Federal Aviation Administration (FAA) regulations that individuals be exposed to no more than a one-in-a-million chance of serious injury due to commercial space launch and re-entry operations.¹⁴¹⁴ Code of Federal Regulations (CFR) 14 CFR Part 431, Launch and Reentry of a Reusable Launch Vehicle, Section 35 paragraphs (a) and (b), Federal Register Vol. 65, No. 182, September 19, 2000, p. 56660.

¶NASA has not actively followed public risk acceptability standards used by other government agencies during past Orbiter re-entry operations. However, in the aftermath of the Columbia accident, the agency has attempted to adopt similar rules to protect the public. It has also developed computer tools to predict the survivability of spacecraft debris during re-entry. Such tools have been used to assess the risk of public casualties attributable to spacecraft re-entry, including debris impacts from commercial launch vehicle malfunctions.¹⁵¹⁵ "Reentry Survivability Analysis of Delta IV Launch Vehicle Upper Stage," JSC-29775, June 2002.

¶Responsibility for Public Safety

¶The Director of the Kennedy Space Center is responsible for the ground and flight safety of Kennedy Space Center people and property for all launches.¹⁶¹⁶ M. Tobin, "Range Safety Risk Assessments For Kennedy Space Center," October 2002. CAIB document CTF059-22802288; "Space Shuttle Program Requirements Document," NSTS-07700, Vol. I, change no. 76, Section 5-1. CAIB document CAB024-04120475. The Air Force provides the Director with written notification of launch area risk estimates for Shuttle ascents. The Air Force routinely computes the risk that Shuttle ascents¹⁷¹⁷ Here, ascent refers to (1) the Orbiter from liftoff to Main Engine Cut Off (MECO), (2) the Solid Rocket Boosters from liftoff to splashdown, and (3) the External Tank from liftoff to splashdown. pose to people on and off Kennedy grounds from potential debris impacts, toxic exposures, and explosions.¹⁸¹⁸ Pete Cadden, "Shuttle Launch Area Debris Risk," October 2002. CAIB document CTF059-22682279.

¶However, no equivalent collaboration exists between NASA and the Air Force for re-entry risk. FAA rules on commercial

¶space launch activities do not apply "where the Government is so substantially involved that it is effectively directing or controlling the launch." Based on the lack of a response, in tandem with NASAʼs public statements and informal replies to Board questions, the Board determined that NASA made no documented effort to assess public risk from Orbiter reentry operations prior to the Columbia accident. The Board believes that NASA should be legally responsible for public safety during all phases of Shuttle operations, including reentry.

¶Findings:

¶F10.1-1 The Columbia accident demonstrated that Orbiter breakup during re-entry has the potential to cause casualties among the general public.

¶F10.1-2 Given the best information available to date, a formal risk analysis sponsored by the Board found that the lack of general-public casualties from Columbiaʼs break-up was the expected outcome.

¶F10.1-3 The history of U.S. space flight has a flawless public safety record. Since the 1950s, hundreds of space flights have occurred without a single public injury.

¶F10.1-4 The FAA and U.S. space launch ranges have safety standards designed to ensure that the general public is exposed to less than a one-in-a-million chance of serious injury from the operation of space launch vehicles and unmanned aircraft.

¶F10.1-5 NASA did not demonstrably follow public risk acceptability standards during past Orbiter re-entries. NASA efforts are underway to define a national policy for the protection of public safety during all operations involving space launch vehicles.

¶Observations:

¶O10.1-1 NASA should develop and implement a public risk acceptability policy for launch and re-entry of space vehicles and unmanned aircraft.

¶O10.1-2 NASA should develop and implement a plan to mitigate the risk that Shuttle flights pose to the general public.

¶O10.1-3 NASA should study the debris recovered from Columbia to facilitate realistic estimates of the risk to the public during Orbiter re-entry.