HOUSTON — A vast army of as many as 10,000 investigators is trying to solve the puzzle of what destroyed the space shuttle Columbia, an effort that will cost as much as half a billion dollars, according to projections by government agencies involved in the inquiry and outside experts.
The estimated total would far exceed the roughly $175 million spent investigating the 1986 Challenger explosion, which involved a seven-month search-and-recovery mission in the Atlantic Ocean that cost $100 million by itself.
The investigative cost is separate from other financial fallout of the accident, including possible modifications to the orbiter fleet and institutional changes at NASA recommended by the Columbia Accident Investigation Board.
Accident investigations of all types have grown steadily more ambitious in recent decades, as the public and Congress have come to expect definitive answers to disasters, said Bernard Loeb, former head of aviation safety at the National Transportation Safety Board.
"Far more is expected today than 10 years ago," Loeb said. "Once you have demonstrated what you can do, more is expected. There is an expectation that these investigations are going to go to the end of the world to determine what happened."
No fixed budget has been set for the Columbia investigation, which is continuing under a White House declaration that authorized the massive effort shortly after the Feb. 1 crash. It includes a dizzying assortment of federal offices, ranging from the Environmental Protection Agency to the U.S. Forest Service.
"In terms of cost and breadth this is going to be the largest aircraft accident investigation ever," said Michael Barr, director of University of Southern California's aviation safety program. "I just can't think of anything that will compare. It's just mind-boggling."
The costliest airplane accident investigation involved TWA Flight 800, in which a 747 exploded after takeoff from New York in 1996, said Ted Lopatkiewicz, a spokesman for the National Transportation Safety Board. The official cost of that inquiry was $35 million, not including FBI efforts that ruled out terrorism as the cause.
Beyond the heightened public expectations, the Columbia investigation is driven by another imperative: NASA cannot afford to lose another space shuttle without shutting down the human spaceflight program for as much as a decade.
The space agency needs all three of its orbiters to support the international space station. Thus, when it returns to flight, NASA must have far greater confidence in the reliability of the system than at any time since flights began in 1981.
"To the public, the astronauts are still heroes," Loeb said. "It is important to this country. And there are questions about whether we should have manned versus unmanned spaceflight. Therefore, there is a need to determine what happened."
To make that determination, the Columbia Accident Investigation Board, the formal group appointed to determine the cause, has said it is "leaving no stone unturned." It is reviewing millions of pages of documents, sending members to manufacturing plants and government laboratories all over the country, and ordering a range of laboratory tests. It is also holding a series of public hearings to take testimony and gather evidence.
The board has not given an overall cost estimate or a timetable for its investigation, said spokeswoman Laura Brown. In many conversations that retired Adm. Harold W. Gehman Jr., who is heading the investigation, has had with members of Congress, they have expressed support for the board's efforts, Brown said.
"The admiral is very conscious of cost issues," Brown added.
The board is operating with $10 million from a $50-million appropriation by Congress after the Feb. 1 accident. The other $40 million is being held by NASA to cover its costs. The money, however, is not paying for the salaries of government employees assigned to the investigation. The board includes a number of high-ranking military officers and civil service employees, whose salaries are borne by their own services.
As the investigation pushes forward, the federal government must bear the expense of maintaining the program, with its nationwide workforce of 17,000, while the shuttle remains grounded -- a tab that could run as much as $10 million per day. Many of those employees are continuing their normal activities that involve maintaining the orbiters and preparing for future missions, said NASA spokesman James Hartsfield.
The total cost also does not include potentially expensive modifications to the space shuttle and institutional changes at NASA that may result from the board's recommendations. Nor does it include the loss of the orbiter itself, which originally cost about $2 billion to manufacture nearly 25 years ago.
NASA is already setting into motion efforts to improve the external tank's spray-foam insulation, which broke off on launch and may have damaged the orbiter.