麻豆传媒

DURING Columbia鈥檚 lift-off from the Kennedy Space Center launch pad, debris from the huge external fuel tank was seen falling off and striking the fragile thermal protection tiles on the underside of the craft. While the shuttle was in orbit, teams of engineers scrambled to analyse the launch video, and turned cameras on military spy satellites to photograph the shuttle鈥檚 underside and assess the damage. Others analysed its potential effects, with inconclusive results.

Sounds familiar? The landing came two days later, on 14 April 1981. During the shuttle鈥檚 fiery re-entry into Earth鈥檚 atmosphere, observers on the ground and the astronauts themselves were hoping and praying for the best, but fearing the worst. It was the maiden voyage of the space shuttle, and it returned to Earth safely. When its commander, John Young 鈥� NASA鈥檚 most experienced astronaut, who had walked on the Moon and is the very epitome of the fearless, gruff, reserved American with the 鈥渞ight stuff鈥� 鈥� stepped out of the orbiter, he was smiling exuberantly. He trotted down the steps, and after exchanging a few greetings headed back under the shuttle and spent a long time gazing up at its shiny, black-tiled surface. He looked surprised to be alive.

Everyone following that mission knew how he felt, having shared some of the suspense of those two days. The tiles, one of the shuttle鈥檚 most vulnerable parts, had been the subject of controversy for years. They were a possible 鈥渟ingle-point failure鈥� 鈥� components for which there was no back-up. Nobody knew then whether the shuttle could return safely with even the slightest amount of damage to the tiles which protect its aluminium skin 鈥� and the people inside 鈥� from temperatures of up to 1500 掳C. A few damaged tiles had the potential to lead to what NASA in its inimitable understated way refers to as 鈥渁 bad day鈥� 鈥� a day like 1 February 2003. The image that was in everyone鈥檚 minds during Columbia鈥檚 first flight was precisely the one that came to pass nearly 22 years later.

During the 112 flights in between, tiles have been damaged many times by ice or debris falling from the external tank. With so many warnings about the fragility of the tiles, why has nothing been done to improve their safety? In his scathing final report for NASA on the investigation into the Challenger disaster in 1986, the late physicist and Nobel laureate Richard Feynman suggested the root cause for what had happened on that awful flight, which until it was equalled last week had been the worst space disaster to date. It was, Feynman said, a cause far deeper than faulty O-rings 鈥� the immediate cause of the accident. It was a matter of NASA culture.

Feynman had identified a deadly kind of complacency within NASA: recurring problems that were not well understood became familiar over time and were eventually just accepted. When a problem occurs, 鈥渢he fact that this danger did not lead to a catastrophe before is no guarantee that it will not the next time, unless it is completely understood,鈥� he wrote. 鈥淲hen playing Russian roulette, the fact that the first shot got off safely is little comfort for the next.鈥�

Was that same culture still evident in what happened to Columbia? The pattern of events is eerily familiar. In mission after mission, tiles have been damaged to a greater or lesser extent. Time and again, teams have analysed the damage and its potential consequences. And time after time, the shuttles made it back safely, the tiles were replaced for the next flight, and tile damage came to seem less scary.

But every time it happened, the inspections and analysis were done with the full knowledge that if they did find signs of potentially catastrophic damage, there was little anyone could do about it. Repairing the tiles while in orbit isn鈥檛 possible. Often in the past, if it had become clear that a landing was too risky to attempt, the shuttle could perhaps have docked with the International Space Station and the crew remained there for weeks or even months 鈥� long enough to be rescued by a subsequent shuttle mission. But the latest mission was the first in three years that could not involve docking with the ISS. Columbia was in the wrong orbit, at the wrong altitude, so this was never an option.

Why did NASA never develop a way to repair the tiles in orbit? According to NASA鈥檚 Chief Flight Director Milt Heflin, the last time that option was seriously considered was in the late 1970s, when the agency looked into giving astronauts a tile repair kit. The plan was considered impractical and was scrapped.

But that was a long time ago. Doug Perovic, chairman of the department of materials science and engineering at the University of Toronto, told 麻豆传媒 this week that there has been considerable progress in high-temperature ceramics since then, and that a repair kit is feasible. 鈥淎bsolutely, there鈥檚 no reason you couldn鈥檛 do it,鈥� he says, suggesting that a portable thermal spray or plasma spray could be used by a space-walking astronaut to fill in any chipped or missing tiles.

But Jeffrey Hoffman, a former shuttle astronaut who now teaches at MIT, says that he has seen no signs of complacency regarding tile problems. He says developing a repair kit might have encouraged a false sense of security. 鈥淚t was decided, I think correctly, that instead you need to fly with enough confidence in the tiles [that repairs are not needed].鈥� But he agrees that, it may be time to look at the question again.

Critics argue that this is the kind of thing NASA might have been pursuing already if it hadn鈥檛 been faced with a decade of dwindling budgets, reduced manpower and cost overruns on the ISS that caused money to be diverted from the shuttle programme. In fact, the man who chaired NASA鈥檚 own Aerospace Safety Advisory Panel for 15 years has warned, in very harsh terms, of the dangers of these trends in the agency. In a letter delivered last spring after his forced resignation from the panel, Richard Blomberg wrote: 鈥淚 have never been as concerned for space shuttle safety as I am right now. All of my instincts suggest the current approach is planting the seeds for future danger.鈥�

Blomberg鈥檚 main concern was that upgrades that could have improved shuttle safety were being abandoned because a replacement vehicle was to be developed, so it wasn鈥檛 worth the investment. Yet it鈥檒l be another two decades before a replacement for the shuttle flies.

Hoffman warns against jumping to conclusions about underfunding or other external causes for the Columbia tragedy. 鈥淲e don鈥檛 know what the problem was, so how can people be trying to assign blame? It doesn鈥檛 accomplish a whole lot until we know what caused the accident.鈥�

And many insist that the culture at NASA has changed for the better since the Challenger disaster. In stark contrast to the stonewalling and cover-ups that marred the first weeks after that accident, this time the agency has been bending over backwards to share any information that it has. And communication about safety issues has opened up dramatically. 鈥淚 think the attitude at NASA has changed entirely,鈥� says General Donald Kutyna, a retired US Air Force general who was a member of the Challenger commission. 鈥淚鈥檓 confident they鈥檝e learned the lessons.鈥�

But not everyone is convinced. Apollo veteran Buzz Aldrin says that 鈥渦nderfunding has been rather prevalent the last ten years or so鈥�. The only vehicle currently being developed as an alternative way to get astronauts to and from the space station is the Orbital Space Plane, a capsule that would have to be launched atop one of the US鈥檚 new expendable rockets, the Delta 4 or the Atlas 5. But Aldrin says using the rockets for crewed missions would be risky. 鈥淚鈥檓 concerned with a brand new expendable. There鈥檚 a lot of challenges and expense.鈥�

Keith Cowing, a former NASA payload integration specialist who now runs a website called NASA Watch, agrees that the agency has been stretched thin by budget cuts. 鈥淣ASA is on the cusp of doing injury to its safety capability,鈥� he says. 鈥淧eople are really stressed.鈥� Did that play a part in this particular accident? 鈥淚 can鈥檛 say that,鈥� he emphasises. But the ongoing tile problems may well be a sign that the kind of acceptance of risk that Feynman warned against is still present.