IN A move reminiscent of Nobel laureate Richard Feynman鈥檚 experiment during the Challenger inquiry in 1986, another scientist has used kitchen-sink physics to shed light on the fate of the space shuttle Columbia in February.
Douglas Osheroff of Stanford University in California, also a Nobel prizewinner in physics and a member of the Columbia Accident Investigation Board, says tests he has conducted on shuttle insulation at his kitchen table disprove NASA鈥檚 theory about why foam insulation came off the craft鈥檚 external fuel tank.
In simple tests on a piece of shuttle foam glued to a piece of steel, Osheroff found that the foam would have not have blistered and separated from the fuel tanks in the way NASA has suggested. NASA envisaged nitrogen from the air liquefying in cavities in the foam where it makes contact with the cold fuel tank, and then boiling offafter lift 鈥� off. But this would only cause harmless cracks, Osheroff says, noting that NASA has never subjected the theory to adequate tests. CAIB chairman Hal Gehman was more forthright, describing NASA鈥檚 claim as 鈥渉okum鈥�. The team is now looking for other causes for the loss of the foam.
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Feynman鈥檚 famous demonstration at the Challenger inquiry in 1986 involved dipping a piece of a rubber O-ring in a glass of iced water. It showed that the material becomes brittle and unable to form a proper seal when too cold. NASA had been told such tests would take 6 months.
Osheroff鈥檚 finding emerged last week during the final public hearing on the Columbia disaster, when it became apparent that NASA鈥檚 wish for an early restart to shuttle operations might not be fulfilled. While NASA鈥檚 administrator, Sean O鈥橩eefe, hopes to launch a space shuttle by the end of the year, even he admitted that will be a stretch. The reason is that even now, more than 4 months after the accident, new problems keep coming to light. And the fact that these problems exist shows that NASA needs fixing just as much as its spacecraft.
Last week鈥檚 testimony made it clear that the shuttle鈥檚 managers had missed a number of signs warning of potential problems, had never even performed some simple and inexpensive tests on key components, and had failed to satisfy the agency鈥檚 own written requirements for such basic safety procedures as daily meetings of its management team during missions.
As a result, the board鈥檚 final report, to be issued in about a month, is expected to call for some sweeping changes in the way NASA oversees the whole shuttle programme.
It is also becoming clear that a lot more things other than just the tank鈥檚 insulating foam are going to have to change to make shuttles safe. Several other technical issues are also being investigated, including one that has emerged as another potentially catastrophic item: exploding bolts that might hit the shuttle and cause even more damage than the foam.
The 60-centimetre bolts, weighing 40 kilograms each, connect the shuttle鈥檚 external tank to the two 46-metre solid rocket boosters for the first 2 minutes of flight. Once those boosters have burnt out, the bolts are severed by explosive charges and the two halves are supposed to be caught by bucket-like 鈥渂olt catchers鈥�. But the board found that the strength of the catchers provided virtually no room for safety. And amazingly, these crucial flight components had never been tested before they were used.
While these bolts were almost certainly not a factor in Columbia鈥檚 demise, they clearly have the potential to damage heat shielding or other critical parts in future launches. But any change in the shuttle鈥檚 hardware runs the risk of introducing some new problem, so extensive testing of any proposed modifications will be necessary.