For the Olympic flame's first underwater relay in 2000, at the Great Barrier Reef, designers created a special solid-fuel torch that worked like a distress flare.
The Chinese may also have had to adapt their torch to extreme environments, including Mount Everest. But at least their fuel won't freeze.
American Chemical Society senior scientist Jerry Bell said: "Even if it's cold, propane is going to vaporize. And I'm pretty sure that's what they're going to do when they go up Everest."
Bell is confident that Everest's air isn't so thin that it will snuff out the flame.
Fourteen Thousand Torches
Comprehensive details on this year's torch's inner workings are elusive so far.
"I don't know why it should be a secret," Bell said. "It can't be that complicated, and it can't be vastly different than it's been in the past."
About a decade ago torches were equipped with pilot lights that relit the larger, more photogenic flame when it blew out.
"Pretty much the guts have been designed in a similar way ever since," Bell said.
Ever since Atlanta 1996 each runner is also given a fresh new torch to burn through, as opposed to reusable torches or replaceable fuel canisters.
"We talk about the Olympic torch. But there are thousands of them, because they only last for 20 minutes or so," Bell said.
The Sydney and Athens games each manufactured about 14,000 torches for their respective relays.
In his experience in the last two Summer Olympics, Kelso said, sudden gusts of wind and mishandling by relay runners caused the most flameouts.
This year the most common causes of extinguished torches could be anti-Chinese-government protesters. On Tuesday officials in Paris put out the torch three times due to interruptions by activists.
But not to fear, backup flames are near—all derived from the flame used to light the first 2008 torch at ancient Olympia in Greece.
"They hedge their bets and distribute [flames] to different places. So if they lose the torch flame completely, they can relight it," Kelso said.
The "insurance" flames are kept lit in miners' lanterns—at least one of which travels with the relay at all times.
If the flame has to fly, it travels in these lanterns, which keep it contained and therefore comply with no-open-flame rules for airplanes.
"It's an enormously complicated logistical nightmare," Kelso said of the torch relay, which this year will involve an unprecedented number of participants.
But no matter how large the relay gets, or how exotic its route becomes, the flame at the start is the flame you get burning in the Olympic cauldron at the end, Kelso said.
"[Organizers] are very, very careful about maintaining the integrity of the flame."
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