The miners, who only yesterday learnt they may be stuck until Christmas, are suffering from dehydration and have each lost eight-to-10 kilograms in the 21-day ordeal, Mr Manalich said.
While their spirits remain high, the minister said maintaining their emotional stability was vital. Games including dominoes and ludo would be sent down the drill hole and they had asked President Sebastian Pinera for wine to celebrate Chile's National Day on September 18.
Paradoxically, the miners' weight loss may prove useful. The rescue plan involves an Australian machine, the Strata 950, boring a hole into a chamber adjacent to the workers' refuge. The hole will be just wide enough to winch the miners out one by one.
'Cascade of rocks'Creating it will also produce a cascade of rocks and debris, which the trapped men will have to work to clear.
"It's extremely fragile," Mr Manalich said
Australian mining giant BHP Billiton is providing the rig and operators. Coal Services, an Australian company specialising in occupational health and safety, mine rescue and workers compensation, has reportedly been asked to provide remote tele-locators for the rescue.
Such a long rescue effort is "unheard of" in the industry, said Rob McGee, an official at the US Mine Rescue Association.
Drillers must bore through the "unstable geology" of the Atacama Desert to reach the miners, said J. Davitt McAteer, who investigated a blast at a West Virginia coal mine that killed 29 people in April.
'Lots can go wrong'Freeing the miners is "still a hell of a problem," McAteer said in a telephone interview. "Lots of things can go wrong. You've got to be lucky and be good as well."
The technique of lifting workers from a man-sized hole first proved successful in 1963 after David Fellin and Henry Throne were pulled out of the Sheppton coal mine in Pennsylvania after being trapped for 14 days. A similar rescue effort at a coal mine in Crandall Canyon, Utah ended in failure after six miners and three rescuers were killed, McAteer said.
"If you drill too fast, the drill hole will deviate and not hit the target," said Bruce Kennedy, principal mining engineer at Tucson-based SRK Consulting, which advises mining companies worldwide. "If the ground is fractured up, the drill hole may collapse."
The trapped miners have access to more than two kilometers of tunnels and a small refuge with benches. They are sleeping on the ground with blankets.
Chile's rescue plan will surpass a 25-day rescue of three coal miners in a flooded mine in Guizhou, China. Australian's Todd Russell and Brant Webb miners walked free in May 2006 after being trapped for two weeks almost 1000 metres underground in a gold mine at Beaconsfield, Tasmania.
"Maybe we can help in the psychology of the trapped miners and their families," astronaut Jose Hernandez, who last year embarked on a 13-day mission on Space Shuttle Discovery, wrote in a Twitter posting.
