Copiapo, Chile (CNN) -- The 33 miners trapped inside a Chilean mine since August 5 have been told for the first time that they could be stuck underground for as long as four months, the head of the rescue operation said Friday.

But Andre Sougarret, the mines manager for the state mining company, and Chilean government representative Jimena Matos also said they are working on a "Plan B," which could help speed up the rescue process.

"Last night, a third probe reached where the miners are and that probe, or the bore hole made by that probe, could form the basis of our plan B," said Sougarret, declining to offer specifics.

Officials expect drilling on a rescue shaft, a process that workers have said could take four months to complete, to begin this weekend.

Still, even under the best-case scenario, the trapped miners will be underground for quite some time -- posing a host of practical and psychological problems. To help solve them, Chilean officials are looking in unlikely places.

An official at NASA, the U.S. space agency, said on Friday the organization has been asked by Chile to help provide nutritional and behavioral health support to the miners. A four-person team, including two physicians and a psychologist, are planning to go to Chile next week, said Michael Duncan, NASA's lead on the Chile effort.

NASA has a long history in dealing with isolated environments and thinks experiences in space and underground are not too different, he said.

"It's an opportunity to us to bring the space-flight experience back down to the ground," said Duncan.

The workers, trapped 2,300 feet below the surface, have been trying to keep their spirits -- and the spirits of their loved ones -- from flagging. They sent a video message to their families Thursday in which they expressed thanks for the efforts under way to free them and displayed occasional flashes of humor and patriotism.

"We know what you've all been doing for us," said one man. "You haven't left us alone. We want to send applause to you." At that, the men broke into applause.

Throughout the 25-minute, high-definition video, one miner guided the hand-held camera ahead of him, its path illuminated by the light on his mining helmet. The video views were grainy and sometimes out of focus.

The video showed the 50-square-meter (about 540-square-foot) living space occupied by the men since they were trapped by the collapse of a mine shaft. Some appeared heavily bearded, all of them were stripped to the waist. A thermometer showed 29.5 degrees Celsius, (about 85 degrees Fahrenheit), a little cooler than officials had estimated.

Some of the men were standing, others were lying down. "Oh, you're sleeping on a box-spring bed," joked one man to another, who is sprawled out on a pile of rocks.

On a crate sat a set of dominoes; on a wall were two first-aid boxes. Nearby were two stretchers.

One miner said to his family: "Be calm. We're going to get out of here. And we thank you from the bottom of our hearts for your efforts." At that, the other miners broke into applause again.

The tenor of most of the comments was calm, though one man's emotion cut through. "Thank you to everybody," he said. "I send you a big hug in the name of our Lord." As he spoke, his voice cracked.

Out of the view of the camera, as one miner finished his message, another could be heard saying, "Get us out of here soon."

Family members who saw the video in a private screening said their loved ones appeared thin, but healthy and in good spirits. Several said many of the relatives cried as they watched and listened.

Doctors have given the miners advice about how to keep their limited living space clean: Portions of a 1-meter-high (3.3 feet), 40-meter-long (about 130 feet) shaft are being used as a latrine.

It is connected to the main cabin, which is being used for sleeping, washing and praying.

The men's sole lifeline to the outside world is a tube approximately 8 centimeters (3.2 inches) in diameter, through which food, water, clothing, video and radio equipment and whatever else is needed are stuffed.

Health Minister Jaime Manalich told reporters Thursday that, on average, each man has lost 22 pounds (10 kilograms) since they became trapped three weeks ago, and dehydration remains a threat. But a survey of the men indicates that at least nine miners are still too overweight to fit through the proposed rescue shaft, he said.

Three or four of the miners are showing signs of anxiety and depression, Manalich added.