Sept. 20, 2006  -- So will the third time be the charm for the Atlantis crew? They spent Tuesday night trying to determine what the mysterious object was that was seen floating away from the shuttle early Monday morning.

The Mission Management Team has now ruled out that something hit the shuttle as it was in orbit. The sensors that indicated "hits" were reacting to the Forward Control System maneuver, which is part of the preparation for landing.

But did that same maneuver knock something lose from the shuttle? That's what the crew will be looking for in their inspection.

Space Station Program Manager Wayne Hale admits this isn't something they could have, or would have done before the Columbia accident.

"We never were able to do this before, but now that we can, we might as well. It is better to take a look than wonder what we might have missed," Hale said.

So the Atlantis crew will unberth the space shuttle robotic arm and survey the orbiter's skin.

This additional inspection is something this crew has already done twice. It is tedious and time consuming, because the crew and those who analyze the data that is down-linked, or looking for the tiniest of cracks that could allow damaging heat to penetrate the shuttle during re-entry.

The orbital boom sensor system was designed after the Columbia accident to help NASA see what could not be seen on Columbia.

After the Columbia accident, investigators were initially skeptical that the 1.67-pound hunk of foam that struck Columbia's left wing could have brought down the orbiter over Texas in 2003, killing its crew of seven.

Subsequent tests, though, proved even a much smaller piece of debris could cause catastrophic damage under the worst circumstances.

Inspecting an orbiter when it is flight adds days to each mission, but it is time well spent, Hale said.

The objects that were seen by Mission Control and the astronauts on Atlantis are gone. So analysts are left with video images to determine what was floating off the shuttle.

Hale says it is too early to dust off the other contingency plan -- the safe haven, or rescue plan.

Nov. 11 is the day NASA has circled as a launch date for STS 300 if Discovery needs to be launched to save Atlantis.

The question still haunts many to this day: What could have been done to save Columbia's crew? Was a rescue even possible?

Admiral Hal Gehman, who headed the Columbia Accident Investigation Board, told ABC News during the investigation, the question of what could have been done -- if anything -- bothered him for months.

"If something could have been done, then all of a sudden, it's not just a golden opportunity that was missed. It actually is a very very serious, very very serious failure of the system," Gehman said.

It goes without saying that the flight directors, engineers, and astronauts at NASA would have done anything within their power to save the crew of Columbia -- if they had known how much damage had been done to Columbia.

The plan developed by the Columbia Accident Investigation Board was risky -- but many wanted to believe it could have succeeded.

NASA would have raced to launch the shuttle Atlantis with a skeleton crew. It would have rendezvoused with Columbia, orbiting as close as 50 feet away, each shuttle's open payload bays facing one another at a 90-degree angle. A tethered astronaut would carry two spacesuits to Columbia's crew, and then escort them two at a time back to Atlantis.

Once empty, Columbia would have been sent plummeting into the ocean by remote control.

If a rescue wasn't feasible for the crew of Columbia, what about future crews who might face the possibility of flying home in a crippled space shuttle?

NASA now has a rescue plan on the drawing board for every shuttle mission it launches until the shuttle fleet quits flying in 2010.

A crew of four from the nest shuttle mission STS 116, which is scheduled to launch in December, has already trained for a rescue mission, and they would be ready to launch in Discovery if the call came from NASA headquarters.

Flight Director Paul Dye trained to run a rescue mission for STS 114. He says the clock is already ticking to process Discovery for a possible rescue mission.

"I think that the pressure where absolutely everything needs to go right, of course there is some margin, down at the Cape -- processing a vehicle and making sure everything comes together for launch day is really going to be incredible," Dye said.

Commander Steve Lindsey flew STS 121 earlier this summer, and trained as a rescue crew for STS 114.

"Everybody in our office would volunteer to do this if it needed to happen, because the other crew members that are up there are our friends," he said.

He sees this as a mission that is -- in some ways -- routine business for an astronaut.

"Because the crew would have been on orbit probably close to 60 days by the time we get them down, in 45 to 60 days they are probably going to be de-conditioned much like space station crews are, so the plan is we are actually going to fly all of the crew members down on the mid deck on the lower deck in recumbent seating flat out and they will have the full crewing, full oxygen suits," he said.

"On orbit, because you are in zero G [gravity], you shouldn't think square footage but you should think volume -- in terms of volume we have plenty of space for 11 people on board. Obviously when we hit the G field it will be a little different, but they will all be strapped in, but we have a planned place to deal with that and we think we can get everybody down OK," he said.

A possible rescue mission would be a race against time. Atlantis would have to be processed and rolled to the launch pad, then launched safely, to retrieve a crew that is seeking "safe haven" on a space station that is barely able to house two crew members, without the burden of seven more.

Wendy Lawrence flew on STS 114 and also trained to be part of the rescue crew on the other end. She knows it wouldn't be easy.

"As soon as we dock, in essence the clock is ticking, but we know the number of days and the estimate is the space station could support us for 43 days," she said. "That number gets folded back into the processing flow for the next shuttle. Part of our launch decision is making sure the next shuttle could launch within that 43-day period."

Lawrence was in charge of figuring out where to put everyone on her mission.

"We will be packed in there like sardines -- but it's funny, because three of us were in the astronaut class of '92 and we were called 'the sardine class,' so it's only appropriate," she said. "But it will be a sea of astronauts in orange spacesuits packed in pretty tightly."

But the pressure to pull off the impossible would be intense. Think back to the effort to save the crippled Apollo 13, 25 years ago. The entire world was glued to the unfolding drama for days.

Dye said he understands the pressure: "First off, if we need [to do it], it has to work. I mean we are going to be going up to bring home a crew that has no other way to come home."

But even if Atlantis had to be jettisoned into the ocean because it is damaged too badly to fly back to earth, it still might not mean the end of the shuttle program.

"We would still have a couple of orbiters," Dye said. "I remember people saying after the Challenger crash that if we ever lost another vehicle, we would never fly again."

But now the space shuttle has a shelf life of just three more years. It will stop flying in 2010. NASA needs to fly 15 more missions to finish the International Space Station, and would like to fly two missions to stock the ISS with spare parts.

Then there is the question of the Hubble space telescope. Hubble's batteries are running low and it won't survive 2007 without a rescue flight from a space shuttle, a flight NASA won't commission until the successful landing of the next shuttle flight.