The shuttle Discovery docked with the international space station today in a dramatic mission simulation that included presumed foam debris impacts to the orbiter's right wing leading edge and an aft rocket pod during the make-believe climb to space.

Senior managers, launch team members and reporters gather in the Firing Room to simulate liftoff of Discovery earlier this week. Photo: NASA

The simulation, which began Wednesday with a mock launch from the Kennedy Space Center, is designed to put NASA's post-Columbia management system to the test while giving the shuttle crew and mission control team a chance to sharpen their skills.

Flight directors and members of NASA's mission management team even staged faux news briefings complete with questions from public affairs officers playing the roles of reporters.

"It's been great. Everybody's played really hard," MMT Chairman Wayne Hale said late Friday. "This is like a real flight, they are playing hard and we've had a lot of emotion, which is good, that means people are taking it seriously, but it hasn't gotten out of hand. People are being reasonable in their conclusions and I think that's very good."

Said John Shannon, a senior member of NASA's mission management team: "This is like a play. This is our dress rehearsal. I'm just blown away by the fidelity of this thing, how many people are participating."

For launch, the MMT gathered at the Kennedy Space Center earlier this week for a full-fledged dress rehearsal countdown led by launch director Mike Leinbach and NASA test director Jeff Spaulding.

Five reporters, including this writer, were allowed to sit in on an early morning MMT meeting Wednesday to clear the launch team for a simulated fueling and later, observed the terminal countdown from the firing room in Kennedy's Launch Control Center.

The countdown was relatively straight forward and while a few problems cropped up that required extensive troubleshooting, the simulated liftoff occurred on time at 5:55 p.m. But seconds after launch, the simulation team began throwing problems at Discovery's crew and flight controllers in Houston, including simulated impacts by foam debris from Discovery's external fuel tank.

Columbia was brought down Feb. 1, 2003, by wing leading edge damage caused by a chunk of external fuel tank foam insulation that broke away during ascent.

Discovery's tank has been modified to prevent large pieces of foam from breaking off in flight. While it's not possible to completely eliminate foam shedding, Hale said Wednesday he's optimistic the tank will be deemed safe enough to launch after two years of work to minimize debris.

"In a perfect world, you would say the biggest thing that can come off the tank can't possibly hurt the (wing leading edge)," he said. "In a worst-on-worst kind of case, you can't say that, even after what we've done. But what we can say is in a realistic sense ... from what is reasonable to happen, we have sufficient safety margin."

To make absolutely sure the tank performs as expected, at least the first two shuttle missions will be treated as test flights. New high definition television tracking cameras will photograph Discovery's real launch in May with unprecedented resolution and other cameras on the shuttle, the tank itself and the orbiter's twin solid-fuel boosters will provide extensive photographic coverage during the climb to space.

In addition, cameras aboard two modified jets will "shoot" the shuttle through booster separation, the astronauts will photograph the tank in space and military spy satellites will snap classified photographs of the shuttle to look for signs of damage.

Sensors mounted just behind the wing leading edge panels will record the force and location of any impacts, the shuttle's crew will use laser sensors mounted on the end of a long boom to scrutinize the wing leading edges from the outside and the crew of the international space station will photograph the heat-shield tiles on the belly of the orbiter during Discovery's final approach.

The severity of any actual damage in a real flight will dictate NASA's response. Minor damage might be deemed acceptable for re-entry as is. More serious damage could raise the prospect of a spacewalk repair job and in cases where the issue was not clear cut - or the damage is obviously too severe for a repair - the astronauts could move into the space station and await rescue by another shuttle.

While no one expects any significant foam shedding during Discovery's May 15 launching, this week's simulation has forced mission managers to exercise all of the post-Columbia inspection techniques in a real-world scenario.

During Wednesday's mock launch, commander Eileen Collins had to deal with a fuel cell glitch seconds after liftoff and was told the center main engine's nozzle was leaking hydrogen. The shuttle's main engines shut down slightly early, resulting in a 35 foot per second shortfall in velocity. To save fuel, the crew was told not to perform a maneuver that would have let them photograph the external tank from an overhead window.

More worrisome to mission managers, two debris shedding events were noticed in ascent photography and radar tracking. By Thursday, the second day of the simulated mission, photography and radar analysis had identified at least nine "debris events," including damage to tiles on the shuttle's right rear rocket pod and a possible impact around leading edge panel No. 6 on Discovery's right wing.

The Discovery astronauts, working in a flight simulator at the Johnson Space Center, spent flight day two inspecting the 44 reinforced carbon carbon - RCC - leading edge panels on both wings, along with the ship's RCC nose cap, using a new boom-mounted laser system attached to the end of the shuttle's robot arm.

Aside from the use of computer graphics and animation in place of actual video from space, this writer, observing from the mission control room at the Johnson Space Center, could not tell the difference between the simulation and an actual mission as lead flight director Paul Hill led his team through the complex inspection work.

But in what might be a surprise to at least some observers, mission managers overseeing Discovery's simulated docking with the international space station Friday afternoon - two full days after launch - still did not yet know for sure whether the RCC impact had caused any damage.

Data from the laser scanner used to inspect the leading edge Thursday was inconclusive, officials said today, and close-up, targeted inspections were to be simulated Saturday. In addition, photos of the shuttle's belly taken by the crew of the space station during Discovery's final approach earlier today, showed unusual white speckles across the black heat-shield tiles that now must be investigated.

Senior managers said the pace of the simulation gave a sense of how long it will take NASA and contractor engineers to collect the data they would need in an actual flight to determine whether or not the shuttle had been damaged during launch or if repairs might be needed.

"We know we have some warning signs, we know we had some different debris events, we know we had one of those events gave us an indication on a wing leading edge sensor," Shannon said late Thursday. "That doesn't tell you if you have damage or not, it tells you potentially you had a hit in that area.

"The thing is, we go from a lot of data that's pretty low fidelity - from the imagery, from all the ground stuff, the external tank camera and the radar stuff - it's not very good fidelity but it tells you hey, something was going on and it clues you in to the next stage, which is what we're doing now and you go look carefully.

"It's going to be a little frustrating because you say OK, maybe they've got something here, here and here but it's going to take a few days to collect the data to see what is there. ... This is extremely complex."

In a real flight, the mission management team would not expect to have an impact site fully characterized and understood until flight day six. That is when the MMT would have to decide whether a shuttle could return to Earth as is, whether repairs were needed or whether a crew might have to abandon ship and use the space station as a "safe haven."

"It's really going to take us until flight day six to get all the reports, all the data, do all the analysis and come to a conclusion," Hale said. "Other than being anxious to get the answer, that's OK."

This week's simulation is working through that analysis and decision-making timeline in exhaustive detail.

"I would characterize the process as extremely realistic," Shannon said. "The systems engineering and integration guys are tracking nine different debris cases, the data collection's going on, two of them could be fairly significant. ... It's such a great, real-time prep for us to get real problems coming down, crunching them through all the people, all new processes, all the debris assessment stuff, this is all new. ... Just going through this whole cycle is so valuable."

The simulation was scheduled to end Friday evening, but the mission management team planned to work through the weekend assessing the impact data and debating all of the options they could face in a real flight.

Asked about the deliberate pace of the post-launch analysis during a real flight, John Muratore, a senior shuttle manager at the Johnson Space Center, said "my impression is this is going to be high drama for 14 days."

NASA hopes to move Discovery to launch pad 39B at the Kennedy Space Center around March 25. The launch window opens May 15 and closes June 3. The next launch window opens July 12.

"I think we're in pretty good shape," Hale said Wednesday. "We're working a number of problems on the orbiter, but that is fairly typical. ... The real issues we've got, I don't think it's orbiter processing. I think we're within the box on orbiter processing on Discovery. The real issue we've got is getting closure to the engineering analysis.

"We have to have the engineering analysis complete that proves it's safe to fly before we can go fly. If that means go park Discovery at the beach for an extra month, then so be it. Now, I don't think it's going to come to that. But we have got to prove it's safe to fly before we light the fuse."