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Astronauts will inspect shuttle heat shield Wednesday BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: September 19, 2006 The Atlantis astronauts will spend their early morning hours Wednesday using the shuttle's robot arm to examine the ship from top to bottom and stem to stern for any signs of damage or missing hardware that might explain the source of a mysterious object that apparently floated away from the orbiter earlier today. Concern about that object prompted NASA to delay Atlantis' return to Earth by 24 hours, from Wednesday to Thursday, to give the astronauts and engineers time to make sure the ship's heat shield and other critical systems are healthy before committing the ship to a fiery re-entry. Shuttle Program Manager Wayne Hale said late today he's hopeful whatever the object might be it's not something that poses a threat to the shuttle or its crew. He said it may be something as simple as a plastic shim that shook out from between two tiles during pre-landing tests earlier today.
Whether activation of the shuttle's hydraulic system or jarring test firings of the shuttle maneuvering jets today could have shaken the shim free is not yet known. The shim does not pose any threat to the shuttle, but engineers don't yet know if it is, in fact, what showed up in the downlinked television views. Likewise, it's not yet known whether a second object spotted by commander Brent Jett that was seen floating away from the shuttle shortly after noon is a problem or not. But Hale said engineers have dismissed earlier concern about eight potential impact "events" detected by wing leading edge sensors. Analysis of timing data shows the sensors were simply responding to vibrations induced by the shuttle's hydraulic system during a routine pre-landing flight control system checkout.
To make sure Atlantis' heat shield is, in fact, intact, the astronauts will unlimber the shuttle's robot arm for a five-hour overnight inspection. Cameras on the 50-foot-long robot arm should be able to spot any critical damage to the shuttle's wing leading edge panels or heat-shield tiles that's above the threshold need to cause problems. "This data is not like the very fine, almost microscopic inspections we've done of the (wing leading edge panels) before," Hale said. "We think if this piece came off (the heat shield), this is going to be easy to see. So we can look further back, we can scan faster, we can do it with less delicate sensors. This is a standard television camera and by going down the line at a relatively slow pace you can see right away is there something big missing or is it generally in good shape? This inspection is appropriate for the concern that we might have something like that." If poor lighting or other problems associated with oblique viewing angles develops, the astronauts will use the arm to pick up a 50-foot-long heat-shield inspection boom for a more thorough inspection or a focused look at a particular area of interest. If the boom has to be used, the long crew day could prompt NASA to delay re-entry until Friday to make sure the crew has time to rest up after a busy day in space. If no problems are seen during the robot arm survey, Atlantis likely will be cleared for landing Thursday at the Kennedy Space Center. The shuttle has enough on-board supplies to remain in orbit until Saturday. The weather forecast for Thursday and Friday calls for good conditions at the Kennedy Space Center. Here is an updated timeline of overnight activity (in EDT and mission elapsed time): 09/19/06 Tue 09:45 PM 10 10 30 Crew wakeup Tue 11:45 PM 10 12 30 Robot arm survey 09/20/06 Wed 04:45 AM 10 17 30 Crew lunch Wed 05:45 AM 10 18 30 Orbiter boom sensor system unberth (if needed) Wed 06:40 AM 10 19 25 OBSS survey (if needed) Wed 09:55 AM 10 22 40 OBSS berthing (if needed) Wed 10:30 AM 10 23 15 Robot arm powerdown (if needed) Wed 01:45 PM 11 02 30 Crew sleep begins Wed 09:45 PM 11 10 30 Crew wakeup 09/21/06 Thu 05:19 AM 11 18 04 Deorbit burn (orbit 186; if no problems seen) Thu 06:21 AM 11 19 06 Landing at the Kennedy Space Center Thu 06:55 AM 11 19 40 Backup deorbit ignition (orbit 187) Thu 07:57 AM 11 20 42 Backup landing opportunity "The crew's going to wake up about (9:45 p.m.), we will let them get up and do the normal things they do in post sleep for about two hours, get breakfast, start their day, then we will start a survey of the vehicle with the remote manipulator system cameras that we think will take about five hours. "The goal of that survey is to get the general sense to make sure we're not missing any large pieces of the thermal protection system. We don't think we are, but this is to make sure. We think at the end of that survey we will be in a very good posture to believe we are good to come home. "However, we have built an option into the plan that after the crew's lunch period they can get the orbiter boom sensor system out and spend another three hours with that additional boom looking at some hard-to-see areas." With the OBSS attached to the robot arm, the astronauts have the ability to inspect virtually the entire shuttle, including all areas of the belly that would be of critical concern for re-entry. But the robot arm alone should be able to do the trick, Hale said. Anything large enough to cause problems is well within the detection of the arm's cameras. The shim stock, for example, was easily visible during Atlantis' final approach to the international space station Sept. 11. Camera views showed the reddish, rectangular piece of plastic sticking up at an angle between tiles on a door used to cover one of two external tank propellant feedline entrances in the belly of the shuttle. Engineers determined the shim posed no threat to the shuttle and would harmlessly melt or blow off during re-entry. As a result, NASA managers decided to simply leave it in place. "If we are satisfied at the crew's lunch hour that we have a good inspection and we believe there's nothing untoward, then we won't get the OBSS out and we'll come home normally (Thursday). "One of the things I think a lot of folks have talked about quite a bit as the most likely candidate is that piece of shim stock that we saw sticking out from the underside of the orbiter ... on flight day three as we approached the international space station. It's very likely the flight control system checkout provided the impetus, the shock, the vibration ... that shook that loose and it floated out. We don't know for sure, but it's a highly likely candidate. "If, in fact, we go look and that piece of shim stock is missing, we had quite the interesting debate in the Mission Management Team about whether that in itself was sufficient and we could just quit there. The discussion came to the conclusion that no, since we've got the arm out and we can't conclusively prove one way or the other that it was the shim stock, we ought to go complete the survey and make sure we don't see anything else that would cause us any concern." Engineers do not believe the mystery object was the result of an impact with orbital debris or a micrometeoroid. A high-energy impact would have imparted a higher departure velocity to any debris and other sensors likely would have detected the disturbance. Engineers also haven't found any signs of unusual temperatures on the shuttle that might otherwise be expected if a thermal blanket or heat-shield tiles were missing. "We're just doing what I would call due diligence here," Hale said. "We have the capability to remain in orbit until Saturday, we have the tools to go off and make sure we are safe for re-entry so we have no reason, in fact, not to go take a look and put every concern to rest. And that's what the plan is built to do and executing this plan we think we'll have a good feeling about coming home on Thursday." But if the inspections keep the crew up late, NASA managers may opt to "give them another day on orbit to rest up before the critical entry phase" to make sure "we have a well rested and prepare crew to fly the critical phases of entry and we don't want to do that with folks who are tired or overly concerned about anything. So we're going to put all that to rest." Here is a list of all the available landing opportunities through Saturday at the Kennedy Space Center, Edwards Air Force Base, Calif., and Northtrup Strip at White Sands, N.M. (all times in EDT): DATE ORBIT D/O BURN LANDING SITE 09/21 186 05:14 AM 06:22 AM Kennedy Space Center 09/21 187 06:46 AM 07:54 AM Northrup Strip 09/21 187 06:50 AM 07:57 AM KSC 09/21 188 08:20 AM 09:27 AM Edwards Air Force Base 09/21 188 08:22 AM 09:29 AM NOR 09/21 189 09:56 AM 11:03 AM EDW 09/22 201 04:02 AM 05:10 AM KSC 09/22 202 05:37 AM 06:45 AM KSC 09/22 203 07:07 AM 08:15 AM EDW 09/22 203 07:09 AM 08:16 AM NOR 09/22 204 08:43 AM 09:50 AM EDW 09/22 204 08:45 AM 09:52 AM NOR 09/22 205 10:19 AM 11:26 AM EDW 09/23 217 04:24 AM 05:32 AM KSC 09/23 218 05:56 AM 07:03 AM NOR 09/23 218 06:00 AM 07:08 AM KSC 09/23 219 07:30 AM 08:37 AM EDW 09/23 219 07:32 AM 08:39 AM NOR 09/23 220 09:06 AM 10:13 AM EDW
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