NASA says tank appears to have performed well
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 9, 2007
Preliminary analysis of launch photography indicates about nine small bits of foam insulation came off the shuttle Endeavour's external fuel tank during the climb to space Wednesday. But only three are believed to have possibly struck the orbiter and there are no obvious signs of any impact damage, officials said today.
"Very quiet day at the Mission Management Team," said MMT Chairman John Shannon. "It looked like the launch was extremely successful yesterday. About all we did in the way of data assessment was, we looked at the external tank photography that's automatically taken at separation and we saw nothing significant. It looks like the tank has been very consistent over the last several flights and there was good performance out of it from a debris standpoint. We're not looking at anything significant at all."
The three incidents listed by Shannon occurred at 24, 58 and 173 seconds after launch. The first incident may have involved a bit of "purge barrier" used around a propellant feed line prior to launch that appeared to strike the rear of the shuttle's body flap. Similar debris events have been seen on past flights and no major damage was found.
The second piece of debris appeared to cause slight discoloration, or a spray, when it hit the shuttle's right wing, but Shannon said "it's really, really hard to see" and engineers do not believe it represents a serious problem. The third event happened well beyond the first 135 seconds of flight when the air is still thick enough to produce the kind of impact velocities that can cause damage.
Shannon said all three areas will be photographed in detail Friday - along with the rest of the shuttle's heat shield - during final approach to the international space station. In a now-routine post-Columbia maneuver, commander Scott Kelly will guide Endeavour through a slow 360-degree back flip just a few hundred feet below the lab complex so the station crew can photograph the heat shield with powerful digital cameras.
It will take several more days for analysts to review launch photography, radar data and wing leading edge sensor data recorded during launch and laser scans of the shuttle's nose cap and wing leading edge panels that were carried out by the astronauts today. Along with the rendezvous pitch maneuver photography expected Friday, engineers also must assess film from cameras mounted in the shuttle's twin solid-fuel boosters that will provide additional views of Endeavour's fuel tank. Shannon said film from the boosters should be in hand by late this weekend, after the spent boosters are towed back to port.
Along with giving engineers high-resolution views of the heat shield, the rendezvous pitch maneuver Friday also is expected to confirm two doors on the belly of the shuttle that cover propellant feedline inlets after external tank separation are properly closed for re-entry.
"We believe the ET doors are closed as expected," said shuttle flight director Matt Abbott. "We did see a few indications early on that things may have been, in terms of the mechanism, not completely seating. But that later cleared. We'll be looking at the photography taken during the r-bar pitch maneuver tomorrow, which will help make us very confident the doors are closed."
Abbott said engineers were continuing to develop plans to cope with the failure of a pressure sensor controller that has disabled the automatic system used to activate and deactivate heaters used by liquid oxygen tank No. 2 in the shuttle's fuel cell system. The shuttle uses three fuel cells that combine oxygen and hydrogen to produce electricity and, as a by product, water.
"In order to force the oxygen and hydrogen out of the tanks, we require heaters that cycle on and off," Abbott said. "As the heaters come on and build up pressure in the tank, it forces the oxygen ... out of the tanks. With the failure, we're going to have to use manual heater control, the automatic control is not functional on that tank, and that's going to mean a little bit of a change in some of our planning for the rest of the mission."
Engineers consider the issue an inconvenience and Abbott said he didn't expect any impact on the mission.
"It will probably develop into an every-other-day kind of thing," he said. "It will require some baby-sitting in terms of probably every 30 to 45 minutes early on to power the heaters on and power them back off. Later on in the mission, it will get to where the heaters need to be on for maybe four or five minutes and then off for an hour and a half or so. It'll vary as the oxygen is used up out of the tank. We don't really have any concerns about being able to do that, we have plenty of days where we've got the crew on the flight deck and they'll be able to handle that without any problem."
Abbott said the pressure control problem is the only glitch of any significance and that given Endeavour is making its first flight since December 2002, "the vehicle is very, very clean."
"It's really a testament to the fantastic job the folks at the Kennedy Space Center did over the past four-and-a-half years getting the vehicle ready to fly," he said.