Crew completes evening of heat shield inspections
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: March 12, 2008
The Endeavour astronauts unlimbered the shuttle's robot arm overnight and inspected the ship's nose cap and wing leading edge panels with a laser scanner on the end of a 50-foot-long boom. The areas of the orbiter that experience the most extreme heating during re-entry appeared in good shape to the untrained eye, including the nose section where launch imagery indicates a possible bird or debris strike about 10 seconds after liftoff. Additional inspections are planned during final approach to the space station Wednesday night and lead Flight Director Mike Moses said early today it's too soon to say what, if anything, might have struck the shuttle.
"I took a look at the video before I came over here," he told reporters during a mission status briefing. "It's really hard to tell. It looks like it's not coming from the orbiter and you can't really tell if it strikes the orbiter or not. You could go either way. You could say it hits somewhere on the nose or it passes behind the SRB (solid rocket booster) and doesn't actually come anywhere near us.
"So, I guess the bottom line is we don't know what it is yet, we're still looking at it. ... The initial look at the still photos from ascent didn't show anything. We got some real quick flyby video today (during the heat shield inspection), nothing obvious showed up. But I'm certainly not the expert and the teams will take a look at that. We'll know in the next day or two if anything is on the nose we didn't expect."
The fully fueled shuttle weighs 4.5 million pounds on the launch pad and accelerates - straight up - to a velocity of 120 mph in the first 10 seconds of flight. Moses said that's not fast enough to cause any major impact concern and "if we did have an impact there, it probably would be no problem." The foam insulation that struck the shuttle Columbia's left wing with catastrophic results in 2003 impacted with a relative velocity of some 530 mph.
A bird was hit by the shuttle Discovery's external tank during launch of the first post-Columbia mission and Moses said it's possible a bird was involved in the incident 10 seconds after Endeavour lifted off. But, he added, "I can't even begin to speculate on what it could be. And to be honest, even speculating that it didn't come from the orbiter is maybe a little premature as well. We should let the experts do the math. We got some good video at least that shows it in multiple frames so they'll be able to do a trajectory analysis to see where that came from."
During the climb to space early Tuesday, a signal processing card failed resulting in a loss of telemetry from a group of left-side aft rocket thrusters. Because flight controllers cannot detect possible fuel leaks in those jets, three primary thrusters in the left-side orbital maneuvering system rocket pod will not be used for the remainder of the flight. Engineers are working on a software patch that should recover the use of smaller left-side vernier jets in time for Endeavour's rendezvous with the space station Wednesday night.
"That will give us back the vernier jets for rendezvous, which gives us the fine control we like to have," Moses said. "But bottom line, even if the verniers for some strange reason just did not recover again, no mission impact to mission duration. But our plan is to recover those with this software patch."
One other glitch during launch involved the shuttle's flash evaporator cooling system, or FES. The FES is used primarily during launch and re-entry, when the shuttle's cargo bay doors are closed and radiator panels are not deployed, to get rid of the heat generated by the ship's electronics. During launch Tuesday, the primary A-channel FES controller failed to work properly, forcing an alternate controller to take over.
"We actually have three separate controllers we can use for the FES," Moses said. "We switched over to the B controller and it worked fine. Once we got on orbit and opened up the payload bay doors, we went back to the A controller. It got really close to the control band, but couldn't quite keep up and shut itself down again. A little later we switched it to a different mode ... and again, we saw a similar signature, it just wasn't able to control.
"It probably points to some kind of sensor problem in a controller, a feedback problem, it's hard to tell. The good news is, we saw no signs of icing, no problems at all with the FES system itself and FES pri B is working great. So at this time, we're going to go ahead and declare FES pri A failed and we're not going to do anymore troubleshooting with it. Pri B is working great for us and we don't expect any problems. So it's no mission impact with the FES."
Along with inspecting the nose cap and wing leading edge panels late Tuesday and today, the astronauts checked out the spacesuits that will be used during five upcoming spacewalks. They also pre-staged equipment and supplies that will be moved over to the station after docking Wednesday.
"Once we dock, we have a lot of gear we have to haul over to the ISS airlock in preparation for the EVAs we'll be doing out of the station's airlock," Moses said. "In addition to that, later on today the crew is going to continue on with the scans with the OBSS (orbiter boom sensor system) and to get us ready for rendezvous tomorrow (Wednesday night), they'll do a tools checkout of the systems they use up on the flight deck - the hand-held laser system, the laptop computer systems they use to help with rendezvous. They're also going to check out the docking system, power it up, extend the ring and have the docking system ready for docking."
Finally, Moses said sensors mounted behind the wing leading edge panels worked as planned during launch Tuesday and did not detect any unusual vibrations that would indicate any significant debris strikes. He also said a new Nikon flash system worked as expected, allowing a camera in the belly of the shuttle to photograph the external tank after separation in orbital darkness. The imagery is under assessment.
The astronauts are scheduled to go to bed around 8 a.m. Wakeup is expected shortly after 4 p.m. Rendezvous operations begin around 5:33 p.m. with the terminal phase initiation rocket firing on tap at 8:42 p.m. Docking is expected at 11:25 p.m.