Shuttle heat shield cleared; crew to open new module
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: February 12, 2010
The shuttle Endeavour's heat shield - the protective tiles on the ship's belly and the critical carbon composite nose cap and wing leading edge panels - has been cleared for re-entry after a detailed analysis of post-launch imagery and sensor data, NASA officials said Friday.
Only three "areas of interest" were identified during the analysis and Cain said none of them posed any additional risk.
A small ceramic insert over a bolt in a carrier panel that helps hold one of the cockpit windows in place backed out slightly during launch, posing a potential risk for hitting the shuttle's tail fin if it released during re-entry.
A similar issue developed during at least one previous shuttle flight and in that case, the insert did not release. Cain said engineers do not expect Endeavour's to release, either, but even it did it could not cause any critical damage.
"The rudder-speedbrake on the vertical tail was an area we had determined that it could transport to," Cain said. "But all the assessment, the analyses of the associated critical systems in the vertical tail, including the rudder and speedbrake actuator areas as well as the leading edge of the vertical tail, the object just would not have enough energy to impart critical damage to any of those systems. And so we're not concerned about that."
Another area of interest was a tile on the top of the crew cabin that has a small crack in one corner. The tile had been repaired but the fix apparently failed and the crack re-opened. As with the insert, Cain said engineers do not expect any pieces to break away during re-entry but even if one did, it would not have enough energy to cause any damage.
The third area of interest involved a so-called flipper door seal that was seen protruding above the surface of Endeavour's left wing after launch. The seal covers part of the interface between the back of the wing and the elevons that help control the shuttle's flight in the atmosphere.
"There is no issue with that seal protruding as it is," Cain said Friday. "We don't expect it to do anything during entry in terms of peeling back any further or breaking off or anything like that.
"If it should somehow liberate, which is absolutely not expected, it has the potential for impacting one of the elevon control surfaces at the back of the wing. But again, it doesn't have the mass or the energy to do anything other than ... something superficial and nothing of any critical nature at all."
The analysis also showed no issues with the thermal environment under the lifted seal.
Aboard the shuttle-station complex Friday, the crews focused on preparations for activating the new Tranquility habitation module attached to the Unity module's left-side port during a spacewalk overnight Thursday.
The hatch leading into the new module is expected to be opened just after 9 p.m. Power will not be routed to the module's circuitry until after the first of two ammonia coolant loops is connected and activated during a spacewalk overnight Saturday.
Using flashlights and portable ventilation ducts, the crew plans to open the module this evening and move the vibration isolation system used by one of the station's exercise machines inside, followed by a carbon dioxide removal rack.
"The systems will not be activated, so it will be a little bit dark in there and it won't have the ventilation fans going, but we will have the crew going in there, they will be working to prepare and outfit node 3, getting it ready," said space station Flight Director Bob Dempsey.
Tranquility, also known as node 3, was launched with a seven-window cupola attached to its outboard end. Later this weekend, the station's robot arm will be used to remove the cupola and attach it to Tranquility's Earth-facing port.
One of the station's two robot arm control stations will be moved into the cupola once it is activated, providing a direct view for operators performing maintenance or capturing approaching supply ships.
"One of the main activities (overnight Friday) will be preparing the cupola for its relocation," Dempsey said. "What this will entail is opening the hatch to the cupola, putting in a cover that will be in place once the cupola is removed and provides protection to that port when it's exposed to space, capping some valves so we have good seals there and don't have any paths to vacuum. Then we will close the hatch and get ready to depress the cupola in preparations for its relocation.
"The crew will also be working on outfitting the vestibule between the ISS and node 3, attaching computer cables, data cables, various power cables and so forth. And then the crew will be working inside the module, getting ready for relocating some of the racks later on."
The new module eventually will house the U.S. segment's water processing system, urine recycling equipment, oxygen generator, carbon dioxide scrubber and the NASA toilet. But the crew is holding off the relocation of the water processing racks until engineers have had time to assess the performance of the station's repaired urine recycling system.
Endeavour's crew delivered a new distillation assembly centrifuge and an external filter to address two problems that had degraded the system's performance in recent weeks. The new hardware was installed Thursday and the crew is now using the system while engineers monitor its operation.
"There are actually two issues," Dempsey said. "Coming out of what's called the waste water tank assembly as it goes into what's called the liquid separator, as part of the processing we believe there's some biological material that's been sort of growing in there, gunk or fungi or something like that, and the external filter assembly that we attached will help filter that out before it gets into the rest of the (system)."
The other issue is unexpected calcium buildups that caused problems for the distillation assembly. The fix for that issue was to reduce the amount of liquid in the system at any given time.
Cain said Friday the system was operating at a slightly reduced pressure, but it's not yet clear whether that indicates a problem or is simply the result of the new filter and operating philosophy.
Here is an updated timeline of today's activity (in EST and mission elapsed time; includes revision F of the NASA television schedule):
EST........DD...HH...MM...EVENT 02/12 04:14 PM...04...12...00...Crew wakeup 06:04 PM...04...13...50...ISS daily planning conference 07:14 PM...04...15...00...Node 3 vestibule outfitting (part 1) 07:19 PM...04...15...05...Spacesuit resizing 07:24 PM...04...15...10...SSRMS walkoff to lab module 07:49 PM...04...15...35...Spacesuit power harness replacement 08:09 PM...04...15...55...EVA tools configured 08:54 PM...04...16...40...SSRMS releases node 2 09:09 PM...04...16...55...Node 3 hatch open 09:39 PM...04...17...25...EVA tool audit 09:39 PM...04...17...25...Node 3 vestibule outfitting (part 2) 10:09 PM...04...17...55...QD familizariztion 10:19 PM...04...18...05...Node 3 port IMV cap 10:44 PM...04...18...30...Node 3-Cupola hatch open 11:19 PM...04...19...05...Node 3 port CDC install 11:39 PM...04...19...25...Crew meals begin 02/13 12:39 AM...04...20...25...Node 3 overhead IMV cap 12:59 AM...04...20...45...Node 3V AP cap removal 01:04 AM...04...20...50...Node 3 VAP cap removal 01:14 AM...04...21...00...Node 3 vestibule outfitting (part 3) 01:54 AM...04...21...40...Node 3 PPRV cap removal 01:59 AM...04...21...45...ARED vibration isolation transfer 02:29 AM...04...22...15...PAO event 02:49 AM...04...22...35...EVA-2: Equipment lock preps 02:49 AM...04...22...35...Equipment lock preps 02:59 AM...04...22...45...ARS rack transfer 05:24 AM...05...01...10...PAO event 05:49 AM...05...01...35...ISS evening planning conference 06:39 AM...05...02...25...EVA-2: Mask/pre-breathe 07:24 AM...05...03...10...EVA-2: Airlock depress to 10.2 psi 07:44 AM...05...03...30...ISS crew sleep begins 08:14 AM...05...04...STS crew sleep begins