Return to Flight
By William Harwood
CBS News/Kennedy Space Center
The following copy originally was posted on the Current Mission space page at http://cbsnews.com/network/news/space/current.html.
Comments, suggestions and corrections welcome!
TABLE OF CONTENTS
09:20 a.m., 07/17/06, Update: Shuttle Discovery returns to Earth UPDATED at 10:20 a.m., 11:10 a.m. and 3:40 p.m. with revised landing time, crew quotes and additional details
Under an overcast sky, the shuttle Discovery glided to a smooth touchdown on runway 15 at the Kennedy Space Center today, closing out a successful space station repair and resupply mission that appears to clear the way for resumption of station assembly in September.
With commander Steve Lindsey at the controls, Discovery settled to a tire-smoking, high-speed touchdown at 9:14:43 a.m. A few moments later, pilot Mark Kelly deployed the shuttle's braking parachute, the ship's nose gear dropped to the runway and Discovery rolled to a stop to close out a voyage spanning 5.3 million miles and 202 complete orbits since blastoff July 4.
"Wheels stopped, Houston," Lindsey radioed mission control.
"Roger wheels stopped. Welcome back, Discovery," astronaut Steve Frick replied from Houston. "Congratulations on a great mission expanding our knowledge and experience with orbiter repair and bringing the space station back to a full crew complement."
"Thanks. It was a great mission, a really great mission," Lindsey said. "Enjoyed the entry and the landing."
Mission duration was 12 days 18 hours 36 minutes and 48 seconds.
Lindsey, Kelly flight engineer Lisa Nowak, Piers Sellers, Mike Fossum and Stephanie Wilson plan to spend the night in Florida before flying back to Houston on Tuesday.
"It's a thrill and a pleasure to be here again, especially under these circumstances," NASA Administrator Mike Griffin told reporters after landing. "In fact, it's such a great day I don't think even a press conference can spoil it."
Griffin expressed optimism that Discovery's flight will pave the way to launch of the shuttle Atlantis late next month on the first in a series of daunting space station assembly missions. But he said NASA would not launch Atlantis before completing a detailed analysis of Discovery's mission.
"This is as good a mission as we've ever flown," he said. "But we're not going to get over confident, we're going to keep looking at the data and we're going to make our decisions based on the data just as we did on this flight. We have to take it flight by flight. We've got 16 flights to go to assemble the station and hopefully do a Hubble (Space Telescope) repair. And that's what we want to do, but we've got to take it one flight at a time."
Still, Discovery's mission was a clear step in that direction. NASA Launch Director Mike Leinbach said an initial inspection of the shuttle turned up no surprises.
"We had to search for dings to the tile and the couple that we saw were very, very minor," he said. "Just a great looking vehicle."
Discovery's descent began over the eastern Indian Ocean when Lindsey and Kelly fired the shuttle's twin braking rockets at 8:07 a.m. to drop the ship out of orbit. Five minutes before the "burn," Kelly started auxiliary power unit No. 1, a hydraulic powerplant with a small leak in its hydrazine fuel system.
Engineers concluded Sunday the leak was most likely nitrogen gas used to pressurize APU 1's hydrazine fuel tank and not an actual fuel leak. APU 1 appeared to run normally throughout Discovery's descent today as did the shuttle's other two redundant hydraulic power units.
The only technical issue occurred late in the descent when one of two air data probes failed to deploy. But it eventually slipped into place and in any case, the other probe deployed on time and worked properly.
The major concern all morning was the weather, with rain clouds popping up near the runway well after Discovery's braking rockets were fired. Flight director Steve Stich told Lindsey to switch from runway 33 to 15 to avoid possible showers toward the south end of the runway.
"I would give Steve a perfect 10 today," Stich said later. "He did a superb job. ... It was a perfect landing."
There were no obvious problems during final approach and landing and infrared views of the shuttle on the runway showed normal looking APU exhaust puffing from ports by the shuttle's tail fin. Technicians did not detect any hydrazine vapors near the shuttle's aft compartment.
"Houston, Discovery, looks like everybody's off and I'm about to go off comm," Lindsey radioed a few minutes past 10 a.m. "I just wanted to tell Steve (Stich) and Steve (Frick) and the entire entry team it was a pleasure working with you today. Really enjoyed it. It was a fun entry, it was beautiful!
"At the high mach numbers at night going towards dawn - I just wanted to describe the picture for you - we could see the bright orange glow above and I could see the Earth moving below and it was just spectacular. We actually also saw the moon through the plasma. So it was a great entry and a great landing. Appreciate working with you and training with you."
"Thanks very much for those words, Steve," Frick replied. "We appreciate it. It was an exciting entry for us, too, and we envy you the view. We look forward to seeing you when you get back to Houston."
"All right, I can't wait," Lindsey said. "Talk to you later."
The astronauts, wearing blue jump suits, were greeted on the runway by Griffin, Leinbach, Bill Gerstenmaier, director of spaceflight, space center Director Jim Kennedy and other senior managers.
Smiling and looking none the worse for two weeks in weightlessness, Lindsey and his crewmates took a moment to inspect the shuttle's heat shield, walking about under the orbiter, pointing up at Discovery's belly from time to time and discussing the flight with Griffin. There were no obvious signs of damage in wide-angle television views. "I'd like to just thank the folks at Kennedy Space Center for a really, really clean vehicle," Lindsey said, standing with his crew mates in front of Discovery. "This is my fourth flight and I've done four walkarounds and I've never seen a vehicle as clean as this one is.
"We had two major objectives on this flight. The first one was to complete the return-to-flight test objectives and the second one was to get us ... back for space station assembly. And I think we accomplished both of those objectives and we're ready to go assemble station and we're ready to start flying shuttles on a more regular basis.
"And finally, I'd like to thank this crew standing here," Lindsey said. "They were absolutely superb the entire flight, I couldn't have asked more out of them, they were nearly perfect. They got everything done that we needed to get done. I actually had to throttle them back to give them a little bit of time off. They were all focused, they did a great job and it was a privilege for me to serve with them. Thanks a lot. We're going to go see our families now. Have a good day."
The 115th shuttle mission was a make or break flight for NASA, coming nearly a full year after Discovery's launch on the first post-Columbia mission. The unexpected loss of foam insulation from the ship's external fuel tank showed the space agency still had work to do.
After months of redesigns, computer modeling and exhaustive testing, Discovery was cleared for blastoff July 4 on a flight to pave the way for the resumption of space station assembly.
During their two weeks in space, Lindsey and company delivered fresh water and more than 3.2 tons of supplies and equipment to the international space station and carried out a successful spacewalk to fix a stalled robot arm transporter on the complex that had to be restored to normal operation before station assembly can proceed.
Discovery also ferried European Space Agency astronaut Thomas Reiter to the outpost, boosting crew size back the three for the first time since downsizing after the Columbia disaster. Reiter was launched aboard Discovery as part of a commercial contract between ESA and the Russian space agency, Roscosmos.
Spacewalkers Fossum and Sellers rode on the end of a long boom attached to the shuttle's robot arm, demonstrating its possible use as a shuttle repair platform. Thanks to a one-day mission extension, Sellers and Fossum also staged a third spacewalk to test wing leading edge repair techniques. The exercises may help pave the way for an eventual flight to service the Hubble Space Telescope.
In the near term, Discovery's flight was a critical milestone for NASA. Facing a Bush administration 2010 deadline for completing the space station and retiring the shuttle, NASA needs to ramp up station assembly as soon as possible to finish the lab complex before time runs out. Discovery's flight doesn't guarantee success, but it at least clears the way for assembly flights to resume.
"I think we were all hoping for two things to come out of STS-121," Sellers said during an orbital interview. "The first thing is that the shuttle would fly with no problems, no big dings on ascent and we'd have a clean vehicle. We seem to have achieved that.
"The second thing is, that we would leave station in good shape and ready to pick up the assembly sequence and the line would be drawn where it was rubbed out before Columbia, we would start again with the next mission and continue the assembly. I think we're there now. We repaired the external equipment that will allow the assembly to continue. So, two for two!" Said space station flight director Rick LaBrode: "All in all, it was just a great mission. This is just a roaring success for the station team and we're ready to proceed with assembly ops."
Throughout the mission - the day after launch, during docked operations at the station and even after their departure - the astronauts carried out time-consuming, inch-by-inch inspections of Discovery's fragile heat shield to make absolutely sure nothing was damaged during the climb to space or after reaching orbit.
As it turned out, Discovery's foam-covered external fuel tank performed well and the shuttle's heat shield tiles suffered only a few cases of very minor damage. NASA managers were elated at the performance of the tank after a frustrating year of redesigns and exhaustive testing.
"All the work that all the folks have done on the ET ... and how clean the 121 tank is kind of gives everybody a really good feeling that we're getting there, we're going in the right direction," said lead flight director Tony Ceccacci. "You've seen how clean the vehicle is and that's just a testament to all the work that everyone has done."
In an orbital interview, Nowak agreed, saying "we feel like we've done all the tests and met the objectives and we feel like the whole program is back on track to assemble the space station and move on back to the moon and to Mars. And we're looking forward to all of that."
With Discovery back on the ground in Florida, NASA engineers will now turn their attention to the shuttle Atlantis, scheduled to blast off around Aug. 27 or 28 on a mission to deliver a set of huge solar arrays to the space station.
Atlantis is expected to be hauled out to launch pad 39B around Aug. 1. A practice countdown is on tap Aug. 10 and NASA managers will meet Aug. 15 and 16 for a formal flight readiness review to assess Atlantis' processing and to set an official launch date. The launch window opens Aug. 27 or 28 - a final decision hasn't been made - and closes Sept. 7.
"Someone asked the other day if the space shuttle was back," shuttle program manager Wayne Hale said today. "When we lqunched and looked at the external tank, we saw exactly what we predicted. We delivered about 4,000 pounds of scientific equipment to the international space station versus about 300 pounds of scientific equipment that had been delivered in the last four years by our international partners.
"And in addition to that, we brought the third crew member up to the international space station and made vital repairs on it. We made a number of repair related activities that proved that our repair capability is getting more and more robust. And of course, the orbiter worked in an almost flawless manner.
"So yes, I think the conclusion is the shuttle is back," Hale said. "We are launching in just about six weeks from today on probably the most complicated assembly mission that's every been scheduled in human space flight before and we have the team that is now practiced and battle hardened and ready to go do that.
If all goes well, NASA will close out 2006 by launching Discovery in mid December on another station assembly flight.
08:10 a.m., 07/17/06, Update: Shuttle braking rockets fired
Flying upside down and backward over the eastern Indian Ocean, commander Steve Lindsey and pilot Mark Kelly fired Discovery's twin braking rockets at 8:06:55 a.m. for three minutes and two seconds, slowing the shuttle by 206 mph. That was enough to drop the far side of the shuttle's orbit deep into Earth's atmosphere, setting up a landing at the Kennedy Space Center around 9:14:06 a.m. This status report will be updated after landing or as conditions warrant.
08:00 a.m., 07/17/06, Update: Discovery cleared for entry
Entry flight director Steve Stich has cleared the Discovery astronauts to fire their braking rockets on time at 8:06:50 a.m. to set up a landing on runway 33 at the Kennedy Space Center around 9:14 a.m. Earlier concern about electrically active anvil clouds north of the space center dissipated and Stich felt comfortable enough to give the crew a "go" for the deorbit burn. Astronaut Mike Bloomfield, assessing the weather in a shuttle training just, told flight controllers the shuttle would fly into a broken deck of clouds around 16,000 feet above the landing site but would break out into the clear around 10,000 feet. He also reported smooth air and no turbulence.
05:40 a.m., 07/17/06, Update: Payload bay doors closed for entry
The shuttle Discovery's payload bay doors have been closed and latched for re-entry and the ship's flight computers are now running OPS-3 entry software. The astronauts and the mission control team at the Johnson Space Center in Houston are continuing to monitor the weather while pressing ahead toward a deorbit rocket firing at 8:07 a.m. Landing at the Kennedy Space Center remains targeted for 9:14 a.m.
04:20 a.m., 07/17/06, Update: Discovery astronauts gear up for entry
Keeping tabs on the weather, the Discovery astronauts are gearing up for re-entry and landing today at the Kennedy Space Center to close out a successful space station repair and resupply mission.
Flying upside down and backward over the eastern Indian Ocean, commander Steve Lindsey and pilot Mark Kelly plan to fire Discovery's twin braking rockets at 8:06:55 a.m. for three minutes and two seconds, slowing the shuttle by 206 mph. That's enough to drop the far side of the shuttle's orbit deep into Earth's atmosphere, setting up a landing at the Kennedy Space Center around 9:14:06 a.m.
Lindsey, Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossom and Stephanie Wilson plan to close Discovery's cargo bay doors around 5:30 a.m. to rig the ship for entry.
There are no problems of any significance aboard Discovery and flight controllers are confident the shuttle's three hydraulic power units, including one with a known but very small leak of either nitrogen gas or toxic hydrazine fuel, will operate normally during the descent.
But the weather could pose problems for Lindsey and his crewmates. Forecasters with the Spaceflight Meteorology Group at the Johnson Space Center in Houston predict a chance of showers in the landing area due to a stationary front north of the Florida spaceport. But forecasters said early today they are hopeful the showers will dissipate.
"We think we have a good shot," astronaut Steve Frick radioed the crew from Houston. "OK, that sounds great," Lindsey replied.
Discovery has two landing opportunities today, one at 9:14 a.m. and the second, one orbit later, around 10:50 a.m. If Lindsey and company can't make it back to Florida today, they'll remain in orbit one more day and try again Tuesday. The forecast for Tuesday is somewhat worse and entry flight director Steve Stich said Sunday he would activate the shuttle's backup landing site at Edwards Air Force Base, Calif., if re-entry slips to Tuesday.
Here is the timeline for today's landing attempt. Note: The time of deorbit ignition for the first landing opportunity has moved 20 seconds earlier than previously posted. The times below reflect that change (all tiems in EDT and subject to change):
TIME EVENT _____________________________________________________ 01:08:00 AM Crew wakeup (flight day 14) 03:13:00 AM Group B computer powerup 03:28:00 AM Navigation system alignment 03:43:00 AM Laptop computer teardown 04:09:00 AM Deorbit timeline begins 05:27:00 AM Payload bay door closing 07:47:00 AM Mission control 'go' for deorbit burn 07:53:00 AM Astronauts strap in 08:02:00 AM Single APU start (APU 1) 08:06:55 AM Deorbit ignition (duration: 3:02) 08:09:57 AM Deorbit burn complete (velocity change: 206 mph) 08:42:13 AM Entry interface (altitude: 400,000 feet) 08:47:19 AM 1st roll command to left 08:57:10 AM 1st left-to-right roll reversal 09:00:40 AM C-band radar acquisition 09:07:42 AM Velocity less than mach 2.5 09:09:50 AM Velocity less than mach 1 09:10:11 AM Shuttle banks to line up on runway 09:14:06 AM Landing BACKUP LANDING OPPORTUNITY 09:23:00 AM Mission 'go' for deorbit burn 09:38:00 AM Single APU start (APU 1) 09:43:25 AM Deorbit ignition (dT: 3:01; dV: 205 mph) 09:46:26 AM Deorbit burn complete 10:18:04 AM Entry interface (altitude: 400,000 feet) 10:23:04 AM 1st roll command to left 10:36:21 AM 1st left-to-right roll reversal 10:43:25 AM Velocity less than mach 2.5 10:45:34 AM Velocity less than mach 1 10:46:12 AM Shuttle banks to line up on runway 10:49:48 AM Landing 11:23:00 AM Deorbit backout (if re-entry waved off 24 hours) 11:48:00 AM Group B computer powerdown 04:23:00 PM Crew sleep begins 12:23:00 AM Crew wakeup (07/18)
04:00 p.m., 07/16/06, Update: Astronauts eager for landing; flight director optimistic about weather
The shuttle Discovery is in excellent condition for landing and with a successful space station repair and resupply mission now in the books, NASA should be clear to resume assembly flights with launch of shuttle Atlantis in late August, Discovery skipper Steve Lindsey said today.
"It's been very, very clean throughout the mission, we've had very, very few issues with it," Lindsey said of Discovery in an interview with CBS News. "The vehicle's been clean, the (external fuel) tank looked pretty clean, we got a clean bill of health today to enter after inspecting for micrometeorite damage yesterday and the day before. So I think this vehicle has done great."
As for Discovery's mission to deliver supplies to the international space station, to repair a critical robot arm transporter and to ferry a third full-time crew member to the lab complex, Lindsey said "we achieved all of those objectives."
"Two big objectives were to get the space station ready for assembly as well as bring the crew back up to three people," Lindsey said. "I think we are ready to go back to space station assembly and start flying the shuttle, hopefully, as soon as August.
"Having said that, we'll stay vigilant with the shuttle, we'll continue watching it, taking care of it, paying attention to ice-frost ramps and areas like that. Just because we're going to be back to flight doesn't mean we're going to change the way we're operating. We're going to be very careful, very cautious, look at everything and we'll leave no stone unturned as we continue with this program."
NASA managers hope to launch Atlantis as early as Aug. 27 to install a huge set of solar panels on the end of the station's main solar array truss. To ensure good lighting for photo documentation, and to avoid a conflict with the planned launch of a Russian Soyuz rocket carrying the station's next crew, Atlantis must get off the ground between Aug. 27 or 28 and Sept. 7.
If the shuttle isn't off the ground by then, the flight will slip into late October at the earliest.
Asked if he was concerned about pressure to get Atlantis off in the September window, Lindsey said he was confident NASA managers would make the right decisions.
"Every program and project I've ever been involved in, every one I know of, there is schedule pressure," he said. "And there are other kinds of pressures, too. There is technical pressure, their are cost pressures, all those are a part of every program and project that I know of. ... As long as we can carefully balance those pressures, I think we'll be fine.
"The diligence that went into launching us ... I think the same will happen for Atlantis. We will shoot for August and if something happens and we can't make August, then we'll go for the next launch date. I'm not worried about it, everybody's paying attention, we're especially conscious of that sort of thing and we talk about it a lot. So I think the program will make the right decisions."
But first, entry flight director Steve Stich and his team must make the right decision about when to bring Discovery back to Earth. In a pre-entry briefing today, Stich said the only concern is the weather, with forecasters predicting a chance of showers that could cause problems.
Discovery will have two chances to land at the Kennedy Space Center Monday, the first at 9:14 a.m. and the second around 10:50 a.m. If the weather doesn't cooperate - and it looks slightly better for the first opportunity than the second - Lindsey and his crewmates will remain in orbit an extra day.
In that case, Stich likely will activate the shuttle's backup landing site at Edwards Air Force Base, Calif., and bring Discovery down on one coast or the other Tuesday. The forecast in Florida calls for possible showers Tuesday while Edwards is expected to be "go" Monday and Tuesday. The shuttle has enough on-board supplies to remain in orbit until Wednesday.
"The weather looks fairly reasonable for tomorrow," Stich said. "Of course, at the Kennedy Space Center in the summertime, even though it's a morning landing, they're always looking at a chance of showers and that's the main thing we're looking at tomorrow. There's a frontal boundary just to the north of the Kennedy Space Center and they're worried about that front pushing to the south and causing showers. That's about the only concern for weather."
Otherwise, he said, Discovery is in excellent condition for landing.
Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossom and Stephanie Wilson spent the day packing up and rigging Discovery for entry. Thomas Reiter, the European Space Agency astronaut who blasted off with Lindsey and company July 4, was left behind on the space station to boost crew size back to three for the first time since downsizing in the wake of the Columbia disaster.
Discovery's mission featured one of the busiest flight plans in recent memory, with dual robotic arm operations virtually every day, three spacewalks and work to move tons of supplies and equipment from the shuttle to the station.
"I've got to tell you, about the first seven to nine days, depending on what your role was on this flight, it was a pretty tough timeline," Lindsey told CBS News. "It was tough. This is my fourth flight and it's probably the toughest one I've ever seen.
"We actually did, on flight day 10, get about three quarters of a day off where everybody could just kind of goof off. I actually ordered the crew, because i couldn't get them to stop, they were not allowed to work and they had to go look around station, tour station, take pictures and just have fun. I think everybody took advantage of it, came out of it refreshed and ready to pick up with the last part of the mission."
10:30 a.m., 07/16/06, Update: Discovery cleared for entry; no debris impacts seen; APU 1 looks good
NASA managers reviewing laser scans of Discovery's nose cap and wing leading edge panels have found no signs of any micrometeoroid impacts and have cleared the shuttle for re-entry Monday, weather permitting, to close out a space station repair and resupply mission.
In a brief chat with shuttle commander Steve Lindsey, mission control also said engineers believe a leaking hydraulic power unit that was tested earlier today can be safely used during re-entry and landing at the Kennedy Space Center.
Entry flight director Steve Stich has decided not to staff NASA's backup landing site at Edwards Air Force Base, Calif., Monday and instead to focus on Florida only. The crew will have two landing opportunities on successive orbits, the first leading to a touchdown at 9:14 a.m. and the second around 10:50 a.m.
If they can't make it back to Florida Monday because of weather or any other problems, Discovery will remain in orbit an extra day and likely land Tuesday in either Florida or California.
"After finishing the review for the port and starboard wings and the nose cap, they did not see anything new so they all look pretty good," astronaut Steve Frick radioed from the Johnson Space Center. "For weather ... the clouds shouldn't be an issue tomorrow, however there's still a chance of showers for the first rev and a little higher chance probably for the second rev. There's a front extending off into the Atlantic and depending on how it moves tonight, it may be close enough to cause some showers in the area. So we'll be looking real close at that. Edwards is looking real good both tomorrow and Tuesday if we need it."
"OK, we copy that," Lindsey said. "And is the vehicle cleared for entry?"
"That's affirm, I'm being told I can use that word. You are cleared for entry."
"OK, thanks," Lindsey said. "And a question about tomorrow. Will we land no matter what? Or will we just go for KSC tomorrow?"
"Tomorrow is KSC only," Frick replied. "For Tuesday, we'll look at other sites. But for tomorrow, we're just calling up KSC. However, the weather does look good for the West Coast for at least the next two days."
"OK, copy that."
Frick then passed on the latest thinking about APU 1, the hydraulic power unit in Discovery's engine compartment that is leaking either nitrogen gas or toxic hydrazine fuel. Engineers believe the small leak is nitrogen, used to pressurize the tank, and that more than enough will be available for entry.
While they cannot rule out a more hazardous hydrazine leak, results from a test run earlier today indicate APU 1 can safely be used for a normal re-entry and landing.
"They are feeling more and more confident it's likely not an internal ... hydrazine leak," Frick said. "There's always the chance, but we're feeling a little bit more comfortable with it. So the plan for APU 1 tomorrow will be nominal ops, we're not going to try to start it early or do anything unusual to burn extra hydrazine out of there. We'll be looking at it close like we did to day during FCS (flight control system) checkout. And it looked just fine today."
"OK, we copy that," Lindsey said. "Sounds great, thanks."
04:30 a.m., 07/16/06, Update: APU 1 runs normally during flight control system checkout
A hydraulic power unit with a leak in its fuel system was fired up early today as part of an otherwise routine flight control system checkout aboard the shuttle Discovery. A quick look at telemetry from APU 1 indicated normal operation and no obvious problems, but it will take several hours to make sure the leak rate stayed constant as engineers predicted.
Shuttle commander Steve Lindsey and pilot Mark Kelly began the hydraulic power test portion of FCS checkout around 4 a.m., turning on APU 1 to test the hydraulic actuators that will be used for steering during re-entry Monday.
"Discovery, Houston, just for a summary of part one three, we saw normal activity on all of the secondary actuator check," astronaut Steve Frick radioed from mission control in Houston. "Everything looked good to us. Also, the quick look on APU 1, we saw normal fuel useage, normal parameters for all of its run time."
"OK, great news," Lindsey replied. "Thank you, Steve."
APU 1 is on of three redundant powerplants in the shuttle's main engine compartment that generate the hydraulic pressure needed to move the ship's wing flaps, rudder, body flap and landing gear. The pressure in APU 1's hydrazine fuel tank has been dropping ever so slightly since launch July 4, indicating a leak of either nitrogen gas, used to pressurize the tank, or a leak of toxic hydrazine.
Because engineers cannot tell which material is leaking, mission managers have to assume it's hydrazine, an extremely hazardous material, and plan accordingly. Mission Management Team Chairman John Shannon said Saturday the team's strategy was as follows: If the leak stayed constant during the FCS checkout, APU 1 will be considered healthy enough for normal use during entry. If the leak worsened, the astronauts will simply run APU 1 until all of its fuel is exhausted and then return to Earth Monday with two operational APUs.
"It will be a good test for us, because it will start the APU up, it will run the APU, it will put it through some vibration, all the things we would expect to do prior to entry," Shannon said. "And then we'll just go and assess the leak.
"I would sway it's going to take between six and 12 hours to see if the pressure decay rate has changed at all. If there's a significant change, then the ops team will go burn it off just because you would have lost confidence in the integrity of the system. I don't expect that to happen."
Based on the quick-look data, no immediately obvious change was seen.
Here is an updated timeline of today's activity in space (in EDT and mission elapsed time; includes revision Q of the NASA TV schedule):
01:08 AM 11 10 30 Crew wakeup (flight day 13) 03:58 AM 11 13 20 FCS checkout 05:08 AM 11 14 30 Cabin stow begins 05:08 AM 11 14 30 RCS hotfire 08:58 AM 11 18 20 Crew meal 09:58 AM 11 19 20 L-1 communications check 1 09:58 AM 11 19 20 Entry video setup 11:38 AM 11 21 00 L-1 communications check 2 12:03 PM 11 21 25 PAO event (all crew members) 12:23 PM 11 21 45 Deorbit briefing 12:30 PM 11 21 52 Mission status briefing on NASA TV 12:53 PM 11 22 15 PILOT landing training 01:08 PM 11 22 30 Wing leading edge gear stow 01:28 PM 11 22 50 Laptop computer teardown 01:33 PM 11 22 55 Ergometer stow 01:58 PM 11 23 20 NC7 rocket firing 02:03 PM 11 23 25 KU antenna stow 05:08 PM 12 02 30 Crew sleep begins 06:00 PM 12 03 22 Daily video highlights reel on NASA TVIn the crew's morning "execute package" of timeline changes and instructions from mission control, flight controllers jokingly signed off after a successful mission.
"This is the last execute package youÕre going to get from us," flight controllers wrote. "We've had it. We're done with execute packages, finished, over, our cooked indicator has popped, the fat lady is singing (and she's not singing the Aggie War Hymn). No more... O.K., maybe that's a little bit of an exaggeration.
"Actually, if the truth be told, we really have enjoyed working this mission and if the Ku antenna wasn't going to be stowed (today), we would gladly do another execute package. Thanks for making this a great mission - one we're proud to be part of. Take care and see you back in Houston - and we'll buy the first adult malted beverage."
08:30 p.m., 07/15/06, Update: Quick-look at wings, nose cap show no obvious problems; Suffredini confirms shortened launch window for next shuttle flight
A quick-look assessment of post-undocking laser scans of the shuttle Discovery's nose cap and wing leading edges shows no obvious impact damage from space debris or micrometeoroids. Final clearance to proceed with landing Monday at the Kennedy Space Center will not be given until Sunday, however, after a detailed assessment is completed. "From what they've looked at, there's nothing of any concern that we can report at this time," astronaut Lee Archambault radioed the crew from Houston late today. "So all looks good. Of course, the analysis will continue to crank out overnight and through tomorrow, and hopefully we'll have final words tomorrow."
"Thanks for the update," shuttle commander Steve Lindsey replied.
In the meantime, a key test is on tap early Sunday to assess the health of a hydraulic power unit that has a small leak in its fuel system. Lindsey and pilot Mark Kelly plan to fire up auxiliary power unit No. 1 around 3:58 a.m. Sunday as part of an otherwise routine flight control system check out.
APU 1 is on of three redundant powerplants in the shuttle's main engine compartment that generate the hydraulic pressure needed to move the ship's wing flaps, rudder, body flap and landing gear. The pressure in APU 1's hydrazine fuel tank has been dropping ever so slightly since launch July 4, indicating a leak of either nitrogen gas, used to pressurize the tank, or a leak of toxic hydrazine.
Because engineers cannot tell which material isleaking, mission managers have to assume it's hydrazine, an extremely hazardous material, and plan accordingly. Mission Management Team Chairman John Shannon says the team's strategy is unchanged from Saturday: If the leak doesn't get worse during the FCS checkout, APU 1 will be considered healthy enough for normal use during entry. If the leak worsens, the astronauts will simply run APU 1 until all of its fuel is exhausted and then return to Earth Monday with two operational APUs.
"The mission operations team put together their final plan," Shannon said. "The ops team will use APU 1 during the flight control system check out, they will run it the normal amount of time then they'll go assess it, make sure the leak rate did not change.
"If the leak rate changes at all, if it's perceptible to the ops team, they will burn it off, burn all the fuel out of that hydrazine system. We don't expect that to be the case. Assuming everything looks good after flight control system check out, that APU will be used as the first APU that's started pre deorbit burn and then used nominally throughout the entry."
Shannon said one member of the MMT dissented with the majority opinion, arguing "that maybe we did not know enough about the conditions back there and suggested we go ahead and burn it off for extra caution. But the other 31 people I polled were all in agreement that we go with the nominal plan."
The concern is that a major hydrazine leak could result in a fire late in re-entry under worst-case conditions. While engineers believe the leak is more likely nitrogen, which poses no threat, NASA's flight rules require conservatism to ensure the team errs on the side of caution.
A shuttle can safely land with just one operational APU, but APU 1 is required to deploy the ship's landing gear. If APU 1 isn't available for use Monday, Kelly will use a backup system to deploy the gear, firing pyrotechnic charges to blow the doors open and release the hooks that hold the gear in place. While that's never been done before, the system is redundant and Shannon said it would pose no problems for Discovery's crew.
APU 1 will be run for five to six minutes early Sunday to provide the power needed to check out the hydraulic system and movement of Discovery's aerosurfaces.
"It will be a good test for us, because it will start the APU up, it will run the APU, it will put it through some vibration, all the things we would expect to do prior to entry," Shannon said. "And then we'll just go and assess the leak.
"I would sway it's going to take between six and 12 hours to see if the pressure decay rate has changed at all. If there's a significant change, then the ops team will go burn it off just because you would have lost confidence in the integrity of the system. I don't expect that to happen."
In addition to the FCS checkout and test firings of Discovery's maneuvering jets, Lindsey and Kelly also will carry out tests to troubleshoot an erratic controller in the ship's flash evaporator cooling system. The system, used to cool the shuttle's electronics after the ship's payload bay doors are closed, is difficult to test on the ground and NASA wants to collect as much data as possible to speed any possible repairs.
NASA hopes to launch the shuttle Atlantis around Aug. 28 on a long-awaited mission to restart assembly of the international space station. Discovery must be "turned around" quickly to serve as a potential rescue shuttle in case of problems that might prevent Atlantis from safely returning to Earth at the end of mission STS-115.
As reported here Friday, a conflict with the planned launch of a Russian Soyuz capsule carrying the station's next crew - Expedition 14 - has forced NASA to shorten Atlantis' launch window. As it now stands, according to station program manager Mike Suffredini, the window will open Aug. 28 - possibly as early as Aug. 27 if lighting permits - and close Sept. 7, nearly a week earlier than had been planned.
That's because NASA managers and their Russian counterparts want to ensure a separation between the shuttle's undocking and the arrival of the Soyuz to give the station crew time to make preparations and to adjust their body clocks to a different schedule.
For a variety of reasons, the Soyuz must take off by Sept. 18. Any later and the Soyuz carrying the station's outgoing crew would return to Earth about 10 days later in darkness. The Russians are using a recovery team with new personnel and want to ensure mostly daylight conditions for the recovery operation.
So the shuttle/Soyuz launch window will work like this: If Atlantis takes off between Aug. 28 and Sept. 3, the Soyuz carrying the Expedition 14 crew to the station will blast off from the Baikonur Cosmodrome Sept. 14. If Atlantis goes between Sept. 4 and Sept. 7, the Soyuz will take off Sept. 18. For a shuttle launch on Sept. 7, for example, Atlantis would dock with the lab complex Sept. 9 and undock Sept. 17. That would provide a three-day cushion between undocking and arrival of the Soyuz.
If Atlantis doesn't get off the ground by Sept. 7, NASA will stand down and the Soyuz launch will move back to Sept. 14. The next daylight launch window for the shuttle opens Oct. 26 and closes Oct. 29.
01:45 p.m., 07/15/06, Update: Updated deorbit burn and landing times through Wednesday
Flight controllers have updated deorbit burn and landing times for the shuttle Discovery. Here are all the landing times and sites from Monday through Wednesday (in EDT and subject to change):
SITE..REV...DEORBIT.....LANDING Monday, July 17 KSC...202...08:07 a.m...09:14 a.m. (planned) NOR...203...09:42 a.m...10:46 a.m. KSC...203...09:43 a.m...10:50 a.m. EDW...204...11:19 a.m...12:20 p.m. NOR...204...11:22 a.m...12:21 p.m. EDW...205...12:56 p.m...01:54 p.m. Tuesday, July 18 KSC...218...08:19 a.m...09:21 a.m. EDW...219...09:48 a.m...10:50 a.m. NOR...219...09:50 a.m...10:52 a.m. KSC...219...09:56 a.m...10:56 a.m. EDW...220...11:23 a.m...12:24 p.m. NOR...220...11:26 a.m...12:26 p.m. EDW...221...01:01 p.m...01:58 P.m. Wednesday, July 19 KSC...233...06:47 a.m...07:51 a.m. KSC...234...08:23 a.m...09:25 a.m. EDW...235...09:52 a.m...10:54 a.m. NOR...235...09:54 a.m...10:56 a.m. EDW...236...11:28 a.m...12:28 p.m. NOR...236...11:31 a.m...12:30 p.m.
11:45 a.m., 07/15/06, Update: Entry ground tracks, data posted; mission status update
The Discovery astronauts are wrapping a final inspection of the shuttle's right-side wing leading edge panels and reinforced carbon carbon nose cap as part of a "late inspection" to look for signs of damage from micrometeoroids.
Lead flight director Tony Ceccacci said it will take engineers a day to assess the laser scans and compare the data to inspections conducted July 5, the day after Discovery reached orbit. Assuming no problems are found, NASA's Mission Management Team will give the crew a "go" Sunday to press ahead for deorbit and landing Monday at the Kennedy Space Center.
"As you saw today, we had a by-the-book undocking from the station," Ceccacci said. "Everything went per the procedures. ... After the crew gets done with the inspection, they'll be berthing the OBSS (inspection boom) and the shuttle robotic arm, getting it ready for entry. They'll be doing additional tasks to get the vehicle ready for entry, starting their cabin stow and such."
Commander Steve Lindsey, pilot Mark Kelly and flight engineer Lisa Nowak will check out the shuttle's re-entry systems Sunday, test one of the shuttle's cooling systems and test fire a hydraulic power unit that appears to have a small fuel leak. If the leak stays constant, the crew will use all three of Discovery's auxiliary power units - APUs - during re-entry Monday. If the leak in APU 1 worsens, however, the astronauts will restart the power unit, run it until its fuel is exhausted and return to Earth using APUs 2 and 3.
Ceccacci said NASA's Mission Management Team should complete its assessment of Discovery's nose cap and wing leading edges tomorrow afternoon.
The Spaceflight Meteorology Group at the Johnson Space Center is predicting cloudy weather at the Kennedy Space Center Monday with a deck of broken clouds at 10,000 feet, broken at 25,000 feet, light winds and showers within 30 nautical miles of the runway. Virtually identical conditions are expected Tuesday.
NASA has posted entry ground track maps and predicted entry milestones:
http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts121/mission_docs/landing.html Here is that data, plus standard re-entry milestones (all times in EDT):
TIME EVENT Orbit 203 Deorbit to Kennedy Space Center 07:47:00 AM MCC 'go' for deorbit burn 07:53:00 AM MS seat ingress 08:02:00 AM Single APU start 08:07:15 AM Deorbit ignition (dT: 3:02; dV: 206 mph) 08:10:17 AM Deorbit burn complete 08:42:33 AM Entry interface (altitude: 400,000 feet) 08:47:39 AM 1st roll command to left 08:57:30 AM 1st left-to-right roll reversal 09:08:02 AM Velocity less than mach 2.5 09:10:10 AM Velocity less than mach 1 09:10:31 AM Shuttle on the HAC 09:14:26 AM Landing Orbit Deorbit to Kennedy Space Center 09:23:00 AM MCC 'go' for deorbit burn 09:29:00 AM MS seat ingress 09:38:00 AM Single APU start 09:43:25 AM Deorbit ignition (dT: 3:01; dV: 205 mph) 09:46:26 AM Deorbit burn complete 10:18:04 AM Entry interface (altitude: 400,000 feet) 10:23:04 AM 1st roll command to left 10:36:21 AM 1st left-to-right roll reversal 10:43:25 AM Velocity less than mach 2.5 10:45:34 AM Velocity less than mach 1 10:46:12 AM Shuttle on the HAC 10:49:48 AM Landing
06:30 a.m., 07/15/06, Update: Shuttle Discovery undocks from space station
The shuttle Discovery undocked from the international space station early today, leaving European Space Agency astronaut Thomas Reiter behind to boost crew size to three for the first time since downsizing in the wake of the Columbia accident.
Undocking occurred on time at 6:08 a.m. as the two spacecraft sailed high above New Zealand.
"And we have physical separation," a Discovery astronaut said as the shuttle's docking system disengaged.
"Discovery, station, roger, we're watching here in the cameras," station flight engineer Jeff Williams radioed. "Have a safe journey back, soft landings and we'll see you on the ground in a few months."
With pilot Mark Kelly at the controls, Discovery drifted straight away from the station, pulling out in front to a distance of about 400 feet before beginning a slow loop up and over the international outpost.
The shuttle's departure trajectory was designed to keep Discovery within about 40 nautical miles of the station until the astronauts can complete a final survey of the shuttle's nose cap and right wing leading edge panels.
They inspected the left wing leading edge Friday, looking for any signs of damage from impacts by micrometeoroids or space debris. Lisa Nowak and Stephanie Wilson will use Discovery's robot arm and a long inspection boom today to make laser scans of the ship's reinforced carbon carbon nose cap and right wing leading edge panels beginning around 9 a.m.
If any serious problems are found, Discovery has enough propellant on board to re-rendezvous with the space station. But if the wings and nose cap are sound, Discovery will leave the area and the crew will begin gearing up for a landing opportunity Monday at the Kennedy Space Center. Based on the latest calculations by mission control, the shuttle's twin braking rockets will be fired at 8:11 a.m. Monday for a landing at 9:14 a.m.
Here is an updated timeline of today's activities in space (in EDT and mission elapsed time):
TIME DD HH MM EVENT _____________________________________________________ 07/15/06 01:08 AM 10 10 30 STS crew wakeup (flight day 12) 01:38 AM 10 11 00 ISS crew wakeup 03:38 AM 10 13 00 Farewell ceremony 03:53 AM 10 13 15 Hatch closure 04:28 AM 10 13 50 Centerline camera installation 04:38 AM 10 14 00 Group B computer powerup 04:38 AM 10 14 00 Orbiter docking system leak check 05:23 AM 10 14 45 Undocking timeline begins 06:08 AM 10 15 30 UNDOCKING 07:08 AM 10 16 30 Shuttle separation burn 07:43 AM 10 17 05 Group B computer powerdown 07:43 AM 10 17 05 Crew meals begin 08:43 AM 10 18 05 Robot arm maneuvers to survey attitude 08:58 AM 10 18 20 OBSS starboard survey 10:08 AM 10 19 30 ISS: PMA-2 depressurization 10:28 AM 10 19 50 OBSS nose survey 11:00 AM 10 20 22 Mission status briefing on NASA TV 12:28 PM 10 21 50 OBSS berthing 01:33 PM 10 22 55 Shuttle robot arm powerdown 03:24 PM 11 00 46 NC-5 rocket firing 05:00 PM 11 02 22 Post-MMT briefing on NASA TV 05:08 PM 11 02 30 STS crew sleep begins 06:00 PM 11 03 22 Daily video highlights reel on NASA TVRevision P of the NASA television schedule has been posted on the CBS News STS-121 Quick-Look Page.
08:00 p.m., 07/14/06, Update: 07:50 p.m., 07/14/06, Update: MMT defers APU decision until after test firing Sunday; updated deorbit and landing times
Editor's Note...
This story has been updated with the results of today's Mission Management Team meeting to discuss APU landing strategy. MMT Chairman John Shannon provided additional details, but our earlier story is essentially unchanged. Engineers continue to study a variety of options on the assumption hydraulic power system No. 1 has a small hydrazine leak. APU 1 will be fired up during a routine flight control system checkout Sunday. If the leak rate doesn't get worse, the unit likely will be used during entry Monday. If it does worsen, engineers will run the unit until the fuel is exhausted and Discovery will return to Earth with just two operational APUs. Quotes and details from Shannon have been added to our story.
Astronauts Lisa Nowak and Stephanie Wilson, dubbed the "robo chicks" by mission control, used the space station's robot arm to detach a 10-ton cargo module from the lab complex and remount it in Discovery's cargo bay for return to Earth. Engineers, meanwhile, continue assessing the health of the shuttle's hydraulic system but senior managers are optimistic the issue will not have a major impact on Discovery's re-entry and landing Monday.
The shuttle has three auxiliary power units - APUs - to provide the hydraulic power needed to move the ship's wing flaps, rudder, brakes and runway steering system during re-entry and landing. Any one operational APU can provide the hydraulic power needed for a safe landing, but three are on board to provide redundancy and NASA has complex flight rules governing how APUs must be managed in the event of failures.
Earlier this week, engineers noticed a very small pressure decay in the fuel tank of APU 1. It could be leaking nitrogen gas used to pressurize the system or it could be leaking hydrazine. If it's the former, there are no problems for landing; at the current leak rate, more than enough nitrogen would be available to fully pressurize the fuel tank.
If the leak is hydrazine, however, engineers will need to convince themselves the leak won't get worse before proceeding with a "nominal" re-entry. While the shuttle can land with just one operational APU, hydrazine is a dangerous material and leaks are definitely frowned upon. In addition, APU 1 is the only hydraulic system that can deploy the shuttle's landing gear. If APU 1 is out of action, pilot Mark Kelly would have to manually fire pyrotechnic charges to deploy the gear.
Shuttle program manager Wayne Hale said in an interview with CBS News today that he's optimistic APU 1 will work normally during re-entry and landing Monday at the Kennedy Space Center. But the jury is out until engineers complete their analysis.
"We actually went through all the flight rules yesterday at the MMT (Mission Management Team meeting) and the rule would say if it's suspected to be hydrazine, which as we've said, this little bitty pressure decay could be a few drops of hydrazine leaking, from the letter of the law you have to declare that that APU could potentially not be there for landing.
"But losing one APU is still nominal end of mission," Hale said. "We might think real hard about the weather rules, you don't want tight weather wherever you're going. You look around at the weather a little bit for higher ceilings, lower crosswinds, all that kind of stuff and you pick the best place to go."
Forecasters with the Spaceflight Meteorology Group at the Johnson Space Center are predicting good weather at the Kennedy Space Center on Monday with showers more likely Tuesday.
"I've got this real optimistic weather forecast, which worries me four days out," Hale joked. "The forecast will change, and this one's only got one direction to change."
MMT Chairman John Shannon said it's unlikely engineers will be able to rule out a hydrazine leak in APU 1. As a result, the astronauts will fire up APU 1 on Sunday as part of a routine flight control system checkout. After the test, engineers will monitor the fuel tank pressure. If the leak stays the same, APU 1 likely will be used in the normal fashion for re-entry Monday.
If the leak worsens, however, Shannon said the astronauts will be told to restart APU 1 and run the unit until all the hydrazine is exhausted. They would then fly back to Earth with just two operational APUs, which Shannon said was a "certified" procedure.
"The consensus of the team was the best thing to do with this small a leak rate is to go run it for flight control system checkout on Sunday morning," Shannon said. "Then we'll shut it down and we'll go look at the pressure trace. I fully expect to see we won't have any change at all and if that's true, I would expect we'll use it for a nominal entry.
"If we did see a change in the decay rate, it got higher - it has a long way to go to get above flammmability limits - but if it changed, that would say it's not really a stable situation and the operations team would go ahead and burn it off in orbit and get all the hydrazine out of that tank. We'd re-enter on two APUs.
"Two APUs is fine, it's certified," Shannon said. "It's not as good as three APUs. You'd lose some things with hydraulic system No. 1 not being active, the most important probably is that you don't hydraulically deploy your landing gear, you end up doing a pyro deploy. ... While that is perfectly certified and it is dually redundant, you'd rather do a hydraulic deploy."
An analysis shows that at the current leak rate, even if it's hydrazine, there is no ignition threat. But Hale agreed with Shannon that "the potential for a hydrazine leak is a very serious concern."
"What I am feeling very good about is the team has put a full court press on understanding what's going on and what the potential outcomes are and put together a plan to deal with it as best we can. We're going to get another report at today's MMT.
"So far, the news would indicate that if this is indeed a hydrazine leak, and again, we can't tell, but if indeed it's a hydrazine leak and stays at this level, it will pose no credible hazard to us. The real key question is, how good do we feel about the potential this will not get worse?"
According to NASA's flight rules, a presumed hydrazine leak is grounds for declaring an APU failed, Hale said, "but the real operative rule says, and I can't quote you the words exactly, but it says with a credible expectation of combustion. Again, at this leak level, there's no credible expectation of combustion. I would say there's a very good chance the crew will come down to a nominal entry. However, the jury is still out, the folks are still doing the analysis. If they come back and say we need to go, after we undock, and burn it off ... until the tank bottoms out ... that's a decision we still have a couple of days to talk about."
A senior manager familiar with the discussions told CBS News the flight rules assumed a leak of liquid hydrazine. In this case, the leak rate is so small the presumed hydrazine vaporizes instantly and is vented to space.
Shannon agreed late today, saying the engineers who wrote the flight rules said they were intended for much larger leaks. Sensors show APU 1's plumbing is tight downstream of a set of fuel valves. The presumed leak, therefore, is many feet away from the APU itself and far from any hot spots that could provide an ignition source.
Otherwise, Discovery's nearly trouble-free mission has increased Hale's optimism about launching the shuttle Atlantis around Aug. 28 to restart space station assembly. The only wild cards today are the APU issue and whether any extensive inspections or work are required on Atlantis; resolution of a shuttle cooling system issue that may or may not be a problem; and troubleshooting to explain slightly higher pressures in main engine No. 3 during a post-shutdown purge.
NASA's official launch window for Atlantis opens Aug. 28 and closes around Sept. 13. But because of a potential conflict between the planned launch of a Russian Soyuz capsule carrying the station's next crew, NASA may be forced to close the shuttle window Sept. 9 or even a few days earlier. Hale said he has asked the shuttle team to look into the possibility of launching the next mission a day or two earlier than Aug. 28 if possible.
Resuming space station assembly represents a major step forward for NASA and managers are elated with the results of Discovery's flight.
"All in all, it was just a great mission," said Rick LaBrode, lead space station flight director. "This is just a roaring success for the station team and we're ready to proceed with assembly ops."
The shuttle-station crew transferred more than 7,000 pounds of equipment and supplies from the Leonardo cargo module to the space station. For return to Earth, the module was loaded with around 4,600 pounds of no-longer-needed equipment and trash. Another 1,800 pounds or so of equipment was transferred from Discovery's crew cabin to the station, along with 171 gallons of fresh water, a by product of the shuttle's fuel cell system.
"This particular flight, we've transferred more payload cargo than any other shuttle flight," LaBrode said.
The astronauts planned to spend the afternoon using the shuttle's robot arm and a long sensor boom to closely inspect Discovery's left wing leading edge for any signs of impact damage from micrometeoroids. The flight plan called for the shuttle's nose cape and right wing leading edge to be inspected Saturday, after Discovery undocks from the international space station.
Nowak and Wilson ran into problems with the space station's robot arm that took time to resolve. The port wing inspections were delayed and rather than forcing the crew to work into their sleep preparations, flight director Norm Knight gave commander Steven Lindsey the option of eliminating the inspections all together.
"The program does not consider this mandatory," astronaut Lee Archambault radioed from mission control. "It's highly desireable, but not mandatory. We don't want to push you into this."
But Lindsey said he and pilot Mark Kelly would press ahead with the port wing inspection as planned to get it out of the way today.
Assuming no problems are found after the inspections are completed post undocking Saturday, the shuttle crew will depart the area and begin packing up for re-entry and landing Monday. The Spaceflight Meteorology Group ss predicting light winds and scattered clouds at landing time.
Here are all the deorbit ignition and landing times for Discovery's crew through next Wednesday at the Kennedy Space Center (KSC), Edwards Air Force Base, Calif. (EDW) and Northrup, N.M. (NOR). "Rev" refers to the shuttle's orbit (all times in EDT and subject to change):
SITE..REV...DEORBIT......LANDING Monday, July 17 KSC...202...08:11 a.m...09:14 a.m. (planned; updated times) NOR...203...09:35 a.m...10:39 a.m. KSC...203...09:40 a.m...10:42 a.m. EDW...204...11:09 a.m...12:11 p.m. NOR...204...11:11 a.m...12:13 p.m. EDW...205...12:45 p.m...01:46 p.m. Tuesday, July 18 KSC...218...08:18 a.m...09:21 a.m. EDW...219...09:47 a.m...10:51 a.m. NOR...219...09:49 a.m...10:52 a.m. KSC...219...09:54 a.m...10:56 a.m. EDW...220...11:23 a.m...12:25 p.m. NOR...220...11:25 a.m...12:27 p.m. EDW...221...12:59 p.m...02:00 P.m. Wednesday, July 19 KSC...233...06:56 a.m...08:00 a.m. KSC...234...08:32 a.m...09:35 a.m. EDW...235...10:01 a.m...11:04 a.m. NOR...235...10:03 a.m...11:06 a.m. EDW...236...11:37 a.m...12:39 p.m. NOR...236...11:40 a.m...12:41 p.m.
03:10 p.m., 07/14/06, Update: NASA, Russians assess launch options for Soyuz, next shuttle flight
NASA and the Russian space agency are discussing launch options that almost certainly will shorten the launch window for the agency's next shuttle flight. It now is expected to open Aug. 27 or 28 and may close a week or so earlier than planned because of a requirement to provide time for the station crew to sleep shift between the departure of a U.S. space shuttle and the arrival of a Russian Soyuz capsule.
Based on a photo documentation requirement to launch Atlantis on the next shuttle mission in daylight - and to ensure external tank separation in daylight - NASA had been planning on a launch window that opens Aug. 28 and closes Sept. 13.
But the Russians are scheduled to launch the next full-time station crew aboard a Soyuz capsule Sept. 14, docking two days later. Joint U.S. and Russian flight rules require a separation between the departure of a shuttle and the arrival of a Soyuz to give the station crew time to adjust their body clocks for different sleep shifts and to make necessary preparations.
If the shuttle launch was delayed until the end of the original window - Sept. 13 - and if the Russians tried to stick with their original launch date - Sept. 14 - the Soyuz would arrive at the station while the shuttle was still there, boosting the combined crew to 12, violating long-standing agreements and greatly complicating the shuttle crew's space station assembly work.
If Atlantis took off Sept. 13 and the Russian delayed the Soyuz until after undocking, launching the next station crew no earlier than Sept. 24, re-entry and landing of the outgoing station crew would occur Oct. 4, long before sunrise in the Kazakhstan landing zone.
The Russian recovery team includes new personnel for this flight and space managers do not want the new team to face a nighttime landing and recovery operation the first time around.
To resolve the potential conflict, U.S. and Russian space managers are discussing options that would shorten the shuttle launch window and delay the Soyuz launch to Sept. 18 or 20. On board will be Expedition 14 commander Michael Lopez-Alegria, Soyuz commander Mikhail Tyurin and Japanese space tourist Daisuke Enomoto.
Assuming a launch on Sept. 20, the Soyuz would dock Sept. 22 and the outgoing station crew - Expedition 13 commander Pavel Vinogradov, Jeff Williams and Enomoto - would return to Earth Sept. 30. While re-entry would occur in pre-dawn darkness in Kazakhstan, the sun would rise in time for recovery crews to do the bulk of their work in daylight.
Backing up from a Soyuz launch on Sept. 20, Atlantis must undock by Sept. 19. That means launch cannot occur any later than Sept. 9. For a Soyuz launch on Sept. 18, Atlantis must be off the pad by Sept. 7.
Shuttle program manager Wayne Hale has formally asked the Air Force Eastern Range for an Aug. 28 launch slot for Atlantis. In an interview with CBS News, Hale said he has asked shuttle managers to look into whether the flight could be moved up a day or so to add a bit more cushion to the front end of the launch window.
"We have four or five days of contingency (time in Atlantis' processing schedule) right now, which is less than what historically we've needed," Hale said. "But based on a really outstanding performance by the Kennedy folks, there's some probability we would have four or five days where the vehicle's out at the pad and we could launch earlier.
"So I have asked the imagery folks to take a look again at the predicted lighting, and it's not outside the realm of possibility when they run the lighting predictions with the final space station trajectory and so on and so forth, that the 27th might become available. That would ease a little bit the traffic model of the station."
He said station program managers "have been talking very hard with their Russian partners about that."
"The Russians really would like to kind of go pretty close to the schedule they've established, which doesn't leave a lot of room for weather days in Florida," Hale said. "So the earlier we can count down, the more likely we are to get off in time to deconflict the traffic."
Assuming the Russians stick to their guns and only delay the Soyuz launch by a few days, Atlantis' crew will lose a week or so off the back end of their launch window. And if Atlantis isn't off the ground by the time the window closes, the next daylight launch opportunity will be a short window opening Oct. 26 and closing Oct. 29.
At the Kennedy Space Center, engineers are readying Atlantis for rollout to the launch pad around Aug. 2. Work is already underway to address a handful of minor problems seen during Discovery's current flight, including replacement of additional gap fillers on the shuttle's belly and replacement of insulation blanket patches.
Engineers say any additional inspections or work required because of problems experienced by Discovery's hydraulic power system can be accomplished at the launch pad.
A wild card is an apparent problem with the helium pressurization system aboard Discovery that is used to operate main engine valves and to flush left over propellant out of the system after main engine cutoff - MECO - in orbit.
Engineers studying data from Discovery's launch noticed an eight- to 10-pound-per-square-inch shift in the helium pressure used to purge main engine No. 3 after MECO.
That shift was considered "to be of note and caused them some concern there might be a blocked filter or a check valve or something else," Hale said.
The issue did not affect the performance of engine No. 3 but the helium system is used to control the operation of the powerplants and engineers want to make sure whatever caused the purge problem is not something potentially more serious.
Hale said Discovery's engines will be removed shortly after landing to permit detailed tests and inspections. As of this writing, however, there are no indications of any similar problems aboard Atlantis.
02:00 p.m., 07/14/06, Update: Leonardo module back in payload bay; Hale optimistic about APU issue
Editor's Note...
This story has been updated with the results of today's Mission Management Team meeting to discuss APU landing strategy. MMT Chairman John Shannon provided additional details, but the story is essentially unchanged. Engineers continue to study a variety of options on the assumption hydraulic power system No. 1 has a small hydrazine leak. APU 1 will be fired up during a routine flight control system checkout Sunday. If the leak rate doesn't get worse, the unit will be used during entry Monday. If it does worsen, engineers will run the unit until the fuel is exhausted and Discovery will return to Earth with just two operational APUs.
Astronauts Lisa Nowak and Stephanie Wilson, dubbed the "robo chicks" by mission control, used the space station's robot arm to detach a 10-ton cargo module from the lab complex and remount it in Discovery's cargo bay for return to Earth. Engineers, meanwhile, continue assessing the health of the shuttle's hydraulic system but senior managers are optimistic the issue will not have a major impact on Discovery's re-entry and landing Monday.
The shuttle has three auxiliary power units - APUs - to provide the hydraulic power needed to move the ship's wing flaps, rudder, brakes and runway steering system during re-entry and landing. Any one operational APU can provide the hydraulic power needed for a safe landing, but three are on board to provide redundancy and NASA has complex flight rules governing how APUs must be managed in the event of failures.
Earlier this week, engineers noticed a very small pressure decay in the fuel tank of APU 1. It could be leaking nitrogen gas used to pressurize the system or it could be leaking hydrazine. If it's the former, there are no problems for landing; at the current leak rate, more than enough nitrogen would be available to fully pressurize the fuel tank.
If the leak is hydrazine, however, engineers will need to convince themselves the leak won't get worse before proceeding with a "nominal" re-entry. While the shuttle can land with just one operational APU, hydrazine is a dangerous material and leaks are definitely frowned upon. In addition, APU 1 is the only hydraulic system that can deploy the shuttle's landing gear. If APU 1 is out of action, pilot Mark Kelly would have to manually fire pyrotechnic charges to deploy the gear.
Shuttle program manager Wayne Hale said in an interview with CBS News today that he's optimistic APU 1 will work normally during re-entry and landing Monday at the Kennedy Space Center. But the jury is out until engineers complete their analysis.
"We actually went through all the flight rules yesterday at the MMT (Mission Management Team meeting) and the rule would say if it's suspected to be hydrazine, which as we've said, this little bitty pressure decay could be a few drops of hydrazine leaking, from the letter of the law you have to declare that that APU could potentially not be there for landing.
"But losing one APU is still nominal end of mission," Hale said. "We might think real hard about the weather rules, you don't want tight weather wherever you're going. You look around at the weather a little bit for higher ceilings, lower crosswinds, all that kind of stuff and you pick the best place to go."
Forecasters with the Spaceflight Meteorology Group at the Johnson Space Center are predicting good weather at the Kennedy Space Center on Monday with showers more likely Tuesday.
"I've got this real optimistic weather forecast, which worries me four days out," Hale joked. "The forecast will change, and this one's only got one direction to change."
MMT Chairman John Shannon said it's unlikely engineers will be able to rule out a hydrazine leak in APU 1. As a result, the astronauts will fire up APU 1 on Sunday as part of a routine flight control system checkout. After the test, engineers will monitor the fuel tank pressure. If the leak stays the same, APU 1 likely will be used in the normal fashion for re-entry Monday.
If the leak worsens, however, Shannon said the astronauts will be told to restart APU 1 and run the unit until all the hydrazine is exhausted. They would then fly back to Earth with just two operational APUs, which Shannon said was a "certified" procedure.
"The consensus of the team was the best thing to do with this small a leak rate is to go run it for flight control system ceckout on Sunday morning," Shannon said. "Then we'll shut it down and we'll go look at the pressure trace. I fully expect to see we won't have any change at all and if that's true, I would expect we'll use it for a nominal entry.
"If we did see a change in the decay rate, it got higher - it has a long way to go to get above flammmability limits - but if it changed, that would say it's not really a stable situation and the operations team would go ahead and burn it off in orbit and get all the hydrazine out of that tank. We'd re-enter with on APUs.
"Two APUs is fine, it's certified," Shannon said. "It's not as good as three APUs. You'd lose some things with hydraulic system No. 1 not being active, the most important probably is that you don't hydraulically deploy your landing gear, you end up doing a pyro deploy. ... While that is perfectly certified and it is dualy redundant, you'd rather do a hydraulic deploy."
An analysis shows that at the current leak rate, even if it's hydrazine, there is no ignition threat. But Hale agreed with Shannon that "the potential for a hydrazine leak is a very serious concern."
"What I am feeling very good about is the team has put a full court press on understanding what's going on and what the potential outcomes are and put together a plan to deal with it as best we can. We're going to get another report at today's MMT.
"So far, the news would indicate that if this is indeed a hydrazine leak, and again, we can't tell, but if indeed it's a hydrazine leak and stays at this level, it will pose no credible hazard to us. The real key question is, how good do we feel about the potential this will not get worse?"
According to NASA's flight rules, a presumed hydrazine leak is grounds for declaring an APU failed, Hale said, "but the real operative rule says, and I can't quote you the words exactly, but it says with a credible expectation of combustion. Again, at this leak level, there's no credible expectation of combustion. I would say there's a very good chance the crew will come down to a nominal entry. However, the jury is still out, the folks are still doing the analysis. If they come back and say we need to go, after we undock, and burn it off ... until the tank bottoms out ... that's a decision we still have a couple of days to talk about."
A senior manager familiar with the discussions told CBS News the flight rules assumed a leak of liquid hydrazine. In this case, the leak rate is so small the presumed hydrazine vaporizes instantly and is vented to space.
"We're not at the flammability limit with this leak rate, with it vaporizing," he said. "We know it's vening overboard. So we're not worried about building up in the aft until about 15 minutes before touchdown. At some point, the air pressure will rise enough so it's not going to be vapor anymore. So from now until then, we're not hurrying up to declare this APU failed."
Shannon agreed late today, saying the engineers who wrote the flight rules said they were intended for much larger leaks.
Otherwise, Discovery's nearly trouble-free mission has increased Hale's optimism about launching the shuttle Atlantis around Aug. 28 to restart space station assembly. The only wild cards today are the APU issue and whether any extensive inspections or work are required on Atlantis; resolution of a shuttle cooling system issue that may or may not be a problem; and troubleshooting to explain slightly higher pressures in main engine No. 3 during a post-shutdown purge.
NASA's official launch window for Atlantis opens Aug. 28 and closes around Sept. 13. But because of a potential conflict between the planned launch of a Russian Soyuz capsule carrying the station's next crew, NASA may be forced to close the shuttle window Sept. 9 or even a few days earlier. Hale said he has asked the shuttle team to look into the possibility of launching the next mission a day or two earlier than Aug. 28 if possible.
Resuming space station assembly represents a major step forward for NASA and managers are elated with the results of Discovery's flight.
"All in all, it was just a great mission," said Rick LaBrode, lead space station flight director. "This is just a roaring success for the station team and we're ready to proceed with assembly ops."
The shuttle-station crew transferred more than 7,000 pounds of equipment and supplies from the Leonardo cargo module to the space station. For return to Earth, the module was loaded with around 4,600 pounds of no-longer-needed equipment and trash. Another 1,800 pounds or so of equipment was transferred from Discovery's crew cabin to the station, along with 171 gallons of fresh water, a by product of the shuttle's fuel cell system.
"This particular flight, we've transferred more payload cargo than any other shuttle flight," LaBrode said.
The astronauts planned to spend the afternoon using the shuttle's robot arm and a long sensor boom to closely inspect Discovery's left wing leading edge for any signs of impact damage from micrometeoroids. The flight plan called for the shuttle's nose cape and right wing leading edge to be inspected Saturday, after Discovery undocks from the international space station.
Nowak and Wilson ran into problems with the space station's robot arm that took time to resolve. The port wing inspections were delayed and rather than forcing the crew to work into their sleep preparations, flight director Norm Knight gave commander Steven Lindsey the option of eliminating the inspections all together.
"The program does not consider this mandatory," astronaut Lee Archambault radioed from mission control. "It's highly desireable, but not mandatory. We don't want to push you into this."
But Lindsey said he and pilot Mark Kelly would press ahead with the port wing inspection as planned to get it out of the way today.
Assuming no problems are found after the inspections are completed post undocking Saturday, the shuttle crew will depart the area and begin packing up for re-entry and landing Monday. The Spaceflight Meteorology Group ss predicting light winds and scattered clouds at landing time.
Here are all the deorbit ignition and landing times for Discovery's crew through next Wednesday at the Kennedy Space Center (KSC), Edwards Air Force Base, Calif. (EDW) and Northrup, N.M. (NOR). "Rev" refers to the shuttle's orbit (all times in EDT and subject to change):
SITE..REV...DEORBIT......LANDING Monday, July 17 KSC...202...08:11 a.m...09:14 a.m. (planned; updated times) NOR...203...09:35 a.m...10:39 a.m. KSC...203...09:40 a.m...10:42 a.m. EDW...204...11:09 a.m...12:11 p.m. NOR...204...11:11 a.m...12:13 p.m. EDW...205...12:45 p.m...01:46 p.m. Tuesday, July 18 KSC...218...08:18 a.m...09:21 a.m. EDW...219...09:47 a.m...10:51 a.m. NOR...219...09:49 a.m...10:52 a.m. KSC...219...09:54 a.m...10:56 a.m. EDW...220...11:23 a.m...12:25 p.m. NOR...220...11:25 a.m...12:27 p.m. EDW...221...12:59 p.m...02:00 P.m. Wednesday, July 19 KSC...233...06:56 a.m...08:00 a.m. KSC...234...08:32 a.m...09:35 a.m. EDW...235...10:01 a.m...11:04 a.m. NOR...235...10:03 a.m...11:06 a.m. EDW...236...11:37 a.m...12:39 p.m. NOR...236...11:40 a.m...12:41 p.m.
10:25 a.m., 07/14/06, Update: Undocking timeline
Revision O of the NASA TV schedule is posted on the CBS News STS-121 Quick-Look Page. And here is the timeline for the shuttle Discovery's undocking from the international space station Saturday (in EDT and mission elapsed time):
TIME DD HH MM EVENT _____________________________________________________ 05:00 AM 10 14 22 Sunrise 05:28 AM 10 14 50 Noon 05:39 AM 10 15 01 U.S. solar arrays feathered 05:40 AM 10 15 02 Russian solar arrays feathered 05:56 AM 10 15 18 Sunset 06:08 AM 10 15 30 UNDOCKING 06:09 AM 10 15 31 Initial orbiter separation (+10 seconds) 06:10 AM 10 15 32 ISS holds current attitude 06:13 AM 10 15 35 Range: 50 feet 06:15 AM 10 15 37 Range: 75 feet 06:21 AM 10 15 43 Range: 150 feet 06:31 AM 10 15 53 Sunrise 06:37 AM 10 15 59 Range: 400 feet 06:40 AM 10 16 02 Separation burn No. 1; start fly over 06:52 AM 10 16 14 Shuttle directly above space station 06:52 AM 10 16 14 Shuttle in separation burn attitude 06:59 AM 10 16 21 Noon 07:08 AM 10 16 30 Separation burn No. 2 07:28 AM 10 16 50 Sunset
06:10 a.m., 07/14/06, Update: Astronauts confident Discovery in good shape for entry; say NASA has turned the corner after Columbia disaster, ready to resume station assembly
The Discovery astronauts closed up the Leonardo logistics module today and geared up to detach it from the space station and re-install in the shuttle's cargo bay for return to Earth. With undocking from the station on tap Saturday, shuttle pilot Mark Kelly said the crew has accomplished virtually all of the mission's objectives, clearing the way for station assembly to resume this fall.
"We're getting close to meeting all our mission objectives," Kelly told CBS News during an in-flight interview. "Our commander, Steve Lindsey, right now about 30 feet behind us is closing out the logistics module. We've completed all the (supply and equipment) transfers, we've completed all the objectives with our three EVAs (spacewalks), the space shuttle Discovery's in great shape for a return trip home on Monday."
Asked if Discovery's flight will help NASA turn the corner and shift its focus from recovering from Columbia to resuming space station assembly, spacewalker Mike Fossum said he hoped so, adding "we needed this mission to get a lot of these objectives (accomplished), to reinforce our ability to do our own inspections, to test our ability to get access to different places on the shuttle's wing and underbelly if we needed to get there to do repair. We've done some testing on the future repair capability. So we're feeling good about that, we've answered a lot of those questions almost completely and I think we're ready to get rolling."
Before the 2003 Columbia disaster, when NASA was gearing up to begin the same stretch of assembly missions currently facing the agency, mission managers frequently spoke of the "wall" of spacewalk challenges facing construction crews.
Piers Sellers, who joined Fossum for three spacewalks during DiscoveryÕs current mission, agreed "there's really a lot to be done. It is kind of a wall."
"Every flight has got to get through its EVA tasks and install its equipment before the next flight can go," he said. "I mean, that's really the way the sequence works, so it's going to be a lot of hard work. ItÕs a lot of hard work for a lot of people on the ground working furiously to make this happen."
NASA hopes to resume station assembly flights with launch of the shuttle Atlantis around Aug. 28 to mount a huge solar array and a massive rotary joint on one side of the station's main truss. The Russians plan to launch a fresh space station crew later in September and bring two outgoing crew members back to Earth. If all goes well, Discovery will return to the lab complex in late December to continue building the solar array truss, to deliver another full-time station crew member and to give European Space Agency astronaut Thomas Reiter a ride home.
"This flight and the one last summer, together they're the 'return to flight' missions and we feel like we've done all the tests and met the objectives and we feel like the whole program is back on track to assemble the space station and move on back to the moon and to Mars," robot arm operator Lisa Nowak told another reporter. "And we're looking forward to all of that."
In a morning execute package of daily instructions to the crew, flight controllers said Nowak and crewmate Stephanie Wilson had completed more robotic arm work than any other shuttle crew.
"Good morning, Discovery," the morning message to the crew read. "We hoped you enjoyed your time off (Thursday), Ōcause guess what, itÕs time for more arm ops. Unofficially, we believe this flight has had the most robotic operations to date. The PDRS and ROBO folks would like to say thanks to you all, and especially the 'ROBO chicks.' They have definitely earned the title.'
Today, the "robo chicks" plan to use Discovery's robot arm and a long inspection boom to carry out laser scans of the shuttle's left wing leading edge panels. After undocking Saturday, they will re-inspect the shuttle's nose cap and starboard leading edge panels for any signs of damage due to impacts that might have occurred after the ship reached orbit.
Here is an updated timeline of today's activities (in EDT and mission elapsed time; includes NASA TV sked/rev. O):
01:08 AM 09 10 30 STS crew wakeup (flight day 11) 01:38 AM 09 11 00 ISS crew wakeup 03:48 AM 09 13 10 MPLM egress 04:03 AM 09 13 25 MPLM deactivation 04:03 AM 09 13 25 PAO event (combined crew) 04:23 AM 09 13 45 Middeck transfers 05:28 AM 09 14 50 Spacesuit transfer 05:53 AM 09 15 15 MPLM vestibule depressurization 07:13 AM 09 16 35 Crew meals begin 08:13 AM 09 17 35 SSRMS grapples MPLM 08:23 AM 09 17 45 MPLM bolts backed out 09:00 AM 09 18 22 Mission status briefing on NASA TV 09:08 AM 09 18 30 MPLM pulled away from Unity 10:43 AM 09 20 05 MPLM berthed in shuttle bay 11:23 AM 09 20 45 SSRMS ungrapples MPLM 11:38 AM 09 21 00 SSRMS grapples MBS 12:28 PM 09 21 50 SSRMS ungrapples lab 01:18 PM 09 22 40 OBSS port survey 03:13 PM 10 00 35 Rendezvous tools checkout 05:00 PM 10 02 22 Post MMT briefing on NASA TV 05:08 PM 10 02 30 STS/ISS crew sleep begins 06:00 PM 10 03 22 Daily video highlights reel on NASA TVThe so-called "late inspections" were added to the flight late in the crew's training flow after engineers decided the risk of catastrophic damage from such orbital impacts warranted an additional looks.
Kelly said engineers "don't really know what the risk is. It's pretty low, we've been flying space shuttles for a long time and we've never had any kind of critical damage from a micrometeoroid. So it's pretty remote."
Before launch, Steve Poulos, manager of the orbiter projects office at the Johnson Space Center, said the odds of a catastrophic impact due to space debris or micrometeoroids "is about 1-in-210, something on that order." By doing the late inspections, the odds will improve to 1-in-280 and possibly as low as 1-in-350, based on the performance of the sensor package on the end of the inspection boom.
It will take ground engineers a day or so to assess the late inspection data, but "based on what we've seen over the last 10 days, the inspections we've done, we've got a great ship," Kelly said. "It's ready to come home. We'll be doing that on Monday morning and it's going to be a safe landing, hopefully at the Kennedy Space Center if the weather's good.
"The space shuttle is ready to go and after this flight, I think we're really in a good configuration and we're pretty much set up to continue assembly of the space station and continue to fly the shuttle, hopefully like we did before 2003."
Asked how confident he is about the health of Discovery's heat shield, Kelly said: "We're real confident. We're going to look at it one more time, but based on what we've seen so far, knowing what the risk is, I think all of us feel really comfortable."
"Looking out the window the other day and looking down both wings, they're looking like they're in great shape, similar to when we saw them when the orbiter was being processed," he said.
The only technical problems of any significance are a very slight pressure decrease in the fuel tank of an auxiliary power unit, or APU, and trouble with stuck thermostats in a second APU.
Engineers are not yet sure whether the leak is nitrogen, used for pressurization, or hydrazine, the volatile fuel that powers the APU. Either way, Kelly said the leak was so small it was not a major concern.
"It's pretty minor," he said.
But given the critical nature of APUs, NASA engineers are keeping a close eye on the hydraulic powerplants. For readers interested in additional details, here's the latest thinking on the issue from NASA's Mission Management Team:
APU 3 GG/Fuel Line/Pump/Valve Heater Š As a quick review, both the A and B heaters appear to be controlling the upper limit on the overtemp thermostat. We are currently on the A heaters and the system is controlling well. Functionally, there are no issues with operating on the overtemp thermostat. We are still investigating the fault tree to try and determine what would cause both the A and B control thermostats to fail. Some work was done at KSC in this area, but neither of the control thermostats was disturbed. The leading theory continues to be that either the thermostats or the heaters may have locally debonded. Workarounds exist for the next failure - if the B heater failed, we would switch back to the A. If that B heater failed, we would change attitudes after undocking to keep APU 3 warm or ask you to perform switch throws to manually control the heaters. If the heater fails on, the crew reaction time is about an hour after you get the alarm so there are no concerns for out of control temps on the fuel line.
APU 3 is not considered failed for entry or to even have a loss of redundancy. There is one small delta for entry - weÕll swap to the B heater in the entry checklist to meet the APU injector temperature limits and likely turn the heaters off after APU 3 start.
APU 1 Tank Pressure Decay Š The APU 1 fuel tank pressure continues to decay slowly. As of today it does not appear that we will be able to conclusively determine if the leak is N2 or hydrazine. The pressure decay has remained stable throughout the mission and there is no reason to assume that the leak rate will change. If the leak is GN2, we have lost about 18 psi so far and will have lost 33 psi by EOM - there will be plenty of GN2 still remaining to support entry operations on the APU. The minimum start pressure is 100 psi and we expect to be at 213 psi for EOM.
If the leak is hydrazine and of course we are not sure of that, we have lost about 10 lbs so far and will have lost 17 lbs by EOM. The leak rate of hydrazine is calculated to be 18 cubic centimeters per hour - very small. At this leak rate and based on the pod environment, analysis has shown that the hydrazine will phase directly into vapor and not form ice or liquid. The vapor exits the vent doors on orbit and there is a minimal concentration remaining. In fact at this leak rate, the hydrazine vapor concentrations will remain well below the flammability limits in the aft compartment for entry. This theory is somewhat corroborated by the fact that there are no indications of localized cooling on any temp sensors that would be indicative of a liquid fuel leak. Of course that also supports the possibility that the leak is N2, which is obviously the best case.
As mentioned yesterday, the N2 fill Quick Disconnect (QD) did have a leak preflight prior to the APU confidence run, but after cycling the QD poppet the leak was cleared (fairly common occurrence) and a flight cap is currently installed on the QD. It is still not clear that this preflight N2 leak could be related to the in-flight leakage we are seeing. The pre-flight data has been reviewed and there was no fuel leak observed pre-launch.
For information the APU 1 and 2 fuel tanks are located on the port sidewall of the aft compartment about 8 feet below the APUÕs which are near the top of the 1307 bulkhead. The teams continue to work around the clock on the ground to quantify the effects of the small N2 or fuel leak and the forward plan for entry.
05:30 a.m., 07/13/06, Update: Shuttle crew enjoys day off; MMT updates APU issue
The Discovery astronauts took the day off today, relaxing and enjoying the view from space after a hectic week in orbit highlighted by three spacewalks and work to transfer supplies and equipment to the international space station. Texas Gov. Rick Perry plans to call fellow Texas A&M graduate Mike Fossum later today and flight engineer Lisa Nowak will join Fossum for two media interviews. Engineers, meanwhile, continue analysis of two seemingly minor issues with Discovery's hydraulic system.
In the morning "execute package" of instructions and timeline changes uplinked to the astronauts, mission control passed along some ideas for spending an off-duty day in space:
Good morning, Discovery. Since today is an off-duty day for you, the planning shift team has come up with a few ideas* to help you pass the time:The morning execute package also included the latest thinking from NASA's Mission Management Team about the status of two of Discovery's auxiliary power units, or APUs, which provide the hydraulic power necessary to operate the shuttle's aerosurfaces, landing gear brakes and nose wheel steering during entry and landing.1. Who can toss the laptop the furthest down the station before it bounces off the wall (of course, we would appreciate it if you use Station assets for this one).
2. Arm wrestling: Big [robot] arm vs. little arm, David and Goliath II, the battle begins.
3. Boom toss - toss the [robot arm inspection] boom between arms (just donÕt tell the Canadians if you lose it)
4. Take all the CWCs [water transfer bags] into the Crew Lock, close the hatch, empty the CWCs and go for a swim (PBAs might be needed).
5. Lawn darts (if you need a target, remember thatÕs an Aggie compatible task)
6. Marco polo (the whole fish-out-of water thing would need to be tweaked though)
7. We could up-link a few appropriate computer games for you if you like - Asteroids, Space Invaders, or Star Wars' Wing Commander.
And last but not least, hereÕs a haiku from our GC,
Day of Freedom Launch
Leonardo and Spacewalks
Crew now Chillaxin'
Enjoy your day off, itÕs well deserved.
*None of these ideas have been approved by the MMT
The shuttle is equipped with three APUs and can safely land with just one. But given the critical nature of the system, engineers pay close attention when anything out of the ordinary occurs.
In a brief call to the crew late Wednesday, mission control told shuttle commander Steve Lindsey that engineers were monitoring two unrelated issues with APUs 1 and 3. The pressure in APU 1's fuel tank appears to be decaying faster than expected, indicating a possible hydrazine fuel leak or a leak in the nitrogen (N2) gas system used to provide pressurization. And APU 3 is experiencing heater problems.
Both issues may be related to work done before Discovery's launch, but that remains to be seen. Here is the MMT explanation of what has been observed to date:
APU 1 Tank Pressure Decay - The APU 1 fuel pressure is decaying differently than the other two tanks which is indicative of a small N2 or hydrazine leak. The data is very subtle so it has taken eight days to detect this change in slope between the three APU fuel tank plots. APU 2 and APU 3 shows a normal pressure decay of 6 psi over the eight days of the mission. This is due to the temperature change in the tanks which is caused by a 9-10 degrees Fahrenheit decrease in the tank temperatures as the aft structure cools. It takes some time to see this change because ascent does a good job of warming up this part of the vehicle.At present, these do not appear to be serious issues, but given the critical nature of the APU system they bear watching. More information will be posted here as it becomes available.APU 1 Tank pressure has dropped a total of 22 psi over these eight days which is indicative of a leak which is most likely N2. The Entry Flight Director, CB (astronaut office) Reps, and the entire APU community are meeting several times daily to understand the data and determine a forward plan of action. There was an N2 leak at the QD (quick-disconnect) panel during a portion of the STS-121 OPF (orbiter processing facility) flow that was later fixed; that has many in the community thinking that the leak is N2. Analysis is in work to determine if it is feasible to leak hydrazine based on the very slow leak rate and the propensity of hydrazine to freeze and slow an actual fuel leak. We hope to have more details on this subject (Thursday) but as of today there is no change to any mission plans based on the data collected. The APU is not considered failed and the N2 pressure will be more than 100 psi above the lower operating limit at EOM (end of mission).
APU 3 GG/Fuel Line/Pump/Valve Heater - Both the A and B heaters appear to be controlling at their upper limit on the overtemp thermostat. Initially the B heater appeared to fail ON, as indicated by the Supply Line Temp, increasing from ~82 deg F to 190 deg F. The heater then operated nominally for two cycles, and then failed ON again. MMACS (mission control mechanical systems officer) asked to reconfigure the heater to the A system, where it is also operating on the overtemp thermostat.
There are a few theories on the failure mode that could affect both the A and B heaters. This area was reworked before STS-121 with a new sealant such that the heaters were removed and rewrapped. If the wrap came loose on orbit, it would bias both thermostats cold and would appear as a failed on heater. If the heater is debonded, a similar signature would be expected. The teams continue to meet multiple times each day on this topic and additional data will be provided as the analyses mature. APU 3 is not considered failed for entry at this time and there are no significant impacts to entry operations.
The Mission Management Team congratulated the Discovery astronauts on the successful completion of their third spacwalk Wednesday and told the crew a lost spatula posed no threat of returning to the shuttle-station complex.
Shuttle and station managers "were extremely happy with the results of EVA 3 including the get-ahead task of transferring the grapple bar to ISS. FYI - The spatula that was released inadvertently during the EVA is well clear of the orbiter and ISS. It was 4 miles in front of the ISS/Shuttle at crew sleep on FD9 and continues to move in front of and below the ISS with the distance increasing about 2 miles each rev."
Here is an updated timeline of today's activities (in EDT and mission elapsed time):
TIME...........DD...HH...MM...EVENT 07/13/06 01:08 AM...08...10...30...STS crew wakeup (flight day 10) 01:38 AM...08...11...00...ISS crew wakeup 03:43 AM...08...13...05...Crew off duty time begins 04:13 AM...08...13...35...ISS European Space Agency PAO event 09:03 AM...08...18...25...Crew meal 09:08 AM...08...18...30...ISS Russian PAO event 10:00 AM...08...19...22...ESA, Russian briefings replay with translation 10:03 AM...08...19...25...Crew off duty time resumes 10:18 AM...08...19...40...ISS CPA installation 11:00 AM...08...20...22...Mission status briefing on NASA TV 12:53 PM...08...22...15...MPLM cleanup 12:58 PM...08...22...20...Texas Gov. Rick Perry calls Mike Fossum 01:23 PM...08...22...45...MPLM racks configured 01:23 PM...08...22...45...MSNBC, FOX News interviews Fossum and Nowak 03:30 PM...09...00...52...ISS-14 crew news conference 05:08 PM...09...02...30...STS/ISS crew sleep begins 06:00 PM...09...03...22...Daily video highlights reel on NASA TV
05:00 p.m., 07/12/06, Update: NASA managers pleased with third successful spacewalk; engineers monitor hydraulic system
The Discovery astronauts chalked up a third successful spacewalk today, demonstrating repair techniques that could help a future shuttle crew fix damage to a ship's wing leading edge panels. While engineers will not be able to fully assess the repair tests until samples are returned to Earth for laboratory analysis, flight controllers said they were pleased with the crew's performance.
"This might sound like a broken record, but we had a very successful flight day nine today," said lead flight director Tony Ceccacci. "We completed the last of our three planned EVAs (spacewalks) for the mission. Not only did we accomplish all our high priority objectives, but we also did get one of our get-ahead tasks completed."
Just before bidding the astronauts good night, mission control informed commander Steve Lindsey that engineers were monitoring two potential issues with the shuttle's hydraulic system.
Auxiliary power unit - APU - No. 1 has shown signs of a very slow leak in its fuel tank, or perhaps a problem with the nitrogen gas system used to pressurize it. So far, the pressure has dropped about 22 pounds per square inch since the unit was shut down following launch July 4.
In addition, thermostats in heaters used to keep APU 3 at the proper temperature acted a bit erratically today, resulting in a slightly broader range of temperatures than usual. But Lindsey was told both APUs are considered operational and available for use during re-entry next Monday.
"What this could be is a number of things," astronaut Lee Archambault in mission control said of the presumed leak in APU 1. "It could be an N2 leak, it could be a fuel decay, it could be none of the above and something completely different. Of course, the MMT (Mission Management Team) and MER (mission evaluation room) is looking at it. But for now, we are ops nominal on APU 1 and we expect to use it during entry."
The shuttle is equipped with three APUs to generate the hydraulic power needed to move the shuttle's engine nozzles during launch and its wing flaps, body flap, rudder/speedbrake and landing gear brakes during re-entry and touchdown. While a shuttle can safely land with just one operational APU, "we're keeping a couple of sets of eyeballs on it," Archambault promised Lindsey.
The astronauts then signed off for the night.
"Tomorrow, the crew is going to get a well-deserved day off," Ceccacci said. "Basically, the only thing they'll be doing at the end of the day is starting the MPLM (cargo module) closeout activities and just doing the standard taking a break, looking out the window and enjoying the day in orbit."
Tomas Gonzalez-Torres, the lead spacewalk officer in mission control, said astronauts Piers Sellers and Mike Fossum were able to complete five test panel repairs during today's spacewalk, about the same number engineers expected based on pre-flight simulations.
Using spatulas to spread on a thick sealant called NOAX, short for "non-oxide adhesive experimental," Sellers and Fossum attempted to fill in deliberate cracks and gouges similar to what might be expected from ascent impact damage.
NOAX is very sensitive to temperature, which can cause gases to bubble out of the mixture. In weightlessness, such bubbles can combine and merge inside the material, forming a void when it hardens.
"You don't want a direct path down through into the damage area," Gonzalez-Torres said. "The repair itself, you're trying to have a protective layer, a protective coating."
During re-entry, when wing leading edge temperatures can exceed 3,000 degrees, "you have some slight erosion," he said. "If you have that erosion and you get into a void and that void actually goes all the way down to the damage, you haven't enacted a good repair. So we want to minimize those voids and make sure whatever voids we do have, if we've done a good repair, they shouldn't be one big void that wouldn't be able to protect us."
Sellers and Fossum practiced applying the material in thin layers, working it with spatulas to help with "outgassing" and then smoothing it in place. Then another thin layer would be applied.
Gonzalez-Torres said the test samples will be subjected to thermal-vacuum cycling after their return to the Johnson Space Center, along with 3D laser scans, CT scans and finally, arc jet testing to see how well the repairs stand up to re-entry temperatures.
Based on video from the astronauts, it appeared the material was properly applied and that the new layer-by-layer technique resulted in fewer bubbles than astronauts experienced during tests last year.
The spacewalkers ran into one minor problem when one of six spatulas used for today's repair work floated away from Sellers unnoticed. Flight controllers said it posed no threat.
Asked to rate his concern over the lost spatula and earlier problems with safety tethers, Ceccacci said, "If that's all that happened, we're happy."
"You're kidding yourself not to expect little things like that to happen," he said. "If that's all that happens, you know, like everyone was talking about forgetting to lock the tether or unlock it, if that's all that happens, we're happy with that."
02:35 p.m., 07/12/06, Update: Spacewalk ends
Astronauts Piers Sellers and Mike Fossum re-entered the space station's Quest airlock module, closed the hatch and began repressurization at 2:31 p.m. to officially end the third and final spacewalk planned for Discovery's mission.
The 68th spacewalk staged in the space station era lasted seven hours and 11 minutes, pushing Sellers' and Fossum's three-EVA total to 21 hours and 29 minutes. The total for all 68 station-era spacewalks now stands at 412 hours and 23 minutes by 42 U.S. astronauts, 13 Russian cosmonauts, one Frenchman, one Canadian and one Japanese astronaut. Sellers, a veteran of three previous spacewalks, has now logged 41 hours and 10 minutes of EVA time.
Today's spacewalk ran 41 minutes longer than originally planned after flight controllers asked the astronauts to move a robot arm grapple fixture to a different mounting point on the station's hull.
"Time for dinner and a shower," Sellers said as he finally made his way to the airlock."
Sellers and Fossum complete simulated repairs of five out of 10 samples of nose cap and wing leading edge material mounted in a pallet at the back of the shuttle's cargo bay. Using a high-tech caulk gun, the astronauts squeezed out dollops of NOAX, a heat-resistant sealant, and used spatulas to spread the material into cracks and gouges.
A major question mark is how the thick material sets up in the extreme temperatures and weightless environment of space. Trapped air can cause bubbles that can affect the materia's ability to reject heat.
"I'm looking at (sample) 4," Fossum said as he wrapped up the second of two repairs. "The bubbles ... appear only to be in the finishing layer. They're so small, kind of like a rash, they're not the big ones that seem to come up when you're lifing a lot of material. This will be very interesting to see how it cures out over the next week or so. When I finished them, they both looked very much alike. Now, 3 has noticeable bubbles that have formed under the surface. One of them at least is probably three or four millimeters across."
During cleanup, the astronauts did an inventory of their tools to make sure nothing was left behind.
"So Mike, you have six total spatulas, is that correct?" pilot Mark Kelly asked.
"Negative, five," Fossum said, indirectly referring to one that was lost earlier by Sellers.
"OK, yeah, that's correct," Kelly said.
"Rub it in, Mark, rub it in," Sellers laughed.
"I'm not rubbing it in. It's been a long day."
"You're torturing me," Sellers said. "That was my favorite spatch."
Flight controllers later told the astronauts not to worry about it, that the spatula did not pose any sort of "FOD" (foreign object debris) threat in the cargo bay.
11:15 a.m., 07/12/06, Update: Heat shield sealant 'behaves well,' astronauts report
Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 3:55
Astronauts Piers Sellers and Mike Fossum are wrapping up their simulated heat shield repair work, touching up and smoothing out an experimental sealant they've spread over deliberately cracked and damaged panels of wing leading edge material.
"The best practice for this is to have an old house in Houston," Sellers said as he used a putty knife to smooth the NOAX sealant.
"Done that," laughed Fossum.
"Yep, renovating an old house, that would do it," shuttle pilot Mark Kelly agreed from Discovery's flight deck.
Working at a pallet mounted in the back of the shuttle's cargo bay, Sellers and Fossum troweled on NOAX and "worked it" with spatulas to get suspended air bubbles out. The material is very sensitive to temperature changes, hardly bubbling when the shuttle is in orbital darkness and then outgassing in direct sunlight.
"On the whole, the material's behaving very well. You agree, Mike?"
"Yeah," Fossum said.
"Looks kind of like thick peanut butter now?" Kelly asked.
"Yeah. It's tearing now a little bit. But it's OK," Sellers said.
A few minutes later, Sellers reported he had lost one of his applicator spatulas.
"Guys, I've got to tel you, I think my spatula's escaped," he said. "I don't see it on me."
"OK, we'll take a look," Kelly said.
"Is it caught on me anywhere?
"No, it's not on those hooks," Fossum said.
"Man, it escaped, how 'bout that?"
A few minutes later, he added "I think it's gone, gone, gone."
The spacewalkers currently are finishing up a final two samples. They then plan to use an experimental infrared camera to photograph the samples, two in sunlight and two in shadow, to test the camera's ability to spot damage in reinforced carbon carbon panels.
09:35 a.m., 07/12/06, Update: Repair tests underway; sealant applied to test panels
Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 2:15
Astronauts Piers Sellers and Mike Fossum began their first heat shield repair test run around 9 a.m., after Fossum relatched a loose safety tether. Using a high-tech caulk gun, Sellers squeezed out thick NOAX sealant on a wing leading edge sample with deliberate cracks and/or gouges. The idea is to find out how the heat-resistant material performs in weightlessness, how easy or difficult it might be to spread over cracks using putty knife applicators and how suspended air bubbles out at higher temperatures.
"OK. We're starting to get goo," Sellers said as he squeezed the trigger ofthe caulk gun. "Got goo, good goo!"
"You're going to want to push it into the exposed carbon carbon, swiping in multiple directions and you want to wet the surface," Kelly advised from the flight deck.
"This is taking a little bit of force," Sellers commented. "Really a small, like, kid's marble's worth..."
"We're gonna fill that groove pretty soon," Fossum said.
"It continues to come out after I've shut the valve off," Sellers said.
The NOAX did not bubble, or outgas, as much as the astronauts expected, in large part because it was applied in shadow and not in direct sunlight. Tests on the ground show the material works best when applied when the temperature is between 100 and 35 degrees and dropping.
"It feels like soft putty," Sellers commented. "It's a little stiffer than expected and it's tearing a little. ... This is not like wet stuff, Mark, but sticky stuff."
"Yeah, it's freezing, it's cold," Fossum agreed.
"Now it's behaving, as it's cooled off more, like clay."
"So it doesn't seem like it's outgassing very much, does it?" shuttle pilot Mark Kelly asked from Discovery's flight deck.
"No at all," Sellers said.
"It was a little bit at first, when it sets in thicker layers, you could see some bubbles rising," Fossum said.
"I saw a tiny bit when it came out, but now it's doing nothing," Sellers said.
"I think we want to just keep working it here until it starts outgassing some more," Kelly advised.
For a NOAX repair to be effective, the material must be worked with a spatula to remove any air bubbles that could reduce its heat rejection capability. The reinforced carbon carbon nose cap and wing leading edge panels experience the most extreme heat during re-entry - more than 3,000 degrees - and any repair must be able to stand up to that hellish environment.
Sellers and Fossum are filling cracks in test panels with NOAX, working the material in and then applying a "finishing" layer to smooth it out. Sellers said the NOAX pulled, or tore, as he tried to spread it but he said it wasn't a major problem.
The test samples will be analyzed back on Earth and subjected to re-entry level temperatures in an arc jet facility to find out how well the material works.
Views from the astronauts' helmet cams showed Sellers working the NOAX into various sample panels, working the material like caulk with a putty knife. He said it had the consistency of peanut butter.
"This is quite hard work," Sellers said. "I'm getting warm, just mashing stuff in, compensating for the arm."
Fossum said the NOAX "was definitely like thick putty. It is smooth in consistency, so it goes on fairly easily in that regard."
In direct sunlight, the material appeared quite pliable and it outgassed as expected.
09:00 a.m., 07/12/06, Update: Fossum fixes loose tether
Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 1:40
Astronaut Mike Fossum ran into another problem with safety tethers today. Moving toward the back of Discovery's cargo bay for wing leading edge repair tests, flight controllers noticed the far end of his safety tether, hooked on a space station hand rail, appeared unlocked.
"Houston, Discovery. Just to let you know we're looking at it in camera A, the elbow camera, and based on what we see, Mike, we suspect it's unlocked. It's really hard to tell, but we think it's unlocked."
"OK, it could happen," Fossum replied. "That would be a first for me, but that could happen."
Flight controllers then asked Fossum, using a second tether as a backup, to make his way back to the space station tether point. When he got there, he discovered the latch was, in fact, unlocked.
"Sure enough, there it is," he radioed. "Good catch, guys."
"And Houston, Discovery, thanks, good catch," shuttle pilot Mark Kelly radioed from the cockpit. "It's now locked."
This was Fossum's second run in with safety tethers. During the crew's first spacewalk last Saturday, he and Sellers struggled to retract an 85-foot-long tether only to find the reel mechanism was locked. During their second spacewalk Monday, latches holding Sellers' emergency jet backpack in place somehow disengaged, but the backpack was tethered and later tightened down by Fossum.
The incidents had no impact on the results of the spacewalks and the astronauts were never in any increased danger.
08:20 a.m., 07/12/06, Update: Infrared camera tested
Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 1:00
Astronaut Piers Sellers, anchored to the end of the space station's robot arm, was maneuered to a point high "above" one of the shuttle Discovery's wings today to photograph critical leading edge panels with an infrared camera. The goal was to assess the camera's ability to collect infrared data that might help engineers assess the health of the wing leading edge panels.
Astronaut Mike Fossum, meanwhile, made his way to the back of Discovery's cargo bay to set up tools and equipment at a worksite pallet where the astronauts will test leading edge panel repair techniques. Sellers, on the arm, was maneuvered to the work site by the robot arm.
"Hey Mike, you're doing great. You're doing great, right on time," Sellers radioed Fossum.
"Well, I'd hoped to be there with the box open by now, but that's not happening today," Fossum said as he moved aft along the port payload bay sill.
07:25 a.m., 07/12/06, Update: Spacewalk begins
Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 0:05
Floating in the Quest airlock module, astronauts Piers Sellers (call sign EV-1; red stripes on suit) and Mike Fossum (EV-2; no stripes) switched their spacesuits to internal battery power at 7:20 a.m. to officially begin a planned 6.5-hour spacewalk.
This is the 68th spacewalk of the space station assembly era, the third for Sellers and Fossum and the 21st staged out of the Quest airlock. Going into today's outing, 58 U.S., Russian, Japanese, French and Canadian astronauts had logged 405 hours and 12 minutes of station-based spacewalk time, including 14 hours and 18 minutes by Sellers and Fossum.
The goal of today's spacewalk is to test repair materials and techniques that one day could be used to repair relatively minor damage to the shuttle's wing leading edge panels.
05:30 a.m., 07/12/06, Update: Sellers, Fossum don suits, prepare for spacewalk
Astronauts Piers Sellers and Mike Fossum have donned their spacesuits and are in the final stages of preparing for a planned six-and-a-half-hour spacewalk to test wing leading edge repair techniques. Preparations are generally on schedule and the spacewalk should begin around 7:13 a.m.
A detailed preview of today's excursion was posted Tuesday. A detailed flight plan update is available in the crew's Daily Execute Package for Flight Day 9. Here is a summary timeline (in EDT and mission elapsed time):
TIME DD HH MM EVENT __________________________________________________________________ 05:28 AM 07 14 50 EVA-3: Spacesuit prebreathe 06:28 AM 07 15 50 EVA-3: Crew airlock depressurization 07:13 AM 07 16 35 EVA-3: Airlock egress 07:28 AM 07 16 50 EVA-3: Station robot arm (SSRMS) setup 07:28 AM 07 16 50 SSRMS foot restraint installation 07:58 AM 07 17 20 ISS meals 08:03 AM 07 17 25 SSRMS moves to RCC repair demo work site 08:08 AM 07 17 30 EVA-3: Payload bay setup; IR RCC photography 08:48 AM 07 18 10 EVA-3: Heat shield repair demonstration 08:58 AM 07 18 20 ISS crew resumes MPLM transfers 11:48 AM 07 21 10 EVA-3: Payload bay cleanup 12:33 PM 07 21 55 EVA-3: SSRMS cleanup 12:48 PM 07 22 10 SSRMS moves to airlock 01:08 PM 07 22 30 SSRMS foot restraint removal 01:28 PM 07 22 50 EVA-3: Airlock ingress 01:28 PM 07 22 50 SSRMS moves to cargo module demate inspection point 01:43 PM 07 23 05 EVA-3: Airlock repressurization 01:58 PM 07 23 20 Post EVA spacesuit water recharge 05:08 PM 08 02 30 Crew sleep begins
06:00 p.m., 07/11/06, Update: Heat shield repair demonstration spacewalk on tap Wednesday
The Discovery astronauts are set for a third spacewalk Wednesday, this one to test tools and a temperature-sensitive sealant with the consistency of peanut butter that may prove useful for repairing small cracks or other minor damage to critical wing leading edge panels.
Astronauts Piers Sellers and Mike Fossum are scheduled to begin the planned six-and-a-half-hour excursion around 7:13 a.m. Wednesday, exiting the international space station's Quest airlock module and making their way to a sample pallet at the back of Discovery's cargo bay.
Compared to two earlier spacewalks - one to test a long inspection boom as a work platform and another to repair a stalled robot arm transporter on the space station - Wednesday's outing "is more like a kind of a careful, meticulous lab experiment," Sellers said.
"Mike and I are going to be very careful, (pilot Mark Kelly is) going to coach us through this on how to get the material to the right temperature and apply it to a set of samples. It really is lab work and we're going to do the best, most careful job we can."
The repair demonstration ranked third on NASA's spacewalk priority list and was only added to the mission timeline when Discovery's flight was extended a day.
Some engineers questioned whether the spacewalk was justified, arguing laboratory testing on the ground is adequate for assessing the strengths and weaknesses of the repair materials and procedures. Given the inherent risks associated with any spacewalk, those engineers favored "real work" content more directly focused on building or servicing the international space station.
Lead flight director Tony Ceccacci disagreed, but only mildly.
"The key thing you're getting out of this is how does the material behave in zero G?" he said. "It was the lowest priority EVA, but we have the time and I think overall it's worth doing. As Mike Fossum and the crew said, we're going to get some really good data out of this. From where I stand, and since we did get that extra day, I think it's worth doing."
So does Sellers, who said in an interview that NASA is making a serious effort to develop viable repair techniques.
"It's been in parallel with the main effort, which is to stop stuff falling off the (external fuel) tank, remove the problem at its root cause," he said. "But knowing what we know about foam, you can't guarantee that nothing will fall off. And if something falls off, you can't guarantee it won't hit the orbiter. So it's prudent to try and develop some repair techniques.
"I think these repair techniques are going to be limited in capability," he said. "You cannot repair huge damage to the heat shield. i don't think it can be done. But maybe, who knows, if you see some nicks you don't like it might be a good idea to get yourself some insurance. It's nice to have that capability."
Ever since Columbia went down three years ago, NASA and contractor engineers have been struggling to come up with reliable techniques for repairing minor damage to the shuttle's thermal protection system - TPS - tiles and the reinforced carbon carbon panels protecting the nose and wing leading edges from the extreme heat of re-entry. Repairing Columbia-class damage is not considered possible.
During Discovery's last flight a year ago, the astronauts tested modest techniques for repairing tile damage and while those procedures are not yet officially certified for use, the equipment and repair material were on board again in case it was actually needed.
This time around, Sellers and Fossum will focus on techniques for repairing small cracks and other damage to wing leading edge panels and nose cap material mounted in a special carrier at the rear of Discovery's cargo bay.
The nose cap and wing leading edge panels experience the most extreme heating during the return to Earth - more than 3,000 degrees Fahrenheit - and developing repairs that can stand up to the extreme environment of re-entry is a daunting technological challenge.
"The main focus is to evaluate repair techniques for cracks in the carbon carbon material that makes up the leading edge of the shuttle," Sellers said in a NASA interview. "This is hard, black material; it's laid down a bit like fiberglass layers of carbon matting with resin, then matting, then resin built up in layers. This was the material that got damaged during Columbia's launch. So obviously we're very interested in trying to find a fix for it.
"We're going to take up some materials ... and test different techniques for repairing these on a special set of samples in the back of the payload bay of the shuttle. That's going to be the bulk of the content of that EVA. But we're also testing an infrared camera which, basically, sees heat or the disturbing of heat flows in materials. We can see how well that does at picking up cracks in the carbon carbon."
Small cracks in the RCC material might not be visible to the human eye, Sellers said, "but the heat will have to flow around the crack, it can't jump across the crack. So, the surface temperature is distorted. And, hopefully this infrared camera that detects heat will be able to see some changes in heat flow around crack fields."