Shuttle mission preview: Trucking cargo to space
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: April 4, 2010
The shuttle Discovery, carrying a crew of seven and 10 tons of supplies and equipment bound for the International Space Station, is poised for blastoff April 5 on a three-spacewalk mission to deliver ammonia coolant, experiment hardware, a darkroom, a crew hygiene station and an experiment sample freezer.
The Discovery astronauts also plan to deliver spare parts for the station's water recycling system in an ongoing effort to work the bugs out of the complex life support equipment before the shuttle's retirement later this year.
"We didn't really know how to design this hardware at the beginning," said Bill Gerstenmaier, NASA's chief of space operations. "We did as good as we could and now we're actually working those bugs out. This is important for us to have the shuttle around for these couple of flights so we can get the water systems and the life support systems up and operating."
Mission managers cleared Discovery for launch after deciding a failed helium isolation valve in the ship's right-side aft rocket pod posed no significant threat to crew safety or meeting the flight's objectives. Likewise, a review showed suspect ceramic inserts around critical bolts were unlikely to shake free and pose an impact threat during launch or re-entry.
With Discovery ready to go, spacewalker Clay Anderson, veteran of a long-duration stay aboard the station in 2007, said the crew was anxious to get on with a complex mission.
"The biggest objective is to bring the multi-purpose logistics module, the MPLM, and attach it to the station so that we can empty it," he said. "The MPLM has all sorts of cargo and supplies, experiments, racks, food, clothing. We need to get all that stuff onto the station (to make) it easier for them to sustain themselves over time.
"Then the second really big task that we have are the EVAs, the spacewalks that Rick Mastracchio and I will do. The main point of those is to replace a couple key pieces of hardware, the ammonia tank assembly on the outside of the station and then a rate gyro assembly that helps the station understand what its attitude is."
The space station is equipped with two independent coolant loops that dissipate the heat generated by the lab's electrical systems by circulating ammonia coolant through large radiator panels.
"ItÕs like Freon in your air conditioner at home but we use ammonia on the outside of the station," Anderson said. "So we have a huge tank, it's about (1,700) pounds. It's probably the size of a double refrigerator-freezer component and it lives on the backside toward the center of the station and there are actually two, one on the right and one on the left. The one on the left has recently been changed out by another shuttle crew. So we're going to change the one on the right."
Discovery's launching continues an extremely busy period in the life of the space station, coming three days after the planned launch of a Russian Soyuz capsule from Kazakhstan carrying three fresh crew members - cosmonauts Alexander Skvortsov, Mikhail Kornienko and NASA astronaut Tracy Caldwell Dyson.
If all goes well, the Soyuz TMA-18 spacecraft will dock with the station April 4 and its crew will join Expedition 23 commander Oleg Kotov, Japanese astronaut Soichi Noguchi and NASA flight engineer Timothy Creamer. The expanded Expedition 23 crew will, in turn, welcome the Discovery astronauts to the lab complex two days after the shuttle's launching.
"It really brings out the essence of our International Space Station and our program that we could have a shuttle and a Soyuz launching within days of each other and how we can integrate and add to the already complex nature of what we do and the business we're in," Caldwell said before launch.
With the shuttle program facing retirement later this year after a final four missions, the space station program is racing the clock to complete the outpost and stock it with supplies and spare parts before the heavy lift orbiter is grounded for good.
Kirk Shireman, deputy manager of the space station program at the Johnson Space Center in Houston, said that along with the final four shuttle missions, the program expects three more Soyuz crew launches this year, four Soyuz landings, six launches of unmanned Progress supply ships, launch of a European Space Agency Automated Transfer Vehicle resupply mission and six station-based spacewalks above and beyond the EVAs planned by visiting shuttle crews.
"So you can see, it's a busy time," he said. "The program focus is turning away from assembly. We're looking forward to fully utilizing ISS and extending the International Space Station to 2020. We'll have a very busy year and we're very much looking forward to it."
Discovery's liftoff from pad 39A at the Kennedy Space Center is targeted for 6:21:25 a.m. EDT on April 5, roughly the moment Earth's rotation carries the shuttle into the plane of the space station's orbit. The shuttle has enough power to launch five minutes to either side of that "in-plane" moment but NASA typically targets the middle of the 10-minute window to maximize ascent performance.
Joining shuttle veteran Alan Poindexter, the commander, on Discovery's flight deck will be rookie pilot James Dutton, veteran spacewalker Mastracchio and flight engineer Dorothy Metcalf-Lindenburger, a former high school teacher and astronomy enthusiast making her first flight.
Seated on the shuttle's lower deck will be shuttle veteran Stephanie Wilson, Japanese astronaut Naoko Yamazaki, making her first flight, and Anderson.
Assuming an on-time liftoff, Poindexter will guide Discovery to a docking at the space station's forward port around 3:44 a.m. on April 7. Late that evening, the Leonardo multi-purpose logistics module, loaded with 8.5 tons of supplies and equipment, will be pulled from the shuttle's cargo bay and attached to the space station's Unity module just after midnight.
The next day, Mastracchio and Anderson will stage the first of three spacewalks needed to install the ammonia coolant tank on the space station's main power truss. A spent ammonia tank will be removed and placed back in the shuttle's cargo bay for return to Earth and relaunch later this year.
Discovery is scheduled to undock from the station around 3:55 a.m. on April 16, setting up a landing back at the Kennedy Space Center around 8:29 a.m. on April 18.
The daylight landing time is the result of a recent decision to switch from a southwest-to-northeast "ascending node" re-entry trajectory, one that carries a Florida-bound shuttle over the Pacific Ocean, Central America and the Caribbean, to one that will carry Discovery from northwest to southeast over the heartland of America.
This will be only the second such "descending node" entry since the Columbia disaster. Shuttle Program Manager John Shannon said the change was ordered to give the crew more time to complete the required supply transfers and to move the landing from darkness to daylight. He said the shuttle would not fly over any population centers on its way down and that a NASA analysis showed the risk to the public was minimal.
"Post Columbia, we were very deliberate in trying to determine risks to people on the ground if we had a vehicle break up," he said. "We did some extensive modeling of what debris envelopes would be created for different vehicle breakups. It's a difficult thing to talk about, but it's important work we do.
"You take a look at the ground track of the vehicle and you look at the different debris footprints for breakups at different altitudes and then you sum all that together and you come up with a certain risk to the population. What we have done here is take a very close look and make sure the descending node opportunities, which will go over the United States, do not put any major population areas at risk and that our general population risk is below those limits that were set."
By switching to a descending node entry, "the significant advantage you get for the crew timeline really said this was the way to go," Shannon said.
The return route will be familiar to Wilson and Anderson. They were part of the STS-120 crew that flew the only other post-Columbia descending node entry in November 2007.
While only four more shuttle flights are officially on the books, scheduled for launch April 5, May 14, July 29 and Sept. 16, NASA managers are holding out hope that a fifth mission will be added to the manifest, a flight that would use the external tank and boosters set aside for an emergency rescue mission in case of problems with the last currently planned flight.
Launching a fifth mission with a crew of four, NASA could rely on the space station and Russian Soyuz ferry craft to provide emergency return capability, eliminating the need for a dedicated shuttle rescue flight.
President Barack Obama plans to visit the Kennedy Space Center during Discovery's mission to discuss the shuttle program's looming retirement, projected job losses and his administration's proposed cancellation of NASA's Constellation moon program.
If the administration ultimately supports an additional shuttle flight, as urged by Sen. Bill Nelson, D-Fla., and other lawmakers, NASA officials believe all five flights could be completed before the end of the calendar year. But a decision is needed by late April, officials say, for crew selection, training and flight planning.
A BUSY MISSION FOR DISCOVERY'S CREW
The initial stages of Discovery's mission will follow NASA's post-Columbia template, designed to make sure any damage to the shuttle's fragile heat shield is spotted and fully assessed.
Following launch, the astronauts will beam down digital pictures and video of the shuttle's external tank to help engineers determine the health of the foam insulation on the ship's external tank.
That imagery, combined with footage shot from the ground and a camera mounted on the side of the huge fuel tank will show whether any insulation or other debris fell away during launch and impacted Discovery's heat shield tiles or the reinforced carbon carbon wing leading edge panels that experience the most extreme heating during re-entry.
On the second day of the mission, the astronauts will unlimber Discovery's robot arm and attach a 50-foot-long extension equipped with a laser scanner and camera. Using the orbiter boom sensor system, or OBSS, the crew will scan the leading edge panels on both wings and the RCC nose cap to look for any signs of impact damage.
Anderson and Mastracchio, meanwhile, will test their spacesuits and the tools they plan to use during their upcoming spacewalks while Poindexter and Dutton carry out two rocket firings to fine-tune the shuttle's path to the space station.
Using digital cameras with 400 mm and 800 mm lenses, Kotov and Creamer will photograph the underside of the orbiter to look for any signs of damage. They also will photograph the shuttle's upper surfaces and downlink the imagery to Houston for detailed analysis.
From there, Poindexter will manually guide Discovery up to a point about 400 feet directly in front of the space station with the shuttle's nose pointed toward deep space and its open payload bay facing a docking port on the forward end of the Harmony module.
"We wake up in the morning of rendezvous day and get right to work setting up our tools and making sure that we have all the equipment we need for the rendezvous," Poindexter said. "The folks on the ground have been working hard up to this point to get us to the right point to execute the rendezvous. We do a series of burns or maneuvers to bring the shuttle up underneath the space station at about 1,000 feet.
"We fly directly below the station to a distance of about 600 feet and from there we'll execute the rendezvous pitch maneuver, which allows the space station crew to image the orbiter's thermal protection system with some high-powered cameras. We'll then manually fly the shuttle up in front of the station to a distance of about 400 and then slowly back it into the space station's docking port. That's all done manually from the aft cockpit and I've got a lot of help on the flight deck with some real professional crew members who are doing most of the hard work."
After leak checks, hatches between Discovery and the station will be opened and Kotov and his crewmates will welcome Poindexter and company on board.
It will be a reunion of sorts for Wilson, Anderson, Dyson and Mastracchio, who all flew together on previous shuttle/station missions.
"I think it rocks, I'm really excited," Dyson said before launch. "These are some great friends of mine on the shuttle, I've flown with some of them, I've trained with some of them and I've shared a lot of dinners and good times with these folks. And I'm delighted for them and just ecstatic that the timing worked out for us to be in space together."
After a short safety briefing, the combined crews will get to work, transferring the spacesuits needed by Anderson and Mastracchio to the station's Quest airlock module and using the lab's robot arm to pull the OBSS out of the shuttle's cargo bay. The station arm will hand the OBSS off to the shuttle's robot arm for a possible "focused" inspection later, if any signs of heat shield damage are spotted.
The next day - flight day four - Wilson and Dutton will use the station's robot arm to pull the Leonardo MPLM out of Discovery's cargo bay so it can be attached to the Unity module's Earth-facing, or nadir, port. Loaded with cargo, the module weighs 27,274 pounds, including the 9,632-pound weight of the MPLM itself.
After a break for lunch, the astronauts will prepare the vestibule between Unity and Leonardo, open hatches and enter the cargo module for the first time. Mastracchio and Anderson, meanwhile, will close out the day by spending the night in the Quest airlock module at a reduced pressure of 10.2 pounds per square inch.
The so-called "campout" procedure helps spacewalkers purge nitrogen from their bloodstreams and prevent the bends after working in NASA's 5-psi spacesuits.
Assuming an on-time launch, the mission's first spacewalk will begin around 1:40 a.m. on April 9. It will take three excursions to move the new ammonia tank into position, remove the old tank, plumb the new assembly in its place and then move the old tank back to the shuttle.
"I think the biggest challenge of every EVA of this magnitude is the integration of the robotics and the EVA guys," Mastracchio said. "It's a real team effort. Inside, we'll have Stephanie and Jim working the arm, we'll have Dottie calling the shots as (spacewalk coordinator) and then Clay and I outside. And of course, we're working closely with the ground.
"The real challenge here is this ammonia tank that we're moving is taking three EVAs, or part of three EVAs, to get it done. Our first EVA, we'll remove the new ammonia tank from the shuttle and get it onto the station (where) we'll temp stow it. The second EVA, we'll actually swap the two ammonia tanks, the new one for the old one and then on the third EVA, we'll be moving the old tank from the space station into the space shuttle's payload bay for return. That's the biggest challenge. Between each EVA, we'll have to move the robotic arm, it has to walk off to a new work site. So there's a lot of teamwork and a lot of integration involved."
During Anderson's 2007 stay aboard the station, he participated in a spacewalk with Mastracchio during a July shuttle assembly mission.
"Rick and I are very familiar with each other," Anderson said. "We have a lot of hours of pool time together, we understand each other's strengths and weaknesses and we really enjoy working together. I think that in and of itself bodes well for what we're going to do on these three EVAs."
During the first spacewalk, Anderson and Mastracchio will disconnect ammonia and nitrogen pressurization lines from the old tank, then move to the shuttle's cargo bay where they will detach the new ammonia tank assembly from its mount and hand it off to the station's robot arm.
Wilson and Dutton, operating the space arm, will move the new ATA to a temporary mounting point on the crane's mobile base. While that is going on, the spacewalkers will install a replacement rate gyro assembly and then move to the far left end of the station's solar power truss to loosen bolts holding a massive battery pack in place. The batteries will be replaced on an upcoming shuttle flight.
"What I'll look forward to the most on these EVAs, we'll actually be crawling out to the farthest reaches of the station on the left side to do some work on some batteries out there," Anderson told CBS News. "Plus, Rick gets to go out to the Japanese Exposed Facility and do some work and then I'll be on the other side on the Columbus module doing some work and I've never seen those views.
"When I was up there and did my spacewalks before, it was a totally different configuration, so I'm really looking forward to being out on the edge, if you will, and seeing the views that we have and taking some pictures and just having a little bit of fun."
While Anderson and Mastracchio are working outside, the astronauts inside the station will be working to unload the Leonardo MPLM. Among the items scheduled for transfer during the spacewalk are the minus 80-degree experiment sample freezer, known by the acronym MELFI, and a new crew cabin, the fourth and final U.S. cabin to be moved to the station.
NASA's original plan was to equip the sleep station with a curtain-like liner to turn it into a bathing and hygiene cabinet.
"It's a space shower," Shireman said. "We don't really take showers on board the ISS, but people need to bathe and shampoo their hair and because it can release free water, we like to do it in a place that won't allow the water to float and get into avionics, electrical equipment, that can cause damage.
"So we actually put a liner in there. It's not as simple as you would think. It's not just a shower curtain, it's a little more complicated than that. But it's a station with privacy where the crew members can go and clean up. A very important thing from a health standpoint and also a psychological standpoint."
But with the arrival of the Soyuz TMA-18 spacecraft, the Expedition 23 crew will include three Russians. The Russian segment of the station only has two crew sleep stations and a third will not be available until 2012 when a new Russian lab module is launched. NASA may let the Russians use the new U.S. crew cabin as needed until then and instead use the toilet compartment in the Tranquility module as a hygiene station.
Following the first spacewalk, the astronauts will spend flight day six moving supplies and equipment out of the MPLM and into the station, including an experiment rack and the Window Observational Research Facility, or WORF. The WORF rack will be installed in a bay in the U.S. Destiny lab module that features a high-quality window. Along with limiting stray light, the facility will provide attachment points for various still and video cameras, as well as other optical instruments, for enhanced Earth observations.
The next day, after another airlock campout, Anderson and Mastracchio will devote flight day seven to their second spacewalk. After unbolting the old ammonia tank assembly, Wilson and Dutton will move it to a crew equipment cart on the front side of the station's main power truss and the spacewalkers will secure it with tethers.
The arm then will move to the new ATA, grapple it and move it into position for installation in the power truss. Manually maneuvering the massive tank, the astronauts will move it into place, install four bolts and reconnect the ammonia and nitrogen pressurization lines.
"During each of the EVAs, we have to hold the ATA, this ammonia tank, up over our heads," Mastracchio said. "It's about an 1,800-pound tank, I think. Clay's going to do it on EVA 1; then I do it on EVA 2. We're going to be holding this tank over our heads, trying to control it while Jim and Stephanie come in and grapple it. So I'm a little concerned about trying to have the stability to hold that tank nice and firm and steady ... so they can come in and grapple it."
With the new tank in place, Mastracchio and Anderson will move to the front side of the truss, untether the old tank and hand it off to the robot arm. The old tank will be temporarily mounted on the mobile base station where the new tank was stowed after its initial removal from the shuttle's cargo bay.
The next day - flight day eight - the combined crews will enjoy a half day of off-duty time, after which they will continue with MPLM unloading. Along with moving muscle atrophy experiment hardware into the station, they also will install a panel in the new seven-window cupola to fix a clearance problem that has prevented installation of a robotics work station.
The cupola, attached during a February shuttle mission as part of the new Tranquility module, will provide robot arm operators with panoramic, line-of-sight views to approaching cargo ships and work sites around the station.
Flight day nine will be devoted to the third spacwewalk and completing the ammonia tank transfer tasks. The robot arm will carry the depleted tank from its temporary storage point on the mobile base station to the back of Discovery's cargo bay where Mastracchio and Anderson will bolt it in place for the return to Earth.
With the old tank secure, Anderson, his feet anchored to the end of the robot arm, will be moved to the outboard side of the European Columbus module to retrieve an experiment mounting plate assembly. He and Mastracchio will mount the plate in the shuttle's cargo bay. Anderson then will move to the Canadian Special Purpose Dexterous Manipulator robot to install a second camera while Mastracchio replaces a camera light on the Destiny module.
"EVA 3 is kind of a miscellaneous EVA," Anderson said. "We have lots of different tasks we're going to do. Most notably we'll do some work with the Special Purpose Dextrous Manipulator that we like to call DEXTRE. I'll be doing some work on that one. I'll remove some thermal insulation that's been there for a while that needs to go away. I'll take that out and also I will be working on installing a camera that goes onto one of the camera locations, and Rick will also be doing some camera work, but he'll be doing it in a different place, on the lab module. There's a camera that needs to be fixed. It needs to be removed and replaced and RickÕs going to do that task."
The astronauts will wrap up equipment transfers from the MPLM the following day, hold a traditional in-flight news conference and take another half day off.
Flight day eleven will be devoted to completing the MPLM transfers and deactivating the cargo module. After hatches are closed, motorized bolts will be driven to detach the module from Unity's nadir port, and the station's robot arm will move it back to Discovery's cargo bay for the trip home.
After that, the combined crews plan to gather in the Harmony module for one final time to bid each other farewell. Hatches between the spacecraft will be closed at the end of the day and the docking port depressurized.
The next morning, with Dutton at the controls on Discovery's flight deck, Discovery will undock and depart.
"It's the day I'm really looking forward to," Dutton said. "The pilot's big moment of glory is getting to do the fly around of the space station. So we'll undock, back away around 400 to 450 feet in front of the space station and then begin to fly a maneuver over the top in front of the space station, essentially complete a 360-degree arc around the space station.
"Then we'll continue to maneuver to essentially break out of our orbit with the station, so we'll get a real panoramic view. As big as the station is now, I can't really imagine how breathtaking that will be, getting to see it from every perspective. But it's a day I'm really looking forward to."
Leaving the station behind, the shuttle astronauts will use the ship's robot arm and the OBSS one final time to inspect the nose cap and wing leading edge panels to make sure no damage has been incurred since the flight day two inspection earlier in the mission.
Assuming no problems are found, the crew will spend the next day packing up for landing back at the Kennedy Space Center on April 18.