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| Giving the ISS a Doorway to Space |
| The second phase of the assembly of the International Space Station reaches completion during the STS-104 (ISS Assembly Flight 7A) mission aboard Atlantis, the fourth shuttle mission of the year, the 10th shuttle flight to the expanding station and the 105th flight in Space Shuttle Program history. Five astronauts, commanded by veteran shuttle flier Steve Lindsey, an Air Force lieutenant colonel, will help from ISS Expedition Two Flight Engineers Susan Helms and Jim Voss install a 6½-ton Joint Airlock to the starboard berthing mechanism of the station's Unity module. It will be used by resident crewmembers and visiting shuttle crews to conduct spacewalks, using either American or Russian spacesuits. Expedition Two Commander Yury Usachev will monitor ISS systems during the delicate airlock installation procedure and the initial testing of the airlock itself. Once it is installed and activated, the airlock will symbolize the completion of the so-called Phase Two of ISS construction, giving the station a capability for spacewalks with no shuttle present. Scheduled for launch no earlier than the late afternoon of June 14, 2001, from Launch Pad 39-B at the Kennedy Space Center, Atlantis will reach the ISS for a docking two days later. Its arrival will set the stage for three spacewalks by veterans Mike Gernhardt and Jim Reilly to install the massive chamber and four high-pressure tanks, two oxygen and two nitrogen. The tanks will be used to pressurize and depressurize the new airlock. The third spacewalk will be the first to be conducted from the new ISS airlock. Lindsey is joined on Atlantis by Pilot Charlie Hobaugh, a Marine Corps captain and first-time flier, and Janet Kavandi, a shuttle veteran. She will be responsible for shuttle robot arm operations in support of the spacewalks. Helms and Voss will use the station's Canadarm2 robot arm to grapple and install the airlock on Unity on the first spacewalk by Gernhardt and Reilly. Built at a cost of $164 million (including associated tanks), the airlock consists of two separate chambers. The equipment lock, the larger of the two, has room for spacesuits and environment equipment, which will be used by spacewalkers to suit up and prepare for their excursion outside the station. The crew lock, which is separated from the equipment lock by a hatch, is the portal from which the spacewalkers will open the outer hatch to begin their excursions. The crew lock contains lighting, handrails and internal umbilical assemblies to provide power and communications for the spacewalkers until they put their suits on internal battery power. It is similar in size to the shuttle's airlock. Once installed, the airlock will undergo a series of tests by ground controllers and station crewmembers to verify that its environmental, communications and telemetry systems work before Gernhardt and Reilly venture out of it for the first time on the ninth day of the mission. During the second and third spacewalks, Helms will use the Canadarm2 to grapple and unberth two pressurized oxygen tanks and two pressurized nitrogen tanks from the Spacelab double pallet in Atlantis' cargo bay. She will hand them off, one by one, to Gernhardt and Reilly for installation on the new airlock. Kavandi will operate the shuttle's smaller Canadian-built robot arm from Atlantis' aft flight deck to maneuver the spacewalkers. It will be the second time robotics from two spacecraft will be employed in ISS assembly. The hatches between Atlantis and the ISS will be closed and opened twice for the first two spacewalks to maintain the proper cabin pressure for each vehicle. But once the new airlock is installed and activated, hatches can stay open between visiting shuttles and the station during future flights during docked operations. Most of Atlantis' mission will be devoted to installing and outfitting the airlock, but the shuttle crewmembers also will transfer cargo and water to the station. Kavandi will be in charge of cargo transfer operations, helped by Lindsey, Hobaugh and Reilly. In addition, during a week of joint activity between the shuttle and station crews, Atlantis' astronauts will conduct an experiment called SIMPLEX, an acronym for Shuttle Ionospheric Modification with Pulsed Local Exhaust. It studies the sources of high frequency radar echoes created by shuttle engine firings in space. The crew will also shoot scenes of its visit to the ISS on the large format IMAX camera, a 65mm color movie camera system. More than a mile of film will be shot during the mission. The 11-day flight will end with Atlantis' landing in the early afternoon of June 25 on the 3-mile-long runway at the Kennedy Space Center. Day 1 - Launch Atlantis' crew will launch at the end of its day during a precisely timed, few-minutes- long launch window that begins the process of rendezvous with the International Space Station. Once in orbit, they will power up and activate heaters on the airlock in the cargo bay to keep it from being damaged by the cold of space. Crewmembers will go to sleep about five hours after launch. Day 2 - Equipment Checkouts, Rendezvous Preparations Atlantis' crew will spend its first full day in space checking out equipment that will be used for upcoming major activities -- spacesuits and spacewalking gear; the shuttle's robotic arm; and the controls and tools used for the final rendezvous and docking with the station. The crew also will power up and prepare the shuttle's docking system and perform several engine firings to optimize the rate at which Atlantis' closes in on the station. Day 3 - Rendezvous and Docking Plans call for Atlantis to dock with the International Space Station on Flight Day 3. The shuttle and station crews will open hatches and transfer some equipment and supplies, including water bags. They will then close the hatches and Atlantis' cabin pressure will be lowered to 10.2 pounds per square inch in preparation for the next day's spacewalk. Day 4 - First Spacewalk; Joint Airlock Installation The first spacewalk focuses on airlock installation. The spacewalkers will help as Helms, using the station's robotic arm, lifts the new station airlock from Atlantis' payload bay and moves it to the station's Unity module. During much of the almost seven-hour spacewalk, Reilly will work from a foot platform attached to the end of the shuttle's robotic arm, operated by Kavandi. After the spacewalk, crewmembers inside the station will attach connections to the airlock to prevent thermal damage. Day 5 - Airlock Activation After an overnight Airlock leak check, the day's activities will be largely devoted to airlock activation. Tasks include removing Common Berthing Mechanism motor controllers and connecting remaining utilities in the vestibule linking Unity with the airlock. Crewmembers will enter the airlock to do more activation tasks, stow some equipment and check out the oxygen and nitrogen activities. Day 6 - Spacewalk Preparation, Additional Airlock Activities Astronauts will check out spacesuits and other spacewalking equipment and install a hatch between the equipment lock and the crew lock of the new airlock. The hatch was launched in the endcone of the airlock. The airlock's depressurization pump will be checked out and the newly installed hatch's seal will be verified. The station and shuttle arms will be prepared for the next day's activities. Day 7 - Second Spacewalk The second spacewalk is to last about 5½ hours. The internal hatches between the shuttle and station will be closed at the end of Flight Day 6 so Atlantis' cabin pressure can be lowered in preparation for the second spacewalk. The major objective is to attach and connect an oxygen and a nitrogen tank. Helms will operate the station arm to lift the tanks from the shuttle's payload bay and maneuver them to the new airlock. At the airlock, Gernhardt and Reilly will latch the tanks in place and connect cables and hoses. Day 8 - Rest and Spacewalk Preparation Shuttle and station crews are to get the first half of the day off. The second half will be used to prepare for the third spacewalk. Some equipment and supplies will be transferred, including the Protein Crystal Growth - Enhanced GN2 Nitrogen Deware experiment. Day 9 - The Third Spacewalk The third spacewalk will be the first conducted from the new space station airlock. It may include a new protocol, developed by former commercial diver Gernhardt, to purge nitrogen from the spacewalkers' bodies - essentially exercising while breathing oxygen. Primary objective is to install the final two tanks -- one oxygen and one nitrogen - outside the airlock. Day 10 - Shuttle-Station Hatch Closing, Undocking, Flyaround The shuttle and station crews will close hatches between the spacecraft. Lindsey and Hobaugh will undock Atlantis from the station. With Hobaugh at the controls, Atlantis will do a flyaround of the complex before departing. Day 11 - Pre-Landing Checkouts, Cabin Stow Activities include the standard day-before-landing flight control checks of Atlantis by Lindsey and Hobaugh as well as the normal steering jet test firing. The crew will spend most of the day stowing away gear on board the shuttle and preparing for the return home. Day 12 - Entry and Landing The Kennedy Space Center, Fla., is the preferred landing site. |
