Space Shuttle Discovery To Return To Kennedy At 1:14 P.M. ET Saturday; President Obama Chats With Crew
Shuttle, Station Have To Dodge Debris In Cluttered Space Environment
Spacewalking astronauts attached the final major segment to the giant International Space Station and unfurled immense solar arrays spanning 240 feet, so that the station now has reached its full size in appearance.
That is a signal achievement, because the space shuttle fleet retires next year, and only the shuttles have the brawn and capacity to haul huge structural components to the station. NASA now is in a race against time to finish the station. Shuttles must carry a huge load of spare parts to the laboratory, refurbish the Hubble Space Telescope and carry a $1.5 billion experiment to the station.
This all means that every mission is critical, and the sterling performance of this latest mission has been hugely welcome for NASA leaders.
Space Shuttle Discovery, after a brilliant launch and uphill climb to space, has performed great work in hauling the final major structure to the station, the S6 truss, where it was attached to the orbiting laboratory.
The immense solar arrays unfurled without binding, catching or splitting. In some earlier missions, solar array deployments were difficult and trouble-plagued, so NASA leaders were elated that didn’t occur this time.
Rather, the main problem on this mission is that the shuttle and space station have encountered is that space junk has come whizzing perilously close to the two conjoined spacecraft, forcing them to shift orbit, even as astronauts take refuge in either the shuttle or the Soyuz escape vehicle.
These are brief, minor problems that crew members solved with little difficulty. About the only problem was that spacewalkers used brute force but couldn’t free a jammed cargo platform. So they tied it down and left it for crew members on some future mission to deal with it.
Later, the orbiting crew members received a congratulatory long-distance call from President Obama, as he sat surrounded by key members of Congress and other dignitaries.
The shuttle is set to undock from the space station and head back to Earth, landing at 1:14 p.m. ET Saturday.
But it didn’t look so rosy a few weeks ago.
The Discovery journey on the STS-119 Mission was delayed for weeks while NASA and contractor experts wrestled with problems involving the hydrogen fuel system. (Please see Space & Missile Defense Report, Monday, March 9, 2009, and Monday, March 16, 2009.)
This was a crucial mission, because it brought the station up to full electrical generating power, a critical must if the station is to double its crew size from three to six. Power demands also are driven by all the laboratories that have been added one by one to the station, from nations including Japan, the European Union, Russia and the United States (actually built by Italy).
Another vital advance initiated during the Discovery mission is on a more mundane, but nonetheless indispensable, level: the space shuttle hauled to the station a machine that turns astronauts’ urine and body moisture into drinking water.
This will be important not only on the station when it has the full six-member crew, but also for later voyages, especially two-and-a-half-year journeys to Mars, where there is no possibility of bringing enough drinking water for astronauts on such a long trip.
With six crew members, the station will need all of its systems functioning fully.
Astronauts Steve Swanson and Joseph Acaba prepared a worksite so that the future STS-127 Mission spacewalkers can more easily change out the Port 6 truss batteries later this year. On the Japanese Kibo laboratory they installed a second Global Positioning Satellite antenna that will be used for the planned rendezvous of the Japanese HTV cargo ship in September. They photographed areas of radiator panels extended from the Port 1 and Starboard 1 trusses and reconfigured connectors at a patch panel on the Zenith 1 truss that power Control Moment Gyroscopes.
Their spacewalk lasted six hours, 30 minutes. It was Swanson’s fourth spacewalk and Acaba’s first, and the 122nd spacewalk in support of station assembly and maintenance, totaling 768 hours, 33 minutes.
After struggling with a balky pin that kept an unpressurized cargo carrier attachment system (UCCAS) from fully deploying, they tied UCCAS safely in place. Engineers will evaluate the issue.
NASA also is continuing its research and study of heat shield issues. Heat shields became a salient concern when a piece of foam insulation broke free from an external fuel tank and smashed a hole in the heat shield on the leading edge of Space Shuttle Columbia in 2003. Later, when Columbia attempted to return to Earth, searing hot gases of reentry rushed into the wing, heating it to the point of structural failure. The ship and crew of seven were lost.
In a new heat shield experiment, Discovery is flying one heat shield tile underneath its left wing that will have a bump raised 0.25 inches so that heating effects will be monitored at about Mach 15 during reentry, when the smooth, laminar flow of air close to the shuttle’s surface becomes turbulent or is disrupted. This information will support computer modeling and design efforts for the shuttle and NASA’s next-generation spacecraft, the Orion space capsule. Discovery should return Saturday.