Discovery dazzles with nighttime ascent to space
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: December 9, 2006
Running two days late, the shuttle Discovery thundered into orbit tonight, lighting up the night sky for hundreds of miles around as NASA kicked off a critical flight to conduct electronic bypass surgery on the international space station.
In the space agency's first night launch since 2002, Discovery's huge solid-fuel booster flashed to life at 8:47:35 p.m., instantly pushing the fuel-laden 4.5-million-pound spacecraft skyward atop 500-foot tongues of sky-lighting fire.
Accelerating through 140 mph in just 10 seconds - straight up - Discovery wheeled about its long axis and arced away over the Atlantic Ocean, blazing through the dark sky on a trajectory up the East Coast of the United States.
The 5,000-degree flame from its twin-solid fuel boosters was visible for hundreds of miles around, putting on a spectacular show. Despite earlier concern about high winds and possible low clouds, conditions improved as launch time approached and it was clear sailing for Discovery.
Two minutes and five seconds after liftoff, the two boosters were jettisoned, their combined 2.6 million pounds of solid propellant exhausted, and Discovery continued its ascent on the power of three hydrogen-fueled main engines.
With the boosters gone, live television views from a camera mounted on Discovery's external fuel tank became too dim to spot any debris possibly falling from the tank. But the view was stunning as the exhaust from the main engines interacted with the surrounding atmosphere to create a eerie, never-before-seen plume around the back of the vehicle.
No obvious signs of foam shedding could be seen during the most dangerous phase of flight, the first minute and 40 seconds or so when air density is high enough to result in high impact velocities.
Eight-and-a-half minutes after liftoff, the shuttle slipped into its planned preliminary orbit, the dimming plume flaring as maneuvering jets pushed the orbiter away from the tank.
"It probably is the most complex shuttle mission we've had yet," NASA Administrator Mike Griffin said in an interview with CBS News.
Joining Polansky aboard Discovery are pilot William Oefelein, flight engineer Bob Curbeam, Nicholas Patrick, Joan Higginbotham, Swedish astronaut Christer Fuglesang and Sunita "Suni" Williams. Williams will remain behind on the space station when Discovery departs and German astronaut Thomas Reiter, launched to the lab complex in July, will come home in her place.
"We have a message for the crew of Discovery," station skipper Mike Lopez-Alegria radioed Houston after the shuttle reached orbit. "Congratulations. ... It's a wonderful achievement. We're going to turn our porch light on so they can find us."
Space station-bound shuttles must take off at roughtly the moment Earth's rotation carries the launch pad into the plane of the lab's orbit. That moment moves 23 minutes earlier per day, resulting in alternating periods of lighted and nighttime launch opportunities.
NASA suspended night launchings in the wake of the Feb. 1, 2003, Columbia disaster to ensure good lighting, on the ground and in orbit, for photo documentation of the shuttle's external tank. The goal was to monitor the performance of the tank's foam insulation and to spot any debris impacts on the shuttle's heat shield.
But ruling out night launchings severely restricted NASA's launch opportunities. After two successful daylight flights in July and September, NASA managers concluded the redesigned tank was performing well and that the risk of a night launch was justified by the need to meet the Bush administration's 2010 deadline for finishing the station and retiring the shuttle.
As it turned out, the light from Discovery 's booster plumes provided enough illumination for at least some of NASA's launch cameras. Radars were positioned along the shuttle's ground track to look for signs of debris and a WB-57 jet flying off shore to one side of the shuttle's flight path photographed the orbiter using a powerful telescope with infrared and optical cameras.
But launch photography is not really required to determine if the current mission is at risk. An exhaustive orbital inspection will spot any signs of damage in greater detail than is possible with ground-based instruments. The major downside to a night launch is possibly not spotting a near miss that might pose a threat to the next mission.
"We're not relying on those ascent-based observations for the safety of that particular flight," said shuttle Program Manager Wayne Hale. "We're relying on the inspection of the heat shield, which we do in excruciating detail on orbit now to make sure they're safe to come back."
With two successful flights going into Discovery's launch campaign, Hale said, "we are as confident as we are likely to get that it's safe to return to the kind of operations that we simply must adopt if we're going to complete the international space station by 2010."
No obvious problems were seen during this evening's climb to space, but flight controllers won't know for sure how the shuttle's heat shield fared until a detailed inspection by the astronauts on Sunday. Additional inspections will be carried out by the station's crew during final approach prior to docking Monday afternoon.
Discovery's mission is considered one of the most challenging flights in space history.
Station construction has now reached the point where an interim power system, designed to support the station during its initial assembly, needs to be phased out. With the installation of new solar arrays in September, NASA is finally ready to activate the lab's permanent power grid, a major step that sets the stage for attachment of European and Japanese research modules.
But in order to do that, the Discovery astronauts and station crew must first retract one wing of the older solar arrays providing interim electricity to the U.S. segment of the station. If that goes well - and no one knows whether the fragile array wing will, in fact, retract smoothly - commands will be sent to begin slowly rotating the new set of arrays installed in September.
Flight controllers then will power down the lab's major circuits, two at a time, while spacewalking astronauts unplug and re-plug electrical cables into different sockets.
Precisely timed computer scripts will set electro-mechanical switches to begin routing power from the new arrays and the remaining older array wing through four big circuit control boxes called main bus switching units, or MBSUs, mounted in the center of the station's main solar power truss. The MBSUs, in turn, will send array power to a host of transformers, circuit breakers and other components to provide precisely regulated 124-volt DC power to the station's myriad systems.
But the MBSUs will begin heating up as soon as the power begins flowing. In a high-stakes race against the clock, the astronauts and flight controllers must quickly activate powerful pumps to push ammonia coolant through cold plates and radiators to keep the MBSUs and other components from overheating.
"This is pretty much your classic chicken-or-egg scenario here," said Paul Hill, mission operations manager at the Johnson Space Center in Houston. "You have to have active cooling to the switch boxes (main bus switching units, or MBSUs) in order to route power through them. You have to have power flowing through the MBSUs in order to power the cooling equipment."
It will take two virtually identical spacewalks - and hundreds of commands and cable switches - to reconfigure the station's four major circuits. There is little margin or error and a fair amount of uncertainty. While the MBSUs have at least been tested in space to confirm electrical continuity, the ammonia coolant system has never been activated or tested in space.
"We have these big boxes in the middle of the space station, big switch boxes," Hill said of the MBSUs. "You've got four pairs of solar arrays (when the station is complete) and you've got all these finger-thick copper wires that run from the solar arrays to the middle of the truss. Those are the boxes that, for an assembly-complete station, you want all your power flowing from and then going down to our converters that then flow power to individual pieces of equipment.
"In order to reconfigure the electrical system and the cooling system so we have the permanent cooling system up and we're flowing all power through these main switching boxes, we've got to power off a hell of a lot of equipment so we can safe those individual copper lines, disconnect them and reconnect them to where we want them. That will be a case where we'll have to power off almost all the U.S. segment one way or the other throughout that whole process."
Should any significant problems develop - an ammonia leak, an electrical glitch, a computer commanding issue - that might prevent the activation of a cooling system, the astronauts could be forced to quickly switch back to the interim power system, cutting of the flow of electricity to the MBSUs while engineers in Houston consider alternatives.
"What makes this mission singularly unique is the choreography between what we're doing in orbit and what the ground is doing because of the amazing amount of ground commanding to go ahead and power down and re-power the ISS electrical system while we're out there doing spacewalks," Polansky said in an interview.
"So yeah, we hold our breath like everybody else while the ground sends the commands and then wait to find out how it's going to work."
Said Curbeam, the lead spacewalker on the mission: "It is very complicated. The thing I think is kind of cool about it is, we have these three spacewalks, the second two, the big player in them both is mission control. ... The pressure is on those guys.
"While they have to be very slow and deliberate about how they do it, they can't be too slow because the clock's ticking on us. There's got to be a point where they say OK, it's going to be fine, you guys press on or OK, we have to back out of it and go back to (interim) power and we have to undo everything we did and then talk about what we're going to do after that."
In that case, the pressure will quickly switch back to the astronauts.
"Our tasks are relatively straight forward as long as you don't run into any of the contingencies," he said. "And that's the big deal. We probably train for contingencies more than most crews because we know that's where the devil is."
INDEX | PLUS | NEWS ARCHIVE | LAUNCH SCHEDULE
ASTRONOMY NOW | STORE
© 2014 Spaceflight Now Inc.