Delayed Launch May Deliver A Rocket's Red Glare for July 4
Monday, July 3, 2006
CAPE CANAVERAL, July 2 -- Flight controllers for the second day in a row Sunday scrubbed the launch of space shuttle Discovery, poised for liftoff beneath murky gray skies as lightning crackled and thunderstorms rumbled. NASA officials said they will try again Tuesday.
"We have scrubbed for the day," shuttle launch director Mike Leinbach told mission control at 1:14 p.m., only a few minutes after mission Commander Steven Lindsey and Discovery's six other crew members had been strapped into their seats. Launch had been scheduled for 3:26 p.m.
NASA decided to "stand down" Monday to top off onboard supplies of liquid hydrogen, used as fuel in powering the shuttle's electric system during flight. The hydrogen, despite being cooled several hundred degrees below zero Fahrenheit, boils off as it sits in fuel cells on the launchpad.
Leinbach said he and flight director Steve Stich conferred about noon Sunday after a clearing trend in the weather suddenly reversed, and decided two hours early to scrub the mission to provide extra time for refueling, a difficult and painstaking process. A full load of hydrogen should give the shuttle enough electricity to add a day to its 12-day mission.
Leinbach said the team will attempt to launch Tuesday, at 2:38 p.m., and Wednesday, if necessary. Bad weather is predicted for Monday, but some improvement is expected Tuesday. At no time Sunday were launch chances rated any better than 30 percent.
Should Tuesday bring a successful launch, it will mark the first time in the shuttle's 25-year history that the craft -- in effect an enormous rocket -- launched on Independence Day. John Shannon, chairman of the mission management team, called it "a great gift NASA can give to the nation."
But Leinbach noted that each weekend or holiday scrub costs about $1 million in materials and labor, and should the next two launch attempts fail, the team would have to order another stand down to refuel. At that point, engineers could decide not only to replenish the hydrogen in the fuel cells, but also to refill the spherical storage tanks that hold liquid hydrogen and liquid oxygen for the 500,000-gallon external tank that fuels the shuttle's main engines.
That process can last three or four days, but Leinbach said at some point it must be done, because draining and refilling the external tank after each scrub results in fuel loss that cannot be made up by normal tanker deliveries. Eventually, engineers must stop trying to launch and top off the storage tanks.
Discovery's mission will focus on restocking the international space station, repairing station machinery and testing new shuttle equipment. In addition, the shuttle will deliver European Space Agency astronaut Thomas Reiter to the station to join Commander Pavel Vinogradov and Flight Engineer Jeffrey Williams, bringing the station's complement back up to three for the first time since space shuttle Columbia disintegrated over Texas in 2003.
Shuttle officials have cautioned for a week that midsummer afternoons in central Florida are generally rainy. NASA, however, must launch Discovery in the afternoon so it will be on course to intercept the space station and remain in daylight after liftoff so cameras can photograph the external fuel tank when it is released. Damage caused by fragments of foam insulation from the external tank caused the Columbia disaster, and such fragments have remained the program's chief concern since.
In contrast to Saturday, when a bright morning raised hopes for a smooth launch, Sunday began with thunderstorms stalking across Florida's midsection, bathing the Kennedy Space Center in periodic deluges. Around 11 a.m. the weather cleared, but even as the astronauts reached Discovery around noon, clouds began to swirl again over launchpad 39B.
Just before 1 p.m., the Space Center declared a lightning alert, sending technicians scurrying inside. Leinbach scrubbed the launch 20 minutes later. "There was no hope that the weather would clear in time to meet the launch window," launch commentator Bruce Buckingham said over NASA television.
At the time of the scrub, the launch facility had been in violation of at least four launch criteria for virtually the entire day: cloud cover; lightning; the presence of lightning-bearing clouds, known as "anvils"; and potential electricity in the air.