NASA Clears Space Shuttle Discovery for Saturday Launch

Weather Still a Concern as Shuttle Countdown Continues
The space shuttle Discovery sits atop NASA’s Pad 39B at Kennedy Space Center (KSC) in Cape Canaveral, Florida on June 29, 2006. The shuttle will launch NASA’s STS-121 mission on July 1, 2006. (Image credit: NASA TV/KSC.)

CAPE CANAVERAL, Fla.-NASA cleared the space shuttle Discovery and its seven-astronaut crew for flight Thursday as the clock ticks down towards a July 1 planned launch.

"We are ready to go for Saturday and do what NASA does best," said John Shannon, NASA's deputy shuttle chief and head of the STS-121 Mission Management Team (MMT), here at Kennedy Space Center.

Shannon said no major technical issues are afflicting the spacecraft or its launch stack, and that 21 top mission managers and engineers voted unanimously to forge ahead with Discovery's STS-121 mission-NASA's second shuttle flight since the 2003 Columbia accident-after a two-hour meeting.

Discovery's STS-121 mission will test new external tank safety modifications and deliver vital supplies to two astronauts currently circling Earth aboard the ISS.

But only if the weather will cooperate.

Weather officials said that the threat of isolated showers, thunderstorms and thick clouds, which could trigger lightning during Discovery's planned 3:48:37 p.m. EDT (1948:37 GMT) launch time, give the planned space shot a 60-percent chance of staying on Earth.

In fact, the lightning hazards prevented pad workers from loading Discovery with the liquid hydrogen and liquid oxygen fuels used to generate power during the spacecraft's 12-day mission to the International Space Station (ISS). The seven-hour operation was slated to begin at 1:00 p.m. EDT (1700 GMT) today, but launch officials were concerned that a lightning strike could ignite the super-chilled propellant in the event of a leak.

"We're a little bit behind schedule now," said NASA launch director Michael Leinbach. "We have plenty of hold time remaining in the countdown so right now I don't see this as a big issue."

Discovery's upcoming spaceflight will continue tests of shuttle heat shield inspection and repair techniques demonstrated during NASA's first post-Columbia flight-STS-114 aboard Discovery-last summer.

NASA's STS-121 astronaut crew, commanded by shuttle veteran Steven Lindsey, will also deliver European Space Agency (ESA) spaceflyer Thomas Reiter to the ISS, where he will join Expedition 13 crew of Pavel Vinogradov and Jeffrey Williams. Reiter's arrival will return the space station to its three-person capacity after more than two years of limited, two-person crews.

"ESA and indeed Europe is very proud to be part of what's going on at the moment," said Alan Thirkettle, ISS program manager for ESA. "We're very excited about the idea of one or our astronauts, Thomas Reiter, joining the space station crew for a six-month increment for the first time on ISS."

But first Discovery must leave Earth, a problematic endeavor if current forecasts-which predict a 60-percent chance of weather-related flight rule violations-continue throughout the first few days of the STS-121 launch window, which extends from July 1 through July 19.

"We're in good shape, we're just waiting for the weather to clear for us," Leinbach said.

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Tariq Malik

Tariq is the Editor-in-Chief of and joined the team in 2001, first as an intern and staff writer, and later as an editor. He covers human spaceflight, exploration and space science, as well as skywatching and entertainment. He became's Managing Editor in 2009 and Editor-in-Chief in 2019. Before joining, Tariq was a staff reporter for The Los Angeles Times covering education and city beats in La Habra, Fullerton and Huntington Beach. In October 2022, Tariq received the Harry Kolcum Award for excellence in space reporting from the National Space Club Florida Committee. He is also an Eagle Scout (yes, he has the Space Exploration merit badge) and went to Space Camp four times as a kid and a fifth time as an adult. He has journalism degrees from the University of Southern California and New York University. You can find Tariq at and as the co-host to the This Week In Space podcast with space historian Rod Pyle on the TWiT network. To see his latest project, you can follow Tariq on Twitter @tariqjmalik.