NASA Prepares Space Shuttle Discovery for Final Launch Today

A fuel leak and crack on the space shuttle Discovery's huge external tank has forced NASA to call off any attempts to launch before Nov. 30 – the latest in a series of delays for the spacecraft's final voyage.
A fuel leak and crack on the space shuttle Discovery's huge external tank has forced NASA to call off any attempts to launch before Nov. 30 – the latest in a series of delays for the spacecraft's final voyage. (Image credit: NASA/Troy Cryder)

CAPE CANAVERAL, Fla. ? NASA is preparing the space shuttleDiscovery to launch on one final mission today (Nov. 4) to end its 26-yearspaceflying career. But the weather is not on the shuttle's side.

Discovery, NASA's workhorse orbiter, is due to blast off at3:29 p.m. EDT (1929 GMT) from the seaside Launch Pad 39A here at Kennedy SpaceCenter. The mission has already been delayed several days due to last-minuteglitches, and faces an 80 percent chance of bad weather for today's launchattempt.

Still, with NASA's shuttle fleet set to retire next year,today's launch attempt will be the beginning of the end for Discovery. The shuttleis making its 39th and last spaceflight with this launch and is the first ofNASA's three shuttles to be retired. [GRAPHIC:NASA's Space Shuttle ? From Top to Bottom]

"There's a lot of excitement in the air," NASAtest director Scott Payne said in a preflight briefing.

Discovery is NASA'soldest space shuttle currently in service, and will embark on one finalmission to haul critical spare parts to the station, as well as a storage roommodule and a humanoidrobot to assist the crew of the orbiting laboratory.

Discovery's historic finalliftoff has been delayed several days due to leaky helium and nitrogen sealsthat were found in the shuttle's aft engine section, and a last-minute electricalanomaly in a backup computer controller in one of Discovery's main engines.

Engineering teams were able toaddress the problems in time for Discovery to make its final ascent to theInternational Space Station later today.

The weather, however, is iffy for launch. Current forecasts predicta mere 20 percent chance of favorable conditions in the area, with the biggestthreats being showers and thunderstorms near the launch site.

If bad weather preventsDiscovery's launch today, NASA could try again on Friday. The space agency hasuntil Sunday, Nov. 7 ? and possibly Monday ? to fly Discovery before itscurrent launch window closes.

The shuttle's final six-astronautSTS-133 crew is made up of commander Steve Lindsey, pilot Eric Boe, andmission specialists Alvin Drew, Tim Kopra, Michael Barratt and Nicole Stott.

Discovery's 11-day mission will include two spacewalks,during which mission specialists Drew and Kopra will perform maintenance taskson the exterior of the station.

Discovery's STS-133 mission will be the orbiter's finalvoyage into space beforebeing retired along with the rest of the NASA's shuttle fleet next year.

"It's a remarkable team that gets her ready tofly," Payne said. "They put their heart and soul into this one. Theyknow it's her last flight. She's now poised to take to the skies, and when shegoes, she's going to take a little bit of every one of us with her."

Follow Staff Writer Denise Chow onTwitter @denisechow asshe covers Discovery's final space voyage from Cape Canaveral, Fla. Click here formission updates, new stories and a link to NASA's live webcast coverage.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at:

Denise Chow
NBC News science writer

Denise Chow is a former staff writer who then worked as assistant managing editor at Live Science before moving to NBC News as a science reporter, where she focuses on general science and climate change. She spent two years with, writing about rocket launches and covering NASA's final three space shuttle missions, before joining the Live Science team in 2013. A Canadian transplant, Denise has a bachelor's degree from the University of Toronto, and a master's degree in journalism from New York University. At NBC News, Denise covers general science and climate change.