Space shuttle Discovery blasted off for the last time on Thursday, carrying six astronauts and a load of supplies, spare parts and a robot for the International Space Station.

The shuttle lifted off at 4:53 p.m. EST (2153 GMT) from the Kennedy Space Center, riding a flame-tipped pillar of smoke across the Atlantic Ocean as it soared toward space.

The launch was delayed three minutes when a range safety computer shut down before the planned 4:50 p.m. EST (2150 GMT) liftoff. The problem was resolved with seconds to spare, clearing Discovery for launch.

The launch was the 133rd for the 30-year-old shuttle program, with up to two flights remaining before the three-ship fleet is retired later this year.

Discovery made 39 of those flights, including both return-to-flight missions following the fatal Challenger and Columbia accidents.

"I think what will be most difficult will be on landing day when we know that that's the end of her mission, completely," said launch director Mike Leinbach.

The shuttle carries a storage room, a spare parts platform and a prototype humanoid robot for the space station, a $100 billion project of 16 nations nearing completion after more than a decade of construction 220 miles (354 km) above the Earth.

The shuttles are being retired due to high operational costs and to free up money to develop new vehicles capable of traveling beyond the space station's orbit.

Space shuttle Discovery crew members, Mission Specialist Nicole Stott (L), Mission Specialist Michael Barratt (C) and Benjamin Drew Jr. wave as they depart their quarters with other astronauts for the launch pad at the Kennedy Space Center in Cape Canaveral, Florida, February 24, 2011. [Photo/Agencies]

Space shuttle Discovery crew members (clockwise from left), Pilot Eric A. Boe, Benjamin Drew Jr., Mission Specialist Nicole Stott, Mission Specialist Steve Bowen, Mission Specialist Michael Barratt and Mission Commander Steven Lindsey depart their quarters for the launch pad at the Kennedy Space Center in Cape Canaveral, Florida, February 24, 2011.[Photo/Agencies]