Watch the NASA Space Shuttle Discovery Launch

For a final time, the NASA Space Shuttle Discovery launch is set for 4:50 p.m. Thursday.

The six astronauts assumed their seats inside space shuttle Discovery. According to NASA, Commander Steve Lindsey and Pilot Eric Boe are in the forward seats on the flight deck. Mission Specialists Alvin Drew and Nicole Stott are set in the seats behind them. Steve Bowen and Michael Barratt are strapped in on the lower level.

At Cape Canaveral in Florida, the countdown clock has paused at T-20 minutes for a 10-minute built-in hold. The Discovery shuttle's launch countdown for mission STS-133 is to resume at 3:45 p.m.

Watch the final lift-off of the Discovery shuttle on NASA TV.