The countdown is on at Cape Canaveral in Florida with fingers crossed that it will be third time lucky for the space shuttle Discovery.
Its crew are ready to blast off on what is US Independence Day. Two previous attempts at the weekend were cancelled due to bad weather but conditions today are good.
The planned launch comes after NASA eased concerns over a small crack in the craft’s fuel tank.
A wedge of foam was found to have broken away but experts at the agency say there are no serious problems and that it won’t prevent them going ahead.
NASA is painfully aware of the potential consequences of foam shedding. It was behind the loss of the shuttle Colombia in 2003. All seven crew members died.
Today Discovery’s seven astronauts are making their final preparations for a mission vital to the programme’s future – among them, British-born Piers Sellers and German Thomas Reiter.