By Rob Coppinger in Orlando

Today’s launch of Space Shuttle Discovery for International Space Station (ISS) logistics mission STS-121 from Kennedy Space Center’s (KSC) launch pad 39B has been cancelled and the next attempt will be Tuesday 4 July at 13:38.

The agency had planned to launch today at 13:26 and the cancellation announcement came at about 12:18, moments before Discovery’s hatch was to be closed after the crew boarded the orbiter. The countdown had reached T-1h 15min 1s, for a 10min window lasting from 14:21 to 14:31.

clouds over vehicle assembly building 

 Dark storm clouds hang over KSC's Vehicle Assembly Building 

The launch had been delayed 23h38min from the original 1 July 14:48 target time, due to concerns over the presence of electrified anvil clouds in the area.

The orbiter was to have launched during a 9min window lasting from 14:43 and 40s to 14:54 and 2s.
Under launch rules anvil clouds, which hold electrical charge from storms after they have dissipated, cannot be within 32km (17nm 3cables) of the Shuttle or its possible abort flight paths.

NASA determined that there were anvil clouds within 32km of KSC. STS-121 is the eighteenth US mission to the ISS and it would be the 32nd flight for Discovery.

The mission commander is Steven Lindsey and his crew of five NASA astronauts comprises, pilot Mark Kelly, mission specialists Michael Fossum, Lisa Nowak, Stephanie Wilson and British-born Piers Sellers; and European Space Agency astronaut Thomas Reiter joins them to be transported to the space station to become the third member of the current ISS Expedition 13.

This second return to flight mission will see supplies delivered, and during two or three extra vehicular activities Shuttle thermal protection system tile repair techniques tested and a replacement communication umbilical reel assembly for the ISS’s mobile transporter fitted.


Source: Flight International