NASA has been forced to delay its manned shuttle launch from Cape Canaveral to the International Space Station (ISS) until July after a hydrogen leak was found during week for the second time.

NASA started fueling Endeavour's fuel tank on Tuesday, delayed by several hours due to bad weather, and was excited to launch the shuttle towards ISS only to discover another hydrogen leak.  The launch was scrubbed at 1:55 a.m. EST when engineers discovered the pinhole-sized leak that may have been escaping from a vent line.

The same problem forced NASA to delay the first scheduled launch on June 13, and flight engineers are concerned about the leak.  The shuttle requires 500,000 gallons of liquid oxygen and liquid hydrogen, and hydrogen is extremely volatile, which led NASA to have strict regulations on how much gas is able to be outside the shuttle prior to launch.

The U.S. space agency hopes to launch shuttle Endeavour on July 11.  The launch cannot take place from June 22 to July 10 because the ISS's orbit and angle of the sun would overheat the shuttle and damage the shuttle's computer systems.

NASA is desperately trying to finish construction on the ISS prior to September 30, 2010, when the current space shuttle fleet will be retired.  The space agency has eight manned missions left before it will retire the current shuttle fleet and rely on the Russian space program to ferry astronauts and supplies into space.

The shuttle Endeavour launch delay will allow the Lunar Reconnaissance Orbiter to be launched from Florida, as the launch was delayed once already because of shuttle Endeavour.