NASA tries again to launch the space shuttle Endeavor, Monday, despite a good chance of rain, threatening to delay the mission for the fifth time in power.

The rain is a particular danger to the plans out today because of an exposed propeller in the nose of the craft. The plastic usually propeller guards - one of 44 small rocket thrusters on the spacecraft used for minor changes course - came yesterday during the failed fourth launch Endeavor lose.

Although the case does not pose any risk to the launch yesterday (the label is designed to fail during startup anyway) if moisture into the booster, which can freeze in the ice and make the propeller useless.This means that if rain falls on the pillow, the agency probably will have to suspend today's launch is scheduled for 6:51 EDT (2251 GMT).

"The idea is that if it rains after starting with a risk of moisture in the fuel and you do not want to freeze," says NASA spokesman Allard Beutel. NASA would probably not start with a propeller with impaired mobility, but not essential for takeoff.

While Sunday's launch attempt was canceled because of thunderstorms near the launch pad and landing here at Kennedy Space Center, there really is no rain fell Endeavor Launch 39A.

"If we had rain on the platform would have found us with security," said Beutel of today's launch plans.The rain is a serious threat to attempt escape Endeavor today, with a 60 percent chance of thunderstorms forecast. Despite the gloomy forecast, NASA decided to start feeding the shuttle's massive external tank in preparation for the launch this morning, just in case the weather cooperates.

"They thought it was worth at least take the opportunity," said Beutel.If you cancel today's launch, NASA could try again tomorrow if the ground staff have enough time to move the engine cover. This procedure takes three to four hours, because the giant rotating service structure of scaffolding at the launch pad to be moved into place to provide access to computers on the nose of Endeavor.

If the process can be completed at the time, NASA may be able to push the launch window for a few days, but the shuttle is scheduled to retire in order to allow a ship to unmanned Russian cargo launcher space station later this month.

"We can talk with the Russians, and maybe we can get some extra time," said Beutel.Often delayed Endeavor's mission is to build up a visit to the ISS to install the supply of spare parts and a new research field that must be submitted by the Japanese Kibo laboratory. Today is the fifth attempt to take off the ship hit in their mission STS-127, which was held due to bad weather and an irritating gas leak, which has been repaired.