Discovery Launch Delayed Until Summer

NASA on Tuesday pushed back the launch of space shuttle Discovery from May until at least July because of a faulty fuel tank sensor.

A similar problem briefly delayed last summer's launch of Discovery on the first shuttle flight since the Columbia disaster in 2003.

NASA said it needs the time to open up the spacecraft's hydrogen fuel tank and replace the sensor, which gave an electrical current reading that was slightly off. The space agency plans to replace the three other sensors in the tank, too, to be safe.

The space agency had been working a tight schedule to meet the May launch date and had little room for any technical problems that might crop up.

In recent months, NASA has concentrated heavily on modifying the shuttle's big external fuel tank to prevent large pieces of foam insulation from breaking off during liftoff. That problem doomed Columbia and its seven astronauts.

The fuel tank sensor was not the only problem facing the space agency. Discovery's robotic arm was removed on Monday after a small crack was found over the weekend.

NASA managers had been debating whether to replace or repair the robotic arm, and the launch delay now gives them time to ship the arm back to Canada for repairs.

Technicians discovered the crack over the weekend using a visual magnifier and ultrasound equipment. The inspections were ordered after a work platform bumped the robotic arm more than a week ago while the workers were trying to clean up glass in the shuttle's payload bay.

The robotic arm has been used to inspect the outside of the shuttle with a camera, construct the international space station and release and retrieve satellites.

Last month, NASA announced that if it could launch Discovery in either May or July, that it would attempt three shuttle flights this year.

The shuttle Columbia's seven astronauts died in 2003 when a large piece of foam struck a wing during liftoff. This left an unnoticed hole that let in fiery gases, which shattered the spacecraft after it entered the atmosphere on its way toward a landing.

NASA engineers thought they had fixed the problem before last summer's space mission. They were disappointed when a one-pound piece of foam flew off Discovery's fuel tank during launch. It turned out to be just one of 16 pieces of foam that broke off.

NASA engineers and technicians also are keeping their eyes on two other problems: engine seals that caused a leak test failure and a minuscule metal shard in the filter screen of Discovery's 12-inch liquid oxygen feed line.