Published: Aug 11, 2010 4:36 PM EDT
Updated: Aug 11, 2010 1:36 PM EDT

CAPE CANAVERAL, Fla. (AP) - Space station astronauts are gearing up for their second spacewalk in five days and they hope to have better luck with the urgent repair job this time.

The International Space Station has been operating with only half its usual cooling capability ever since a critical pump failed one-and-a-half weeks ago.

On Wednesday, astronauts Douglas Wheelock and Tracy Caldwell Dyson will attempt to remove a failed pump that spewed toxic ammonia coolant the last time they tinkered with it.

Flight controllers have devised a new plan to avoid any more major leakage. They've already lowered the pressure in the disabled cooling line.

A spare pump would be installed during a third spacewalk this weekend. The first spacewalk was Saturday.