Florida ? Spacewalking astronauts relied on brute force Wednesday to remove a broken coolant pump that has hampered operations at the International Space Station.

Their first attempt at emergency repairs to the cooling system was thwarted last weekend by a large ammonia leak.

This time, to everyone’s relief, there was no burst of toxic ammonia from a stubborn connector, just a few frozen flakes that drifted harmlessly away.

“That’s great news,” astronaut Douglas Wheelock reported.

“That’s awesome news,” Mission Control agreed.

The urgent repair job — now expected to require two more spacewalks — is considered one of the most challenging in the 12-year history of the space station. The cooling system is crucial for keeping electronics from overheating, and half of the system was knocked out when the ammonia pump failed 1 1/2 weeks ago.

Science research is on hold and unnecessary equipment is off until the pump can be replaced. Engineers suspect an electrical short in the pump led to the shutdown.