Spacewalking astronauts relied on brute force to remove a broken coolant pump that 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.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.