NASA has delayed the Orbital Sciences launch to resupply the International Space Station (ISS) and ordered an urgent repair to the external cooling loop.

NASA announced in a press release the decision to go forward with a spacewalk and will hold a television news briefing Wednesday at 3 p.m. to review the mission. Expedition 38 astronauts Michael Hopkins and Rick Mastracchio will perform the spacewalks on Dec. 21, 23 and 25.

The spacewalk will be to repair a broken external cooling loop that malfunctioned last week. Astronauts aboard the ISS were not in any danger, but the problem needed immediate attention. Just after the malfunction, ISS astronauts were able to use its backup as a quick fix, but a repair will now be needed to ensure the backup does not fail as well.

Astronauts previously attempted to make the fix while aboard the ISS, but NASA soon determined a spacewalk was necessary to repair the external valve. Hopkins and Mastracchio will use a spare valve kept in an external stowage unit.

Mastracchio is a veteran when it comes to performing spacewalks and the mission will be a first for Hopkins, a graduate of the University of Illinois. Joe Tanner, another UI alum and spacewalk veteran told the News-Gazette there is one thing Hopkins cannot prepare himself for.

"What you're not ready for is the actual emotional experience of being in the vacuum of space and how cool that is," said Tanner, who is now a college professor in Colorado. "When you first pop out of the hatch, you know this is a different environment."

The third spacewalk may not be necessary, as it is possible Hopkins and Mastracchio make the fix on Saturday and/or Monday. If they do need an additional day, it will be the second time in history astronauts have ventured out on a spacewalk on Christmas Day, the first time being in 1973.

NASA will air coverage of the first spacewalk beginning at 5:15 p.m. Saturday on their website NASA.gov.