Coolant system fails aboard space station

From Chicago Tribune: Coolant system fails aboard space station
Spacewalks are planned this week to repair system

WASHINGTON — A malfunction aboard the International Space Station had NASA scrambling this weekend as astronauts and engineers worked to repair a coolant system that failed after a power surge on Saturday night.

The cooling loop — one of two onboard — keeps the station from overheating and the six-member crew now must rely on the one remaining system with no backup. While there is no immediate danger, the loss of the second cooling loop could be disastrous.

With the worst in mind, astronauts shut down nonessential equipment — including at least one rack of experiments that was transferred to another hold, according to one NASA official — so the remaining coolant system wouldn't be overtaxed.

NASA also began planning for a repair mission later this week, after an attempt to restart the broken coolant system failed on Sunday. The agency blames the breakdown on a pump module that uses ammonia to keep the station cool.

"We're pretty confident that it was the pump module itself that failed," said NASA spokesman Rob Navias. "There was a spike in current a few minutes before 8 p.m. Eastern [Saturday] that tripped the circuit breaker and took the pump module down."

The $100 billion station has two spares onboard and the tentative plan is for astronauts Doug Wheelock and Tracy Caldwell Dyson to replace the broken pump during a spacewalk on Thursday. A second spacewalk then would be done two or three days later to attach the necessary wires and fluid lines and "bring it to life," Navias said.

The new mission means an earlier spacewalk will be cancelled or postponed. That spacewalk, also to be done by Wheelock and Caldwell Dyson, was to prepare the station for a new piece to be brought by the space shuttle Discovery in November.

The incident so far has had little direct impact on the crew — other than a rude awakening that came Saturday when alarms sounded after the cooling system failed. Despite the broken pump, the station has remained at its usual climate of 75 degrees with moderate humidity.

"This had no impact on environmental factors," Navias said.

Still, the incident could rekindle a months-long debate about NASA's future.

The agency plans to retire the space shuttle after two or three more missions — a move that has worried some lawmakers because NASA does not have an immediate replacement spacecraft.

Plans are under way, but until NASA or the private sector builds a successor, the U.S. must rely on Russia and other international allies to ferry crew and cargo to the station, which orbits at about 200 miles above Earth.

That has led some lawmakers, such as U.S. Rep. Bill Posey, R-Rockledge, to call for the continuation of shuttle flights until there is a replacement to ensure that the station can be stocked with crew and supplies through 2020, which is the current plan.

But keeping the shuttle flying is expensive and NASA officials have raised concerns that they cannot continue shuttle flights and build a new spacecraft that could travel beyond low-Earth orbit on an annual budget of about $19 billion.