THE International Space Station has been forced to shut down many of its systems after a coolant leak.

NASA has confirmed the station is having problems with its coolant system due to a faulty valves. Early reports of the difficulties appeared in tweets from the station's crew and support staff.

The crew are struggling to restore pressure to the coolant system that keeps the vital systems, including life-support, at a regular temperature. This can vary wildly depending on whether the space station is in sunlight or in the Earth's shadow.

While not presenting an immediate threat to the station's crew, it can be serious if unsolved.

Some of the space stations' systems have been shut down in order to reduce the strain on the temperature control equipment. Others have been re-routed to the working cooling system.

NASA spokesman Josh Byerly told NBC that one of the station's two cooling loops, known as Loop-A, shut down due to an anomalous temperature imbalance. NASA had to urgently reroute the coolant systems to prioritise life support systems, electrical systems and science experiments.

"The crew was never in any danger," Byerly said. "They worked to keep the freezers going. ... They're fine for the near future."

A NASA statement says the pump module on one of the space station's two cooling loops which circulates ammonia outside the station to keep equipment cool automatically shut down when it reached pre-set temperature limits.

"The flight control teams worked to get the cooling loop back up and running, and they suspect a flow control valve actually inside the pump itself might not be functioning correctly," it reads. "At no time was the crew or the station itself in any danger."

As a precaution, the three Russians, two Americans and one Japanese crew members aboard shut down some operating systems to reduce the power load.

The crew is preparing for bed as ground teams collect more data and consider what repairs and further trouble-shooting may be required..

LINK: The ISS coolant system explained

The internal cooling loops of the affected modules are showing elevated temperatures as a result of the Loop A issue. #ISS — ISS Updates (@ISS101) December 12, 2013

Loop A NH3 outlet temp reached a minimum of -34.7°C and is now warming up again. Loop B is coping well with the additional loads. #ISS — ISS Updates (@ISS101) December 12, 2013

@r0eland It is important to have both up and running, so Mission Control is working on that, but there is no danger to the crew at this time — ISS Updates (@ISS101) December 11, 2013

@Glenn_OBX If the valve continues to misbehave, the Loop A Pump Module would have to be replaced. Series of spacewalks. — ISS Updates (@ISS101) December 11, 2013

Loop A NH3 Outlet Temp did increase steadily for about half an hour, but is now dropping once again. Currently at -26°C. #ISS — ISS Updates (@ISS101) December 11, 2013

Problem on #ISS - a Flow Control Valve (FCV) for ammonia coolant is having trouble. Many systems shut down. Details: http://t.co/RFjJQWON0l — Pete (@Space_Pete) December 11, 2013

Loop A flowrate and outlet pressure now increasing and the temperature has started to rise as well. #ISS http://t.co/UoxhtmsOiE — ISS Updates (@ISS101) December 11, 2013

Loop A NH3 outlet is now at -32°C. Teams are looking at repair/recovery options while making sure #ISS remains in a safe configuration. — ISS Updates (@ISS101) December 11, 2013

A Flow Control Valve within the External Thermal Control System of #ISS is causing trouble. Loop A is too cold: http://t.co/UoxhtmsOiE — ISS Updates (@ISS101) December 11, 2013

The exterior of the International Space Station experienced a coolant leak back in May which required two astronauts to undertake a space walk to rectify the problem.

It is not known whether this current incident is related to the earlier problem.

The International Space Station, which had its fifteenth anniversary this week, is equipped with escape pods which could return the astronauts to earth in the event of an emergency.

The ISS occupants took to the escape pods during an incident last year in which a piece of space junk came near to the station, however the junk passed on and the pods were not used.

Originally published as Space Station coolant leak