.@astro_timpeake entering the airlock too. Thermal cover is now closed #spacewalk
Not the first experience of a water leak in a spacesuit
Space controllers are taking no chances after an incident in 2013 when Italian astronaut Luca Parmitano discovered his helmet was starting to fill with water during a spacewalk.
His ventilation system had sprung a leak. Liquid doesn't flow under microgravity, so the water sat in his helmet, forcing him to cut short his spacewalk.
"I started going back to the airlock and the water kept trickling," Parmitano has said.
"It completely covered my eyes and my nose. It was really hard to see. I couldn't hear anything. It was really hard to communicate.
"I couldn't breathe through my nose - I felt isolated and when I tried to tell ground that I was having trouble finding my way, they couldn't hear me, and I couldn't hear them either.
"Instead of focussing on the problem - which was I may drown with the next gulp of air - I started thinking about solutions."
Parmitano gradually felt his way back to the airlock and made it safely back inside.
Steady progress wrapping up the spacewalk
After the decision to end the spacewalk early, mission controllers are watching closely in Houston as the crew heads back to the airlock.
Nasa says the astronauts are "not in any danger whatsoever".
Send us your comments: The weekend starts here
Incredible. Enjoying an end of week pint in my 'local' watching Tim Peake's spacewalk on my smartphone, thinking how we often take technology for granted. It all seems so far away from the Neil Armstrong days, yet space hasn't changed.
Get in touch: Tim Peake 'a real hero'
Another contribution to the soundtrack discussion...
It has to be David Bowie but perhaps not the obvious choices of Starman, Life on Mars or Space Oddity. My choice would be Heroes as Tim Peake is a real hero, or Let's Dance because of the beautiful choreography of weightlessness.
Astronauts head back to airlock
The two astronauts were more than four hours into the planned six-and-a-half hour spacewalk when the problem happened.
Nasa says Tim Kopra reported a small water bubble in his helmet and with the essential work completed the decision was made to terminate.
Nasa says the crew are not in any danger but are being told to return to the station as a precaution.
#Spacewalk terminated by lead Flight Director. @Astro_Tim & @Astro_TimPeake headed back to airlock. Major task accomplished.
BreakingSpace walk to be ended
The space walk is being terminated after Tim Kopra reported a small amount of water in his helmet.
Send us your comments: Stars are comparatively faint
A response to Gary Burrows' question, below...
The reason no stars are ever seen in space walks is due to how dim they are compared to the other objects in view of the camera. If the camera panned around to show nothing but the blackness of space, the camera's exposure could be easily adjusted to see the stars. As it is, the Earth, the ISS, and the astronauts are all much much brighter than the stars and the camera's exposure is adjusted accordingly. If you increased the exposure so that the stars could be seen, the view on your TV screen would be so bright you wouldn't be able to make out anything at all - you'd be blinded!
Tribute Tims line up for Tim Peake and Tim Kopra
Reid Wiseman, an astronaut who has previously completed a very similar spacewalk, is guiding the two Tims from mission control today, at Johnson Space Center in Houston.