Astronauts prepare for Christmas spacewalks to replace pump
Sen— Astronauts will begin a series of unscheduled spacewalks tomorrow to replace a coolant pump after part of it failed on the International Space Station.
NASA astronauts Rick Mastracchio and Mike Hopkins were ordered into action after a faulty valve caused the pump to stop functioning correctly on 11 December.
Spacewalks have been hastily arranged for Saturday, Monday and, if necessary, Wednesday which is Christmas Day. If that goes ahead, it will be the first spacewalk carried out on Christmas Day since 1974.
That happened during the Skylab 4 mission when NASA’s Gerald Carr and William Pogue stepped outside to retrieve film from a telescope and to photograph Comet Kohoutek.
The spacewalks will be the first for Hopkins. Mastracchio has already made six, notching up 38 hours and 30 minutes of extra-vehicular activity (EVA).
There are two coolant loops on the ISS which circulate water and ammonia to carry heat away from the complex electronics systems on the orbiting outpost. The failure of one does not endanger the astronauts, but NASA is keen to ensure a backup is restored as quickly as possible.
They will replace it with an existing spare pump module that is stored on an external stowage platform on the ISS.
The first spacewalk is scheduled for Saturday at 7:10 a.m. EDT when the spacewalkers will set up the worksite on the S1 truss. Monday’s spacewalk will include the removal of the old pump module and the installation of the spare. If necessary a third spacewalk would then occur on Christmas Day to complete installation of the new part.
A NASA briefing explains how the spacewalks will be carried out. Credit: NASA TV
While Expedition 38 astronauts Mastracchio and Hopkins carry out the actual EVAs, Wakata will operate the station’s robotic arm to manoeuvre the spacewalkers at the worksite. Each spacewalk is expected to last about six hours 30 minutes.
The astronauts have been warned to prepare for ammonia leaks during their spacewalks. Leaks have occurred while astronauts disconnected cables during previous repair spacewalks. If ammonia flakes land on a crew member’s suit, the spacewalkers will need to go through a series of decontamination steps before re-entering the space station.
The pump problem has caused NASA to delay the first commercial supply mission by Orbital Sciences’ Cygnus spacecraft, which was due to launch from Wallops Island, Virginia, atop an Antares rocket, on Thursday night. It will now launch in mid-January at the earliest.
In May, Expedition 35 Flight Engineers Chris Cassidy and Tom Marshburn carried out a spacewalk to examine and replace a pump controller box on the ISS’s far port truss after it began leaking ammonia coolant.
Then in July, a spacewalk by Italian astronaut Luca Parmitano was dramatically cut short in an emergency when his helmet began filling with water.
In the Russian side of the space station, Commander Oleg Kotov and Sergey Ryazanskiy are preparing for a pre-planned spacewalk on 27 December. The pair will install a foot restraint, two new cameras, a new experiment plus a payload boom on the Zvezda service module.
Astronauts Rick Mastracchio (left) and Mike Hopkins check a U.S. spacesuit inside the ISS's Quest airlock. Credit: NASA TV