Astronauts embark on spacewalk after space debris triggered one-day delay

The International Space Station is set to receive its second solar power boost in a month during a spacewalk on Thursday. The event comes after a piece of wayward space garbage interfered with plans to carry out the spacewalk Wednesday.

NASA was forced to implement a 24-hour delay so that the space station could fire up its thrusters to move out of the way of the debris, which was identified as a fragment of an old Russian rocket. Near-collisions in space are common, as low-Earth orbit — the area in which the ISS orbits — is becoming increasingly congested with satellites and space junk.

"The crew is not in any immediate danger," NASA noted in a blog post Wednesday.

The spacewalk kicked off Thursday around 8:30 a.m. ET and is expected to last for about seven hours. Live coverage began at 7 a.m. ET on NASA's website.

NASA astronauts Josh Cassada and Frank Rubio are working to install a solar array outside the floating laboratory. Rubio is serving as extravehicular crew member 1 and is wearing a suit with red stripes, while Cassada is wearing an unmarked white suit as extravehicular crew member 2.

Thursday's spacewalk is one of many intended to install rollout solar arrays, called iROSAs, to increase electrical power on the space station.

The first two rollout solar arrays were installed outside the station in June 2021. The plan is to add six iROSAs, which will likely boost the space station's power generation by more than 30 per cent once all are operational.

Two more arrays were delivered to the space station on Nov. 27 aboard the 26th SpaceX Dragon commercial resupply mission, which also carried dwarf tomato seeds and other experiments to the orbiting laboratory. Rolled up like carpet, the arrays weigh 750 pounds (340 kilograms) each and are 10 feet (3 metres) wide.

Cassada and Rubio already installed one outside the space station during a spacewalk on Dec. 3.

During Thursday's spacewalk, the two will install a solar array to increase capacity in one of the space station's eight power channels, located on its port truss.

Once the array is unfurled and bolted into place, it will be about 63 feet (19 metres) long and 20 feet (6 metres) wide.

The original solar arrays on the space station are still functioning, but they have been supplying power for more than 20 years and are showing signs of wear after long-term exposure to the space environment. The arrays were originally designed to last 15 years.

Erosion can be caused by thruster plumes, which come from both the station's thrusters and those of the crew and cargo vehicles that come and go from the station, as well as micrometeorite debris.

The new solar arrays are being placed in front of the original ones. It's a good test because equipment using this same design will power parts of the planned Gateway lunar outpost, which will help humans return to the moon through NASA's Artemis program.

The new arrays will have a similar 15-year life expectancy. However, since the degradation on the original arrays was expected to be worse, the team will monitor the new ones to test their longevity because they may last longer.

While US spacewalks continue, Russian ones conducted by cosmonauts aboard the space station are on hold following the discovery of a coolant leak from the Soyuz MS-22 spacecraft, which is docked to the Russian segment of the space station.

The leak was found Dec. 14 ahead of a planned Roscosmos spacewalk, when liquid began spewing out from the Soyuz.

The external radiator cooling loop of the Soyuz is the suspected leak source, according to a Dec. 15 update from NASA.

The Soyuz MS-22 ferried NASA's Rubio and two Russian cosmonauts to the space station on September 21 and is scheduled to bring them back to Earth in March.