Two astronauts making the first spacewalks took off from the International Space Station on Friday amid growing awareness of the threat posed by micrometeoroids.After a collision that damaged a Russian crewed ferry ship last month.
While the likelihood of a life-threatening impact during a spacewalk is unlikely — at the level of 1 in 23,600 — the threat is “something I think about a lot when preparing for any EVA,” said Keith Johnson of NASA mission. control spacewalk officer.
“The suit is designed to accommodate certain sized holes and still keep crew members alive,” he added. But “there is always risk.”
Floating in the Quest airlock, Japanese astronaut Koichi Wakata and NASA’s Nicole Mann switched their spacesuits to battery power at 8:14 a.m. EST to kick off the planned six-and-a-half-hour expedition. They came out a few minutes later.
They planned to spend the day working on the right side of the space station’s power cage, completing the assembly of a Tinkertoy-like solar panel support bracket and building a second bracket from scratch.
Spacewalkers attached three ISS pop-up solar arrays, known as IROSAs, to brackets mounted on the left side of the power beam, and another IROSA on the right. Two additional roll-out arrays will be released later this year for installation on the brackets that Wakata and Mann are putting together.
The goal is to increase the electrical output of the original set of solar arrays, which deteriorated over the years in the space station’s harsh space environment. Once the IROSA upgrade is complete, the lab will return to full power.
Friday’s spacewalk comes just over a month after a micrometeoroid impact ruptured a coolant line on a Russian Soyuz crew ferryboat on December 14, rendering the ship unusable for a planned crew return in March.
Instead, the RussiansIt will replace the damaged spacecraft without a crew on February 20. The crew of the damaged MS-22 ferry – two cosmonauts and a NASA astronaut – will now spend another six months in space before returning home in September.
The impact was a reminder that astronauts and cosmonauts were conducting spacewalks in the vacuum of low Earth orbit, an environment filled with countless undetectable particles buzzing at extreme speeds, and faced a small but very real threat.
NASA experts conduct a probabilistic risk assessment for micrometeoroids and space debris impacts prior to each spacewalk, based on the astronauts’ most recent assessment of the environment in which they will be operating, and a variety of other factors, including the timing of known meteor showers.
For the most recent spacewalk last month, the calculated probability of puncturing a spacesuit during a six-and-a-half hour EVA was around 1 in 3,800. The probability of a “critical” penetration was of the order of 1 in 21,300. One official said the figures for Friday’s spacewalk were similar.
“Critical” in this case means a penetration greater than 4 millimeters resulting in an uncontrollable loss of oxygen. The micrometeoroid that damaged the Soyuz spacecraft was about 1 millimeter in diameter.
Safety strings and procedures are in place to ensure a speedy return to safety of the space station airlock in the event of a life-threatening problem. The goal is to get back in in 30 minutes or less.
As for impacts, the multi-layer spacesuit is designed to help ensure that a smaller particle breaks up on impact before it can penetrate the innermost layer and allow air to escape.
But there are many unknowns in the calculation, and despite extensive training and contingency plans, “just like every time you get into a car, there’s always risk,” Johnson said.
“But we have to be willing to find the safest way to do it, be prepared for anything that can go wrong, and that’s how we do it to get our team members in that position.”
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