Thread by @MaryRobinette

Want to watch a spacewalk today?

https://twitter.com/NASA/status/1164112911893192704

The livestream is here. I won't get to be with you for the whole thing, because I'm heading to the airport.

Tune in! @nasa's Public Affairs Officers are fantastic.

nasa.gov/multimedia/nas…

@NASA I'm settled in at the airport. Meanwhile, above us, Nick Hague and Andrew Morgan are outside the ISS on a spacewalk.

Let's join them, shall we?

@NASA When they are talking about the CETA cart, that's Crew Equipment and Translation Aid. It runs on a rail, so is technically a train. A very, very slow train.

@NASA All of the instructions that you're hearing are the result of work on the ground at the NBL. People spend time doing "dev runs" in the Neutral Buoyancy Lab.

A development run is basically a rehearsal for a spacewalk held in a giant swimming pool.

They work out the best practises and then create a set of instructions for the astronauts actually doing the spacewalk.

Because space is dangerous and they can only be out there a limited amount of time, you want to remove as many variables as possible.

When they say "handover" what that means is handing the communications from one tracking station to another. There's often a small loss of signal when that happens.

He's putting his APFR into a WIF.

They've already defined APFR as articulated portable foot restraint, which anchors the astronaut to the station.

The WIF is a socket on the outside of the ISS. It stands for Worksite Interface Fixture. However...

When I was working on Fated Sky, I asked @astro_kjell what WIF stood for and he said, "Worksite Interface Fuggedaboutit? At a certain point the acronym just becomes the name."

I told him that I was going to put that verbatim in the novel.

He said, "Abort!"

I did not.

@astro_kjell Drew just said, "black on black."

What that means is that his safety tether is attached and closed. When it is closed, there's a solid black line that forms vs. a broken line, which means it's not secure. When they move the tethers, they say aloud that it is secure.

@astro_kjell Note all the cables? All of them are tethered to Station. One of the challenges of the ISS is that gravity doesn't hold cables down. Everything has to be tied.

Interestingly, lunar gravity was also insufficient to have cables lay flat during Apollo missions.

@astro_kjell When he gets into the APFR, he's going to slip his toes under the front restraint, then slide his heels together, like Dorothy clicking her heels.

There's a wedge on the back of the heels that'll slide into a slot.

Pushing down, like ski boots, would push him away from the ISS

@astro_kjell RET is retractible equipment tether.

I know I say this every time I livetweet a spacewalk, but tethers are everything in space.

@astro_kjell On Nick Hague's left wrist, you can see a checklist. Even with mission control providing guidance, they still have a checklist with them.

@astro_kjell The glove and HAP check is looking for two different things.

1. tears and wear on the gloves. The station has sharp edges from micrometeorites.

2. Helmet Absorption Pad - they are looking to see if it is damp, which might mean a leak in the suit.

@astro_kjell They just referred to a "water intrusion event" by which they mean that an astronaut nearly drowned in space when his PLSS leaked water for cooling

The portable life support system in the suits is 40 years old.

space.com/24835-spacesui…

@astro_kjell Adjusting the thermal settings: The EMU suits have temperature controls on the chest. The astronauts use mirrors on their wrists to see their chest. The labels are all printed backward.

In the NBL, the temperature is controlled externally.

@astro_kjell And now I need to catch my plane back home. Enjoy watching the spacewalk!

@astro_kjell Correction. My flight is delayed, which surprised no one. So! We'll continue watching the spacewalk while I also play #marygoround.

@astro_kjell I love this view with the Earth scrolling below them.

Reportedly, the first time you come out of an airlock, after practicing in the NBL, a part of your brain expects everything to be blue because that's the way it was underwater when you practiced.

@astro_kjell Ooo! A good view of the SAFER here. That's the jetpack that will return an astronaut to the station if they become untethered.

Cosmonauts don't have a similar system.

@astro_kjell My flight is boarding! In theory!