Thread by @MaryRobinette

Remember when I got to go to @NASA to watch a dev run* in the NBL**? The crew on the @Space_Station are doing that spacewalk now. And you can watch it. nasa.gov/nasalive

*dev run = developmental run = rehearsal
**NBL = Neutral Buoyancy Lab = giant swimming pool

If you're an SF writer watching please note that they attach safety tethers AT ALL TIMES. When you hear "Gate closed, slider locked, black-on-black" that's them moving their safety tether. Those are the 3 steps to confirm that it's locked.

They are religious about tethers.

The SF scenario of someone getting knocked off a station by an impact would take a really weird set of circumstances to happen, because they are constantly tethered or otherwise attached.

You can #AskNASA about this spacewalk, but you can also #AskSFwriter, if you're more into the sensory details.

For instance -- In the NBL, you're fighting the water resistance so it's hard to get things to start moving. In space, it's hard to get them to stop.

Another weird piece of space trivia. You'll note that they never slide their gloves on the hand rails. That's because micro-meteorites can cause tiny craters in metal which have sharp edges pointing up. Like little knives.

They are trained to place rather than slide their hands.

Also of note: Because the station orbits the earth every 90 minutes, the spacewalkers are experiencing a sunrise or sunset every 45 minutes while they work.

You've probably heard that in sunlight in space, things heat to 250°, and in the shade, things are -250°. What that means is that the front of a spacesuit is in the sun and its backside is in the shade, so the suit has to be able to handle both extremes simultaneously.

As they're trying to get this cover back in place, you'll note that he is always holding a handrail while pushing, otherwise the force would push him away from the station, rather than shutting the hatch.

Which brings up a point about The Expanse...

You know how on The Expanse, they have those nifty magnetic boots that they activate by pushing down with their heels, ala ski boots?

In zero-g, that force would push you away from the floor before you toggled anything on.

As we're watching, the helmet cam is fixed straight ahead and mounted on top of the helmet, but the astronauts have a much bigger field of vision. It doesn't feel like wearing a motorcycle helmet, because it doesn't grip your head, but the vision range is comparable.

The reason they keep doing glove & helmet checks is cause the gloves are the most vulnerable to damage. The helmet has an HAP, which the Helmet Absorbency Pad, in case the Liquid Cooling&Ventilation Garment leaks. These were added after an astronaut almost drowned on a spacewalk.

After that spacewalk, they also added snorkles in the space suits. So that in a worst case scenario, you can get oxygen from your midrif.

Note: the snorkles often leave bruises on the astronaut's chins when using them in the NBL. That's a 1-G problem. space.com/24027-nasa-spa…

While they are working, bear in mind that their suit is pressurized to 4.3 psi, so as the astronauts are working, it's like having springs in their gloves keeping their hands open. This is part of why a spacewalk is exhausting.

The HUT (Hard Upper Torso) is rigid, which means that the shoulder joints are not right next to the body. So not only does this and the 4.3psi limit your range of motion, it also puts strain on your shoulder for the entire spacewalk.

For writers... You know that terrible hunched posture at the keyboard, where your shoulders are forward and slightly rotated? Like that, but with pressure. And you're in a vacuum. And could die.

But the view is AWESOME.

Notice when he opens the crewlock bag (toolbox) that EVERYTHING inside is tethered the crewlock bag and the bag is tethered as well. Tethers are a religion. If your SF in space does not involve tethers, I will raise my eyebrow at you.

Oh! Did you see them go into sunset on this transit? It's not like a sunset on Earth because there's no light to bend the light. You're on the daylight side of Earth and then you're in darkness. The transition is FAST and the darkness is really dark.

They just mentioned consumables. There are 3 to watch on a spacewalk. O2, battery life, and CO2 scrubber. Of those, the O2 is the easiest to pack, but it's the one we SF writers fixate on.

You'll also notice that labels on the ISS are often inverted in relationship to the astronaut. While there's not really an up and down in space, the engineers install everything on Earth. But on a spacewalk, you pick the best body position for access to what you're working on.

Another difference between the NBL that @Astro_Cady pointed out... Everything is blue because of the water. On the first spacewalk, the blackness is apparently shocking, even though you know to expect it.

This photo is from the dev run of this spacewalk.

Both astronauts have a mirror on their wrists in order to see the switches on the chest of their space suits. The labels on those are written backwards, which is Apollo era technology.

WIF -- Which they are talking about right now... When I asked an astronaut what it meant he said, "Um... We call something a WIF. That's what it is. No idea what it actually stands for. Widget Interface Fuggedaboutit"

Readers: I put that EXACT LINE in FATED SKY.

These are equipment tethers. RET = Retractible Equipment tether, so that bit in the middle of the lower set is like a retractible dog leash.

When they say "Large/small" or "small/small" they are talking about the sizes of the hooks on each end of the tether.

Questions from my dad, who is watching with me: So these guys have never practiced this spacewalk?

Correct. Up through the Shuttle era, astronauts did task-oriented training. They had a limited time in space and took everything with them.

In the ISS era, astronauts do skills-based training because it's a long duration mission. The supplies and the astronauts arrive on the station separately. Over six months to a year, things change, so flexibility becomes super-valuable.

Question from Dad: So the equipment comes up in an unmanned vessel? (Yes.) How do they dock them?

A combination of computer guidance and sometimes they use the Canadarm (robot arm) to reach out and grab the incoming vessel.

See the wire tie he's using now? Funny story about their development. The Russians were at the NBL for some training & saw the twist ties on bread bags. "These are useful!" So they went back to Star City & made larger brass versions of the same thing.

NASA saw them on the ISS and said "These are useful" and now they make them too. So... wire ties. Super-high-tech.

And the reason to not use a zip-tie in space? You have to use a blade to release them. I'll just leave you with that image.

Also. Tethers. I'm just going to keep repeating and pointing out that they are constantly tethering everything.

They are doing a SAFER check right now. That's the Simplified Aid for EVA Rescue (note the acronym within the acronym. Much NASA. So Acronym) which uses nitrogen gas to get the astronaut back to the station if they become untethered. It has 24 fixed-position thrusters.

But... only about 8-seconds of thrust, so they can only do tiny bursts and rely on inertia. To train on this, astronauts use VR. They get "spun" out from the station and have to return.

APFR - Articulated Portable Foot Restraint. To use this, the astronaut slides their toe under a loop at the front, then twist their foot to slide a wedge on their heel into a slot. It's a lateral motion that they can brace against.

Apparently, being in the APFR on the end of the Canadarm is cool and terrifying. Even moving slowly, you still feel the momentum & vector changes and you're attached only with your feet. There is NOTHING to grab hold of.

Also airless space. But a GREAT view.

The "pull and twist test" is exactly what it sounds like. They seat something in a WIF and then pull and twist to make sure it's actually seated.

This is the probe or bayonet of the APFR. That's an astronaut hand for scale in the second picture.

At the NBL run for this, they had a contest to see who could do the worst cat puns, because they are closing the door to the CATS.

Professionals, but also people and often giant goofballs. It's a purrfect combination.

Did you know that we have cordless drills on Earth because NASA created the PGT (Pistol Grip Tool) for use on spacewalks?

In the NBL they make mock-ups of everything that the crewmembers have to interface with on the spacewalk BUT until they get up there, for something like closing the CATS door, they don't actually know what they'll face.

Wow.... that's a gorgeous view from the new camera. I have the ISS app on my phone and the difference is just beautiful.

Speaking of the app... It'll let you know when a spacewalk is happening and let you watch the ISS's views.
play.google.com/store/apps/det…

Speaking of views. An astronaut in a position like this, at the end of the Canadarm, has NOTHING IN VIEW BELOW THEM EXCEPT THE EARTH. Which is 250 miles away.

Even astronauts have the "OH SHIT" hindbrain reaction. Not that they will say that aloud on a hot mic.

You'll hear them warning the astronauts not to touch [X] item. There are different concerns for different items. Examples:
A boom installed on a spring could rebound on the astronaut.
Micrometeorite damage could have caused sharp edges.
Instrument might become misaligned.

"And then we will be mating with cables..."

AND PEOPLE WONDER WHY I HAVE ROCKET INNUENDO IN THE LADY ASTRONAUT NOVELS.

"Temp stow in shade" What this means is that they need to make sure that the thing they are working with isn't in direct sunlight, which can reach 250°. If it's something that's going inside a box, so always in shade at -250°, it will have a short "life" in the sun.

These views... I love it when the crew asks where they are and you can hear the sense of wonder in their voices. I write SF in part because it's as close as I'll get to space.

Honestly, sometimes I turn on the ISS app, just to watch the Earth scroll past.

Space trivia. They use VOX (voice actuation) inside the helmets. You can often tell how difficult something is because the astronaut is breathing heavily enough to trigger the VOX even without speaking.

The thermal cover over the airlock! When an astronaut is on a spacewalk, the outer hatch IS NOT CLOSED, in case they need to return quickly due to an emergency. There's a soft fabric shield that goes over it to maintain the temperature inside the airlock.

The SAFER handle checks. They do these checks because on a shuttle mission (STS-121), a handle was accidentally unlatched, endangering the astronaut. To prevent that...they use tape.

This is a SAFER pack, and the actual controller for use in training.

Here's me trying the VR SAFER simulator @NASA that the astronauts use for training. (I died.)

When this was first created, it was before VR goggles, so they mounted a laptop on the astronaut's head, with a split screen to mimic 3D like a Viewmaster. And bungees to manage weight.

The reference to the EVAAT. That's the last of the runs at the NBL where there finish codifying the procedure to send it up to the @Space_Station.

For writers...
A dev run is a draft.
The EVAAT is the draft you send to your editor.
The spacewalk is publication.

I'm watching the astronauts take photos of each other & drift as they let go of the station. Note: they drift TOWARD the station, not away, due to the safety tether.

So when they need to stay put, use both hands, and an APFR isn't an option, they'll add a "local tether."

Ooo! Ammonia system repair.

IT IS A REALLY NEAT SYSTEM and a potentially catastrophic failure point, so all the astronauts are trained on how to replace fittings. Again, skill-based training and not task-based.

Do you see the silver part on his boots? That's the tab that they use to slot their heels into the APFR (Articulated Portable Foot Restraint.) To engage it, you twist your foot like you're Fossey

In the NBL, the airlock is oriented upside down so when astronauts are egressing, they have to hang upside down in the airlock. The NBL pool is neutrally buoyant, but inside the suits, the astronauts are still experiencing 1-G.

The difficulties in the pool are "NBLisms."

YAY! @astro_ricky and @Astro_Feustel are back in the @Space_Station airlock after a really beautiful spacewalk.

Now we get to talk about getting them out of the space suits!

So first of all, the hatch opens TOWARD the inside of the space station, so that the pressure of the station helsp to keep it shut. You would NEVER design one that opened outward, because the pressure of the station would blow it open.

Next, and this is super-important. Note that the people in the redshirts STAY INSIDE THE SHIP.

It's hard to tell on the livestream, but repressurizing the airlock is REALLY loud. REALLY LOUD.

Note that both astronauts inside the station are wearing ear protection.

The sequence that the astronauts come out of the suit in space is a little different in the NBL than on the ISS. In the NBL, the SAFER is a mockup and part of the HUT. The suit also weighs about 300lbs so they have a "donning rack" to support the weight on Earth.

The helmet has two layers. The inner one is airtight. The outer one is for impact. So that trope of an impact on the helmet cracking it and immediately making it leak is... not right. An impact would have to crack the outer layer first.

At the NBL, they have to depressurize the suit before removing the gloves, or the glove will go shooting across the pool floor.

See the way the astronauts are flexing their hands? The first time I saw that, my puppeteer brain activated because that's EXACTLY what a puppeteer does after using a control that's too tight.

Also, before getting in and after getting out, they do shoulder stretches.

Well! The livestream has ended, so thanks for joining me as I blathered about some of the space stuff I learned working on the LADY ASTRONAUT novels.

Any follow-up questions?

Oh. Right. I have space novels. That maybe you would like to read? You can pre-order them. If you order from @volumesbooks, I'll sign them and stuff.

Here's The Calculating Stars.

volumesbooks.com/book/978076537…

Here’s The Fated Sky, where most of this spacewalk info came to play: volumesbooks.com/book/978076539…

And if you are REALLY geeky, you can join the Lady Astronaut club, which is totally non-binary and open to everyone along the full gender spectrum.

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