Thread by @MaryRobinette

Who wants to watch a spacewalk with me?

Today astronauts Jessica Meir and Christina Koch are replacing batteries outside the ISS while the male astronauts keep the homefires burning inside the station.

https://twitter.com/NASA/status/1217412325461852161

When they say "soft dock" what that means is that they are placing the battery in preparation for locking it down with bolts.

As they work, you can see the variety of tethers that they have. When they transfer a tool from one astronaut to the other, it also involves transferring the tether.

These aren't passed simultaneously to reduce the risk of losing a tool.

The beeps are 'Quindar-Tones'. They were also used in the Apollo missions to trigger the ground station transmitters when there is an outgoing transmission from Earth.

https://twitter.com/schneems/status/1217449789358559232

The CapCom in Mission Control is not using a hot mic. She's in PTT mode since she also needs to communicate with other people in MCC. The spacewalkers are mostly using VOX since their hands are full.

PTT=Push-To-Talk
VOX=Voice Activated

"I have the battery"
"You have the battery."

You'll hear this call and response all the time.

"You have control."
"I have control."

On Earth, you can feel someone else take the weight of a thing. In micro-gravity, you can't. A mistake means losing the thing.

So you confirm.

"I'm egressing to the outboard side."

You'll also hear them tell their plans for movement because peripheral vision is...poor in a space helmet. You turn your head to the side and you just see the interior of the helmet.

So you tell your colleague where you're going.

Also, I love directions in space.

Outboard=away from the station
Nadir=under (toward Earth)
Zenith=over (away from Earth)
Fore=to the front of the ISS (in the direction of orbit)
Aft = back
Port = left
Starboard=right

By the way, the handy way to remember port and starboard is by length of word.

Port = Left
Starboard = Right

Handily, the navigation colors follow the same pattern of shorter to longer

Port = red
Starboard = green

PET = Program Elapsed Time, basically "this is how long you've been doing this thing."

Limiting consumables = Oxygen, CO2 scrubbers, and battery life which are the things that limit the length of a spacewalk.

"You're on the timeline" = The Doctor will be by to pick you-- No. Wait.

It just means that they're on schedule.

"I can go inboard and apply positive pressure."

This is an example of how things are different in the NBL, where they planned the spacewalk, and the actual experience.

Even in the Neutral Buoyancy Lab, you are in a gravity environment. The water provides resistance.

So sometimes you wind up in space and discover that there was a hidden 1 g effect.

Needing someone to apply positive pressure to brace is the sort of thing that might not turn up with water resistance and a bit of gravity helping.

You should also be following @People_Of_Space today. I just learned about the Ingress Aid for the Articulated Portable Foot Restraint.

https://twitter.com/People_Of_Space/status/1217437641815183362

@People_Of_Space Sidenote:

𝘨 =gravity (italicized, lowercase)
G = gravitational constant (capital, not italic)
g = gram, (not italicized, lowercase)

So when you talk about a 1 gravity effect, it's written with an Arabic numeral, a space, then the symbol – e.g., 3 𝘨 NOT 3 gs or 3g.

@People_Of_Space You'll note how the astronaut outside the station tells Drew (a male astronaut) what she needs him to do with the Canada-arm. He reads it back to make certain that there are no misunderstandings.

@People_Of_Space Every time they say "scoop" I think that they are talking about a lighting instrument -- because I come from theater.

They are talking about a special handle -- because they come from space.

@People_Of_Space I did not include an icecream scoop, because in space icecream is square.

(space icecream doesn't get flown because it's crumbly and would be a disaster in microgravity.)

@People_Of_Space Fun fact! I once gave a male astronaut his first taste of astronaut ice cream. I'd been in the NASA gift shop earlier in the day and had picked some up.

He was so excited because they don't fly it.

It's crumbly and the little particles would be a problem.

@People_Of_Space The gap spanner is a cloth tether that literally spans the gap between two handrails.

@People_Of_Space I was about to leave for a flying lesson but the field is IFR.

Instrument Flight Rules = visibility is bad so you have to use instruments to fly.

As a student pilot, I can only go up with VFR. Visual Flight Rules.

Spaceflight, airflight are both acronyms all the way down.

@People_Of_Space Watch the transition to night!

@People_Of_Space PGT = pistol grip tool = a drill.

But a space drill has differences from a terrestrial drill. It needs to handle temperature swings from +250F in the sun to -250 in the shade.

An oil lubricant would seize up, so they use a dry film lubricant instead.

@People_Of_Space The PGT is also very light, to reduce weight on launch. It looks like aluminum but is not.

It's made of Lexan, a polycarbonate (basically plastic with glass) and wrapped in foil tape.

@People_Of_Space Because the suits are bulky and hand fatigue is a big problem, due to pressurization, the handles are built larger with very careful attention to the triggers.

Think about using a drill while wearing something that is an unholy alliance of ski-gloves and hand grip exercise tool.

@People_Of_Space The PGT also turns more slowly than a terrestrial drill (5-60 rpm) and has a wide range of torque. (<1 to 38 foot-pounds)

Stripping a bolt or screw would be real bad. There's no running out to the store to get a new part.