‘Old Woman and the Moon’ Ch. 5 + IRL Oxygen in Spacesuits and Airplanes

Short story continues from prompt, “‘Old Man and the Sea’ but on the moon, with ladies”. For this week’s Science IRL, I talk about the delicate relationship between pressure & Oxygen

Previously…lunar astronaut Serena Santiago departed on her secret mission to seek lunar ice and found instead something a little more out of this world. In the process, her suit’s gloves were damaged. Oxygen and pressure are leaking out of her suit, and she’s hours away from Base…

Moonwalk Back to Chapter 4

Serena counted seven holes on the palm of each glove. Glove breaches were the worst. Up to thirty percent likelihood the repair wouldn’t seal completely.

Thirty percent times fourteen holes.

Watchdog was suddenly beside Serena, its robotic grippers offering up salvation in what amounted to emergency tire patch kits.

Serena grabbed the roll of synthetic patch material that looked about as sturdy as hospital gauze. It would create a bonding matrix that the liquid rubber would stick to even with the velocity of the escaping air blowing against it. She wound three layers tight around her right glove’s palm. Watchdog secured the gauze with duct tape around Serena’s wrist. They repeated the maneuver on the other hand. Next the tube of rubber cement—Serena squeezed generous blobs of the blue-green stuff on each hole, then wiped a thin layer over her whole palm.

Watchdog held out its gripper with an already unwrapped patch cover. Serena pressed her palm as flat as she could against it. Watchdog sandwiched her hand in two grippers and pressed together hard. Serena wished that NASA would have specified that these crew assist bots should have faces—something to focus on if your life was literally in its hands.

They switched to her left hand, which was harder. Since the right hand was patched, there was less area for the air to exit the suit, so it was hissing out at higher velocity. She added an extra layer of patch gauze, used more goop, and Watchdog pressed the cover into her palm for longer.

“You have one hour, three minutes and thirty two seconds of air, and dropping,” Watchdog said.

Dropping.

Of course it was still leaking.

“How fast is the leak? In minutes.”

“Three minutes every ten minutes.”

Less than one hour to change out this backpack. And the more she moved her hands, the faster that leak would get.

She had to return to Base as soon as possible. And she couldn’t pilot the rover and change the backpack at the same time.

“Watchdog, grab that stone. Stow it in the sample locker.”

“We should retu—“

“—I’m not returning to Base without that stone. Stow it then help me with backpack replacement.”

Serena bounded over to the rover and walked up the cargo ramp. Watchdog followed in her footsteps holding the stone in two grippers. A river of purple dust poured in the stone’s wake.

Serena didn’t think anything of it at the time.

Once Watchdog was aboard, Serena toggled the rover to tilt its cargo bed horizontal. She eased herself into sitting on a tool box. Watchdog stowed the stone then settled itself at Serena’s feet. It rummaged in its saddlebags for the wrenches they’d need for backpack changeout.

Serena would need a clear head to go through the procedure.

If she turned autopilot back on, immediately Commander would be in her ear. She didn’t have much choice. The more she moved her hands, the stronger the leak. She couldn’t drive, and the backpack changeout should happen in parallel with closing the distance back to Base.

She took a deep breath.

“Rover, enable autopilot. Return to Base.”

An immediate ping overrode the rover’s audio acknowledgement.

“Santiago, report,” Commander said over the radio.

The time for guilt and shame was later. Now she had obligated the Base to assist. They would take care of repercussions later.

“Location about three hours’ ride southeast toward Shoemaker. My suit has multiple leaks in both gloves. Patches holding but leaking three minutes every ten for now. I have a spare backpack. The exchange process may exacerbate the glove leak.”

“Standby for instruction.”

Instruction: duct tape plastic sample bags around each wrist as a secondary pressure vessel. Serena had to report she had foolishly left all those bags behind when she’d offloaded the unnecessary scientific equipment.

New instruction: let Watchdog replace the backpack and for Serena to sit with her damn hands still while Base recalled the rover via autopilot.

It was hard to sit still on a rover surfing the terrain while air bled out of her hands.

Serena had nothing better to do than watch her suit pressure and air supply deplete. Which was a good way to imagine dying. If pressure dipped under 1psi this far out from Base…

Well. On the plus side, she’d be dead in about a minute.

She watched the stars and for the first time, missed her garden back home.

A mile away from Base, the rover heaved mightily, juddered, then went still. The lights went out.

Serena stared at the walk ahead of her—the lights of Base were plainly visible, in that way that everything on the moon seemed closer than it was—like a mirage.

Watchdog beeped a series of tones, sounding snotty.

“Serena, you must sit in my cargo bucket and I shall carry you.”

Serena laughed at the bot. This was not in its protocol—carrying  three hundred pounds of moonwalker. Also, Serena didn’t take orders from Watchdog.

“Serena, we saw rover cut out. Watchdog sent diagnostics and is presenting an option to carry you,” Commander said.

“I can walk! The holes aren’t in my boot—“

“—Serena, Watchdog is reporting your suit leak has accelerated. Climb aboard. Watchdog will strap you in.”

Watchdog did indeed strap her in. With duct tape. The betrayal stung. She was trussed up like a prisoner going for judgment.

She found herself giggling helplessly imagining how she must look.

The Hab was less than a quarter mile away when Watchdog stopped. Serena’s suit pinged critically low pressure nearly simultaneously.

Watchdog halted and was attaching the two hour backup oxygen bottle from its saddlebags to her backpack before Commander even approved it.

Or maybe Serena wasn’t properly listening.

Her tongue was fizzling like poprocks.

Serena’s training kicked in and she emptied her lungs to the tune of oxygen hissing into her suit at speed. The pressure gauge waggled uncertainly.

Watchdog and Commander were trading snappy comments she couldn’t keep track of.

But maybe she was laughing too loud to hear them.

She thought Watchdog began to move again. Perhaps she was imagining things, but someone seemed to be hauling Watchdog. Who on god’s pockmarked moon had the strength to do such a thing? The white of her rescuers’ suit drew Serena in like moth to flame.

She was falling.

She was following the white light.

She was

~~~~

The lights in the medi-bay bore into Serena’s eyes—appropriate for the interrogation she was under.

Dr. Ramirez was politely interrogating her vitals and briefly removing her oxygen mask to lift a cup with something ghastly to her lips.

Commander Hoffman was interrogating Serena’s intentions less politely. She ticked off offenses on her fingers one by one.

“So you stole a rover, a spare life support pack, a Watchdog, and a suit—billions of dollars-worth of taxpayer assets—and you were planning…?”

“How long have I been out?” Serena croaked.

“Eight—“ this from a surprisingly sturdy-sounding Ramirez.

“—You’ll get a full medical rundown after I’m satisfied, Santiago” Commander snapped. “You’re perfectly fine, thanks to Silva.”

“Commander, I must insist, Santiago is not fine,” Ramirez said. “We just removed her from hyperbaric therapy. I have hours left of treatment protocol. Please.”

He stood up, one hand open toward the door, head bowed in deference.

Serena was spared what surely was fire in Commander’s eyes, but she left without another word.

This Ramirez wasn’t half bad—why had they never spoken before? Serena smiled weakly under her mask.

Ramirez smiled back and ran his hands over his shaved head. “Really good thing Silva is a body builder, eh?”

“Marylin really pulled me that last bit? I thought I was imagining things.”

Ramirez sat next to Serena and lifted the cup again.

“Between you and me, this doesn’t help my hopeless schoolboy crush on her.”

“Ramirez, I made a discovery,” Serena blurted, suddenly inspired. “You should work with Silva to get it. Has the rover been recovered?”

Ramirez gazed at her, his eyes gentled like she was a child who’d just finished a particularly grueling bit of schoolwork. “Ice?”

Serena shook her head. But now confronted with having to say the word ‘alien’ aloud, she couldn’t.

“Better. It’s very hard to explain. I…need help assessing the sample. Help Marylin get a stone from the sample storage on the rover. Then work with her to download the photos from my suit.”

Ramirez sighed. “You’re a bad influence.”

“Billions of taxpayer dollars-worth, don’t you know?”

Ramirez laughed.

To be concluded in Episode 6…

Author’s Note

In which I shake my pom-poms about organic Life Support

What do you think of when you hear the words “environmental sustainability”? Video montages of jungles disappearing and polar bears drowning? Maybe lumbering elephants, great planet-sized commas of whales punctuating vast oceans? Smiling farm children gnoshing on strawberries without a care in the world?

What’s this say to you? “Look what Mother Nature IS—look at the violence of her indifference and the staggering colors of her generosity! Look what you’d be giving up if we upset the delicate balance of her tapestry!”

I think the marketing is missing something, and it’s important to get it right. Fundamentally, human empathy is hard to coax to the table this way. Big, broad, complex problems that fix nice-to-have or distant problems don’t compel us. We need a neurological software upgrade. (For a really fantastic study on this human empathy problem, I recommend Paul Bloom’s book Against Empathy)

When I was young, a swashbuckling privateering type in a fantasy novel said something like, “I admire altruism, but I don’t understand it. I understand want. I understand need.”

This is how I feel about the sustainability messaging, and how—morbidly perhaps—space industry can help.

Empathizing with a proverbial fish out of water is a great, visceral hard line into appreciating Earth for the fundamentals of pressure, temperature, oxygen, etc. Conversely, strawberries and whales are far down Maslow’s hierarchy of human needs, which doesn’t even bother to mention these things. It just assumes you’re on Earth in this blink of an eye cosmic moment. (silly Maslow).

So next time you hear something vague about saving the whales or getting a handle on greenhouse gases, refer instead to the fundamentals of your next breath. This is the only planet we know of today where you can stand naked as the day you were born and not die in 13-90 seconds.

That’s a really tough thing to replicate with technology. Hundreds of millions of dollars-worth of investment have gone toward replicating that in space.

So, if you want to hug a tree, I support you. Or you could just appreciate the luxury of being a human on Earth. Appreciate that your saliva isn’t boiling out of your mouth and organs. Appreciate that each breath is easy and air simply exists and isn’t taxed (yet).

This planet is your organic life support. Appreciate her.

Science In Real Life

What Serena’s depressurization predicament and airline Oxygen masks have in common:

In this chapter, Serena briefly suffers from a dip in pressure inside her suit due to the leak in her gloves and endures dangerously low pressure below what’s referred to as the “Armstrong limit”. {Not for Neil, this was another pilot-type explorer guy}.

The Armstrong limit is the pressure at which water at the human body’s natural temperature (99F) will boil.

That pressure is 1 pound per square inch (psi). At this point, humans will experience a dangerous phenomenon where saliva, tears, urine, and liquid in the lungs begin to boil. As you can imagine, this is fatal if the crisis is not averted in under 60-90 seconds.

In my story, like the old Apollo lunar suits, the air mix in Serena’s suit is actually 100% O2, at only 3.7-4psi. For reference, air at sea level on Earth is about 21% O2 and most of the rest is Nitrogen at 14.7 psi of ambient pressure.

Why, you ask? Why operate a suit at 4psi—so close to the Armstrong Limit of 1psi? Why reduce the pressure at all?

One reason lower pressure is useful in a spacesuit is to make it easier to move and work in. Suits have (so far) been pressurized with forced air. Imagine putting a construction worker on Earth in one of those fun, inflatable sumo suits and asking them to wield a shovel or operate a vehicle. The higher the pressure, the more rigid the suit is, and the more astronauts have to work against the suit to get anything done.

Fun fact, the ambient pressure level and oxygen percentages for NASA’s next generation suits for the Artemis lunar surface missions are very much still in the trade space!

So, we’ve made sense of why we need lower pressure in a suit.

Why 100% Oxygen? Isn’t that crazy flammable?

Way before your internal water boils off at 1psi, you’d start to experience another dangerous phenomenon down around 10psi unless you have access to higher concentrations of Oxygen than your sea level 21%. This phenomenon is called Hypoxia, which anyone who’s Googled why airlines have O2 masks is familiar with. Let’s bring this closer to home and talk about those airline Oxygen masks.

To offset the drop in pressure as the plane climbs in the sky, the cabin begins to pressurize to simulate lower altitudes to keep the Oxygen density comfortable for you to breathe without a mask. If there was a sudden loss of that pressure and you are exposed to the local atmospheric pressure, you have to have access to a higher percentage of O2. This increases the amount of Oxygen you breathe in on each inhale. The average adult human breathes in about .26 grams of O2 at sea level where most of the ~1 liter of air pulled into the lungs is made up of Nitrogen. Starting at only 13,000 feet (well below cruising altitude of ~40,000 feet!), the air density has dropped so you’d only be able to breathe in about .17 grams of O2 on each 1 liter breath. This is the line in the sky at which humans start to lose the ability to concentrate, and feel euphoric before ultimately passing out, or worse, if the situation is not averted.

Photo Credit AircraftSystemsTech.com

Back to Serena’s space suit predicament: at her suit’s pressure of 4psi, she has 100% O2 so on each inhale, her lungs are able to onboard enough Oxygen. But after her suit’s pressure wilts toward 1psi, there’s no amount of available Oxygen to save her because she has that other problem: the water in her body is boiling off!

Fortunately, there’s not a place on Earth where you can accidentally stumble into a 1psi scenario, though you can certainly head to lower pressures on terra firma. Denver, Colorado, for instance, at 5,000 feet, features a drop from 14.7psi to about 12psi, which is sufficiently strange to visitors. Mountain climbers heading for the tallest mountains like Everest (at about 30,000 feet and 4psi) either bring Oxygen tanks, or train hard to adapt to the environment— but this has been incredibly rare! Only 200 people out of the 4,000 that have sumitted Everest managed to adapt without supplemental Oxygen—but that’s a whole other story.

Disclaimer

Though I am aiming to write near-future sci-fi with the boost of accuracy granted me as a space industry professional, there are many ways I take artistic license. Any resemblance to my employer’s or customers’ technology or their private technical development strategies are purely coincidental. I will not write about topics that are too conflicted to avoid the appearance of impropriety. The sci-fi section of my newsletter is fiction inspired by scientific advances that are described in the public domain, or already published at trade shows or other vectors. Primarily, I lean on what NASA and space companies advertise, but quoting and annotating everything as fact or fiction would infringe on the enjoyment of the story. If you have questions or concerns about something I’ve written, please don’t hesitate to reach out!