Sciency Words: Shirt-Sleeve Environment

November 23, 2018

Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of science or science-related terms so we can expand our scientific vocabularies together.  Today’s term is:


I’ve seen this term, or terms very similar to it, in a lot of different places.  It’s usually obvious what it means from context.  A shirt-sleeve environment is an artificial environment where humans can wear ordinary clothing in safety and comfort. The cabin of a commercial airliner is a good example.  So is the interior of the International Space Station.

In the early days of aviation, pilots were far more exposed to the elements than they are today.  They had to wear specialized clothing, especially for high altitude flights.  It gets really cold up there above the clouds, and the air is very thin. Pressure suits were often essential, and in some cases those early pilots needed to bring supplemental oxygen with them.

There were several experiments in the early 20th Century to create safe, pressurized cockpits.  I guess these were technically shirt-sleeve environments, but they still sound to me like tight and uncomfortable spaces.  Maybe you could have worn your normal, everyday clothing in those cockpits, but I doubt you’d want to.

So the first true shirt-sleeve environment (in my judgment) would have been the Lockheed XC-35, built in 1937 for the U.S. Army Air Corps.  It had a pressurized cockpit, crew area, and passenger cabin, so the crew would have had plenty of room to move around comfortably in their comfortable clothes.

Apparently the Army called this a “supercharged cabin,” not a shirt-sleeve environment.  Based on what Google ngram tells me, it seems the term supercharged cabin was replaced with shirt-sleeve environment by the end of the 1950’s, right around the time the American space program was getting started.

As this 1960 paper from Boeing Airplane Company explains, “The term ‘shirt-sleeve environment’ means that the crew would be comfortable in this environment without any special equipment such as pressure suits.” And according to this 1958 paper on the structural stability of spacecraft, “Shirt-sleeves can become the normal flight clothing in sealed cabins under [sea-level type] conditions.  In terms of human performance, the advantages of a sea-level atmosphere have been clearly demonstrated by the experiences of Ross and Lewis during the recent Strato-Lab High 2 and 3 flights.”

In modern space exploration literature, the International Space Station is typically cited as the most impressive shirt-sleeve environment yet constructed.  The term is also used to describe the kinds of habitats we’d like to build for ourselves on the Moon, Mars, and elsewhere in the Solar System.

So remember: when you’re packing your bags for space, you don’t have to be too picky about which shirts you bring.

Sciency Words: Garn Scale

September 7, 2018

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


In 1985, Senator Jake Garn of Utah became the first sitting member of Congress to fly in space.  Florida Congressman Bill Nelson followed a year later.  I guess NASA felt it would be good for somebody in Congress to see firsthand how the money for the space shuttle program was being spent.

Senator Garn’s Wikipedia page quotes several astronauts. Apparently not everyone was thrilled about Garn’s mission, but some of them had nice things to say. Astronaut Charles Bolden, who would later go on to become NASA Administrator, said:

Jake Garn was the ideal candidate to do it, because he was a veteran Navy combat pilot who had more flight time than anybody in the Astronaut Office.

And Charles Walker, one of the astronauts who flew with Senator Garn, had this to say:

[…] I think the U.S. space program, NASA, has benefited a lot from both his experience and his firsthand relation of NASA and the program back on Capitol Hill. As a firsthand participant in the program, he brought tremendous credibility back to Capitol Hill, and that’s helped a lot.

Jake Garn may have had a lot of piloting experience before his mission, and afterwards he may have had a lot of positive things to tell his colleagues in Congress, but the mission itself… well, let’s just say weightlessness did not agree with the senator’s stomach.

As a result, Garn’s name has become something of a slang term at NASA.  The Garn scale is an informal, off-the-cuff system to quantify how space sick someone becomes while in space.  Apparently it’s not unusual, even for the most experienced astronauts, to get a little space sick.

A zero on the Garn scale represents not getting space sick at all.  If you do get sick, you’ll probably score a tenth of a Garn, or a quarter of a Garn—some fractional amount of a Garn.  It’s said that no one has ever reached one full Garn’s worth of space sickness, except of course, Senator Garn himself.

Hopefully the senator has a sense of humor about all this.

Sciency Words: Space Adaptation Syndrome

August 31, 2018

While doing my recent research on hypogravity and its effects on the human body, I’ve seen the term space adaptation syndrome come up a few times. I figured it would make a good Sciency Words post. Then I discovered, to my surprise, that I’d already done this one!

So today I’d like to present to you, apparently for the second time:


Yeah, we could just call it “space sickness,” but this is Sciency Words, so we have to call it “space adaptation syndrome.” Because NASA has a rule that all space related terms must be turned into acronyms, we can also call it “S.A.S.”

Most astronauts experience space adaptation syndrome at some point, usually during training or during their first few days in space. Relapses are also known to happen. As you can imagine, NASA really wants to figure out what causes S.A.S. and how to prevent it. This is one of the reasons they recently left an astronaut in space for almost a full year.

Mr11 Year in Space

This is totally how the year in space mission happened.

At present, S.A.S. seems to be similar to motion sickness. It is also sort of the exact opposite of motion sickness. Think of it this way:

  • Motion sickness: your inner ear senses motion, but your eyes do not (because you’re playing with your phone in a moving car, for example). In this case, your eyes are feeding your brain false information.
  • Space adaptation syndrome: your eyes see that you’re moving (or not moving), but in the absence of gravity, your inner ear hasn’t got a clue what’s going on. So in this case, your eyes are trustworthy; it’s your inner ear feeding false information to your brain.

The good news is that we humans can adapt. Our brains learn to rely less on our inner ears, allowing the business of human space exploration to continue.

The bad news is that once we humans adapt to space, returning to Earth becomes a problem. I’m not talking about bone loss or muscle atrophy. I’m talking about balance. All of a sudden, your inner ear is working again, and your brain has to relearn how to do this balancing and walking stuff.

There is also a concern—and I’m not sure how seriously to take this concern—that the human body might adapt too well to space. You might spend so much time up there, becoming so acclimated to zero-G, that your brain and inner ear will never function properly together again. You’ll never walk again. You’ll never be able to come home. You’ll be stuck in space for the rest of your life.

That would suck.

Or maybe it wouldn’t. To be honest, if I ever get to go to space, I probably won’t want to come back anyway.

P.S.: Here’s a bonus Sciency Word: lead-head. Lead-head is what astronauts call immunity from space adaptation syndrome.

How to Walk in Hypogravity

August 29, 2018

As a science fiction writer, I really wish I knew what it’s like to walk on the Moon or Mars or any other low gravity world.  It would help a lot with that whole “writing from lived experience” thing.  Of course there are ways I could experience hypogravity for myself, but I don’t have that kind of money.  So instead, I’ve turned to medical research papers like this one from Frontiers in Physiology.

First off, let me just say this: I’ve read some really complicated stuff over the years, but I don’t think I’ve ever read anything as complicated as a scientific paper trying to describe how we humans walk.

But if we want to understand what it would really be like to walk on another planet, we have to start by understanding—in meticulous mathematical detail, apparently—how we do this walking thing here on Earth.

Gravity Makes Walking So Much Easier

The mathematical relationship between walking speed, leg length, and gravity was determined back in the 1870’s.  It was later used in what sounds like a rather whimsical research paper about the walking pace of the Lilliputians from Gulliver’s Travels.  And then it was used for more pragmatic purposes to estimate the running speeds of dinosaurs.

For those sorts of calculations, the force of gravity would have been treated as a constant, but gravity can easily be treated like a variable, and that’s when things get interesting.  You see, when you walk, your body uses energy to complete the full arc of a footstep, especially at the beginning when you’re lifting your foot off the ground.  But gravity helps you (perhaps more than you realize) when your foot comes back down to the ground.

So if you reduce the force of gravity, gravity provides you with less assistance, and you end up having to expend more energy to complete each step in your walk cycle.

Walking-Mode vs. Running-Mode

The muscle actions involved in walking and running are different enough that there’s no real grey area between “walking-mode” and “running-mode,” as that paper from Frontiers in Physiology calls them. These two “modes of locomotion” take advantage of gravity in distinctly different ways.  Walking-mode ends up being more metabolically efficient at slower speeds, and running-mode is the more metabolically efficient way to travel at higher speeds.

So what happens when you alter the force of gravity?  The transition point where running-mode becomes more efficient than walking-more changes too. Lower gravity means your body will naturally want to switch modes at a lower speed.

On the Moon, for example, walking-mode only works well when you’re moving very slowly.  To achieve what we might consider a normal walking pace, you’ll have to switch to running-mode.  And if you want to reach Earth-like running speed, you’ll probably have to try hopping-mode or jumping-mode—modes of locomotion that we don’t use often here on Earth except under certain specialized circumstances. Skipping-mode also seems to be more metabolically efficient on the Moon than it is on Earth.

Moon-Walking or Mars-Walking in Science Fiction

I’ve read plenty of Sci-Fi stories set on the Moon or Mars. For the most part, I feel like science fiction writers just mention the reduced gravity thing in passing and then move on with the story as quickly as possibly.  I don’t blame them.  It’s really hard to imagine what hypogravity must feel like, and even harder to communicate that feeling to readers.

But one of my highest ambitions as a writer is to write something that makes you feel like you’re there on the surface of a hypogravity planet like Mars.  I want to capture that experience of “running in order to walk” and “hopping in order to run.”  Hopefully this line of research will someday help me pull that off.

Sciency Words: G-Shortage Illusion

August 24, 2018

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


I guess this isn’t a real scientific term, at least not yet. The authors of this paper are proposing this term to describe a problem people living on the Moon or Mars may have to deal with in the future.  For colonists, many a sprained ankle or broken bone (or punctured spacesuit) will probably be blamed on the G-shortage illusion.

The human inner ear, which regulates our sense of balance, is sort of hardwired for Earth’s gravity.  The inner ear expects you to feel 1 g of force—no more, no less—due to the planet’s gravity, and it uses that 1 g of force to figure out which way is down.

But imagine you’re a fighter pilot doing all kinds of crazy maneuvers in midair.  Your inner ear has to do some math to keep track of where you are, and which was is the ground, so you don’t crash.  Now if you happen to turn your head while simultaneously pulling a hard turn with your aircraft, your inner ear could make a serious miscalculation.

This is a form of spatial disorientation known as the G-excess illusion, because it happens when you’re experiencing excess G-forces. It’s a well documented and well understood phenomenon, and pilots who aren’t adequately prepared for it can end up making fatal errors while flying.

The G-shortage illusion is sort of the same thing, but it’s caused by the opposite reason.  Imagine this time you’re an astronaut on the Moon or Mars or some other world with hypogravity.  You take your first step.  At the same moment, you happen to turn your head.  Your inner ear gets confused, and as a result…

Until I started learning about hypogravity, I didn’t realize how often Apollo astronauts lost their balance and fell over while trying to explore the Moon’s surface.  The G-shortage illusion in action, it seems.  Fortunately no one was injured, and no one damaged their spacesuit… but they could have.

So dear readers, if any of your are planning to move to the Moon or Mars, tread carefully!

P.S.: While researching for this post, I found this article from Naval Aviation Newsvery interesting.  It’s written by an artist who was hired by the Navy to do caricature drawings about various forms of spatial disorientation, like the G-excess illusion.  Those drawings were then used as visual aids in flight safety training.  If you’re interested in how art contributes to STEM, this article is worth a look.

Sciency Words: Hypogravity

August 17, 2018

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


We have a pretty good idea how the human body operates in Earth-normal gravity (1 g).  We also know a lot about how weightlessness (0 g) affects our bodies. But what about values of gravity between 0 and 1 g?  According to this review from the journal Frontiers in Physiology, our knowledge about the human body in so-called hypogravity is shockingly limited.

The word hypogravity combines the word gravity with the prefix hypo-, which comes from a Greek word meaning “under” or “below.”  It’s defined as an actual or perceived gravitational force greater than 0 g but less than 1 g.  The term hypergravity (from a Greek word meaning “over” or “above”) is also used for gravitational forces greater than 1 g.

According to Google ngrams, the term started appearing in print during the 1950’s, which would coincide with the early days of the space program.  My first encounter with this term was in an article titled “Medical Skills for an Interplanetary Trip: The Hostile Environment of Space and the Planet Mars,” which appears in this book about the Mars One program.

I can’t remember ever seeing this term prior to that article, which kind of surprised me at first.  But based on my subsequent research, I think this term is used almost exclusively in the medical field, an area which I’m not well versed in.

According to that paper from Frontiers in Physiology, we know very little about what hypogravity does to us, medically speaking.  Of course we do have the first hand accounts of those few astronauts who’ve walked on the Moon, as well as other records and archival footage from the Apollo program.  Frontiers in Physiology also describes several ingenious ways scientists have learned to simulate hypogravity in the laboratory.  And we have mathematical models to help us predict what hypogravity might do to us long term.

But still, our knowledge and experience with hypogravity “remains fragmentary,” as Frontiers in Physiology puts it.  “Fragmentary” seems like just the right word, because old records, laboratory simulations, and computer models can only tell us so much.  We have very little to go on here.  Just bits and pieces. A few scattered data points.

The human body evolved in a 1 g environment.  Prolonged weightlessness seems to do our bodies a lot of harm, from bone loss and muscle atrophy, to disrupting the balance of our internal fluids, to messing up our equilibrioception (a “sixth sense” most of us don’t realize we have until it’s taken away).  I’d assume hypogravity does less harm than weightlessness.  The question is: how much less?

I guess we won’t really know the answer until we start sending people to live on the Moon or Mars long term, and start finding out which health problems they do or do not develop.

Sciency Words: Encephalization

April 20, 2018

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


I’m going to let my friend Og the Caveman handle the definition of this term.  Og?

Thanks, Og!

The process of encephalization was rather important to humans of Og’s time.  The term refers specifically to the gradual, somewhat clumsy evolutionary process whereby an organism’s brain becomes larger over time.  The word itself derives from the Greek word for brain, which in Greek appears to be a compound word (en+ kephale) meaning “in the head.”

My first encounter with this term was in a recent issue of Scientific American, in an article about the social behavior of whales and dolphins.  According to the article, brain size can be correlated to social behavior.  Animals that have evolved larger brains (relative to overall body mass) tend to have more complex social interactions with each other and also tend to live in larger social groups.  This seems to be true for both primate and cetacean species.

Now it seems pretty clear to me that the word encephalization is intended only to describe the gradual process of brains growing larger over time, over the course of many, many generations of evolution.  It would be totally inappropriate, therefore, to use the term as part of the origin story of some brainiac super villain… to write about an “encephalization machine” that went haywire during a top secret government experiment.

Nope.  It would be woefully inappropriate to use the word in that way.

P.S.: Though if some hack of a Sci-Fi writer were to do that, don’t be surprised if the encephalized brainiac super villain teams up with that Mars rover NASA reprogrammed for science autonomy.