Tuesday, February 16, 2016

How best to Squeeze the body, or Pressure suit design.

First, suits have different functions, like any clothes. As an example, you wouldn't wear football pads swimming, or a SCUBA wet suit hiking in the desert. Because spacesuits are highly engineered structures, they are designed to do there primary function as best as possible.

First, for inside the spacecraft for emergency protection you have an IVA suit. (Intra-Vehicular Activity). Then for outside the spacecraft for spacewalks or planetary walks an EVA suit (Extra-Vehicular Activity). Mobility is the key for either of these. However, in an IVA suit, the engineer is more concerned about reducing bulk and increasing comfort of the suit in an unpressurized sate. Because, unless there is an emergency loss of pressure (Bad thing), the IVA suit will never be pressurized, so you want it to be comfortable when not inflated. An EVA suit on the other hand, is always used pressurized, so it needs to have the best mobility possible. But getting good mobility is very hard to do. Once a suit is pressurized to that minimum required pressure, it turns into a rigid structure. Think of a volleyball un-inflated, then inflated. A huge difference in stiffness. (Volleyballs are inflated very close to minimum suit pressure)

So, how do you make a pressurized balloon around a human body, that, with life sustaining pressure, allows the occupant to move? According to the movies, any fabric bag will do, as long as you add some plumbing fittings on the front, a neck ring and a helmet.

The biggest difference, is Hollywood (in most cases) doesn't care to show a suit as it would look pressurized. So the suit can be baggy, and have all sorts of "cool" looking things on it, that in a real suit, would not be practical or allow the suit to function. The pressuried bit is the main function of a "pressure suit" so you would think you would think that would be important in a design. But since most people have no clue how a suit works, they are blissfully ignorant of this fact.
If you look back a "old" movies, the spacesuits look pretty ridiculous.
It seems that movie spacesuit designs have improved (Read more believable) in recent years, but have they? Many of the suits used in 1950's Sci-Fi movies where based on the real suits of the time.
Here is a "Tomato worm" suit of the 1950's (left) and the suits from the 1950 movie "Destination Moon"






Or from the 1960's the ILC SPD-143 Apollo suit (International Latex corporation) and Major Matt Mason's spacesuit


More recent spacesuit designs in movies want to be slimmer, less bulky, so they copy Mechanical pressure suits (MPC). This design tries to wrap the body with a tight layer of stretch fabric to apply the appropriate amount of pressure to the body.
A suit mock up from MIT (left) and the suit from "The Martian" (Right)

While the idea sounds great "Just slip on the "spandex" body suit and go into space". It isn't very practical. To apply the amount of pressure to the body to keep your blood from boiling, the suit needs to be very tight. In fact, even the tightest Spandex suit wouldn't work. You would die. The MIT suit tries to do this with lines of force across the body in directions that don't change length, but after 15 years of "development" they don't have a working suit, just this mock up. Could it work? Perhaps, MPC suits have been around since the 50's. But they have too many "side effects". Such as, the fact that you are covered with hair and each follicle of hair originates from a "pit" on the surface of your skin. The MPC suit can't apply pressure to these small pits in you skin, so when exposed to a vacuum, the blood pools in these areas giving you a "Hicky" everywhere there is an area of the skin not pressing against the suit. In addition, you have too make sure the suit pressuer on the skinn is very even, or you get "hot spots" on your skin. Like the elastic band of you tighty whities digging into your waist after a long day. So while this is a "cool" idea, it is not as practical as a gas pressure suit.

So while it seems movie spacesuit designs have gotten better, I think the general public's education and familiarity with spacesuits has improved. I mean we have now had people in space for nearly 50 years and continuously for the last 16, so movie costume designers have to make more detailed and complex suit designs these days to make them seem  more realistic. But they still have the same design issues, and most movie suit could not be built to really work. But it's a movie, who cares. In most cases, I'll watch a movie and not care about such things. However, other time it bugs me. In recent years the Studios advertise space movies as superior in there accuracy and promote the fact that scientists and experts have been hired to insure the realism of the film. Perhaps...but no one seems to have hired people that know how real spacesuit have to function.

I mean, how would you hook up the hoses on these helmets from "Interstellar", and still get the helmet on you head?

Also when the suit pressurizes these hoses get stiff and it would be very difficult to turn you head. Why would you add hoses to the back of the helmet anyway? Also the neck area would inflate and the helmet would be pushed up over you head. But I'm nit picking details here. There are however many issues with the suits design and mobility, but you have to really know how suits work and the limits of materials and physics.
BTW the old excuse "But, in the future we will have new materials that....." doesn't hold up. In 60 years of pressure suit design, no material improvement has radically altered the way a pressure suit can to be made. In fact there are very few examples of a material improvement completely changing how we build something to work around physics.

So whats the issue?

A pressurized cloth suit is deceivingly complex. When fabricating a suit from fabric, you have to think of fabric as a bunch of "Cables" that just happen to be woven together. This is because when sewing the suit together, each thread of the fabric has to be tensioned evenly and correctly or your suit, when pressurized will warp and twist into a pretzel. Also, when you pressurize the suit, all these "cables" of your "non-streach" fabric tighten up and the whole garment grows. In fact, it grows a lot.
Here is Orbital Outfitters IS3 IVA suit unpressurized (left) pressurized (right)



The bent over look of the suit under pressure is because the suit is designed to be in a seat and this bend at the waist helps keep the suit from trying to straighten out and push you out of your seat.

If I was to make a cube out of very stiff fabric and pressurize it, it would turn into a ball with nubs where the corners were. Another issue with a suit, is mosy people are not round, we are more oval shaped. When yo make an oval suit and add air pressure, it goes round. Making it difficult to bend these now round joints.

Here is an Apollo suit without it's cover layer. (The white outermost layer, that nevr comes under tension)  You can see all of the cables, bearings, rubber joints. These are what makes this suit work. Without them, the suit would be an un-bendable fabric balloon.


Even with all these specialized joints, you could not bend over and touch the ground.

Why can't you bend easy? As you bend your joints, the volume of the pressure suit changes. As the volume changes, the pressure changes. the greater this volume change, the bigger the pressure increase So, bend you elbow and the volume decreases which causes the suit pressure to rise and this increase of pressure, wants to force the arm back down to the largest possible volume again. The elbow and knee problems are basic and there are many successful solutions, hip joints and shoulder joints on the other hand, which have to move in many directions are the big problem. Bend over at the hips and there is a very large volume change, and the suit wants to spring back.

Here is the IS3 suit in a kneeling position, a bit of a "hat trick" for an all fabric suit.





This is why there are spacesuits made from hard materials. These designs increase the range and ease of mobility greatly by using mechanical design to maintain a constant volume.
 I'm not a good enough writer to explain all of the issues (Nor are you probably wanting to read that much) So just be assured, there are so many things in suit design that are unseen until you have worked with them. Every solution you may think of, has either been tried or has 3 obvious (to a suit engineer) problems that keep that idea from working. Think of spacesuit design, as deep and involved as the game of chess, but you are only given half as many pieces to come up with a wining strategy.

Too a mechanical engineer and "Problem solving junkie" spacesuit design is irresistible.



I'll try to continue this with why these suits have all this hardware, as well as a look at other suit designs...

Thursday, January 23, 2014

What is a spacesuit and why do we need them.


Pressure Suits- AKA Spacesuits

Why do we need space suits? “To go in space.” Well yes, but what is “Space”?
In my 30 years of doing work involving spacesuits either real or movie suits, I have found most people do not have a clear understanding of why spacesuits are used or how they work. If you try to learn about spacesuits from movies, well…. let’s just say you won’t. The network news isn’t much better. In most cases people think a spacesuit is just some sort of one-piece jump suit with a helmet, filled with air. You know, to keep “space” out and protect the astronaut.
But before I talk about the suit, let me paint a picture of the environment it’s protecting you from. Because in order to understand what a spacesuit is and why we need one, you really must first understand how our planet’s atmosphere works. This is one of those subjects that peoples lack of understanding makes it nearly impossible to have that “Ah Ha” moment without a bit of the basic science. So I’ll try to make it as simple and clear as possible. (I know, you hated science class, but it is really very simple.)
We live at the bottom of a very deep ocean, an “Air ocean”. We all know about the earths water oceans, those big deep places that water accumulates. Well we live in something very similar to those but instead of water, air accumulates, and not just in the “deep” places, but over the entire planet, held by gravity. In our water oceans, the deeper you go, the more weight of water is above you and so the pressure goes up. Air does the same thing.
The difference is, a liquid, in this case water, cannot be compressed. While a gas (Air) can be.  So the deeper you go in the water ocean, the pressure goes up, but the waters density does not. Visualize block of hard rubber, no matter how hard you squeeze, it doesn’t get smaller. In our “gas ocean” it’s much different, because a gas can compress with pressure, so the gas at the bottom is much denser than the gas above. Visualize a rubber sponge, the more you squeeze it, the smaller and denser it becomes.
Now, because we are at the very bottom of this “air ocean”, where the air is compressed by the weight of all of the air above, we are used to “dense” air. Which is OK, because we have evolved to function very nicely on this dense, compressed gas we call Air. You have heard the term “sea Level”, that is, as it sounds, where our water ocean begins. As gravity pulls everything towards the center of the earth, heavier object sink to the lowest point (I know, DUH!) the deepest point in our water ocean is about 7 miles, but, If we measure the depth of our air ocean, it is around 65 to 75 miles deep. Sea water is 748 times the density of our air at sea level, this means every 33ft / 10 meters of seawater weighs the same as 75 miles of air. The weight of our atmosphere at sea level is 14.7 Pounds per Square Inch (PSI) or 101.3 Kilopascals. (kPa) (For the metric side of the table) That’s like having a very large house cat laying on every square inch of your body. Given the average person has between 2300 and 3100 square inches of skin, that’s a lot of cats and a lot of pressure. So, why do we care about the pressure?

Our Air is made up of many different gasses, but for now, Oxygen, Nitrogen and Carbon Dioxide are the three we care about here. Nitrogen makes up 78%, or over ¾ of our “Air”. Oxygen accounts for 21% less than ¼. That leaves 1% for all the other gasses. We only use the Oxygen, referred to as O2. The Nitrogen (N2) is “filler” and we don’t use it for bodily functions. So when we breathe in, less than a quarter of our lung capacity is filling with the only gas we need to survive O2. But because we are at the bottom of the air ocean, this O2 is pretty dense, so we are OK with that percentage. In fact, at this “sea level” density if we were to breathe pure oxygen, it would kill us. To give you an idea of how “squishy” gas is and how it compresses and gets denser, remember me saying our atmosphere was between 65 and 75 miles thick, well if you weighed the total amount of our atmosphere, 50% of it is in the bottom 3.5 miles and 90% is in the bottom 10 miles. (For more detail about our atmosphere: http://en.wikipedia.org/wiki/Atmosphere_of_Earth)
Given these facts, most of us cannot function above 27,000 feet without additional oxygen. (There are some humans that have developed the ability to function at very high altitudes without additional O2)  This is why in a commercial airplane, they have those little yellow masks that hopefully you have never had to use. They are there in case of a cabin depressurization. They will supply you with pure O2 so you don’t pass out . This emergency system works great at altitudes below 35,000 feet. However, above 52,000 feet humans run into another issue.

Enough to make your blood boil!

As you lower the pressure around a liquid any gasses trapped in that liquid will come out of the liquid. As you increase pressure on a liquid, you can trap more gasses in it. You see this happen when you uncap a carbonated beverage. Once the cap comes off and the pressure drops, the CO2 bubbles out. Another way you can get gasses to come out of a liquid is add energy in this case, heat. When you boil water, this heat energy causes gasses trapped in the water to come out, this is the bubbling or “boiling” of the water. If you lower the pressure around the fluid, it requires less heat for water to boil. At sea level, water boils at 212 F or 100c. In the city of Denver Colorado, the altitude is 5280 ft or 1609 meters, the pressure is about 15% less than sea level and so water boils at only 202 F/ 94.7C. At Everest base camp (5,545m or 18,192ft.) water boils at only 177F /80C. At the summit 29,029ft / 8848m it drops to 154F / 68C. Well, by the time you get to 52,000 ft, water boils at 97.6 f/ 36.5C or 1 degree below your body temperature. Oops. So even if you had an oxygen mask on, the gas couldn’t get in your blood, as they would already be trying to boiling out. This would result in you suffocating and dying from oxygen starvation and no, you do not explode! (Sorry Hollywood) Now take note, your blood boils at only 9.8 miles, space doesn’t start for another 52.2 miles. But don’t worry long before this happens, you would get altitude sickness, and likely die from symptoms like fluid in your lungs, fever, swelling of the brain, Nausea, Retinal Hemorrhage. However, if you were suddenly exposed to the vacuum of space, as in 2001: A space odyssey or Jim LaBlanc, (http://www.wimp.com/totalvacuum/) you could survive. Your body tissues would swell to perhaps twice size, making you look like a body builder. But because your skin is very strong, your swelling is kept in check and internal body pressure would keep your blood from boiling. However, saliva in your mouth would boil, but as long as you didn’t hold your breath, as this would rupture your lungs, you have about 15 seconds before your brain starts to starve for oxygen and if your were repressurized quickly enough, you could survive.

The Pressure is on

So as you can see, the human body is set up to live at the bottom of Earth’s air ocean and we don’t do so well near the surface (Near space) This is why we need pressure suits. Because without them, our bodies cannot hold oxygen in our blood and our systems can’t cope with the lack of physical pressure around our body. There are two ways to add the pressure to the body, with a fluid, like gas pressure suits or by mechanically squeezing the body known as a Mechanical Counter pressure suit.

Next: How best to squeeze the body…

Tuesday, August 20, 2013

"A Message for Garcia", or another myth about armour.


Over the years I have heard many myths about armour and medieval history. Most of the time now I just shake my head and think how sad. (Although when I was young I believed some of this same BS. and I had a mother who was a librarian.)  But now with the internet, it seemed to me, some myths would be tossed aside, once facts about a subject were so easily accessible. But I was wrong, the internet may make it easy to find facts, but it also makes it easy to spread and elaborate on myths and BS. Since most people do not seem to want to look deeper into a subject or use logic to question things they hear, it is easy to see why with all this available knowledge, myths still perpetuate.

Being in the movie industry, I am often, (and unfortunately) at the heart of a myth spreading vehicle. In my 30 plus years of motion picture work, I have seen authentic, properly represented armour in only a tiny handful of films. Most of these were not main stream Hollywood films.  Hollywood is in love with it’s version of pre 16th/17th Century Europe. Dark, gritty, slovenly conditions and armour that looks like it was made using a rock and a tree stump.  I say pre 16th/17th century because it seems Elizabethan and Cavalier era films are often more accurately represented than earlier history. Although the last couple of films situated in these eras were quit bad. If you go back to the Vikings, Whoa! Hollywood’s version of Viking history would be like depicting 1940’s America as the worst 3rd world country you can imagine. People believe this so much, that if you try to depict the real Viking history, most people wouldn’t believe you.

But earlier this year I read a blog post that seemed to get a reasonable amount of reposts. It was about why you could/ wouldn’t have breast shaped armour in the past. It boggled my mind on how someone could write this, and believe it, let alone the number of people who reposted it without comment or correction. It is so bad, it belongs with Horned Viking helmets and cranes to lift up armoured knights:

Here is an article from the Blog; TOR-COM (http://www.tor.com/blogs/2013/05/boob-plate-armor-would-kill-you )
Never mind the chainmail bikinis—what about those awkward breast plates in armor that we see frequently in fantasy artwork and at the Ren Faire? Whenever women complain about this convention, they are usually shot down for trying to erase women’s true bodies, for insisting that women make themselves more “male” in order to appear strong and capable.
But here’s the thing: those shapely bits of armor would actually get you killed. So the complaint is entirely valid! Now, let’s talk about why.

Let’s start with some relevant history: armor was uncomfortable, guys. It was heavy, hot or cold depending on the weather, and it made you sweat. (Speaking as someone who has donned chainmail shirts before, I can attest to all of these things.) To negate some of its more uncomfortable effects, all armored soldiers wore padded gambesons and the like. Once this padding was added, the shape of the wearer was practically neutralized. So the need for special boob-shaped armor is already suspect at best.
Now we’ll apply some science!

Let’s begin by stating the simple purpose of plate armor—to deflect blows from weaponry. Assuming that you are avoiding the blow of a sword, your armor should be designed so that the blade glances off your body, away from your chest. If your armor is breast-shaped, you are in fact increasing the likelihood that a blade blow will slide inward, toward the center of your chest, the very place you are trying to keep safe.
But that’s not all! Let’s say you even fall onto your boob-conscious armor. The divet separating each breast will dig into your chest, doing you injury. It might even break your breastbone. With a strong enough blow to the chest, it could fracture your sternum entirely, destroying your heart and lungs, instantly killing you. It is literally a death trap—you are wearing armor that acts as a perpetual spear directed at some of your most vulnerable body parts. It’s just not smart.

 
The article has a number of conclusions, or "points of fact" that are wrong, misleading or complete BS.
First:
"armor was uncomfortable" No.  Armour, could be, if improperly made, but armour was everyday technology and very sophisticated. Properly made armour was very comfortable to wear. The issue here, is  currently, there are only 3 or 4 people in the world  making armour, approaching the level of skill of an armourer of the period. So most people who have worn armour today are making conclusions based on ill fitting, poorly engineered armour.  On the jousting show that was on a few years back, one of the guys bragged about “armour bites”, places his armour pinched him or bit into his skin. This is equivalent to a professional race car driver bragging about how many times he crashed because the steering wheel came off in his hand. If armour is made properly, it doesn’t bite you. In fact, it fits like a second skin. Point of fact; Recently I was doing a fitting for a harness, which took a few hours, and at one point I was looking for where I had set down the lower leg armour. A friend pointed out, I was wearing it. I had had it on so long, I had not noticed it was still on.

2: “It was heavy” This is relative, but in this context, misleading. Like stated above, modern reproduction armour is poorly made. In addition, if made for fighting SCA or Steel weapons, it's made much thicker than its historical counterpart. It may not look much thicker, but for example, 12 sheets of notebook paper does not appear very thick or much different in thickness from 6 sheets of paper, but 12 sheets are twice as heavy. Real armour averaged in weight from 30-50 lbs up to specialist jousting armours in the 70 to 100 lbs. Specialist jousting armour is designed for a specific purpose, riding on a horse, in a straight line and hitting an opponent with the point of your lance.  Not just walking around or fighting with a sword or mace. Also quality armour after about 1350 was made from hardened steel. Many of you may not know what "hardened steel" means. Mild steel (what most reproduction armour is made from) and spring steel (what real armour was made from) is like the difference between household window glass and auto windshield glass. By adding chemicals and a different heat process one is considerably tougher and stronger than the other. In armour, to get the same dent resistance and stiffness as its historical counterpart or to satisfy the modern customers desire to have virtually maintenance free armour, most reproduction armour needs to be 1.5 to 3 times thicker in order to approach the properties of spring steel. But even then, mild steel bends and stays bent, where spring steel (hence “spring”) bends and comes back to its original shape. This has a few advantages; One, the armour can be thinner and the plates more “delicate” in construction, Two, it also makes the metal surface harder so thin plates can fit closer together and slide over one another smoother. And perhaps most importantly, the metal can flex and spring back to its original shape, keeping all of the plates closely aligned and smooth.  

 3. it was…“hot or cold depending on the weather, and it made you sweat” Well most clothes are hot or cold depending on the weather, but in my Maximillian armour (a style of armour from the beginning of the 16th century) in direct sun, it isn’t very hot at all. Being polished, it reflects much of the sun’s rays and doesn’t heat up. As far as sweating, well, you do sweat, actually the arming coat is the insulator, not really the armour. However, when I was a  teen, I worked at a movie location/ tourist park called “Old Tucson” located just west of Tucson Arizona. I learned to wear a long sleeve undershirt, a regular shirt with a vest and sometimes a jacket. Yes, in the desert sun. The result, I was much cooler and had to drink less water than the tourist. Why? Because I was protected from the sun’s rays and my bodies sweating was contained by the layers I was wearing, thus controlled. People asked all the time, why I wasn’t seating, I pointed out I was, but far less than they were because my long sleeve shirt was slightly damp and the outer layers kept that moisture from evaporating, thus I did not need to constantly replace that water on my skin to keep cool. But in their shorts and tee shirts, the sweat immediately evaporated and needed to be replenished constantly. I have the same thing in my armour. I wear a long sleeve under shirt, usually linen, with a fitted garment, then the armour. Once your body heats up and starts to sweat, you are “hot”, but then after a while your under shirt becomes damp and your bodies temperature equalizes and it is very comfortable.

 4. To negate some of its more uncomfortable effects, all armored soldiers wore padded gambesons and the like. Once this padding was added, the shape of the wearer was practically neutralized.” Suggesting the padded garment “neutralized” the wearers shape is ridiculous. As described above, some type of under garment was worn, but it didn’t need to be heavily padded. Armour was heavily influenced by fashion so armour was as much style as it was function, so negating the body shape was far from true. In fact, armour and the under garments “shaped” the body to give the wearer the proper silhouette of the particular period. My Maximillian armour gives me a small waist and rounded chest. I haven’t had a small waist since I was 29.

5. Now we’ll apply some science! Let’s begin by stating the simple purpose of plate armor—to deflect blows from weaponry. Assuming that you are avoiding the blow of a sword, your armor should be designed so that the blade glances off your body, away from your chest. If your armor is breast-shaped, you are in fact increasing the likelihood that a blade blow will slide inward, toward the center of your chest, the very place you are trying to keep safe.” Well, I don’t see any “science” here, but to a point, armour’s primary function was to protect. However, there are many examples where fashion far outweighed the need for ultimate protection. Parade armours as well as some field (functional) armours  in later periods were heavily repoussed (embossed with decoration) and the point of a weapon would easily catch on this decoration. Maximillian armour has flutes that run vertically over virtually the entire armour, these too could collect a sword point. They didn’t seem too worried about it. This brings up another fallacy; Armour could not easily be breached by swords, or arrows. Did it happen? Well I’m sure it did, the same way someone wins the Powerball. But the odds are highly against it. By the mid-14th century quality armour was hardened steel and encompassed most of the body. Arrows and swords had little effect, this is why armour was worn. Why you ask did they still use swords and arrows? Because only the very wealthy were wearing full plate armour. Most of the fighting force was not so well equipped.

 6. “The divet separating each breast will dig into your chest, doing you injury. It might even break your breastbone. With a strong enough blow to the chest, it could fracture your sternum entirely, destroying your heart and lungs, instantly killing you. It is literally a death trap” Again, no basis in fact. Properly fit armour will not press an area of your body anywhere near hard enough to cause injury. In addition, a fractured sternum will not destroy your heart and lungs, instantly killing you. This is highly exaggerated BS. For this to happen, you would have to wearing an axe blade inside your armour with its edge resting on your sternum and get hit by a car. (To quote a medical web site: “…sternal fracture from motor vehicle accidents showed a 1.5% incidence of cardiac dysrhythmia requiring treatment and a mortality rate of 1%”, another quote; Management (for fractured sternum)involves treating associated injuries; people with sternal fractures but no other injuries do not need to be hospitalized.)

 So why do we not see armour with “breasts”. Likely, fashion and social conventions. The same reason so many women fought in the American Civil war, disguised as men. It was not considered acceptable for a women to fight. Why don’t men carry purses or wear dresses? Purses are a very convenient way to carry everyday things and skirts are very comfortable, but men have to call them “Kilts”.  “Man bags” are an exception, but carry a stigma, were as a briefcase or back pack does not.

I’m sure there is a psychological reason for people to believe our ancestors were stupid and ignorant, or maybe it’s just because so many people are ignorant, that it perpetuates the syndrome. I thought that people, once given the ability to access facts easily, would become less ignorant, but sadly this does not seem to be true. I have interns and employees who often, when they don’t know something, when asked if they did any research on the subject, answer, “I didn’t know where to look.” “does it make any difference?” or “ I figured you would know”.

 This is not a new problem. Years ago a friend, feeling my “pain” handed me an article called “A Message for Garcia”. Which can be read here: http://www.foundationsmag.com/garcia.html Written in 1899 for an issue of Philistine magazine, this short “filler” article went on to become an international sensation. The phrase “to take a message to Garcia” became a common slang for people taking initiative.

So, this article is my message for Garcia….