Adjusting to gravity and explaining it...

[Razor One]

...to those uninitiated to Science fiction in general.

I'm currently working on a piece of fiction aimed to draw people into Science Fiction. The main character is a girl born on Mars who has to adjust to Earthnorm gravity and then has to deal with three gravities for a brief period of time. For the most part it's a character piece.

In my last workshop, a few of my fellow writers had a bit of trouble understanding my explanation of gravity. Since they're not Sci-Fi nuts I thought they'd be the most help in trying to access an audience not completely familiar with science or science fiction terminology. Here's the relevant excerpt from my second draft.

At 16 years of age, Rihoko was in the prime of her health, but she was struggling against three full gravities of force trying to crush her down into the floor. She had been born on Mars and though she had adapted well to ‘Earthnorm’ gravity she still found it preferable to remain in areas of the Starship Mariner that had less than one G.

That’s what made this area such a good hiding place. The crew knew she hated high gravity. Even they hated the high gravity. But if she was going to get to crew habitation without getting caught this was the way to go.

A few other questions have also risen up as I've been writing this. So far I've stuck to short stories taken out of a longer story I've been considering turning into a novel. If I do decide to go the novel route then I'll need to detail Rihoko's struggle to adjust to Earthnorm. How long would it take for the human body to adjust from 1/3rd G to 1 G? Would she be able to transition to 3 G temporarily? What kind of medical assistance would be necessary, such as walking frames or exoskeletons?

[adam_grif]

Fighter pilots experience G forces much higher than 3, but if the G-forces are acting upwards relative to their body ("negative Gs") 2-3 G is the limit before people pass out or die. 5G is the point at which an average person loses consciousness for regular G-forces, unless they're wearing G-suits in which case the threshold is raised to about 9.

I am unfamiliar with the long-term effects of high-G environments on people. I don't imagine it would be very healthy, would probably strain the cardiovascular system something terrible.

[Broomstick]

Fighter pilots experience G forces much higher than 3, but if the G-forces are acting upwards relative to their body ("negative Gs") 2-3 G is the limit before people pass out or die. 5G is the point at which an average person loses consciousness for regular G-forces, unless they're wearing G-suits in which case the threshold is raised to about 9.

Are you sure about those numbers?

I do know that people can, over time, develop tolerance to g-forces - between that and certain muscle tensing techniques people can briefly tolerate over 5 g's without a g-suit, although around 8-9 g's yeah, you do sort of need one to stay conscious.

However, airplane pilots are sitting down while experiencing such forces, which is different than attempting to stand or walk under such forces.

I am unfamiliar with the long-term effects of high-G environments on people. I don't imagine it would be very healthy, would probably strain the cardiovascular system something terrible.

I suspect it also depends on how fast such forces are imposed - we had a fairly recent thread on that. Slowly increasing g-forces should allow the body to build muscle and strengthen the cardiovascular system.

Personally, I could see someone standing up and walking around under 2 g's. I think it would be unpleasant, and you'd need to be careful not to stand up too fast, and even if you could tolerate the physical strain of running doing so might be dangerous at first because your reactions are all geared to 1 g, not 2. I know from experience that when you first are under 1.5 to 2 g's merely reaching for something right in front of you can be awkward/difficult. The mind/body does adjust fairly quickly, but the coordination to run without falling down might require some retraining, and it can be hazardous to fall under 1 g, much less 2.

However, I doubt the average person is going to be able to move around much under 3 g's, much less someone who grew up under less than that. 3 g's just strikes me as too much to be plausible in the OP scenario.

[Broomstick]

A few other questions have also risen up as I've been writing this. So far I've stuck to short stories taken out of a longer story I've been considering turning into a novel. If I do decide to go the novel route then I'll need to detail Rihoko's struggle to adjust to Earthnorm. How long would it take for the human body to adjust from 1/3rd G to 1 G?

Astronauts/Cosmonauts returning from long periods (measured in months) in microgravity in a couple weeks if I recall. Although some have been able to walk on arrival back on Earth, the are issues with blood pressure, balance, and some other coordination items. This is why space agencies tend to want these folks to sit down and be wheeled around - it's hard to look heroic when you faint from low blood pressure. However, these are people who grew up under 1 g.

Our heroine grew up under 1/3 of that. Presumably, her body has adapted to that. While not as extreme as zero g, it's probably safe to assume her cardiovascular system is not as strong as Earth normal, nor are her bones, muscles, or tendons. It would probably be weeks, at a minimum, before she was up and walking around any significant distance although she might manage bed-to-chair-to-toilet type trips within days. It will be months, at the very least, before she builds up the muscle power to keep up with Earth normal people, years before her bones adapt fully, if at all. She'll tire very easily/rapidly. She be prone to injury, from muscle strains/tears to broken bones if she falls to major ligament/tendon problems if she overdoes activity.

Would she be able to transition to 3 G temporarily? What kind of medical assistance would be necessary, such as walking frames or exoskeletons?

I doubt 3 g is plausible. I sort of doubt it's plausible for an Earth normal human. Well, maybe with years of conditioning. Well, maybe she'd eventually be able to stagger around a short distance.

Let's say our gal is 160 cm tall and 45 kg (yeah, kinda skinny, but remember, she'll have less bone and muscle mass than an Earth girl). Under three g's she'll weigh 135 kg, right? Well, we do have people that height on Earth who weigh that much. They are able to walk, but not terribly far and running is not really an option.

Walking frames would assist in maintaining balance, but, remember, her arms aren't going to be terribly strong, either. She'll be getting around in a scooter at best, perhaps a powered wheelchair of some sort that provides support for her body because most scooters require you to sit upright, and she's going to have trouble with that because her torso/back muscles aren't used to full gravity, much less 3 g's. In fact, even Earth normals will probably be in scooters/power chairs in 3 g's for any significant distance of movement. Really, think about how the morbidly obese move around. Conditioning over very long periods of time might allow for some individuals to do better than that, but you will have to build muscle and that will take time.

A powered exoskeleton could help with the physical effort required to stand, walk, and so on but it won't help the heart beat harder. She'll still be prone to episodes of low blood pressure, feeling faint or even actual fainting. One thing that I really noticed when I started experiencing greater than 1 g on a regular basis was how much harder, and faster, my heart was beating even while just sitting down exerting little physical effort. And I wasn't going as high as 3 g's, it was the 1.5-2 g range. I never felt faint, but then I had had to pass at least a minimum medical exam and I have a healthy cardiovascular system (arguably, better than that of many people my age).

Needless to say, nutritional support will be important. High protein diet, calcium supplements to help build bone, etc. This might be an instance where a very judicious use of anabolic steroids is justified to help build muscle, but it would need to be a low dose so as not to cause adverse effects, particularly in a girl or woman.

[Razor One]

Thanks for the quick responses details everyone! I'm already adjusting a few aspects of the backstory.

Quick spot of detail I forgot to mention (doh!).

From birth to Six, the main character lived in Mars gravity at 1/3rd G.

From age Six she was ramped up to Earthnorm. Would I be correct in assuming at least a years worth of adjustment?

The setting involves rotation to simulate gravity. The Starship is a Rama type cylinder... I still need to math out it's size and rotation as I've been focusing more on character development... the excerpt takes place on the outermost decks, the innermost of course being the area with biomes and living areas and a more moderate .8 - 1.0 G gravity depending on elevation.

The transition to an area of 3 G is brief, 15 - 30 minutes or so before returning to an area with less G's.

[Axiomatic]

I don't see how your readers could understand your explanation of gravity, since you don't actually GIVE one. You mention being in three gravities is a drag. You don't mention that a) what she THINKS of three gravities is actually one gravity to an Earthling or b) what the difference is.

At least in the brief two paragraphs you mentioned above.

You might mention that she's used to weighing a certain amount and how, without having gained a single gram of mass, her body now weighs three times more, and is exhausting to move for that reason.

[Stofsk]

Couldn't you have the same thing for cylinders but simply have the lower-gravity sections be on the next level 'up' toward the core? Let's say the cylinder is large enough and rotating quickly enough to simulate 1G, then you go up to the next level, and it's 0.95 G or whatever. Bit by bit the closer you get to the core the weaker the simulated gravity becomes.

Although a sphere works as well.

[Broomstick]

Or use a wheel habitat - concentric circles joined together, the outer spinning faster than the inner. provide a means to travel between them and you can travel to different levels of "gravity".

You'll also have coriolis forces to contend with as well - which is different than being on a planet. Well, OK, we do have coriolis forces on Earth, with noticeable effect on the weather and which direction water spins when it goes down the drain (though factors such as pre-existing vortices and basin shape can affect and even overwhelm the coriolis force in bathroom drains), but they don't have a noticeable impact to human perception when we're moving around and just above the Earth's surface. They will be more noticeable on a space habitat because size matters.

[Eleas]

TBH, I wouldn't concentrate on the numbers at all, not in narration. Even comparisons of weight seem inordinately clumsy, and she's hardly going to be listing things that are now harder to perform. What she'll feel is the important bit. The frustration of moving as if in treacle and tiring to the point where people start to react to her as if she's an invalid. The dismay when she lets go of things and they drop to the ground much faster (and seemingly "harder") than she's used to. How easy it is for her to get bruises, and how her whole conception of moving and how things ought to move is now wrong.

That's the stuff she'll be thinking about and grappling with, I'd reckon. If I were in that situation, I figure I'd eat a lot, be incredibly morose, only grudgingly do my callisthenics and otherwise not move about much, sleep like an exhausted log (likely in a bed made especially for me, one preferably with medical observation) whenever possible, and worry about my bones breaking.

[TOSDOC]

TBH, I wouldn't concentrate on the numbers at all, not in narration. Even comparisons of weight seem inordinately clumsy, and she's hardly going to be listing things that are now harder to perform. What she'll feel is the important bit. The frustration of moving as if in treacle and tiring to the point where people start to react to her as if she's an invalid. The dismay when she lets go of things and they drop to the ground much faster (and seemingly "harder") than she's used to. How easy it is for her to get bruises, and how her whole conception of moving and how things ought to move is now wrong.

That's the stuff she'll be thinking about and grappling with, I'd reckon. If I were in that situation, I figure I'd eat a lot, be incredibly morose, only grudgingly do my callisthenics and otherwise not move about much, sleep like an exhausted log (likely in a bed made especially for me, one preferably with medical observation) whenever possible, and worry about my bones breaking.
TBH, I wouldn't concentrate on the numbers at all, not in narration. Even comparisons of weight seem inordinately clumsy, and she's hardly going to be listing things that are now harder to perform. What she'll feel is the important bit. The frustration of moving as if in treacle and tiring to the point where people start to react to her as if she's an invalid. The dismay when she lets go of things and they drop to the ground much faster (and seemingly "harder") than she's used to. How easy it is for her to get bruises, and how her whole conception of moving and how things ought to move is now wrong.

That's the stuff she'll be thinking about and grappling with, I'd reckon. If I were in that situation, I figure I'd eat a lot, be incredibly morose, only grudgingly do my callisthenics and otherwise not move about much, sleep like an exhausted log (likely in a bed made especially for me, one preferably with medical observation) whenever possible, and worry about my bones breaking.

Right on, except learn to do it from the 6-year old's point of view. Do you have any direct experience with kids at this age? Be sure to ask them some questions about it too! It would be interesting to see how her own peers, other kids her own age, would respond to her adapting to her new environment too. Some might be sympathetic, some not so much.

Was she born on Mars? Or on Earth before her journey to Mars and other habitats. That might affect how much time it takes to adapt. Also, she's still well in her growth spurts, which may be affect and be affected by her using artificial aids to get around. Think of how much adjusting of an exoskeletal frame is required on a growing individual over the course of that year. Is it causing characteristic scars as she grows? Are their sudden weak points at the metaphyseal growth plates of her bones that were unanticipated in such a young person's transition? Sudden fractures? Is she approaching tachycardia during her year? The circulatory systems' effects will be what her doctors' attentions should be most focused on, especially initially.

[Simon_Jester]

Just a physics note, a good shape for adjusting people to gravity is the rotating sphere. At the equator, the gravity is highest. It goes down steadily as you move to higher latitudes.

So if you have a variety of people who need different gravities, a sphere lets you do it since it does them all at once. A cylinder would have to change its speed for everyone inside (great if the whole community is adapting at the same pace though).

One problem with the sphere is that as you move away from the equator along the inside surface, rotation-induced "gravity" stops pointing towards the floor. If you're standing at forty-five degrees latitude on a rotating sphere, you feel a centrifugal force that is still pushing you away from the axis... which means that the outer surface of the sphere is a forty-five degree slope with the equator being 'downhill'.

To compensate, you have to build all the floors perpendicular to the axis anyway... in which case you might as well just build the habitat like a tuna can; a sphere will just be a less compact way of achieving the same result, with more internal bracing required to maintain structural strength.

[Broomstick]

Well, before I was so rudely interrupted by a major storm this morning, I was going to mention the following...

When people are first experiencing noticably higher g's than they are accustomed to they invariably undershoot when reaching for something. That's because you're used to exerting a certain force to reach something an arm's length away, but under higher g's that same effort won't carry your limb far enough. So if you're reaching for something at, say, shoulder height you will find that the same effort leaves your hand short in distance and short in height. It only takes a few minutes to start compensating, but it's something she's going to notice when she's first adapting. It's part of what's going to make her clumsy. I haven't tried walking under those conditions, but I expect walking might have similar issues where people don't raise their feet up quite enough and wind up tripping over themselves.

(And yes, if you go to a lower g force you will tend to overshoot - even if going from say 1.5 g's back to normal)

If you spend a little time going back and force your brain will learn to compensate. When I was working on steep turns during pilot training, which takes you up to that 1.5-2 g realm, after a couple of half hour lessons you'll be able to go back and forth and compensate pretty automatically. You'll still notice that higher g's takes more effort, but you'll just make the adjustment as soon as you feel heavier and shortly you'll stop that under/over-shooting business entirely.

And it's not like, say, carrying half your bodyweight around in a backpack. Every part of your body weighs more. You can feel the skin on your cheeks sag, if you pay attention you notice your eyelids are heavier, you might feel it in your facial expressions. Female humans old enough to have developed breasts will probably want a really good support bra (but not necessarily an underwire - if you think those babbies can dig in at just one g.... they won't be comfortable at higher forces, m'kay?) Middle aged guys with guts complain about their beer bellies sagging. These effects are not "OMG INTOLERABLE!" and if you're doing anything at all your awareness of them will disappear, but if you're just sitting around then yes, you may well notice this.

Again, as I noted - your heart will be beating faster and harder than you are accustomed to it doing. Not intolerable, not even unpleasant, just noticeable. Think about the difference between how your heartbeat feels when you're just sitting quietly versus a brisk walk. Under high g's your "brisk walk" heart rate might be your new "just sitting around" rate. If you're just sitting around it's probably not an issue but any exertion is going to require a LOT more out of your system. So a person adjusting might appear fairly normal sitting at a table having a conversation but if they attempt to run (and a 6 year old is going to get excited at some point and try it, you just know it) they won't get far, and might even pass out.

Oh, yes - if your blood pressure isn't quite sufficient to get the blood all the way to your brain then, in addition to lightheadedness, you may "see spots", or you may experience tunnel vision, or your vision may go from color to black and white, then tunnel/spot, before you pass out. Other senses can also be affected as well (such as hearing) but visual effects are what most people notice. A six year old child might be less susceptible because, being physically smaller, their hearts won't have to pump blood vertically for as great a distance as an adulthood but they certainly could see these effects if they pushed themselves hard enough. A child attempting to play with other children might have a VERY brief burst of fast movement, after which the child may feel "wobbly" and simply plop down on their butt where they happen to be. A child going through such an adjust might even be taught to lay down flat when feeling such sensations, and children going through this sort of conditioning together might even be taught this as part of games or exercise, as it's going to be the fastest way to make the wobblies go away.

Other games for conditioning for differing g forces could include ball tossing type games, or darts, or anything that retrains the brain to exert a different type of effort to achieve a familiar activity. I could see people who live on spinning habitats of sufficient size playing games like basketball and dodgeball on a regular basis for both exercise and keeping accustomed to dealing with a particular level of g.

And those are the sorts of things you'd use in narrative rather than raw numbers. It may be important to know the numbers so you get the size of things like space habitats correct, but a child is going to be experiencing this as sensations, not equations.