Microgravity-induced muscle atrophy: Implications for long-duration spaceflights | Hacker News Reader

Microgravity-induced muscle atrophy: Implications for long-duration spaceflights

journals.physiology.org

41 pointsKasianFranks45 comments

Here's my design for solving this problem.

Instead of sending one rocket, you send two. You link them with steel cables. Then you rotate them around to generate the required gravity.

Yep, see Netflix film Stowaway for example. Once we get Spacex Starship working, fit 2 of them with Hab modules in the nose. Launch them and connect together at the nose and spin at different rates for moon gravity (G/6) and Mars gravity G/3). Use steel cables to increase radius and reduce required spin rate.

A relatively cheap (for space) setup to get some good actual measurements.

The whole "space is big" thing applies here, you can keep those two bodies super far apart. I don't really see a good reason for that tbh but it's possible. Though if the mission depends on those two bodies traveling together, you better have tons of redundancy or some propulsion systems to recover in case the cable snaps.

Was really thinking of an earth orbiting laboratory setup with a radius of about 250m and rotation speeds of about 2-3 rpm. Need to model it when I have some time. Just to gain actual data on different gravities and durations. The starship has plenty of room for the habs to run experiments on plants and people. Each one has propulsion in case of a cable failure. You’re correct, the cable snapping would be big concern.

> Though if the mission depends on those two bodies traveling together

Nevermind together, if the cable snaps they won't be going to the original destination.

> Artificial gravity is provided to the crew on the way out to Mars by tethering off the burnt out Ares upper stage and spinning up at 1 rpm.

From

Mars Direct: A Simple, Robust, and Cost Effective Architecture for the Space Exploration Initiative, by Robert Zubrin, February 1991

DOI:10.2514/6.1991-329

I wonder if you could bypass these issues with strength training machines designed for space. E.g a squat machine that pushes down from above, cable tension based arm movements, etc. I bet if you're clever you can probably have a small room that can get the essential exercises in and takes up a similar amount of room as a toilet

The ISS has a space barbell:

https://en.wikipedia.org/wiki/Advanced_Resistive_Exercise_De...

Now I'm curious how the results of study posted would be mitigated by the space barbell

I guess the problem remains that the legs still don't need to lift the body weight.

For example in a barbell squat, your shoulders lift the bar, but your legs lift that weight plus your bodyweight. In space, bodyweight is not a factor so your legs only have the same load as the shoulders. So upper body / shoulder might end up being the limiting factor, not giving the legs the same amount of load they would under gravity.

You can always just train like some anime character or kung fu masters:

https://www.youtube.com/watch?v=crKohKpVoAM

That could be solved via a vest that you wear, that has additional cables pulling with a force of the bodyweight. That way you could also do pull ups with your bodyweight.

Off topic. I can't help but wonder why astronauts on board the ISS wear sneakers. They aren't wearing gloves, and don't you mostly move with your hands in zero G? Why wear shoes and socks at all?

Yeah, interesting, at least some cosmonauts on Salyut stations explicitly used legs to float around...

Specifically while doing this exercise, I imagine that the additional padding and weight spreading is more comfortable than doing so barefoot, since the goal is to create lifting force between the floor under your your feet and the cable via your hands. I also imagine that many astronauts do frequently "kick off" objects and walls to start their propulsion/movement around the space station.

More generally - I often wear socks and slippers around the house while otherwise half dressed, because my toes get cold. Warm feet is a luxury.

I wonder if it's really required to have 1g gravity in order to avoid this. It's much easier to artificially create, say 1/6g (moon) gravity by rotation than 1g, since rotational speed required is quite a bit slower.

I wonder how much the rotation speed really matters. It comes down to the tensile strength of the material required to hold everything together I suppose but most metals should be able to handle 1g just fine. Once it's rotating you don't need much energy to keep it going, just enough to overcome any frictional losses from whatever interfaces happen to be required.

There's also the issue of dizziness if rotating fast with a small radius.

Could one become stronger by living in 2g?

would that be similar to weari nb a backpack having weight same to your body?

Not too similar, imagine all the liquids in your body while running at 2g.

To echo some of the points from the aurora book, I think that the human body is really well optimised for 1G environments. We know that there are issues in zero gravity. As you adapt to 2G, you may well get stronger but the stress and strains may have a severe effect on health, life expectancy. Hate to think about the effects on your blood pressure etc

Your great grand kids might eventually cope.

That's actually seen in anime. In Dragon Ball Z, Goku trained in 100 G. I remember thinking it was clever. It reminded me of Spain national football team training for some weeks in La Paz previous to Mexico World Cup in 1986. The idea is enduring harder conditions (> altitude -> less oxygen) to overcompensate.

This is a key assumption of the classic book (and box office bomb movie adaption) https://en.wikipedia.org/wiki/A_Princess_of_Mars

This seems like a real problem for older astronauts who will never be able to gain that muscle back.

Muscle mass is so vital for long term health. 70-year-olds confined to bed rest for just two weeks have been observed to lose significant muscle mass that they most likely will never get back.

Obviously most astronauts are younger than 70. But they're also losing a lot more muscle mass and bone density.

Progress in stem cell treatments might be able to treat that muscle mass loss. We are getting closer to regenerating tissues at will, although obviously the main effort is concentrated on the cardiovascular system and nerves.

You could just give the 70 year olds testosterone replacement and they would gain it back and more, probably

Don't live in microgravity.

Could Ems or sleeping in a spinning drum overcome this?

EMS = electro muscular stimulation? No, not 100%. Astronauts have very good resistance training onboard the ISS at this point. Some of them come back to earth stronger than they left. However, it turns out that your body also needs skeletal loading in order to produce strong bones. That kind of loading comes from having large forces distributed through the entire body. NASA tried a variety of shortcuts around resistance training, but none of them were satisfactory.

A spinning drum is probably the best method short of artificial gravity, but it has a couple problems. A rotating reference frame creates some pretty non-intuitive effects (https://www.youtube.com/watch?v=bJ_seXo-Enc). Research is ongoing about just how fast a human can be spun for a long duration, although data is hard to come by. We also don't know how low of a gravity a human can stay healthy in without intervention like serious exercise. If it turns out that you need 1G, that involves a much larger spinning drum than a G/3 (Mars) or G/6 (Moon) environment. The problem is that we really have no way to simulate those environments for a human.

What about flywheel training? You can do deadlifts, squats etc with it that will produce large spinal/skeletal load even in the absence of planetary gravity due to the inertia. Something like https://exerflysport.com/ or https://exxentric.com/store/kbox/

Given the travel time, any visit to Mars would probably not be short-stay like 1 day. More likely weeks, months or longer.

So you'd have Mars G for time on the surface anyway.

And besides: a few astronauts have already done long duration microgravity, returned to Earth & lived to tell.

Sure, but NASA is concerned about an emergency landing scenario on Mars. Astronauts that crash land while physically incapacitated from long duration microgravity will face near certain death.

One of the saddest parts of the science fiction novel _Aurora_ is that natural born human populations will have serious problems permanently separated from the larger ecosystem they're evolved for.

It's a valid hypothesis. Humanity would need to have an entire engineered biosphere to replace the biome living in our guts, our eyes, our . . everywhere. And anywhere we find that's close enough to Earth to live in, will have . . something else . . almost certainly[1] already there.

Kim Stanley Robinson isn't an easy read if you're on the other side of the political spectrum, but Aurora is comparatively free of his standard preachiness, at least in my ears. I actually disagree with his primary thesis of Aurora, and the novel suffers from some fundamental problems as a story, but the point is still salient. Humans will have to build their own Earth, wherever they end up, either out there or back here. I have a funny feeling we won't learn to treasure our own planet until we find out how much work it is to live on another.

[1] Particularly given the extraordinarily early date of the first Terran lifeforms. It doesn't seem to take too much to get the ball rolling, unless the panspermia theories actually turn out to hold some water.

> I have a funny feeling we won't learn to treasure our own planet until we find out how much work it is to live on another.

Optimistic! I have a feeling we won't learn to treasure our own planet until we fail to reach another. The problems here are simply too massive for us to coordinate spreading to other places.

We'll learn to treasure our own planet when the ecosystem becomes uninhabitable for us and we start going extinct.

"Earth is our spaceship"

>And anywhere we find that's close enough to Earth to live in, will have . . something else . . almost certainly[1] already there.

*No* place is going to be "close enough" to Earth to live in: the closest star system is 4 light-years away, and will take tens of thousands of years to travel to with anything remotely like current technology. The only way we're going to find another planet "close enough to Earth to live in" is if we invent a real, working, practical FTL drive. That's not terribly likely. Well, there is one other possibility: some glowing blue alien substance called "protomolecule" is discovered in our solar system and somehow (through a long, twisting plot arc) takes over an asteroid with 100k people, assimilates their biological matter, crashes on Venus, then travels to the outer system and builds a Ring Gate. Anyway...

Basically, we're stuck with this planet, the not-at-all-like-Earth worlds near it, and the other resources of this system.

The only real way we're going to create a viable, Earth-like colony is to build an O'Neal Cylinder.

I read their "close enough" as in regards to similarity of climate/environment, not in regards physical distance of the other planet from Earth.

I did too, but my point is that even if some planet is really "close" to Earth as far as climate, it doesn't matter because it's too far to get there.

I really think that it would be technically easier to just build a bunch of O'Neal cylinders here near Earth orbit, than to build ships capable of colonizing a distant planet.

Sibling is right, "close enough" == "habitable surface that humans can live on without some life support".

Aurora uses the generation ship model of transport, which . . does not go ideally. Many problems unforeseen for hundreds of years of travel in the utter empty (you hope desperately that it is empty). It's also a fast but not relativistic ship, .07C, at exorbitant energy costs. Hope you like the moon / mercury covered in purple lasers. Relativistic lower-mass vessels with the same technology, I guess, but the impact threat goes through the roof, and it's not a settlement ship. A better way to make the Aurora-style project is a small ship with frozen embryos that get birthed insitu by machines of loving grace. Then you can go faster, smaller.

But it's all talk talk. We're technically capable of doing these things, but I'm not sure we're socially capable of even lunar settlement at this stage of our history. Let alone Mars, the outer system. The Expanse was, in its own way, optimistic about our future. They just had to get medieval to get Earth's gas balance (and probably phosphorous! and who knows what else) back in the normal range.

Heh heh you know it's funny but if we took the solar system as it exists right now, a floating settlement higher up in the Venutian cloud layers would be closest[1] to fitting that bill, in terms of kgs of crap you need to carry around outside with you. Just, yknow, not anyone's typical idea of a "settlement".

[1] And yet so very damn far away.

>They just had to get medieval to get Earth's gas balance (and probably phosphorous! and who knows what else) back in the normal range.

Huh? As I recall, there were some lines in the show stating that Earth's population was significantly higher than it is now.

And, in fact, Earth could easily handle a much larger human population than it has now. The problem is, it can't handle a larger population (or even the same as now) if they all want to live like suburbanite Americans driving 6000-pound SUVs and living in McMansions. If everyone (except the farmers) lived in megacities that looked just like Tokyo, we wouldn't have the climate-warming problem we have now.

>I'm not sure we're socially capable of even lunar settlement at this stage of our history

I think we are, but not as a unified planetary population. One wealthy country, or better yet a bloc of allied wealthy nations, could do it if they really wanted to.

>a floating settlement higher up in the Venutian cloud layers would be closest to fitting that bill

I've thought about this before, and my conclusion is that this kind of colony just makes no sense. It's technically feasible, but the question is: why? What purpose would such a colony serve? A moon colony makes sense: you can do lots of stuff on the moon, like mining or astronomy or low-g manufacturing. What the heck are you going to do in a Venusian cloud city that makes it worthwhile for people from Earth to fund your colony? All colonies in history have required funding (and a lot of it), and that meant that investors were expecting a return somehow. There's no economic incentive to build cloud cities on Venus so people can sit around and play video games or whatever; there's absolutely no resources on Venus that are valuable or accessible.

> The only way we're going to find another planet "close enough to Earth to live in" is if we invent a real, working, practical FTL drive.

That is not the only way, extending lifespan would work as well

Possibly, but there's still huge technological hurdles. Sure, if we could figure out how to make everyone biologically immortal, then a 100,000 year journey wouldn't necessarily require a generation ship, but it does make me wonder how viable it would be socially (would society inside the ship break down and result in the crew destroying themselves somehow). Also, even without worrying about aging, how do you create a completely self-sustaining biosphere for these immortal humans to live in for eons? Building an FTL drive seems, in a way, to be simpler than this. Also, how do you deal with things like asteroid collisions over such a huge distance, at the speeds likely to be gained?

Most sci-fi just doesn't think of this stuff because the idea of a ship traveling for 100s of thousands, or even millions of years, is almost too much to consider for us. Making a ship that takes a few months or years to get somewhere is much easier for us to think about, because we've done such things before, so sci-fi always either invents FTL drive, or just conveniently ignores it and hopes the audience is too ignorant of the vast distances between stars to notice (which they usually are).

They don't call it Spaceship Earth for nothing!

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