The syndrome impairing astronauts’ eyesight | Hacker News Reader

The syndrome impairing astronauts’ eyesight

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120 pointsmarkmassie60 comments

It will not prevent travel to Mars. It's effects can likely be countered. Perhaps by artificial gravity.

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

Not everyone is ready to admit it yet, but IMO there is no long term future for us in space without something like artificial gravity.

I remember back in the 1970s one of the Skylab astronauts came to my college to give a talk. I had read about some problems, so I asked him about the effects of prolonged weightlessness. He was very dismissive, he vehemently denied that there could be any problems at all.

As they say, denial isn't just a river in Egypt. And the denial has been going on for many many decades.

> He was very dismissive, he vehemently denied that there could be any problems at all.

We exist as we do because of the pressures our environment exhibits on us (e.g. gravity)- outside of hubris I can't imagine why folks would think weightlessness would have zero impact.

>We exist as we do because of the pressures our environment exhibits on us (e.g. gravity)- outside of hubris I can't imagine why folks would think weightlessness would have zero impact.

Skylab 2, 3 and 4 specifically tried to study the effects of space habitation on the human body. I seem to remember reading that the later Skylab crews were considered to be in better health when they came back than when they left. Even though it was early, it could explain the dismissiveness. The data at the time might have made it seem that we'd figured it out already.

I am not aware of research on how much gravity is needed to maintain a healthy environment. For example, it is possible that an body as light as Pluto (with only .06 Gs) would offset the majority of the effects of low gravity. If this is the case, then permantant bases on Moons/Planets would face little issues from micro-gravity concerns. If humans require closer to 1G to remain healthy, then these bases become more difficult.

We have already demonstrated that humans can stay in space for over a year while remaining relativly healthy. Further, we can achieve artificial "gravity" with centrifugal force if we needed to.

Additionally, we could also attempt to solve the problem through medical science, and treat the effects of micro-gravity instead of outright preventing it.

That's a great point. Makes me wonder why we're not getting that moon base setup. Seems like a natural first step prior to colonizing Mars. Learn how to survive on the Moon, take that knowledge and apply to Mars.

Artificial gravity is easy. You "just" spin things.

The tricky bit is being able to launch enough mass to build something safe and comfortable to spin; there's a limit to how small you can make your spinning habitat before the difference between "centrifugal force" and gravity is too pronounced for our long term comfort. That's part of why making it cheaper to launch per unit mass is so important. If we could put ten times the mass in space for the same price, the ISS would probably look quite different.

I'm of the same opinion as you in general; what spending years in zero-g has proved is that it's not long-term viable. There's too many ways in which it is not viable to expect us to be able to fix all of them, when indeed it's not clear we can fix any of them with drugs or anything short of massive genetic engineering. We don't know how much gravity is necessary, though I'm inclined to guess closer to .5G than .05G. Once you get enough mass in space, though, that's not really that difficult.

Two skylabs and a really long rope seems pretty achievable. The full wheel from 60's sci fi looks very cool, but two weights on opposite sides of a string seems so much simpler.

This idea is used in Seveneves

https://en.m.wikipedia.org/wiki/Seveneves

>The tricky bit is being able to launch enough mass to build something safe and comfortable to spin;

Is it? I might have a completely busted mental model, but I thought you only need a module-sized mass on one end of a rod the length of things we've already assembled in space (e.g. an ISS truss) and a motor to spin it.

It gets complicated, and the mass budget starts going up fast, if you want other things to be able to dock to it. Two space stations on the opposite side of a long rope (per the other reply) is also not a very compelling story to tell to Congress when you have to admit that astronauts won't be able to travel between those two space stations to speak of, unless, again, you really up the mass budget.

We're space-poor. It's just too darned expensive. Even relatively simple designs are out of our reach right now, if you have to manifest them in real designs with real safety margins and real practical applications, such as being dockable.

> Two space stations on the opposite side of a long rope (per the other reply) is also not a very compelling story to tell to Congress when you have to admit that astronauts won't be able to travel between those two space stations to speak of

I don't get the complaint. Assuming travel from one station to the other is impossible, what's supposed to be wrong with having two smaller stations that don't cripple the health of the inhabitants instead of one bigger one that does?

Still can't dock. You need to be able to dock in the stationar center module.

Congress won't fund two stations.

Again, the problem isn't physics or engineering, it's that we're poor in space. This, and a lot of the other posts, are basically saying "What's so hard about having a job 10 miles away? Just drive there!" to people too poor to own a car, too poor to even dream of owning a car. Yes, it is a simple problem... if space wasn't so expensive to us. (I mean, not trivial, we'd still have to redesign a lot of stuff, but there's no reason to believe there's a fundamental problem.)

This will serve as a reply to you and wlievens:

The objection I questioned was "when you have to admit that astronauts won't be able to travel between those two space stations to speak of". You and wlievens are both pointing out that the scheme is unworkable regardless of the necessity of traveling between one station and the other. That's fine, but it doesn't respond to my question of "who cares that you can't travel between the stations?" It means I was correct to wonder how it could be relevant that travel between one station and the other is impossible. The objection I questioned makes no sense.

On a separate note, if Congress will fund one station, they can't object to a two-station system at the same cost. The number of stations is, again, not relevant to much.

What about grabbing mass from the surface of the moon, junk that's floating around, etc.?

Seems like this might be cheaper than getting it off Earth, right?

Except then you'd need to launch a full blown transport, mining, and manufacturing facility from Earth and assemble it just like the space station. I wouldn't be surprised if such a ship is heavier than the station you're trying to build, even if you strip out life support because the gear necessary to make silicon chips or machine hard metals is massive and numerous.

At first we don't want 2 space stations spinning. We want 2 space crafts spinning and traveling to somewhere where we have enough gravity to survive (mars). All humans on one ship and cargo/return counter weight as other ship linked together by a tether and spinning for the travel duration.

But yeah we still need to lower the launch cost per kg to make it really feasible and super heavy launch vehicles which don't exist at all at the moment. Realistically we would want to launch 40+ tons directly to mars from earth (Falcon Heavy should be ~13 tons so we would need around 3x the power of that). We don't have anything with enough delta v to do that at the moment.

> there's a limit to how small you can make your spinning habitat before the difference between "centrifugal force" and gravity is too pronounced for our long term comfort

There is no such difference. The constraint you probably have in mind is that you want the force of gravity at your head to be the same as the force of gravity at your feet. This is a problem with actual gravity too; see https://en.wikipedia.org/wiki/Spaghettification .

No, the vestibular system gets "annoyed", which is to say, permanently motion sick, if you spin something too small. Our vestibular system is not designed to deal with Coriolis force. You have to keep it below a certain threshold or you'd rather not spin at all... which is, in some sense, exactly why we don't spin the ISS, or, rather, designed something ISS-sized to spin. It's too small. You need a certain size in the rotation axis.

If the solution was just to spin our tin cans the problem would be solved.

From what I read on Wikipedia:

- The Coriolis force is a different effect than the centrifugal force.

- The Coriolis force is unrelated to the radius of the rotating object. This is not true of centrifugal force, so while it doesn't make sense to talk about Coriolis forces resulting from spinning "something too small", it does make sense to talk about them from spinning "something too small" subject to the constraint that the apparent gravity from the centrifugal force meets some threshold such as g.

- The Coriolis force is a tidal effect, inasmuch as it is described by the tidal equations of Laplace ( https://en.wikipedia.org/wiki/Theory_of_tides#Laplace.27s_ti... ). That would make it an example of the tidal constraint that I originally suggested.

Have I made a mistake somewhere? The third point seems kind of shaky.

Now all your space vehicles need to be able to hold together under 1G of force. That means a lot more structure and mass and the cost goes way up.

How about sleeping in a centrifuge? No need for the entire spaceship to spin.

If it was possible to build a gravity sleep chamber, it's very possible that exposing the human body to gravity and zero-gravity on a daily basis would be put more, not less stress on a body than zero-gravity alone.

That's just a random guess. We already lay down for 8 hours and stand up for 16. My random guess is, our fluids would recover with at least some artificial acceleration and why not when sleeping?

If you intend to replicate the effects of standing, you'd need to sleep standing.

Chris Hadfield says that sleeping in 0g is one of the best bits of being in space.

I didn't spec 1G of force. Though, as I, ahem, already said, I do suspect we'll need closer to .5G than .05G. But while it's not quite as evil as the rocket equation, you do get non-linear advantages as you go down the gravity scale. .5 is already much less than half as hard as 1G, and we could perhaps get away with .25.

Here we have a chicken and egg problem; how can we launch the variable-speed lab we really need to figure out how much gravity we need if we can't afford the 1G lab in the first place? Because proper science suggests we ought to be able to test the full range up to 1G. I'm spitballing .5 or .25, but scientifically speaking there's no guarantee the optimal won't be .8, 1.0, or, conceivably, even 1.1 or 1.2G. (Sure, the latter is unlikely, but I can't scientifically rule it out a priori.)

'no long term future for us in space without something like artificial gravity.' and without an answer to the radiation problem.

http://www.wired.com/2014/04/radiation-risk-iss-mars/

Except for Venus with .9 Earth gravity and where colonies floating above the clouds have many advantages over, and may be no more difficult to create than, colonization schemes for Mars or anywhere else in space/away from Earth. https://en.wikipedia.org/wiki/Colonization_of_Venus#Advantag...

I really don't understand why NASA has never done experiments for creating gravity in space. We know how we could make it work.

They have, technically, on Gemini 11 they produced 0.00015g of "gravity".

https://en.wikipedia.org/wiki/Gemini_11

I do wish they would try again with modern technology.

Yes, Zubrin has been advocating for this since 1990.

https://www.youtube.com/watch?v=3UChuIqIKF4&t=1722

His explanation about the real situation with NASA and why the human spaceflight program has not accomplished anything is extremely disheartening.

https://www.youtube.com/watch?v=3UChuIqIKF4&t=417

The real problem is you need to deliver so much material to orbit to create artificial gravity (a rotating space station) it's very expensive.

We could create a simple rotating system with two pods connected by a long cable, but then it's not easy to dock to it, and there are balancing issues.

That should get much cheaper once spacex gets things right.

Even if SpaceX made the launch costs a hundred times cheaper than the shuttle, it would still cost over $500 million and that would only launch a tiny fraction of the mass needed for a full artifical gravity space station. The estimated cost of the International Space Station so far is over $100 billion not including launch costs so even if another company cut costs there by a factor of ten, thats $10 billion, again a small fraction of what you would need. You can cut out bureaucracy and save money with a private company instead of government agencies but this would be a one off design made for space habitation so there really isn't much room to drastically reduce costs. If you want this thing to also travel around the solar system, you'd need to complicate the design even more because the ISS is solar based and has only orbital correction propulsion which is much cheaper.

It's possible but I don't think it will be economical or practical for a long time.

10 billion is about the same order of magnitude as an aircraft carrier. The US has ten.

Yes, but the US Navy builds them one at a time, every 5 years, so $2B/year and they are used to guarantee the cooperation of an important ally/partner with the USA instead of with Russia or China. There is a big cost, but there is a monetary benefit from the deals made by promising to always keep a carrier strike group near someone's shores, ready to defend from foreign aggression.

NASA's budget in 2015 was about $18 billion while the defense budget was just shy of $600 billion. If we lived in a fantasy world where NASA was considered as important as defense, we'd be an interplanetary species by now. Alas, we don't, and when we consider the feasibility of an idea we have to take that into account.

> It's possible but I don't think it will be economical or practical for a long time.

So is there an actual technical path to make things cheaper in the very long run ?

That is entirely unclear due to how the geopolitical landscape has been evolving. SpaceX's major innovations amount to cutting out corporate bureaucracy, cutting operating costs, and taking advantage of economies of scale not available to the last generation of aerospace manufacturers. SpaceX hasn't invested in science, they've invested in engineering and logistics that make them competitive with the current state of the art, up to and including their first stage recovery technology. For example, they use kerosene instead of liquid hydrogen, cutting out the huge manufacturing and storage cost, and because they're not subject to Congressional pork barreling, they don't have to split manufacturing across many states and districts. Whether they can make the leap from basic chemical propulsion to something that can really drop costs by an order of magnitude or two remains to be seen.

> you need to deliver so much material to orbit

Not that much. You'll need an inflatable module (so the wide part can still fit in the cargo fairing of an SLS) and a carousel that can be assembled inside it to rotate and give the crew enough gravity to counteract the effects of the zero-g environment. You'll need power to keep it rotating and radiators to get rid of the heat.

The unfortunate thing is that this cannot be tested attached to the ISS as the vibration would ruin the micro-gravity environment crucial for many experiments there.

I agree that artificial gravity, plus radiation protection, are must haves for long duration deep space flights.

With inflatable structures, artificial G is possible to do with much less mass than you think. Using Bigelow Aerospace's BA330 as a proxy (60kg/cubic meter of habitable space), you would need between 5,000 to 20,000kg to build a 100m long passageway between 1 to 2m across on the interior. Inflatable structures are made from materials that handle tensile loads well (the hoop stress from pressurization in particular).

As an added bonus, the inflatable passageway, besides functioning as a tether, creates usable habitable space, so if one is clever, it is not strictly speaking deadweight mass.

Alex Tolley and I looked at this in detail while working on papers related to our "spacecoach" design pattern, you can find a good intro at https://medium.com/@brianmsf/traveling-to-mars-just-add-wate...

> Inflatable structures are made from materials that handle tensile loads well (the hoop stress from pressurization in particular).

And conveniently, hoop stress due to pressure in a cylinder is twice the axial stress due to pressure, so you're free to add quite a bit of axial stress due to the mass of all the items in your artificial gravity environment!

It may not prevent travel to Mars (for example, on a centrifugal space station), but considering gravity on Mars is 62% lower than here on Earth, I would postulate without some kind of gravity manipulation we are yet to develop (unless we have the energy to build centrifugal colonies on land) then manned missions on Mars would suffer a similar fate.

Until relativity and the standard model can be merged and we can figure out a cause and effect between gravity and other fundamental forces and figure out who to trigger gravity with an electrical switch for example gravity manipulation is not going to happen for quite some time. We'll probably just take the risk and go to Mars and suffer the health consequences.

> We'll probably just take the risk and go to Mars and suffer the health consequences.

Or find a way to treat the problems directly, rather than avoid them using artificial gravity.

Studies going as far back as the 80s show that people in submarines develop myopia:

http://www.ncbi.nlm.nih.gov/pubmed/7457562

The leading theory is that being in a confined space causes the eye to adapt to viewing things up close rather than at a distance.

Anecdote: I saw an article about Native Americans, using a technique of quickly focusing from near to far and back as a means to increase their eyesight range, when I was around twelve years old. Called Eagle Eyes, or something. I have been practicing regularly for eighteen years now, and my eyesight has only improved. I have been looking at computers and books at least a third of my time since. Am I actively preventing myopia? Interesting.

That's really interesting. What were your prescriptions before/after?

I was 20/20 in both eyes before, 20/15 in one and 20/10 in the other now. The last measurement was two years ago.

Are you over 40-45, or under?

Years ago my optometrist suggested I do this exercise. I've been doing it at regular intervals throughout the day for the last 10 years or so. Can't say my eyesight has improved but maybe it's prevented it from getting worse.

"The only proven methods of measuring intracranial pressure are invasive: the spinal tap or drilling a hole into the skull."

Sounds like we need to test/prove something new. I did some searching for a wireless intracranial pressure sensor and didn't find anything, but I bet you could make one. The sensor could be a pair of capacitor plates on the inside of a sealed cavity in a flexible material, with an antenna attached, such that the capacitance changes as the cavity is squeezed by the pressure around it.

To make a measurement, you'd use an external antenna to hit the sensor antenna with an impulse, which would cause it to ring at a frequency proportional to the pressure it's monitoring.

Very simple, no batteries, could be made very small...

[edit] Oh hey, they mention implanted devices. I guess I should have finished reading the article before posting.

So what I'm hearing is that we should send myopic people into space to fix their vision!

Only in theory. The induced hyperopic shift from axial length reduction of the eyeball would likely be reversible after the patient's intracranial pressure is brought back down under control. Moreover it is nearly impossible to find the sweet spot for just the right amount of hyperopic shift to negate preexisting myopia, not to mention that astigmatism cannot be corrected this way.

The more important and irreversible side effects include elevated intraocular pressure leading to glaucoma risks, and poor blood perfusion to the optic nerve leading to non-arteritic anterior ischemic optic neuritis (as mentioned in the article inflamed optic nerve), both result in permanent loss in parts of the visual field. The choroidal folds are unlikely to cause any change in vision though.

So all factors considered, it's really not a great way to correct myopia.

Could overhydration cause similar eye issues, since it also increases intracranial pressure?

Damn, as a guy in OCT research, working with the ATM most advanced OCT imaging systems there are (which we develop ourself) it's been itching me to get one of our systems up there for research. There's currently a Heidelberg OCT on board the ISS, but this thing can do only 2D scans in high resolution. And with our stuff we can do 3D scans in high resolution and even markerless angiography.

Though this comment comes days late -- if the effect cannot be countered, perhaps sending farsighted astronauts to Mars would allow them to arrive with fully-corrected vision.

Gosh, if only we'd been willing to pay for research to tell us if this effect arises in the low gravity of Mars or the Moon as well as in microgravity.

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

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