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The syndrome impairing astronauts’ eyesight

washingtonpost.com

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Re: The syndrome impairing astronauts’ eyesight

#11

Post by jfoutz »

jerf wrote: post #8
PhantomGremlin wrote: post #3

Earlier quoted context omitted.

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,…

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…

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.

Re: The syndrome impairing astronauts’ eyesight

#12

Post by hoorayimhelping »

jerf wrote: post #8
PhantomGremlin wrote: post #3

Earlier quoted context omitted.

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,…

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…

>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.

Re: The syndrome impairing astronauts’ eyesight

#14

Post by jerf »

hoorayimhelping wrote: post #12
jerf wrote: post #8

Earlier quoted context omitted.

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…

> 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.

Re: The syndrome impairing astronauts’ eyesight

#15

Post by thaumasiotes »

jerf wrote: post #8
PhantomGremlin wrote: post #3

Earlier quoted context omitted.

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,…

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…

> 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 .

Re: The syndrome impairing astronauts’ eyesight

#16

Post by thaumasiotes »

jerf wrote: post #14
hoorayimhelping wrote: post #12

Earlier quoted context omitted.

> 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.…

> 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?

Re: The syndrome impairing astronauts’ eyesight

#17

Post by ams6110 »

jerf wrote: post #8
PhantomGremlin wrote: post #3

Earlier quoted context omitted.

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,…

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…

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.

Re: The syndrome impairing astronauts’ eyesight

#18

Post by JoeAltmaier »

ams6110 wrote: post #17
jerf wrote: post #8

Earlier quoted context omitted.

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…

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.

Re: The syndrome impairing astronauts’ eyesight

#19

Post by fractx »

tines wrote: post #13

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.

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