Earlier quoted context omitted.
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?
The syndrome impairing astronauts’ eyesight
51–60 of 62 posts
Re: The syndrome impairing astronauts’ eyesight
#52Earlier quoted context omitted.
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.
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...
Re: The syndrome impairing astronauts’ eyesight
#53It 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,…
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...
Re: The syndrome impairing astronauts’ eyesight
#54Earlier quoted context omitted.
> 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 healt…
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…
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.
Re: The syndrome impairing astronauts’ eyesight
#55Earlier quoted context omitted.
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.
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 struct…
> 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!
Re: The syndrome impairing astronauts’ eyesight
#56Earlier quoted context omitted.
> 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/wi…
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 th…
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.
Re: The syndrome impairing astronauts’ eyesight
#57Earlier quoted context omitted.
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…
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.
Re: The syndrome impairing astronauts’ eyesight
#58Earlier quoted context omitted.
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…
> 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 ?
Re: The syndrome impairing astronauts’ eyesight
#59Though 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.
Re: The syndrome impairing astronauts’ eyesight
#60Earlier quoted context omitted.
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…
> 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.