The syndrome impairing astronauts’ eyesight(washingtonpost.com) |
The syndrome impairing astronauts’ eyesight(washingtonpost.com) |
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.
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 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.
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.
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.
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.
https://en.wikipedia.org/wiki/Gemini_11
I do wish they would try again with modern technology.
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.
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.
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.
https://en.wikipedia.org/wiki/Centrifuge_Accommodations_Modu...
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.
Or find a way to treat the problems directly, rather than avoid them using artificial gravity.
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.
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...
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'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 ?
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.)
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.
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.
Seems like this might be cheaper than getting it off Earth, right?
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.
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?
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 .
If the solution was just to spin our tin cans the problem would be solved.
- 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.
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.)
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.