Author Topic: Zero gravity and Deep Space Habitat  (Read 9915 times)

Offline guckyfan

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Re: Zero gravity and Deep Space Habitat
« Reply #20 on: 05/14/2017 08:52 AM »
The complexity with spin gravity is minor compared to the whole Mars endeavour anyway, so I find the resistance to the concept puzzling.

I find it puzzling how people insist on AG without a trace of evidence it is needed.

I'm curious what you think the threshold is then? We have strong evidence that long term zero-gravity exposure is harmful long-term in spite of regular exercise, and three centuries of biology research will tell you these effects always exist on a sliding scale.

So if you're sure enough that Mars (38.9%) gravity is okay to plan a long-term mission without spin-g, do you think Moon-gravity (16.6%) is okay long term? What about Ceres surface gravity (2.8%)?  Or Phobos surface gravity (0.6%)?

I am not sure Mars gravity is enough. But I think there is a very good chance. Humans have proven over and over to be very adaptable. With moon gravity I am less confident but whoever is interested in settling the moon can try that.

I just say doing a multi year test with humans in spin gravity is absurd and absurdly expensive in money and time. It needs to be done on Mars.

Spin gravity for pregnancies on Mars may technically not the biggest obstacle. But it would be a severe disruption of social life and much harder to justify and find people willing to go there. Spin gravity for in space settlements no doubt is needed. Multi year manned expeditions to the outer solar system may or may not require it. I guess yes it will be needed with flight times beyond 2 or 3 years.

Offline Aussie_Space_Nut

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Re: Zero gravity and Deep Space Habitat
« Reply #21 on: 05/14/2017 10:16 AM »

Aussie_space_nut:

what do you think about this arrangement:



I'm a big fan of keeping things as simple as possible. So having moving "cars" travelling between habs etc I think is just way too complicated. Especially if things go wrong. I like the idea of a fixed and ridgid structure that would allow you to move anywhere inside just in normal clothes.

Nothing is impossible if you throw enough resources at it I suppose.

But I think a fixed structure is way easier to engineer in a safe manner than what you propose which has multiple opportunities for a docking failure, a car to get stuck, etc. Therefore you have to plan for a way to rescue the occupants both in the car and those stranded elsewhere.

Offline mikelepage

Re: Zero gravity and Deep Space Habitat
« Reply #22 on: 05/15/2017 06:13 AM »
I am not sure Mars gravity is enough. But I think there is a very good chance. Humans have proven over and over to be very adaptable. With moon gravity I am less confident but whoever is interested in settling the moon can try that.

I just say doing a multi year test with humans in spin gravity is absurd and absurdly expensive in money and time. It needs to be done on Mars.

Spin gravity for pregnancies on Mars may technically not the biggest obstacle. But it would be a severe disruption of social life and much harder to justify and find people willing to go there. Spin gravity for in space settlements no doubt is needed. Multi year manned expeditions to the outer solar system may or may not require it. I guess yes it will be needed with flight times beyond 2 or 3 years.

Emphasis mine, just to point out that you can't say I have no evidence that low gravity on Mars is harmful, and then come out with a statement like that ;)

I agree humans are adaptable, but Mars gravity is nearly down to a third of biological norms.  I struggle to think of any situation where humans have shown themselves to be that adaptable for long-term undertakings. 

Caloric restriction diets of typically only cut 20-40% of calories, since 50% restriction diets (in rodents at least) attract mortality rates of 50%.  The highest altitude where people have adapted to living (Everest Base camp =6000m) is ~50% atmospheric pressure, and that's only after generations of Nepalese sherpas have become used to living upwards of 4000m. (I choose these examples because these are both things where "mind over matter" runs up against strict biological limits).

In answer to my own question above, I'm guessing the threshold for long-term low gravity adaptation (at least in the first generation of space travellers) is somewhere between 50-75% of Earth gravity, perhaps even as high as 90%.  I would bet that long term colonisation or Mars is going to need a multigenerational adaptation process.

Or perhaps humans will (for the foreseeable future) be like salmon returning upstream to spawn, needing to return to near-1g spin habitats in Mars orbit in order to have children.

Offline guckyfan

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Re: Zero gravity and Deep Space Habitat
« Reply #23 on: 05/15/2017 07:10 AM »

Emphasis mine, just to point out that you can't say I have no evidence that low gravity on Mars is harmful, and then come out with a statement like that ;)

This is getting annoying. My statements are totally consistent. I I never said we have positive proof either direction. It is you who demands a huge cost layout in money and time to try this in AG that IMO are better done in the real martian environment.

Just imagine having an AG environment set up and maintained long enough that children can be born and raised there, just to prepare for getting to Mars, on the assumption it will fail.


Offline Welsh Dragon

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Re: Zero gravity and Deep Space Habitat
« Reply #24 on: 05/15/2017 09:38 AM »
<snip>
For that matter, there's never been life (that we know of) that didn't have 1xg.

<snip>
Except of course all aquatic life.

Offline mikelepage

Re: Zero gravity and Deep Space Habitat
« Reply #25 on: 05/15/2017 10:11 AM »
<snip>
For that matter, there's never been life (that we know of) that didn't have 1xg.

<snip>
Except of course all aquatic life.

Neutral buoyancy !=! zero gravity.


Offline mikelepage

Re: Zero gravity and Deep Space Habitat
« Reply #26 on: 05/15/2017 10:31 AM »

Emphasis mine, just to point out that you can't say I have no evidence that low gravity on Mars is harmful, and then come out with a statement like that ;)

This is getting annoying. My statements are totally consistent. I I never said we have positive proof either direction. It is you who demands a huge cost layout in money and time to try this in AG that IMO are better done in the real martian environment.

Just imagine having an AG environment set up and maintained long enough that children can be born and raised there, just to prepare for getting to Mars, on the assumption it will fail.

Yes it is getting annoying.  It is you saying I'm demanding things I've never asked for.  :(

By all means, I hope SpaceX/NASA/whoever will get to Mars as soon as possible, without AG, because that will most likely be the easiest/quickest way to get it done.  Do science on Mars, explore etc etc.  I'm the last person to get in the way of that.

That said, myself and many other evolutionary biology trained types are dubious about the gravity situation.  We suspect there's a very good chance that some kind of spin gravity will be necessary.  So, in parallel with Mars efforts, we want to set up a lab in LEO/wherever to do AG research, such that if the less-optimistic scenario turns out to be true, we've got a head start on the years of work that will need doing.  If Mars gravity turns out to be fine, then none of the work is wasted anyway, because it helps us build space settlements.

There need not be any conflict between our positions.  I'm just trying to get you to acknowledge where I'm coming from.
« Last Edit: 05/16/2017 04:59 AM by mikelepage »

Offline Welsh Dragon

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Re: Zero gravity and Deep Space Habitat
« Reply #27 on: 05/15/2017 12:39 PM »
<snip>
For that matter, there's never been life (that we know of) that didn't have 1xg.

<snip>
Except of course all aquatic life.

Neutral buoyancy !=! zero gravity.
Of course not. But as far as adaptations required for it, it's effectively the same.

Offline A_M_Swallow

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Re: Zero gravity and Deep Space Habitat
« Reply #28 on: 05/15/2017 12:56 PM »
<snip>
For that matter, there's never been life (that we know of) that didn't have 1xg.

<snip>
Except of course all aquatic life.

Neutral buoyancy !=! zero gravity.
Of course not. But as far as adaptations required for it, it's effectively the same.

Not necessarily. Mammals and fish are nearly symmetrical left to right but they are very different top to bottom. So individual cells and entire organs probably need to know where they are vertically. Even in water gravity can be used to determine which way is up and which may is down - an inert mass will try to sink to the bottom of the cell.

Offline RonM

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Re: Zero gravity and Deep Space Habitat
« Reply #29 on: 05/15/2017 04:52 PM »
A small base on the Moon would allow research into medical effects of 1/6 gee in addition to lunar exploration. It would be interesting to see if such a low gravity reduces or eliminates the issues we have in microgravity. It would provide a third data point to extrapolate the effects of Mars gravity to give us an idea before we run experiments on Mars.

There's international support for some sort of gateway station in lunar orbit. A gateway station and reusable lander would make lunar exploration easier.

SpaceX could land an ITS ship on the Moon, let it sit for a few months as a temporary base, and go back to Earth. They probably want to do some cislunar testing before heading to Mars anyway.

Offline lcasv

Re: Zero gravity and Deep Space Habitat
« Reply #30 on: 06/04/2017 12:47 AM »
HEALTH IS FIRST,HEALTH IS SECOND.... RUSH IS A MISTAKE. AG MUST BE IMPLEMENTED FIRST.

Offline guckyfan

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Re: Zero gravity and Deep Space Habitat
« Reply #31 on: 06/04/2017 06:39 AM »
A small base on the Moon would allow research into medical effects of 1/6 gee in addition to lunar exploration. It would be interesting to see if such a low gravity reduces or eliminates the issues we have in microgravity. It would provide a third data point to extrapolate the effects of Mars gravity to give us an idea before we run experiments on Mars.

There's international support for some sort of gateway station in lunar orbit. A gateway station and reusable lander would make lunar exploration easier.

SpaceX could land an ITS ship on the Moon, let it sit for a few months as a temporary base, and go back to Earth. They probably want to do some cislunar testing before heading to Mars anyway.

I don't think an ITS can loiter on the moon for extended time and then relaunch. Moon day heat from the sun will evaporate the propellant.

I admit I don't like the idea to use moon data to extrapolate to Mars. That may be way off. Worst case  it would give inaccurate arguments against Mars. For Mars research go to Mars, not to the moon.

Offline Jim

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Re: Zero gravity and Deep Space Habitat
« Reply #32 on: 06/05/2017 12:51 AM »

Of course not. But as far as adaptations required for it, it's effectively the same.

No where close to the same thing.  There is still a gravity field and it still affects living organizations.  You don't see fish swimming in all different orientations.
« Last Edit: 06/05/2017 12:52 AM by Jim »

Offline Paul451

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Re: Zero gravity and Deep Space Habitat
« Reply #33 on: 06/05/2017 05:01 PM »
Very belated response:

Counterpoint:
After spending 437 days in space (on Mir in 1994-1995) Valeri Polyakov got out of his Soyuz capsule and walked to the recovery couch.

The test for orthostatic intolerance is not walking a short distance while still on an adrenalin high from a high-g EDL. Rather, it is a measure of the length of time you can stand upright, with a heart-rate around your resting BPM. Ten minutes is the minimum to be considered free of the condition.

Most astronauts experience some degree of orthostatic intolerance. Typically requiring one day of recovery time per mission day. However, the susceptibility varies wildly between individuals and is largely unpredictable on the ground in advance. And even recovery is kind of random, some astronauts will be considered fully recovered and cleared, but weeks later will have a random fainting spell. (And it may be worse than reported because it might damage your chances of reflight, so there's a cultural tendency to hide such issues.)

Flight surgeons I've seen speak on the subject consider micro-g adaptation to be a significant problem. Essentially, "the more we learn, the worse we realise it is."

[Worse, astronauts are strongly selected against anything that might be considered a health risk or susceptibility, based on very ad hoc standards created since the '50s (which are as much gut-feel educated guesses as actual science-based.) Long duration spaceflight research therefore has a strong selection bias that is out of the hands of researchers. So what we are "learning" may be garbage due to the lack of ability to do a proper cohort selection.]

In short, there's little reason to spend billions designing, building, testing a rotating spacecraft to go to Mars

We're already spending billions/yr on a micro-g station which isn't capable of producing high quality human weightlessness research.

As for the cost of an AG Mars transfer vessel: Because of the lack of research into low gravity and spin gravity, we don't know what the optimum numbers are (G-load/RPM). If humans only need a trace of artificial gravity, and can adapt to a fairly high RPM, then it may be that a simple tumbling-pigeon rotation of any MTV would be enough. Or for a large ship like ITS-BFS, even rotation around the long axis could be enough. No giant wheels or risky tethers required.

And such rotation may also simplify systems engineering. Water processing, air circulation and filtering, fuel transfer, sanitary systems, etc. (Prop-tank ullage only needs a milli-g load to settle the liquids. Other systems may be the same.) Simplified engineering, lower costs.

Spending a relatively small amount now to produce data on AG, might save money in the long run.
« Last Edit: 06/05/2017 05:07 PM by Paul451 »

Offline lcasv

Re: Zero gravity and Deep Space Habitat
« Reply #34 on: 06/06/2017 01:24 AM »
PAUL 451:AGREE WITH YOU .CHECK THIS ARRANGEMENT 

Offline Paul451

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Re: Zero gravity and Deep Space Habitat
« Reply #35 on: 06/06/2017 02:15 PM »
PAUL 451:AGREE WITH YOU .CHECK THIS ARRANGEMENT

You've spammed your PDF three times in two pages. Enough.

Offline whitelancer64

Re: Zero gravity and Deep Space Habitat
« Reply #36 on: 06/06/2017 02:43 PM »
Very belated response:

Counterpoint:
After spending 437 days in space (on Mir in 1994-1995) Valeri Polyakov got out of his Soyuz capsule and walked to the recovery couch.

The test for orthostatic intolerance is not walking a short distance while still on an adrenalin high from a high-g EDL. Rather, it is a measure of the length of time you can stand upright, with a heart-rate around your resting BPM. Ten minutes is the minimum to be considered free of the condition.

Most astronauts experience some degree of orthostatic intolerance. Typically requiring one day of recovery time per mission day. However, the susceptibility varies wildly between individuals and is largely unpredictable on the ground in advance. And even recovery is kind of random, some astronauts will be considered fully recovered and cleared, but weeks later will have a random fainting spell. (And it may be worse than reported because it might damage your chances of reflight, so there's a cultural tendency to hide such issues.)

Flight surgeons I've seen speak on the subject consider micro-g adaptation to be a significant problem. Essentially, "the more we learn, the worse we realise it is."

[Worse, astronauts are strongly selected against anything that might be considered a health risk or susceptibility, based on very ad hoc standards created since the '50s (which are as much gut-feel educated guesses as actual science-based.) Long duration spaceflight research therefore has a strong selection bias that is out of the hands of researchers. So what we are "learning" may be garbage due to the lack of ability to do a proper cohort selection.]

In short, there's little reason to spend billions designing, building, testing a rotating spacecraft to go to Mars

We're already spending billions/yr on a micro-g station which isn't capable of producing high quality human weightlessness research.

As for the cost of an AG Mars transfer vessel: Because of the lack of research into low gravity and spin gravity, we don't know what the optimum numbers are (G-load/RPM). If humans only need a trace of artificial gravity, and can adapt to a fairly high RPM, then it may be that a simple tumbling-pigeon rotation of any MTV would be enough. Or for a large ship like ITS-BFS, even rotation around the long axis could be enough. No giant wheels or risky tethers required.

And such rotation may also simplify systems engineering. Water processing, air circulation and filtering, fuel transfer, sanitary systems, etc. (Prop-tank ullage only needs a milli-g load to settle the liquids. Other systems may be the same.) Simplified engineering, lower costs.

Spending a relatively small amount now to produce data on AG, might save money in the long run.

You seem to have missed these parts of my comment:

"Zero gravity does come with some negative side effects, but astronauts are typically not incapacitated by them ... all the evidence suggests that we'd be pretty much fine even with 6-8 months of weightlessness."

I agree that artificial gravity tests would pay dividends later on. The OP's argument is A. weightlessness is an insurmountable obstacle to going to Mars and thus B. build my rotating space station.
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Offline gospacex

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Re: Zero gravity and Deep Space Habitat
« Reply #37 on: 06/06/2017 02:59 PM »
AG is also possible on Mars.

Online Coastal Ron

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Re: Zero gravity and Deep Space Habitat
« Reply #38 on: 06/06/2017 03:21 PM »
AG is also possible on Mars.

While true, I think artificial gravity would be significantly more complex to do on a planet with a partial gravity than it would in zero gravity. And if you have to haul the AG construction components from Earth it would make sense to just have an artificial gravity station in space around the destination planet in question than to consume fuel in taking that mass down to the planet surface.

My $0.02
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Paul451

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Re: Zero gravity and Deep Space Habitat
« Reply #39 on: 06/06/2017 06:01 PM »
You seem to have missed these parts of my comment:
" [...] all the evidence suggests [...] "

Except you didn't respond with evidence, you responded with an anecdote of an astronaut being capable of walking for a short distance to a couch.

The statements of flight surgeons, the published research, and the comments from astronauts describing their recovery, (all discussed ad-nauseam in previous threads), suggests that the damage caused by weightlessness is worse than previously thought. We keep finding new issues, including new long term post-"recovery" damage.

Given the relatively low cost of testing AG (especially animal testing as a precursor), and the relatively low cost of adding low-g/high-RPM to a MTV, it's wasteful madness to spend many tens of billions on a Mars mission without even attempting to see if such AG would help.



AG is also possible on Mars.
While true, I think artificial gravity would be significantly more complex to do on a planet with a partial gravity than it would in zero gravity.

This has also been discussed to death previously. Being on the ground under fairly low gravity does add possibilities that aren't available for a space-habitat, because of the essentially unlimited momentum-sink of the planet. (For example, a banking rail ring.) But it assumes a large capacity for development, which assumes a pre-existing established colony/base, which assumes the problems of low-g can't be too bad. In which case, large AG habitats are probably unnecessary, and whatever the problem is (say foetal development) might be solvable with, say, two hours a day on a centrifuge-bike for the first trimester.

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