Artificial 1g Gravity on Mars vs in Space

Terraformer · 2019-10-18 04:30:56

(Also posted on My Hacienda)

If being used for exercise, how big does a centrifuge have to be? Could we do a full regimen lying down, allowing us to get away with quite a small radius?

Calliban · 2019-10-18 06:18:54

Living in 1g on Mars would mean building big centrifuges with thrust bearings and electric motors to keep them spinning. And they would need a big rotation radius in order to avoid Coriolis sickness. Possible, but not cheap.

louis · 2019-10-18 06:27:05

Depends what we are talking about. In order to get the 1G effect for your muscles and bones all you would need is a suit and boots massing just under twice your body mass. That's probably not going to happen (because it might interfere with work) but I could imagine some weighted clothing being worn in order to maximise the benefits of Mars gravity.

Later, 1G sleep pods might be developed. Also, I think for purposes of gestation and healthy foetal development, it's quite possible women will spend several months in a 1 G environment either on the surface or, more likely, in orbit.

Calliban wrote:

Living in 1g on Mars would mean building big centrifuges with thrust bearings and electric motors to keep them spinning. And they would need a big rotation radius in order to avoid Coriolis sickness. Possible, but not cheap.

Terraformer · 2019-10-18 06:33:44

There's little point to sleeping in 1g. Particularly in space, since it makes more sense to use the central, best shielded part of the spaceship for sleeping.

louis · 2019-10-18 06:53:52

I was thinking of on the Mars surface, if you're living there for maybe 4 or more years. It might be important to prevent eye disease, issues re the heart and problems with the immune system - the micro effects of not living in 1G. On the other hand we might find living in 0.38 G is sufficient to overcome these issues.

Terraformer wrote:

There's little point to sleeping in 1g. Particularly in space, since it makes more sense to use the central, best shielded part of the spaceship for sleeping.

Calliban · 2019-10-18 07:23:52

Terraformer wrote:

There's little point to sleeping in 1g. Particularly in space, since it makes more sense to use the central, best shielded part of the spaceship for sleeping.

Indeed. The effects of 0g on the body are very similar to the effects of bed rest, to the extent that bed rest is used here on Earth as a reasonably good proxy for modelling the effects of zero g. This suggests that a fully grown adult could sleep in zero g with little ill effect, provided that their waking hours were mostly spent in gravity.

But there is another less well known reason for zero g deterioration of bones. Without the force of gravity, new bones cells cannot align themselves properly when attaching to the bone matrix. This is likely to be especially problematic for anyone still growing, especially babies and small children. Everyone sent into space so far has been fully grown. Whether 0.38g is sufficient gravity to prevent issues of this type, I do not know. I am tempted to say 'probably yes' given that 0.38g is still substantial gravity. We won't know for sure until we carry out partial gravity experiments on developing animals in orbit.

Last edited by Calliban (2019-10-18 07:26:47)

SpaceNut · 2019-10-18 19:06:58

So how do we nail down the levels of gravity to see what the line of ailments will be along the line from 0 to 1g increments.

We have no data points and the moon while its not 0g has its own open hazards for man on its surface.

I remembered that Nasa created a microgravity device to simulate on earth what it might feel like once in orbit. I was wondering if its speed could be slowed tosimulate the other levels of gravity.

The Gimbal Rig Mercury Astronaut Trainer

Can we crowd fund a new effort to learn before we get there....

louis · 2019-10-18 19:10:27

I disagree. I think you are confusing the issue of muscle/bone loss for which bed rest is a good 0G analog with other issues for which I don't think bed rest gives the same results.

I think gravitational pull would give the heart muscle the right gravitational workout in your sleep. We don't fully understand the eye and immunity decline issues, but they are likely to be a direct result of 0G, so 1G sleep could help. Obviously this would all need to be tested for effectiveness. A 1G working environment on the Mars surface during hours awake is simply not a practical proposition, I think. During sollight, I think the pioneers should wear weighted suits and boots. Once the base is established, building sleep pods might become a practical possibility.

Yes, one criticism I have of Musk is he seems to blithely assume people can move to Mars, start reproducing successfully and that children can grow up healthily there. I think it could take 50 years or more like 100 years before we have sorted out all the health issues so that humanity can live there healthily, reproduce and grow through childhood successfully. A lot of work to be done!

Calliban wrote:

Terraformer wrote:
There's little point to sleeping in 1g. Particularly in space, since it makes more sense to use the central, best shielded part of the spaceship for sleeping.
Indeed. The effects of 0g on the body are very similar to the effects of bed rest, to the extent that bed rest is used here on Earth as a reasonably good proxy for modelling the effects of zero g. This suggests that a fully grown adult could sleep in zero g with little ill effect, provided that their waking hours were mostly spent in gravity.
But there is another less well known reason for zero g deterioration of bones. Without the force of gravity, new bones cells cannot align themselves properly when attaching to the bone matrix. This is likely to be especially problematic for anyone still growing, especially babies and small children. Everyone sent into space so far has been fully grown. Whether 0.38g is sufficient gravity to prevent issues of this type, I do not know. I am tempted to say 'probably yes' given that 0.38g is still substantial gravity. We won't know for sure until we carry out partial gravity experiments on developing animals in orbit.

SpaceNut · 2022-01-23 14:26:16

bump

SpaceNut · 2022-03-06 15:28:04

https://opentextbc.ca/universityphysics … tal-force/

https://thefactfactor.com/facts/pure_sc … body/6343/

http://www.fmt.if.usp.br/~luisdias/Teac … mmer07.pdf

Stability of the person walking will have the force trying to push you outwards
Each meter towards the center means more force that is throwing you outwards.

http://www-g.eng.cam.ac.uk/125/achievem … /index.htm

https://www.frontiersin.org/articles/10 … 01956/full

We can chose the gravity whether we are larger or not as its from this calculation

I hope that no one thinks that we are walking inside the rotation in this direction.

6-p-059-gif.193695

You are being forced against the wall so you need to stand up on the curve so as to be able to walk up right.

For man we need to stand up on the curved surface.

SpaceNut · 2022-03-12 19:45:10

We do have some of the medical care against the items in this article.
Traveling to Mars Will Wreak Havoc on Our Bodies – Can We Prevent It?

The Strange, Deadly Effects Mars Would Have on Your Body

https://www.nasa.gov/hrp/bodyinspace/
The Human Body in Space

https://pubmed.ncbi.nlm.nih.gov/33298950/

https://www.nature.com/articles/s41526-020-00124-6
Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars

41526_2020_124_Fig1_HTML.png?as=webp

of course we are looking for risk mitigation

41526_2020_124_Fig2_HTML.png?as=webp

https://ttu-ir.tdl.org/handle/2346/87123
The Partial Gravity of the Moon and Mars Appears Insufficient to Maintain Human Health
https://ttu-ir.tdl.org/bitstream/handle … sAllowed=y

http://www.artificial-gravity.com/IAC-1 … slides.pdf

http://ssi.org/2010/SM14-proceedings/De … arroll.pdf

louis · 2022-03-13 17:54:12

My understanding is that the issues of bone and muscle loss in Zero G have been successfully addressed by a combination of space medicine, exercise regimes and "vaccuum trousers". The more subtle negative effects of Zero G still present a problem, but they can be ameliorated somewhat through crew screening, so you eliminate people with genetic predisposition to suffer from Zero G negative effects. That will help a lot.

SpaceNut wrote:

We do have some of the medical care against the items in this article.
Traveling to Mars Will Wreak Havoc on Our Bodies – Can We Prevent It?

The Strange, Deadly Effects Mars Would Have on Your Body

https://www.nasa.gov/hrp/bodyinspace/
The Human Body in Space
https://pubmed.ncbi.nlm.nih.gov/33298950/
https://www.nature.com/articles/s41526-020-00124-6
Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars
https://media.springernature.com/lw685/ … ng?as=webp
of course we are looking for risk mitigation
https://media.springernature.com/lw685/ … ng?as=webp
https://ttu-ir.tdl.org/handle/2346/87123
The Partial Gravity of the Moon and Mars Appears Insufficient to Maintain Human Health
https://ttu-ir.tdl.org/bitstream/handle … sAllowed=y
http://www.artificial-gravity.com/IAC-1 … slides.pdf
http://ssi.org/2010/SM14-proceedings/De … arroll.pdf

SpaceNut · 2022-03-13 19:16:54

With artificial gravity provided we will not need to get medical care for what is not being caused. Vacuum trousers or in this case compression wear will be in the form of the MCP suits to use on mars surface.

tahanson43206 · 2022-03-15 09:55:54

A member of the North Houston chapter of NSS asked RobertDyck for references for his assertion that Large Ship would rotate at 3 RPM. I suspect there are NO references, but am looking forward to seeing whatever RobertDyck provides in response to the request.

In the mean time, I thought of the rotating Starship Avalon in the movie Passengers ...

Google came up with a snippet that provides a clue (or two) I did not have previously...

Google
what was rotation rate of avalon ship in passengers movie
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About 1,540,000 results (0.68 seconds)
“The ship has to rotate about once every 80 seconds to produce 1 G, and because there's no propellant tank on board, you have to be harvesting hydrogen from the near-vacuum of space with that front shield and funneling it back into the ship in order to keep the fusion reactor running and supply propellant to the ion ...Dec 21, 2016
How the physics of interstellar travel figures in 'Passengers ...https://www.geekwire.com › Geek Life

It is likely that someone will contribute a follow up post, giving the radius/diameter of Avalon.

I find it interesting that the movie producers decided to go with 1 G. Since they were "designing" a starship that would travel at sublight speeds for 100 years, they had ample "funding" available, so they went for the real deal.

The Large Ship (Prime) in development in this forum has a rotation rate of 20 seconds, and the gravity on offer is Mars standard.

It seems quite reasonable (to me at least) to suppose that after humans gain some experience with Large Ship (and with rotating space habitats in LEO) there will be decisions made to try for higher G and slower rotation.

I suspect (not having seen his references) that RobertDyck pulled 3 RPM out of a hat, but we'll see.

(th)

tahanson43206 · 2022-03-15 10:01:57

A contributor to Reddit offered this:

User avatar
level 1
polishphysicist
·
5 yr. ago
I think I can estimate the size of the Avalon. The spaceship has three arms, which rotate around a common axis, thus creating artificial gravity. In one of the scenes, the spaceship completes three quarters of a full rotation in 439 frames (17.56 seconds). That gives a period T of 23.41 seconds. The angular velocity:
ω = 2 π / T = 0.268 rad/s.
The centripetal acceleration:
a = ω2 r.
Now, assuming that a = 9.81 m/s2, we get a radius:
r = a / ω2 = 136.2 m
or a diameter of 272.4 m. This article says the structure is about 1 km in length and that seems to agree with my calculations.
I'll let somebody else estimate the size of the Axiom.

I'd like to point out that (apparently) this person used the movie as a way to estimate the rotation rate.

Clearly we have an opportunity to learn more, if anyone has the time to investigate.

What the producers may have planned in the drawing room may not have translated perfectly to the animation.

***
To put those estimates in perspective, Large Ship (Prime) has a diameter of 75 meters.

At this point in human history, I think we will be sufficiently challenged to build Large Ship, let alone something like Avalon.

(th)

GW Johnson · 2022-03-15 11:53:44

The radial acceleration due to spin is a = R w^2, where R is the spin radius and w is the angular velocity in radians/sec. R could be feet, meters, whatever you want. Let’s use meters.

The acceleration level would be measured in m/s^2, which could be converted to standard gees, if you divide the equation by the standard value of Earth’s gravitational; acceleration, some 9.80667 m/s^2 (or 32.174 ft/s^2 if you want to use feet). So n (gees) = a/gc = R w^2 / gc.

Just for giggles, try 56 m radius at 4 rpm. Convert that w to radian/s: w = (4 rev/min) (2 pi rad/rev)/(60 s/min) = 0.41888 rad/s. Then n = R w^2 / gc = 1.0019 gees. That’s really, really close to an even 1 gee. It would be exact at 4 rpm if your radius were 55.89 m. Or, it would be exact at 56 m if your angular speed were 3.9961 rpm. Or anywhere between those extremes.

I like the even 4 rpm figure. You can ratio off that and radius as n (gees) = (your R/56 m) (your rpm/4 rpm)^2. Or to be more exact, ratio it off of n (gees) = (your R/55.89 m) (your rpm/4 rpm)^2. You can solve that for any one item, knowing the other two.

For those who like feet, you need 55.89 m switched to its equivalent 183.4 feet. The equation is then n(gees) = (your R/183.4 ft)(your rpm/4 rpm)^2.

What could be easier?

The biggie here is just how high an w is tolerable very long term by humans. Sources differ on that, but that number is usually said to be somewhere between 3 and 4 rpm. The higher the w, the smaller R can be, and still get 1 full gee. I have seen the limit quoted as high as 8 rpm, by myself, I don’t believe that. I’ve been using 4 rpm as the limit for my investigations. Both Coriolis forces and blood pressure gradient head-to-toe get too big above about 4-6 rpm.

So what is the needed R if you want only 0.38 gee at only 3 rpm? Rearrange the equation: R = n gc / w^2, or from my ratio version, n / (3 rpm/4 rpm)^2 = R/55.89 m. So R = 37.76 m. Or looked at the other way round for an even 38 m at an even 3 rpm: n = (38/55.89)(3/4)^2 = 0.3824 gees.

That’s at your toes. If standing, your head is about 1.6 m higher, at 38-1.6 = 36.4 m radius. Gees there are n = (36.4/55.89)(3/4)^2 = 0.3663 gees. That’s a difference of 0.0161 gees between head and toes. That’s not too bad.

But it gets to be a lot more extreme if you spin faster on a shorter radius. And that’s bad medically. For example, if one uses 5.31 m R at 8 rpm to get 0.3800 gees, that’s at the toes when standing. For a 1.6 m height, the head is at 5.31-1.6 = 3.71 m. Up there, gees are n = 0.2655 gees. The difference head-to-toe is 0.1145 gees, which is getting to be quite significant!

Coriolis forces grow the same sort of way, just a different equation. Both screw people up in long-term exposures.

GW

Last edited by GW Johnson (2022-03-15 11:55:42)

Terraformer · 2022-03-15 13:07:00

If standing, your head is about 1.6 m higher

Only for about half of women and a far smaller proportion of men...

Re. tolerable limits, maybe public transit designers have something to say about how tight a curve can be for a given speed and not make the passengers sick. It is an express goal of a subway/light rail/monorail to NOT be a rollercoaster.

SpaceNut · 2022-03-15 19:48:29

From GW's work I would assume that the inside radius need to be at mars gravity minimum with the large outer radius a do not care as more is better for man in this case its control of the min that we need.

Edit: making the inside circumference the 238 and the outer large means that we are guarantying that we are always above mars surface gravity to make sure we can be healthier as the outer deck would see a bit higher level which if we spend more time on that deck gets man in better shape for landing back on earth.

tahanson43206 · 2022-03-16 07:07:15

I just read this entire topic from the top .... GW Johnson joined the discussion in 2017, along with SpaceNut and Tom Kalbus, and even Louis tossed in a post or two.

The original question was how to set up a 1 G facility on Mars. That led to questions about the need for such a facility. It seemed to me that the best argument FOR such a facility was preparation for a return to Earth, but there might be medical reasons.

The discussion of whether 1 G for sleeping is a good idea led to a useful back-and-forth, with Louis carrying the day (in my opinion) with his observation that eyes benefit from 1 G whether their owner is asleep or awake, but those who pointed out that bed rest is a recognized way of simulating zero gravity were hard n his heels.

Hopefully we (humans) will learn that Mars gravity is sufficient for health of various organs (such as eyes) that need gravity.

Last night's Space Show with Dr. John Hunter included a prediction that Elon Musk will have people on Mars in four years. I think that is overly optimistic but I admit it is certainly possible. I hope the first landed crew includes a doctor who is qualified to study the effects of Mars gravity on humans and other creatures that might be on board.

(th)

Mars_B4_Moon · 2022-07-01 18:08:03

Some news

Space Station Astronauts Suffer Horrific Amount of Bone Loss, Study Finds
https://news.yahoo.com/space-station-as … 18432.html

Lost in space: returned astronauts struggle to recover bone density, study finds. Lack of gravity and weightlessness means the longer astronauts stay in space, the more bone mass they lose.

https://www.theguardian.com/science/202 … tudy-finds

Six months in space leads to a decade's worth of long-term bone loss. During space missions lasting six months or longer, astronauts can experience bone loss equivalent to two decades of aging. A year of recovery in Earth’s gravity rebuilds about half of that lost bone strength, researchers report.

https://www.sciencenews.org/article/spa … ry-gravity

New Mars Forums

Announcement

#51 2019-10-18 04:30:56

Re: Artificial 1g Gravity on Mars vs in Space

#52 2019-10-18 06:18:54

Re: Artificial 1g Gravity on Mars vs in Space

#53 2019-10-18 06:27:05

Re: Artificial 1g Gravity on Mars vs in Space

#54 2019-10-18 06:33:44

Re: Artificial 1g Gravity on Mars vs in Space

#55 2019-10-18 06:53:52

Re: Artificial 1g Gravity on Mars vs in Space

#56 2019-10-18 07:23:52

Re: Artificial 1g Gravity on Mars vs in Space

#57 2019-10-18 19:06:58

Re: Artificial 1g Gravity on Mars vs in Space

#58 2019-10-18 19:10:27

Re: Artificial 1g Gravity on Mars vs in Space

#59 2022-01-23 14:26:16

Re: Artificial 1g Gravity on Mars vs in Space

#60 2022-03-06 15:28:04

Re: Artificial 1g Gravity on Mars vs in Space

#61 2022-03-12 19:45:10

Re: Artificial 1g Gravity on Mars vs in Space

#62 2022-03-13 17:54:12

Re: Artificial 1g Gravity on Mars vs in Space

#63 2022-03-13 19:16:54

Re: Artificial 1g Gravity on Mars vs in Space

#64 2022-03-15 09:55:54

Re: Artificial 1g Gravity on Mars vs in Space

#65 2022-03-15 10:01:57

Re: Artificial 1g Gravity on Mars vs in Space

#66 2022-03-15 11:53:44

Re: Artificial 1g Gravity on Mars vs in Space

#67 2022-03-15 13:07:00

Re: Artificial 1g Gravity on Mars vs in Space

#68 2022-03-15 19:48:29

Re: Artificial 1g Gravity on Mars vs in Space

#69 2022-03-16 07:07:15

Re: Artificial 1g Gravity on Mars vs in Space

#70 2022-07-01 18:08:03

Re: Artificial 1g Gravity on Mars vs in Space

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