# Spaceship: Minimum Gs for health? **URL:** \ **Category:** Factual Questions\ **Created:** [January 8, 2017, 7:01pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643 "2017-01-08T19:01:33Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [January 9, 2017, 7:57pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/21 "2017-01-09T19:57:55Z")
> [@CalMeacham](#): > > Anything smaller would either have to rotate at an angular rate that would make Coriolis forces noticeable, or would rotate too slowly to give you a gee. “Smaller” here is only in terms of radius. The least massive option is just a small habitation module, a tether, and a counterweight on the other end. In some proposals, the counterweight is merely the upper stage of the rocket that launched your module – it’s massive, and it’s already in your final orbit. I’m sure the engineering challenges will be nontrivial, but mostly on the “how does it work in space” end of things. Clearly, Earth-bound engineers have no trouble figuring out how to hang very heavy things at 1 g from a cable. The challenges, I suspect, will be more about how to get power, communications, maneuvering, etc. systems that reliably work on a rotating platform. This isn’t the stuff of Man Will Live In The Stars!, but it’s a much more plausible near term method for figuring out whether 0.1 or 0.5 g is sufficient to prevent physical degradation, and for any manned trip beyond the Moon. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [January 9, 2017, 7:59pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/22 "2017-01-09T19:59:38Z")
> [@levdrakon](#): > > Why is that? Would it introduce a dangerous wobble to the whole station or something? One reason is that spinning part of the station in one direction will make the rest of the station want to spin in the opposite direction. Newton is a harsh mistress. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [January 9, 2017, 8:13pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/23 "2017-01-09T20:13:41Z")
It gets even more fun when you want to rotate the station to maintain a particular orientation to the Earth or Sun, and you have the world’s biggest fly wheel rotating on another axis… ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [January 9, 2017, 8:32pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/24 "2017-01-09T20:32:54Z")
[This](http://www.projectrho.com/public_html/rocket/artificialgrav.php) is arguably the best site on the web for information on all things spaceshippal. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [January 9, 2017, 9:40pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/25 "2017-01-09T21:40:41Z")
> [@levdrakon](#): > > I was wondering if we could make a rotating drum large enough for astronauts to sleep in, so they’d get 8 hrs of simulated gravity per day. Space Station modules are limited to what the current launch vehicles can launch. The largest modules are about 4.5m external diameter. NASA & NASDA once designed a [Centrifuge Accommodations Module](https://en.wikipedia.org/wiki/Centrifuge_Accommodations_Module) (for experiments, not for astronauts to spend time in), but that was only 2.5m diameter. Even if you manage to squeeze in a 4m diameter drum into there, and lie down at the edge of it, you’d still need to rotate it about 10 rpm (6 seconds per rotation) just to get 0.2 G. It’ll take 21 RPM to get up to 1G. I suspect even 10 rpm would cause dizziness. Also, if you’re _standing_ in a 4m diameter drum, then there’s almost no centrifugal force at your head, and maybe 1/2 level on your torso. To make a larger rotating drum, you need a module with a larger internal diameter, or rotate the whole module around an axis. You could use inflatable modules like the one Bigelow Aerospace has already demonstrated, but the larger the diameter, the higher the stress on the skin, so there is a limit to that approach. Or we could build a larger rocket, so we can launch something the size of Skylab again. _Maybe_ that can happen when SLS is ready, but I haven’t heard of such plans. Rotating a whole module should be possible, perhaps by having two modules connected by a tether or truss, and spinning the whole assembly. But how would you get there from the non-rotating section (which is necessary for a zero-G science laboratory)? It takes hours to prepare for a spacewalk. Having a pressurized walkway (floatway?) between the sections would be difficult to do safely - too much chance of accident leading to air loss. ---
**Author:** ![Rocketeer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rocketeer/32/4437_2.png) [@Rocketeer](https://boards.straightdope.com/u/Rocketeer)\ **Post date:** [January 9, 2017, 9:55pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/26 "2017-01-09T21:55:20Z")
> [@mbh](#): > > Spend the first half of the trip accelerating. At the midpoint, flip the ship 180 degrees. Spend the second half of the trip decelerating. That’s what I’d planned. And during the flipover, which would take half an hour or so, you muster any interested novelty-seeking passengers in the ship gymnasium for a quick class in zero-gee maneuvering, taught by a couple old space-hands. Wearing bathing costume, of course, for freedom of movement. The less adventurous passengers can remain in their cabins, equipped with airsickness bags. ---
**Author:** ![Rocketeer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rocketeer/32/4437_2.png) [@Rocketeer](https://boards.straightdope.com/u/Rocketeer)\ **Post date:** [January 9, 2017, 9:56pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/27 "2017-01-09T21:56:55Z")
> [@lazybratsche](#): > > “Smaller” here is only in terms of radius. The least massive option is just a small habitation module, a tether, and a counterweight on the other end. In some proposals, the counterweight is merely the upper stage of the rocket that launched your module – it’s massive, and it’s already in your final orbit. > > I’m sure the engineering challenges will be nontrivial… I seem to remember they tried an experiment with tethered satellites 10-15 years ago and it didn’t go well. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [January 9, 2017, 10:11pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/28 "2017-01-09T22:11:26Z")
There was a discussion of this somewhere, I think it was in the making of 2001. They mentioned that to produce 1G with no deleterious Coriolis effects at the indicated speed - the rotating section of the spaceship would have had to be 300 ft diameter. Otherwise, sudden head movements would cause distress to the inner ears. The problem with a rotating space station attached to s stationary hub is friction. The friction of the bearings will try to drag along the stationary part, and you would have to power it to maintain stationary. Also, consider sealing a large rotating component to a stationary one to maintain 1 atmosphere against a vacuum. You are better off with an elevator that comes to the center on a rotating spoke, then counter-spins at the hub until stationary, then locks onto the stationary hub. Or, like 2001, put the whole rotating part inside the pressure vessel. ---
**Author:** ![erysichthon](https://avatars.discourse-cdn.com/v4/letter/e/d07c76/32.png) [@erysichthon](https://boards.straightdope.com/u/erysichthon)\ **Post date:** [January 9, 2017, 10:18pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/29 "2017-01-09T22:18:51Z")
> [@Rocketeer2](#): > > I seem to remember they tried an experiment with tethered satellites 10-15 years ago and it didn’t go well. Are you thinking of [Gemini 11](https://blogs.scientificamerican.com/life-unbounded/watch-the-first-artificial-gravity-experiment/#) in 1966? Setting that up was an enormous ordeal, but they eventually did get everything spinning smoothly. The artificial gravity produced was negligible, though. ---
**Author:** ![alphaboi867](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alphaboi867/32/3898_2.png) [@alphaboi867](https://boards.straightdope.com/u/alphaboi867)\ **Post date:** [January 9, 2017, 11:02pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/30 "2017-01-09T23:02:07Z")
> [@levdrakon](#): > > Why is that? Would it introduce a dangerous wobble to the whole station or something? > > I was wondering if we could make a rotating drum large enough for astronauts to sleep in, so they’d get 8 hrs of simulated gravity per day. One would think a gym module would make more sense than a sleeping module. Surly the crew would get more benefit out of exercising in simulated gravity than sleeping in it. ---
**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\ **Post date:** [January 9, 2017, 11:34pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/31 "2017-01-09T23:34:21Z")
> [@billfish678](#): > > My conspiracy theory regarding NASA and low G is that they have some inkling that anything other than 1 G leads to total bone “decay” over a period of years…and once that got out…well people living on the moon and mars is pretty much a no go…and that would be bad… Yes, if serious human spaceflight and colonization of places beyond Earth is ever to be a reality, we need data on the long term health effects of a low G environment. And, yes, NASA has not done anything to collect that data. But there’s no reason at all to suppose this is some kind of conspiracy on NASA’s part. I’ve seen it claimed that the International Space Station is the single most expensive object ever built, and it’s a construction project that will take over 20 years to “finish”. Building some kind of spinning space station, or a Moon base–which are the only viable ways I can think of for getting any data on the long term health effects of a low G environment–damn sure wouldn’t be any cheaper or easier. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [January 9, 2017, 11:47pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/32 "2017-01-09T23:47:00Z")
> [@MEBuckner](#): > > Yes, if serious human spaceflight and colonization of places beyond Earth is ever to be a reality, we need data on the long term health effects of a low G environment. And, yes, NASA has not done anything to collect that data. > > But there’s no reason at all to suppose this is some kind of conspiracy on NASA’s part. I’ve seen it claimed that the International Space Station is the single most expensive object ever built, and it’s a construction project that will take over 20 years to “finish”. Building some kind of spinning space station, or a Moon base–which are the only viable ways I can think of for getting any data on the long term health effects of a low G environment–damn sure wouldn’t be any cheaper or easier. Thats why I said conspiracy theory…the implication being that part of the theory is a bit much. You don’t need a giant spinning space station. You need a two decent sized capsules connected by cables or a truss system. And you work UP to one G and a few hundred feet so that the coreolis forces aren’t extreme. Heck, don’t even start with humans for that matter. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 10, 2017, 12:06am UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/33 "2017-01-10T00:06:47Z")
One big edge that low-g has compared to zero-g: If you’re on, say, the Moon, then a 70-kg person can strap on a 350 kg tungsten suit, and have a total weight comparable to what you’d have on Earth. Put the suit on, and your bones would have roughly the same loading, and you could do the usual exercises, and so on (though you’d need to watch out for inertia). But there’s no way to do that in complete zero g, because zero times anything is zero. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [January 10, 2017, 12:09am UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/34 "2017-01-10T00:09:27Z")
Yes, the lead lined “fat man” suit might do wonders with only a decent fraction of 1 Gee. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [January 10, 2017, 1:46am UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/35 "2017-01-10T01:46:22Z")
> [@alphaboi867](#): > > One would think a gym module would make more sense than a sleeping module. Surly the crew would get more benefit out of exercising in simulated gravity than sleeping in it. I was thinking if all you did was lie down on it, it wouldn’t have to be as big. Fly up the pieces and have the astronauts assemble it like a big hamster wheel. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [January 10, 2017, 9:02am UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/36 "2017-01-10T09:02:59Z")
> [@Rocketeer2](#): > > The problem is that, if I boost at 1G, the ship is too fast; I can make it to Mars in 3 or 4 days and Neptune in a couple weeks. Ships like the Titanic still had ballrooms etc yet crossed the Atlantic in 4-5 days. Plus, when the orbits align, Mars will be on the way to Neptune. ---
**Author:** ![Oukile](https://avatars.discourse-cdn.com/v4/letter/o/13edae/32.png) [@Oukile](https://boards.straightdope.com/u/Oukile)\ **Post date:** [January 10, 2017, 7:37pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/37 "2017-01-10T19:37:15Z")
Actually [some scientists](http://news.mit.edu/2015/exercise-artificial-gravity-space-0702) have been advocating placing a small centrifuge in the space station or spaceship and have the astronauts go through centrifugation/workout sessions. The astronauts would not have to move their head during the workouts so the so-called ‘vestibular Coriolis effects’ would not be an issue (by the way ‘Coriolis’ is an incorrect name for this effect). The main researcher on this project is Larry Young, a serious vestibular scientist that I met a few times. I don’t know if they ever got (or will get) a chance to test it in space though. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 10, 2017, 8:01pm UTC](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643/38 "2017-01-10T20:01:20Z")
If you are going to Mars, accelerate at Martian gravity, not Earth gravity. The passengers have got to get used to it eventually. Note that everywhere in the solar system that has a solid surface has a surface gravity of less than Earth’s, so we will have to adapt to this - otherwise we can’t live there. If adapting to low gee requires advanced medical technology then we’ll need to develop such treatment before we set up homesteads on these little worlds. [Previous page](https://boards.straightdope.com/t/spaceship-minimum-gs-for-health/776643.md?page=1)