```From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.science
Subject: Re: How calculate spin velocity to achive artificial gravity?
Date: Sun, 21 Jun 1998 17:49:02 GMT

In article <sozi1.1053\$ZB1.8656060@news.rdc1.sfba.home.com>,
burton <burton@burtonweb.com> wrote:
>that is designed to spin to simulate a percentage of earth-normal gravity,
>what might a formula be to calculate how fast the object would have to spin
>to achive a specific amount of gravity?

Apparent gravity, in m/s^2, is 4*pi^2*r / t^2 , where r is radius in
meters and t is period of rotation in seconds.  Yes, that's pi squared
in the numerator.  Earth-surface gravity is about 9.8 m/s^2.

Note that rotation causes various complications, and there is some doubt
about just how high a rotation rate people can tolerate without problems.
If you want it to be unquestionably okay, about 1 RPM is tops.  If you're
willing to select resistant people and they're not going to be going back
and forth between rotating and non-rotating areas much, 3-4 RPM might be
okay.  Anything beyond that is doubtful.
--
Being the last man on the Moon is a |  Henry Spencer   henry@spsystems.net
very dubious honor. -- Gene Cernan  |      (aka henry@zoo.toronto.edu)

```

```From: "Theodore W. Hall" <twhall@cuhk.edu.hk>
Newsgroups: sci.space.science
Subject: Re: How calculate spin velocity to achive artificial gravity?
Date: Wed, 24 Jun 1998 15:42:12 +0800

Robert Lynn wrote:
>
> I am surprised that a human can even detect a rotation of 1 RPM ...
> Are you sure you don't mean 1 Hz (RPS).
>
> Even at very high rotational rates I am sure that people could
> acclimitise - we do all right even in the very artificial environment
> of freefall.

There's been quite a bit of research on human adaptation to rotation.
Estimates of the upper limit of the "comfort zone" vary:

4 rpm                       [1962, Hill and Schnitzer]
6 rpm   "comfort"           [1969, Gilruth]
2 rpm   "optimum comfort"   [1969, Gilruth]
6 rpm                       [1969, Gordon and Gervais]
6 rpm                       [1973, Stone]
3 rpm                       [1985, Cramer]

In 1975, based on experiments in a rotating room, Graybiel wrote:

In brief, at 1.0 RPM even highly susceptible subjects were
symptom free, or nearly so.  At 3.0 RPM subjects experienced
symptoms but were not significantly handicapped.  At 5.4 RPM,
only subjects with low susceptibility performed well and by
the second day were almost free from symptoms.  At 10 RPM,
however, adaptation presented a challenging but interesting
problem.  Even pilots without a history of air sickness did
not fully adapt in a period of twelve days.

References:

Cramer, D. Bryant.  "Physiological Considerations of Artificial
Gravity."  _Applications of Tethers in Space_, vol. 1, sec. 3,
p. 95-107.  Edited by Alfred C. Cron.  NASA Scientific and
Technical Information Branch, 1985.  Conference Publication 2364:
proceedings of a workshop held in Williamsburg, Virginia, June
15-17, 1983.

Gilruth, Robert R.  "Manned Space Stations - Gateway to our Future
in Space."  _Manned Laboratories in Space_, p. 1-10.  Edited by
S. Fred Singer.  Springer-Verlag, 1969.

Gordon, Theodore J.; and Gervais, Robert L.  "Critical Engineering
Problems of Space Stations."  _Manned Laboratories in Space_,
p. 11-32.  Edited by S. Fred Singer.  Springer-Verlag, 1969.

Graybiel, Ashton.  "Some Physiological Effects of Alternation
Between Zero Gravity and One Gravity."  _Space Manufacturing
Facilities (Space Colonies): Proceedings of the Princeton /
AIAA / NASA Conference, May 7-9, 1975_, p. 137-149.  Edited by
Jerry Grey.  American Institute of Aeronautics and Astronautics,
1977.

Hill, Paul R.; and Schnitzer, Emanuel.  "Rotating Manned Space
Stations."  _Astronautics_, vol. 7, no. 9, p. 14-18, September
1962.  American Rocket Society.

Stone, Ralph W.  "An Overview of Artificial Gravity."  _Fifth
Symposium on the Role of the Vestibular Organs in Space
Exploration_, p. 23-33.  NASA Scientific and Technical
Information Division, 1973.  Special Publication 115: proceedings
of a symposium held in 1970.

--

Ted Hall     <twhall@cuhk.edu.hk>

```

```From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.science
Subject: Re: How calculate spin velocity to achive artificial gravity?
Date: Wed, 24 Jun 1998 14:48:49 GMT

In article <358FE6A7.620EF446@elec.canterbury.ac.nz>,
Robert Lynn  <lynnrg@elec.canterbury.ac.nz> wrote:
>> Note that rotation causes various complications, and there is some doubt
>> about just how high a rotation rate people can tolerate without problems.
>> If you want it to be unquestionably okay, about 1 RPM is tops...
>
>I am surprised that a human can even detect a rotation of 1 RPM, 1 RPM
>implies a radius of about 894m for 1g, 4 RPM implies 56m.  Both of which
>seem pretty damned big.  From my experience of amusement park rides I
>would have said that a couple of meters would be big enough...

Remember, in an amusement-park ride you are generally strapped in and
nearly motionless.  The trouble with rotation comes when you start moving
around, and your inner ear and your eyes start giving slightly different
reports.  The motion sensors in your inner ear are pretty good.

>Are you sure you don't mean 1 Hz (RPS).

Quite sure.

>Even at very high rotational rates I am sure that people could
>acclimitise...

Sorry, wrong -- it's been tried.  Experiments on Earth can't duplicate the
*exact* conditions of in-space artificial gravity, which is why I said
that there was some doubt about the details, but they give a rough
indication of what we can expect.  Nobody gets used to living at 10 RPM,
no matter how long they try.  At 5 RPM, some manage it.  At 3 RPM, almost
(but not quite) everybody can acclimatize, but it takes some time, so
you'd better not be going back and forth between rotating and non-rotating
sections a lot.
--
Being the last man on the Moon is a |  Henry Spencer   henry@spsystems.net
very dubious honor. -- Gene Cernan  |      (aka henry@zoo.toronto.edu)

```

```Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Question about spinning space stations
Date: Wed, 3 Jan 2001 23:02:20 GMT

In article <Pine.GSO.4.10.10101031057130.21590-100000@ux11.cso.uiuc.edu>,
Robert Shimmin  <shimmin@students.uiuc.edu> wrote:
>I'm not contradicting, but that just doesn't make sense.  The body doesn't
>know, can't know, how fast it's being spun if you close the windows.

Sure it can, because it is *not* moving in a straight line.  The whole
point of spin for artificial gravity is, after all, that you *can* feel
the effect of the spin!  The artificial gravity is an obvious effect of
the spin, but there are others too.

You're correct in a narrow sense.  If your head is held absolutely rigid,
say in a clamp, there's no way it can tell.  But people in a space station
are going to want to move around... and that introduces complications like
Coriolis effects.  When you *turn* your head, suddenly the fact that the
station is spinning is highly relevant:  the fluid in your inner ear goes
in unexpected directions as the two rotations combine, and you get
motion-sick.  The only way to avoid this is to make the station rotation
so slow that it contributes almost no effect.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)

```

```Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Date: Fri, 26 Jan 2001 05:40:40 GMT

In article <m3d7dbrwbx.fsf@localhost.localdomain>,
Charles R Martin  <crmartin@indra.com> wrote:
>I can attest to this: one morning, I rode the 2+ gee centrifuge at the
>meant of course that as soon as we were up to speed I turned my head...

I don't think they gave that warning when I rode the thing, although that
was quite a while back...

However, I had some idea of what to expect, so I experimentally turned my
head through quite a small angle, maybe 10deg.  The centrifuge performed a
truly remarkable maneuver.  I turned my head back very slowly, and
refrained from further experiments along those lines.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)

```

```From: Charles R Martin <crmartin@indra.com>
Newsgroups: sci.space.tech
Date: 25 Jan 2001 17:28:02 -0700

cray74@hotmail.com writes:

> In article <3A6DDB95.C990EBF5@nist.gov>,
>   "Paul E. Black" <paul.black@nist.gov> wrote:
> > A spinning space station doesn't make much sense.  How about a
> > spinning track in an otherwise stationary ring instead.  Imagine the
> > equivalent of the sliding walkways at airports, but moving faster.
> > Since the track is a ring, it can be fairly rigid, like a catwalk.
> > The supporting rollers and motors are all stationary, reducing the
> > stresses, and ultimately, the mass.  I put a crude sketch at
> >     http://www.geocities.com/p.black/stationTrack.gif
> >
> > Here are the numbers I've worked out.
> >
> > Given a track with a radius of 6 m moving at 2.8 m/s (6.2 mi/hr or
> > 4.5 rpm),the track and anything stationary on it has about 1/8 G.
> > Running with the track at 5 m/s (11 mi/hr relative, 12 rpm absolute)
> > feels like about 1 G.
> >
> > If the track had a radius of 10 m, the track should move at 5 m/s
> > (11 mi/hr, stationary force is 1/4 G).  Running at 5 m/s is
> > 9.5 rpm absolute and feels like about 1 G.
>
> As I understand, 9.5rpm is pretty nauseating. Turn your
> head under that spin and watch your lunch arc in a funny
> manner through the spin "gravity". :)

I can attest to this: one morning, I rode the 2+ gee centrifuge at the
meant of course that as soon as we were up to speed I turned my head.

The world turned upside down at least 17 times.  Then I put my head
back and it happened again.  The only thing that can possibly compare
to it is the Valsalva test, where they run ice water into your ear.
(Much the same thing happens, and depending on which way the world
turns upside down you can make some diagnostic conclusions about
certain kinds of brain damage.)

I had to be helped from the centrifuge -- my feet wouldn't stay stuck
to that wall no matter *how* much everyone else insisted it was the
ground.  The nistygmus made it hard to place my feet anyway.  And it
was literally _hours_ -- well after lunchtime (I skipped lunch,
however) before my head stopped spinning.

--
"Never laugh at live dragons." -- Baggins
Charlie Martin, Broomfield, CO USA 40 N 105 W

```