Dear Space Settlers,

My name is John and I am a new member. I agree that if one weighs up
the pros and cons of space colonies against planetary surface
colonisation, the colonies win hands down.

But there is one problem that is getting to me but I'm sure you guys
have already figured it out.

If my Maths is correct, a colonies 'floor' rotating about 100 metres
from its axis would have a rotation speed of about 30 metres per
second, this is remarkably fast. If one was to walk against the
direction of orbital motion, surely their strides would be
unmanageably large due to the combined effect on the rotating floor
and their own movement.
The only thing I can think of is friction by the ground on the other
foot. Also, what if they jumped in the air?

How will people in these colonies get from A to B?

Any response would be much appreciated.

John

From:
To:
Sent: Tuesday, October 30, 2001 7:40 AM
Subject: [spacesettlers] New member writes...

[snikt]
> If my Maths is correct, a colonies 'floor' rotating about 100 metres
> from its axis would have a rotation speed of about 30 metres per
> second, this is remarkably fast. If one was to walk against the
> direction of orbital motion, surely their strides would be
> unmanageably large due to the combined effect on the rotating floor
> and their own movement.
> The only thing I can think of is friction by the ground on the other
> foot. Also, what if they jumped in the air?
>
> How will people in these colonies get from A to B?
>

You're doing a common mistake by using "intuitive physics". You're assuming
that, somehow, a person gets completely still as soon as it looses contact
with the inner surface of the colony (e.g., by jumping). But in fact people
have inertia, and a person that jumps inside your colony with a 100 meters
radius will *also* have a speed of 30 m/s perpendicular to the rotation
axis - exactly the same tangent velocity of the floor. Since the floor and
the person have speeds of the same value and direction, the floor will in
fact look still for the person jumping - as when he or she jumps on Earth.

"Intuitive physics" also tell things like "a bomb dropped from a plane will
follow a straight line to the surface and hit the point that was below the
plane at the moment when the bomb was dropped". But in fact bombs dropped
from planes follow a *parabolic* trajectory, due to the same inertial
effects...

> Any response would be much appreciated.
>

By the way, you're welcome! ;-)

> John
[snikt]

Lucio

johnwhills@... wrote:

> Dear Space Settlers,
>
> My name is John and I am a new member. I agree that if one weighs up
> the pros and cons of space colonies against planetary surface
> colonisation, the colonies win hands down.
>
> But there is one problem that is getting to me but I'm sure you guys
> have already figured it out.
>
> If my Maths is correct, a colonies 'floor' rotating about 100 metres
> from its axis would have a rotation speed of about 30 metres per
> second, this is remarkably fast.

Not really, it's about 112km/hour, I've been known to go about that
fast on my way home from work.

> If one was to walk against the
> direction of orbital motion, surely their strides would be
> unmanageably large due to the combined effect on the rotating floor
> and their own movement.

Not at all. It would appear completely normal. The rotating floor
is much heavier than them, so wouldn't move. And they are moving
with the floor, in the same way that you move with the floor in
a plane or coach

> The only thing I can think of is friction by the ground on the other
> foot. Also, what if they jumped in the air?

They'd go up, about as far as they would on earth, and they'd come
back down again basically where they jumped from. No fuss, no
magic; no feeling of oddness because the ground is going at the
same speed they are. It would feel just like it would on earth.

Next time you are in a car moving along a road, I suggest you throw
something up an inch or two- you'll notice it lands right
back in your hand- provided the car is going at a constant speed
it will show no inclination to head for the back seat at all.

> How will people in these colonies get from A to B?

Walk, cycle or drive. More or less normal, although driving can
give some odd effects if you drive too fast.

> Any response would be much appreciated.
>
> John

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding
technological civilization?"
- Gerard O'Neill

Ian Woollard wrote:
>
> johnwhills@... wrote:
>

>
> > The only thing I can think of is friction by the ground on the other
> > foot. Also, what if they jumped in the air?
>
> They'd go up, about as far as they would on earth, and they'd come
> back down again basically where they jumped from. No fuss, no
> magic; no feeling of oddness because the ground is going at the
> same speed they are. It would feel just like it would on earth.
>

Almost, but not quite. Because you are in a rotating environment, if
you jump down from a ladder or something a bit high you won't land
exactly where you expect. That's because things at different altitudes
are moving at different velocities.

There are also strange effects if you throw something. What happens
depends on which way you throw. To people growing up on the colony this
will probably feel quite natural. Also, a good local team could probably
beat the best Earth baseball players if the game is played on the
colony!

--- Ian Woollard wrote:

> Walk, cycle or drive. More or less normal, although driving can
> give some odd effects if you drive too fast.

Yes, the varying gravity when driving fast would be very interesting.

Thankyou all for your contributions,

Unfortunately I could not read Al Globus' posting due to a 'broken
pipe'(???)

I'm pretty sure that at 100m from axis, an accelartion of 9.8ms^-2 is
achieved at a rotation speed of about 31ms^-2 (SQRT(9.8*100)) but it's
not about getting bogged down with numbers.

Lucio's explanation makes absolute sense. My way of thinking came
from reading somewhere that it was easier to walk in one direction
rather than the other, can anyone explain what the physical
explanation for this is and the numerical magnitude of the
opposition/assistance to movement?

Best wishes,

John

--- In spacesettlers@y..., Lucio de Souza Coelho wrote:
> From:
> To:
> Sent: Tuesday, October 30, 2001 7:40 AM
> Subject: [spacesettlers] New member writes...
>
> [snikt]
> > If my Maths is correct, a colonies 'floor' rotating about 100
metres
> > from its axis would have a rotation speed of about 30 metres per
> > second, this is remarkably fast. If one was to walk against the
> > direction of orbital motion, surely their strides would be
> > unmanageably large due to the combined effect on the rotating
floor
> > and their own movement.
> > The only thing I can think of is friction by the ground on the
other
> > foot. Also, what if they jumped in the air?
> >
> > How will people in these colonies get from A to B?
> >
> You're doing a common mistake by using "intuitive physics". You're
assuming
> that, somehow, a person gets completely still as soon as it looses
contact
> with the inner surface of the colony (e.g., by jumping). But in fact
people
> have inertia, and a person that jumps inside your colony with a 100
meters
> radius will *also* have a speed of 30 m/s perpendicular to the
rotation
> axis - exactly the same tangent velocity of the floor. Since the
floor and
> the person have speeds of the same value and direction, the floor
will in
> fact look still for the person jumping - as when he or she jumps on
Earth.
>
> "Intuitive physics" also tell things like "a bomb dropped from a
plane will
> follow a straight line to the surface and hit the point that was
below the
> plane at the moment when the bomb was dropped". But in fact bombs
dropped
> from planes follow a *parabolic* trajectory, due to the same
inertial

Hi John,

I'm a newbie, too! In regars to the problem you mention, if you're
moving with a 31 m/sec tangential velocity, you're at 1G. If you
walk spinward at about 4 mph, or 1.8 m/sec, you're actually rotating
at 32.8 m/sec, and experience around 1.1G. If you walk against the
spin your tangential velocity is only 29.2 m/sec, and you experience
0.87G. Needless to say, at higher, running, speeds the problem
worsens. To avoid this effect, the station diameter needs to be
larger. Many designs are 1 mile or more in diameter, with a
tangential velocity of over 200 mph. There are other nasty effects
with high angular velocities, so larger diameters really help some
other problems, too.

Here is a link to some of these issues.

http://www.spacefuture.com/archive/artificial_gravity_and_the_architec
ture_of_orbital_habitats.shtml

Best Regards,

George Turner

From:
To:
Sent: Thursday, November 01, 2001 1:12 PM
Subject: [spacesettlers] Re: New member writes...

[snikt]
> Lucio's explanation makes absolute sense. My way of thinking came
> from reading somewhere that it was easier to walk in one direction
> rather than the other, can anyone explain what the physical
> explanation for this is and the numerical magnitude of the
> opposition/assistance to movement?
>

If your station is rotating clockwise and you are also walking clockwise,
then you'll get a bit heavier, for you'll add your walking speed to the
rotation speed of the station. If you walk counterclockwise, then you'll
*subtract* your walking speed, and so you'll get lighter. About the
magnitude... Well, assuming that your walking speed is 1 m/s, and
remembering that centrifugal force is proportional to the square of the
rotation speed, then you would get about 6% heavier or lighter, assuming the
rotation speed of 30 m/s that you mentioned. For higher rotation speeds,
obviously the effect would be even smaller.

> Best wishes,
>

Best wishes,

> John
[snikt]

Lucio

Much appreciated George!

John

--- In spacesettlers@y..., Gturner6PPC@y... wrote:
> Hi John,
>
> I'm a newbie, too! In regars to the problem you mention, if you're
> moving with a 31 m/sec tangential velocity, you're at 1G. If you
> walk spinward at about 4 mph, or 1.8 m/sec, you're actually rotating
> at 32.8 m/sec, and experience around 1.1G. If you walk against the
> spin your tangential velocity is only 29.2 m/sec, and you experience
> 0.87G. Needless to say, at higher, running, speeds the problem
> worsens. To avoid this effect, the station diameter needs to be
> larger. Many designs are 1 mile or more in diameter, with a
> tangential velocity of over 200 mph. There are other nasty effects
> with high angular velocities, so larger diameters really help some
> other problems, too.
>
> Here is a link to some of these issues.
>
http://www.spacefuture.com/archive/artificial_gravity_and_the_architec