 |
|
|
|
Next: Larry Niven: Niven web site update
|
| Author |
Message |
External
Since: Aug 15, 2006
Posts: 1
|
(Msg. 1) Posted: Tue Aug 15, 2006 5:15 pm
Post subject: Ringworld Parameters
Archived from groups: alt>books>larry-niven (more info?)
|
|
|
|
| I've been doing some designs with ring-shaped habitats in several 3D
modeling programs, but I'm convinced that if you did the math, none of
the structures would be even near as feasible as the Ringworld itself.
Could anyone give me a hand with the mathematics involved for
calculating things like artificial gravity, required velocities, and
how mass and size would play into all this?
|
>> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
 | |
External
Since: Jul 09, 2003
Posts: 169
|
(Msg. 2) Posted: Tue Aug 15, 2006 5:53 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
logan_mcgrath89.TakeThisOut@hotmail.com wrote:
> I've been doing some designs with ring-shaped habitats in several 3D
> modeling programs, but I'm convinced that if you did the math, none of
> the structures would be even near as feasible as the Ringworld itself.
It sounds like the meaning of the term "feasible" is being stretched
here  . A Niven ring requires structural material to have tensile
strengths many, many orders of magnitude greater than anything we know of.
> Could anyone give me a hand with the mathematics involved for
> calculating things like artificial gravity, required velocities, and
> how mass and size would play into all this?
If you're asking for the equations governing a rotating ring, then they are
a = omega^2 r,
v = omega r,
omega = 2 pi/T.
where r is the radius of the ring, a is the centripetal acceleration
(centrifugal acceleration if you're standing on the inside surface of
the ring), v is the tangential speed of the ring, omega is the angular
speed of the ring, and T is the rotation period of the ring.
If you're asking for the parameters specifically with respect to the
Ringworld, they are here:
http://www.alcyone.com/max/reference/scifi/ringworld.html
--
Erik Max Francis && max.TakeThisOut@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
Sit loosely in the saddle of life.
-- Robert Louis Stevenson |
|
| Back to top |
|
| |
External
Since: Aug 15, 2006
Posts: 12
|
(Msg. 3) Posted: Tue Aug 15, 2006 8:16 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
> If you're asking for the equations governing a rotating ring, then they are
>
> a = omega^2 r,
>
> v = omega r,
>
> omega = 2 pi/T.
>
> where r is the radius of the ring, a is the centripetal acceleration
> (centrifugal acceleration if you're standing on the inside surface of
> the ring), v is the tangential speed of the ring, omega is the angular
> speed of the ring, and T is the rotation period of the ring.
What units are the values best shown in? I attempted to run the
original Ringworld specs through in basic meters and seconds, but
everytime I used <i>omega = 2 pi/T</i> I would get some really sketchy
numbers. It could be that I just don't understand radians, but I think
it's just that I'm not displaying T in the right units. Other than
that, the numbers went through the equations just fine. >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Aug 15, 2006
Posts: 12
|
(Msg. 4) Posted: Tue Aug 15, 2006 8:22 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
> If you're asking for the equations governing a rotating ring, then they are
> a = omega^2 r,
> v = omega r,
> omega = 2 pi/T.
> where r is the radius of the ring, a is the centripetal acceleration
> (centrifugal acceleration if you're standing on the inside surface of
> the ring), v is the tangential speed of the ring, omega is the angular
> speed of the ring, and T is the rotation period of the ring.
What units are the values best shown in? I attempted to run the
original Ringworld specs through in basic meters and seconds, but
everytime I used < omega = 2 pi/T > I would get some really sketchy
numbers. It could be that I just don't understand radians, but I think
it's just that I'm not displaying < T > in the right units. Your
website was a huge help and other than anything involving < T >, the
numbers went through the equations perfectly. >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Jul 09, 2003
Posts: 169
|
(Msg. 5) Posted: Tue Aug 15, 2006 8:34 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
logan_mcgrath89.DeleteThis@hotmail.com wrote:
> What units are the values best shown in? I attempted to run the
> original Ringworld specs through in basic meters and seconds, but
> everytime I used < omega = 2 pi/T > I would get some really sketchy
> numbers. It could be that I just don't understand radians, but I think
>
> it's just that I'm not displaying < T > in the right units. Your
> website was a huge help and other than anything involving < T >, the
> numbers went through the equations perfectly.
You can use any unit system as long as you use proper units of angular
speed and time (period) for that system. In SI, it would be rad/s and
s, respectively.
All the figures shown on the Web site and in SI (with secondary
conversions to more conventional unit systems).
--
Erik Max Francis && max.DeleteThis@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
No need to tell her there's a world out there / She knows / She just
doesn't seem worried at all -- Nik Kershaw >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: May 14, 2005
Posts: 63
|
(Msg. 6) Posted: Wed Aug 16, 2006 11:24 am
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
In article <PM-dnbLLKtM18X_ZnZ2dnUVZ_r-dnZ2d.DeleteThis@speakeasy.net>, Erik Max
Francis wrote:
> If you're asking for the parameters specifically with respect to the
> Ringworld, they are here:
>
> http://www.alcyone.com/max/reference/scifi/ringworld.html
>
Useful.
Hang on. "Ringworld atmospheric composition N2 74%, O2 23%, Ar
2%, He 1%, trace elements < 1%"
I don't recall all that helium being mentioned anywhere. (Maybe
my memory.) But I do recall the presence of a lot of atmospheric helium
being taken as evidence for a long use of fusion reactions in some part
of Niven's work. Mote?
--
Aidan Karley, FGS
Aberdeen, Scotland
Written at Wed, 16 Aug 2006 10:45 +0100, but posted later. >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Jul 09, 2003
Posts: 169
|
(Msg. 7) Posted: Wed Aug 16, 2006 12:09 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
Aidan Karley wrote:
> Hang on. "Ringworld atmospheric composition N2 74%, O2 23%, Ar
> 2%, He 1%, trace elements < 1%"
> I don't recall all that helium being mentioned anywhere. (Maybe
> my memory.) But I do recall the presence of a lot of atmospheric helium
> being taken as evidence for a long use of fusion reactions in some part
> of Niven's work. Mote?
They're from the Ringworld Roleplaying Game, canonicalized by Niven himself.
--
Erik Max Francis && max.DeleteThis@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
Never make a promise or plan / Take a little love where you can
-- Florence, _Chess_ >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Aug 15, 2006
Posts: 12
|
(Msg. 8) Posted: Wed Aug 16, 2006 3:20 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
Erik Max Francis wrote:
> All the figures shown on the Web site and in SI (with secondary
> conversions to more conventional unit systems).
I think I might be using the equation incorrectly.... The angular
velocity is 7.98X10^-6rad/s, but when I plug in the numbers for ω =
2πT <ω = 2(3.1459)(78700s) > I get 4.95x10^5rad/s! When I keep T in
the original units (787ks) I get 4.95x10^3rad/s, so I'm thinking that
there's something wrong with the given value of T. What am I messing
up here? >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Aug 15, 2006
Posts: 12
|
(Msg. 9) Posted: Wed Aug 16, 2006 3:24 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
Erik Max Francis wrote:
> All the figures shown on the Web site and in SI (with secondary
> conversions to more conventional unit systems).
I think I might be using the equation incorrectly.... The angular
velocity is 7.98X10^-6rad/s, but when I plug in the numbers for ω =
2πT <ω = 2(3.1459)(78700s) > I get 4.95x10^5rad/s! When I keep T in
the original units (787ks) I get 4.95x10^3rad/s, so I'm thinking that
there's something wrong with the given value of T. What am I messing
up here?
In a last-ditch attempt, I tried finding T from the other values using
< ω/2π = T > and all I got was 1.27x10^-6. Lord knows what that is! >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Aug 15, 2006
Posts: 12
|
(Msg. 10) Posted: Wed Aug 16, 2006 3:33 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
I just found another equation, but I still have no idea if this is
right.
omega = r v / |r|^2
0.000797 = (1.53^11m x 122000000m/s) / (1.53^11m)^2 Closer numbers,
screwy decimal points, and still doesn't make sense.... >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Jul 09, 2003
Posts: 169
|
(Msg. 11) Posted: Wed Aug 16, 2006 4:25 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
logan_mcgrath89 DeleteThis @hotmail.com wrote:
> I think I might be using the equation incorrectly.... The angular
> velocity is 7.98X10^-6rad/s, but when I plug in the numbers for ω =
> 2πT <ω = 2(3.1459)(78700s) > I get 4.95x10^5rad/s! When I keep T in
> the original units (787ks) I get 4.95x10^3rad/s, so I'm thinking that
> there's something wrong with the given value of T. What am I messing
> up here?
The equation isn't omega = 2 pi T, it's omega = 2 pi/T.
Dimensional analysis should have clued you in here; 2 pi T has units of
s, not s^-1.
--
Erik Max Francis && max DeleteThis @alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
All delays are dangerous in war.
-- John Dryden >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Jul 09, 2003
Posts: 169
|
(Msg. 12) Posted: Wed Aug 16, 2006 4:32 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
logan_mcgrath89.DeleteThis@hotmail.com wrote:
> I just found another equation, but I still have no idea if this is
> right.
>
> omega = r v / |r|^2
>
> 0.000797 = (1.53^11m x 122000000m/s) / (1.53^11m)^2 Closer numbers,
> screwy decimal points, and still doesn't make sense....
You lost some symbols here, the proper equation here is
omega = r cross v/|r|^2.
This equation is also valid, but probably overmuch for what you need.
When r and v are perpendicular (which they are for a rotating ring),
then this simplifies to the scalar equation
omega = v/r,
which is just a rewrite of one of the equations (v = omega r) that I had
written above.
--
Erik Max Francis && max.DeleteThis@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
All delays are dangerous in war.
-- John Dryden >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Apr 10, 2006
Posts: 8
|
(Msg. 13) Posted: Wed Aug 16, 2006 6:21 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Wed, 16 Aug 2006 11:24:37 +0100, Aidan Karley
<doIlookDAFTenoughTOpost DeleteThis @validEMAILaddressTOa.NEWS.group> wrote:
> I don't recall all that helium being mentioned anywhere. (Maybe
>my memory.) But I do recall the presence of a lot of atmospheric helium
>being taken as evidence for a long use of fusion reactions in some part
>of Niven's work. Mote?
Yes. For some reason I can remember the exact line - "One percent or
thereabouts". >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: Aug 15, 2006
Posts: 12
|
(Msg. 14) Posted: Wed Aug 16, 2006 8:15 pm
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
Erik Max Francis wrote:
> The equation isn't omega = 2 pi T, it's omega = 2 pi/T.
>
> Dimensional analysis should have clued you in here; 2 pi T has units of
> s, not s^-1.
Holy poop.... I'm stupid! Thanks, turns out I was entering 2 pi T into
the spread sheet. I ended up doing some number like ω =
360/[T(180/π)], which did work. *laughing*
Thanks! >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
External
Since: May 14, 2005
Posts: 63
|
(Msg. 15) Posted: Thu Aug 17, 2006 12:00 am
Post subject: Re: Ringworld Parameters [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
In article <-7WdnaUCx7XK8H7ZnZ2dnUVZ_qudnZ2d DeleteThis @speakeasy.net>, Erik Max Francis
wrote:
> They're from the Ringworld Roleplaying Game, canonicalized by Niven himself.
>
Awww, what would he know ??? <G>
--
Aidan Karley, FGS
Aberdeen, Scotland
Written at Wed, 16 Aug 2006 23:20 +0100, but posted later. >> Stay informed about: Ringworld Parameters |
|
| Back to top |
|
| |
|
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
|
|
|
|
|
|
FAQ
Search
Profile
Private Messages
Log in/Register/Password
