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Question about Centrifugal Gravity



 
 
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  #1  
Old February 15th 11, 12:35 PM posted to sci.space.tech
James W
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Posts: 1
Default Question about Centrifugal Gravity

So a lot of movies, TV shows, illustrations, etc., show spacecraft
generating "gravity" via rotating hull sections. In many cases, this
rotating section spins around a stationary central hull.

The question I have for those more knowledgeable in this area than I
is: What is the connection between these two sections? Obviously
there shouldn't be a physical connection between the two hull sections
(right?). But would this mean space enough between the spinnning hull
and the stationary hull for the interior atmosphere to escape? Or is
it sealed somehow?

Sorry if this is a beginner's or nitpicker's question; it's just
something that I've been wondering about for a while.

Thanks in advance to everyone who'll help me expand my knowledge
here.

--James

  #2  
Old February 15th 11, 03:08 PM posted to sci.space.tech
Sylvia Else[_2_]
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Posts: 458
Default Question about Centrifugal Gravity

On 15/02/2011 10:35 PM, James W wrote:
So a lot of movies, TV shows, illustrations, etc., show spacecraft
generating "gravity" via rotating hull sections. In many cases, this
rotating section spins around a stationary central hull.

The question I have for those more knowledgeable in this area than I
is: What is the connection between these two sections? Obviously
there shouldn't be a physical connection between the two hull sections
(right?). But would this mean space enough between the spinnning hull
and the stationary hull for the interior atmosphere to escape? Or is
it sealed somehow?

Sorry if this is a beginner's or nitpicker's question; it's just
something that I've been wondering about for a while.

Thanks in advance to everyone who'll help me expand my knowledge
here.

--James


In 2001 A Space Odyssey, it was clear that the entire rotating assembly
was inside the non-rotating pressure hull, so that the issue of air
leakage didn't arise.

In Mission to Mars, that was not the case, and it would have required
some kind of sliding hermetic seal which is probably not feasible.

In practice, the most obvious solution seems to be to rotate the entire
spacecraft, but doing that removes many of the cinematically interesting
scenes.

Sylvia.

  #4  
Old February 17th 11, 03:30 PM posted to sci.space.tech
Jonathan Thornburg [remove -animal to reply][_3_]
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Posts: 137
Default Question about Centrifugal Gravity

James W wrote:
So a lot of movies, TV shows, illustrations, etc., show spacecraft
generating "gravity" via rotating hull sections. In many cases, this
rotating section spins around a stationary central hull.

The question I have for those more knowledgeable in this area than I
is: What is the connection between these two sections? Obviously
there shouldn't be a physical connection between the two hull sections
(right?). But would this mean space enough between the spinnning hull
and the stationary hull for the interior atmosphere to escape? Or is
it sealed somehow?


If you have separate rotating and non-rotating sections (as in, for
example, the movie "2010"), then yes, you need a rotating air-seal
between them. This takes a bit of effort for the engineers, but is
certainly possible.

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

  #5  
Old February 19th 11, 04:03 AM posted to sci.space.tech
Sylvia Else[_2_]
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Posts: 458
Default Question about Centrifugal Gravity

On 18/02/2011 1:30 AM, Jonathan Thornburg [remove -animal to reply] wrote:
James wrote:
So a lot of movies, TV shows, illustrations, etc., show spacecraft
generating "gravity" via rotating hull sections. In many cases, this
rotating section spins around a stationary central hull.

The question I have for those more knowledgeable in this area than I
is: What is the connection between these two sections? Obviously
there shouldn't be a physical connection between the two hull sections
(right?). But would this mean space enough between the spinnning hull
and the stationary hull for the interior atmosphere to escape? Or is
it sealed somehow?


If you have separate rotating and non-rotating sections (as in, for
example, the movie "2010"), then yes, you need a rotating air-seal
between them. This takes a bit of effort for the engineers, but is
certainly possible.


Do you have any references describing how it could be achieved? I've
looked, and I cannot find anything.

Sylvia.

  #6  
Old February 20th 11, 04:51 PM posted to sci.space.tech
Jonathan Thornburg [remove -animal to reply][_3_]
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Posts: 137
Default Question about Centrifugal Gravity

I wrote
| If you have separate rotating and non-rotating sections (as in, for
| example, the movie "2010"), then yes, you need a rotating air-seal
| between them. This takes a bit of effort for the engineers, but is
| certainly possible.

Sylvia Else wrote:
Do you have any references describing how it could be achieved? I've
looked, and I cannot find anything.


I was originally quoting Henry Spencer in this newsgroup
(article , dated 30 June 2003), when he wrote
: Making an essentially zero-leakage rotating joint is not a big problem,
: especially for slow rotation.

I don't have any specific references, but google "rotating shaft seal"
brought up about 285,000 hits just now, many of which looks relevant.
For example, each of
http://en.wikipedia.org/wiki/Rotatin...echanical_seal
http://www.azom.com/Details.asp?ArticleID=504
http://www.mt-online.com/component/c...l?directory=90
http://www.freepatentsonline.com/3088744.html
has some useful general information.

This is quite standard industrial technology. For example, every
ship has a rotating seal where its propellor shaft(s) exits the hull.
Loaded oil tankers may have their propellor shafts more than 10 meters
(33 feet) below the water level, giving an ambient water pressure of
greater than 1 atmosphere. Indeed, submarine propellor-shaft seals
must withstand up to ~50 atmospheres of pressure (= water pressure at
a depth of ~1500 ft).

ciao,

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

  #7  
Old February 20th 11, 04:51 PM posted to sci.space.tech
Allen Thomson
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Posts: 372
Default Question about Centrifugal Gravity

On Feb 18, 9:03 pm, Sylvia Else wrote:

Do you have any references describing how it could be achieved? I've
looked, and I cannot find anything.


Fluidic seals of various sorts are one possibility. See, for example,
http://en.wikipedia.org/wiki/Ferrofluidic_seal

  #8  
Old February 20th 11, 05:46 PM posted to sci.space.tech
Len Lekx
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Posts: 123
Default Question about Centrifugal Gravity

On Thu, 17 Feb 2011 09:30:09 EST, "Jonathan Thornburg [remove -animal
to reply]" wrote:

If you have separate rotating and non-rotating sections (as in, for
example, the movie "2010"), then yes, you need a rotating air-seal
between them. This takes a bit of effort for the engineers, but is
certainly possible.


A bigger problem than the pressure seal would be the need to
transfer control signals and power through the moving section.

Although... given the advancements in wireless technology, that
isn't as big a problem now as it used to be.

  #9  
Old February 20th 11, 10:12 PM posted to sci.space.tech
Robert Heller
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Posts: 17
Default Question about Centrifugal Gravity

At Sun, 20 Feb 2011 11:46:32 EST Len Lekx wrote:


On Thu, 17 Feb 2011 09:30:09 EST, "Jonathan Thornburg [remove -animal
to reply]" wrote:

If you have separate rotating and non-rotating sections (as in, for
example, the movie "2010"), then yes, you need a rotating air-seal
between them. This takes a bit of effort for the engineers, but is
certainly possible.


A bigger problem than the pressure seal would be the need to
transfer control signals and power through the moving section.


Transfering *power* to some sort of moving object is *really old tech.*
-- every rotating electrical device (motors, generators, alternators)
and *electric* subway and commuter trains, and trolly cars need to do
this all the time. Slip rings would work. Presumably, we are not
talking about a solid shaft (like a propeler), but a rotating tube.
Using something not unlike a circular trolly wire with a trolly wheel or
shoe would work. So would a contact shoe against a ring plate.


Although... given the advancements in wireless technology, that
isn't as big a problem now as it used to be.


Right. Control signals could just be encoded as wireless ethernet
packets. And anything critical could be handled by additional slip
rings, much as the power.

Plumbing would be interesting, but also doable -- just a different sort
of concentric rotating seals at the center of rotation.




--
Robert Heller -- 978-544-6933 /
Deepwoods Software --
http://www.deepsoft.com/
() ascii ribbon campaign -- against html e-mail
/\ www.asciiribbon.org -- against proprietary attachments




  #10  
Old February 22nd 11, 02:15 PM posted to sci.space.tech
Jeff Findley
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Posts: 5,012
Default Question about Centrifugal Gravity



In article , lid

says...



On 18/02/2011 1:30 AM, Jonathan Thornburg [remove -animal to reply] wrote:


James wrote:


So a lot of movies, TV shows, illustrations, etc., show spacecraft


generating "gravity" via rotating hull sections. In many cases, this


rotating section spins around a stationary central hull.




The question I have for those more knowledgeable in this area than I


is: What is the connection between these two sections? Obviously


there shouldn't be a physical connection between the two hull sections


(right?). But would this mean space enough between the spinnning hull


and the stationary hull for the interior atmosphere to escape? Or is


it sealed somehow?




If you have separate rotating and non-rotating sections (as in, for


example, the movie "2010"), then yes, you need a rotating air-seal


between them. This takes a bit of effort for the engineers, but is


certainly possible.






Do you have any references describing how it could be achieved? I've


looked, and I cannot find anything.




Nautilus-X (see the link to the Powerpoint in the article below)

http://www.spaceref.com/news/viewsr.html?pid=36068



Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011




 




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