A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Technology
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Question about Centrifugal Gravity



 
 
Thread Tools Display Modes
  #11  
Old February 23rd 11, 01:17 PM posted to sci.space.tech
Peter Fairbrother
external usenet poster
 
Posts: 100
Default Question about Centrifugal Gravity

Sylvia Else wrote:
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.


It can be done at simplest with the kind of rubber seal used in car
engines to keep the oil in, or with various other rotating seals of
greater complexity - but it doesn't usually need to be done.

For instance in a long flight, eg to Mars, you spin up the living
capsule say at one end of a tether and the landing module or whatever at
the other end, and it just stays spinning until a day or two before you
arrive.

For a space station with two sections the airlock between them (you do
want an airlock there!) either mates with the spinning section or with
the stationary section.

When moving from the rotating section the airlock opens to the RS,
people transfer into the airlock, it closes, it unmates with the RS, it
despins, then it mates with the stationary section etc.



In some scenarios the sections should not be in contact, if possible -
the main reason for having two sections is that you want microgravity in
one section and earthlike gravity in the other.

In order to have good microgravity with eg a rotating seal the center of
gravity of the rotating section must be at the center of the seal - but
this causes problems as eg people move around the rotating section. This
also puts pressure on the seal. It may be best to have no actual contact
between the sections, just a transfer airlock.



-- Peter Fairbrother

  #12  
Old June 1st 11, 09:38 PM
neilzero neilzero is offline
Junior Member
 
First recorded activity by SpaceBanter: May 2011
Posts: 22
Default

Quote:
Originally Posted by Peter Fairbrother View Post
Sylvia Else wrote:
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 spinning 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.


It can be done at simplest with the kind of rubber seal used in car
engines to keep the oil in, or with various other rotating seals of
greater complexity - but it doesn't usually need to be done.

For instance in a long flight, eg to Mars, you spin up the living
capsule say at one end of a tether and the landing module or whatever at
the other end, and it just stays spinning until a day or two before you
arrive.

For a space station with two sections the airlock between them (you do
want an airlock there!) either mates with the spinning section or with
the stationary section.

When moving from the rotating section the airlock opens to the RS,
people transfer into the airlock, it closes, it unmates with the RS, it
despins, then it mates with the stationary section etc.



In some scenarios the sections should not be in contact, if possible -
the main reason for having two sections is that you want microgravity in
one section and earthlike gravity in the other.

In order to have good microgravity with eg a rotating seal the center of
gravity of the rotating section must be at the center of the seal - but
this causes problems as eg people move around the rotating section. This
also puts pressure on the seal. It may be best to have no actual contact
between the sections, just a transfer airlock.

-- Peter Fairbrother
I have not seen a good solution other than separate habitats that are tethered together or a very large spoked wheel. A moving seal means considerable air loss into space and/or considerable energy loss to friction. With a fission or fusion power plant, perhaps the energy loss is aceptable. If we find 0.38 g (Mars) is acceptable, the hazard to people is perhaps no worse than moving sidewalks and rotating platforms used in theme park rides, which only stop in an emergency. Neil
  #13  
Old December 13th 11, 07:09 PM posted to sci.space.tech
Joe Pfeiffer
external usenet poster
 
Posts: 23
Default Question about Centrifugal Gravity

Sylvia Else writes:

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.


Rotating seals are a well-established technology in many areas, where a
lot more pressure has to be handled than the mere 15psi of sea level
atmospheric pressure -- auto engines, ship propellers... I don't know
of any on the scale of a rotating space ship hull section, but I
wouldn't be at all surprised to learn it's been done. Likewise, getting
electricity through a rotating interface is also well established:
tanks (as in armored vehicles, not as in something to store liquids!)
use metal rings and brushes.

  #14  
Old January 27th 12, 06:22 PM posted to sci.space.tech
Tony M
external usenet poster
 
Posts: 7
Default Question about Centrifugal Gravity

As a theoretical exercise it is definitely possible to seal two
relatively rotating sections of a spacecraft and have power, data and
plumbing run across. From a practical perspective this would be a
complex, expensive, heavy and fault susceptible assembly, hard to
justify as a feature.

The important question is why would there be a need for relatively
rotating sections? I, personally, cannot think of a good reason. I am
with Sylvia on this one; the entire ship would have to rotate as a
single hull. If there is a need for a non-rotating section (maybe a
science lab) it should be internal to the main hull, not a separate
hull section.

  #15  
Old January 29th 12, 06:41 PM posted to sci.space.tech
Jonathan Thornburg [remove -animal to reply][_3_]
external usenet poster
 
Posts: 137
Default Question about Centrifugal Gravity

Tony M wrote:
The important question is why would there be a need for relatively
rotating sections? I, personally, cannot think of a good reason. I am
with Sylvia on this one; the entire ship would have to rotate as a
single hull.


Things that are more conveniently located in a non-rotating
(a.k.a. "despun") section:
* antennas to communicate with the Earth
* telescopes to observe the target planet
* docking adapters for any sub-spacecraft
* airlocks for any spacewalks
* possibly heat radiators that want to avoid direct sunlight
* Whipple shields against orbital debris (if you're in a high-debris
orbit, i.e., a low-to-moderate-altitude Earth orbit)

--
-- "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

  #16  
Old March 12th 12, 10:33 AM
mickrio mickrio is offline
Junior Member
 
First recorded activity by SpaceBanter: Feb 2012
Posts: 11
Default

Yes,Person precisely standing at the axis of rotation i.e. either of poles , observes no torque hence no external force exerted due gravitational field .
__________________
Pua | pick up artist | Dating Coach
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Question about gravity mathematician Astronomy Misc 2 March 19th 10 06:49 AM
Whats difference between Centripetal and Centrifugal force? G=EMC^2 Glazier[_1_] Misc 3 May 5th 09 02:53 PM
Question about centrifugal force and Bernoulli's law. Robert Clark Astronomy Misc 7 August 29th 06 01:56 AM
tides and centrifugal force Paolo Sirtoli Astronomy Misc 0 July 12th 05 11:05 AM
Centrifugal Force? Benign Vanilla Misc 44 July 19th 04 05:21 AM


All times are GMT +1. The time now is 04:28 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.