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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 |
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#13
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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. |
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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. |
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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 |
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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 .
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