Significance of the solar wind

In article <8b42afac.0409162023.7fc62a07.TakeThisOut@posting.google.com>,
kuyper.TakeThisOut@wizard.net (James Kuyper) wrote:

 > steve.TakeThisOut@antispam.sforbesa.cix.co.uk (Stephen Forbes) wrote in message
 > news:<memo.20040916231157.2877E.TakeThisOut@sforbesa.compulink.co.uk>...
  > > In article <8b42afac.0409160828.132fd765.TakeThisOut@posting.google.com>,
  > > kuyper.TakeThisOut@wizard.net (James Kuyper) wrote:
 > ...
   > > > > ... There are some
   > > > > obvious problems where the loops touch, where the field is
   > > > > horizontal not vertical. This problem will remain as long as
   > > > > there is more than one loop.
   > > >
   > > > The loops touch, and the field is horizontal, only in the region
   > > > between day-streams, where there is little solar wind because it's
   > > > been blocked by the shadow squares. That was an essential component
   > > > of
   > > > my design.
  > >
  > > This doesn't make any kind of sense, your day streams will eventually
  > > cover every part of the Ringworld surface in no more than 15 days.
  > > There is no part of the surface which doesn't receive the solar wind
  > > on a regular basis.
 >
 > Of course. That's why the configuration of the magnetic field needs to
 > change with time. If you pay close attention to my specification,
 > you'll see that the location of the current loop is determined by the
 > location where the day-streams impact the Ringworld. As the
 > day-streams move, so must the the current loops. They don't move
 > physically, of course; the current simply gets re-routed.
 >

It makes sense if you know that someone will always be around to maintain
the system. That person/protector has to replace worn switching units on a
regular basis, keep track of the day-streams so that the field is always
in the right place and possibly other things which haven't immediately
sprung to mind. I cannot see it as an automatic system which is the
hallmark of the Ringworld.
As other thoughts come to mind which relate to this I will mark them with
an asterix.

   > > > >
   > > > > You really should put numbers in and balance it with the current
   > > > > required to produce that field in your coil.
   > > >
   > > > You know of some particular limit on that current? I don't. Without
   > > > a
   > > > limit, I don't see why it matters what the current required is.
  > >
  > > Even superconductors have their limits, if you put too much current
 >
 > "Even" superconductors? Our real world superconductors are rather
 > finicky about magnetic fields. They don't allow magnetic fields to
 > penetrate them. However, a sufficiently strong magetic field will make
 > their superconductivity break down. I think that we have to assume
 > that the Ringworld's Engineers took that into consideration.

Fair enough.

 >
  > > through them they will lose their superconductivity. I know
  > > superconductivity happens because electrons travel in pairs, if you
  > > increase the current too much those pairs will be knocking into other
  > > pairs and break up their relationship, causing resistance.
 >
 > OK. So what is current density limit on Ringworld superconductors? How
 > big are they in cross-section? I don't believe that Niven has ever
 > answered either of those questions. I think that we are therefore
 > entitle to assume that the cross-sections and current density limits
 > were known to the Ringworld Engineers, and were therefore adequate to
 > the task.
 >

I doubt that the superconductor has any structural strength so I would
guess that it was kept as thin as possible. How thin I have no idea but I
would suspect no thicker than 1/10th the thickness of the scrith.

 > ...
  > > Actually its an inverse linear relationship in the plane of the
  > > Ringworld.
  > > The further away from the loop you go, which is the only source of
  > > magnetism generated, the weaker that magnetism becomes.
 >
 > Yes, but only for distance much larger than the size of the current
 > loop. In the immediate vicinity of the loop, the magnetic field
 > follows the same force law as an infinitely long current.

* A little gotcha, if you are throwing the solar wind over the rim wall
and you are allowing for variations in its speed by throwing it well
clear, how are the attitude jets ever going to get any fuel.

 > ...
  > > to remove most of the material. A ring magnet does not produce a
  > > uniform field and neither will your loop which is equivalent to one.
 >
 > I never said that it produced a highly uniform field, only that it
 > would be sufficiently close to uniform.

I don't see it anywhere close to uniform, not for a single loop.
If instead of loops you followed the zig zag pattern of 21 lines over the
width, all around the circumference, you can create a field which needs no
maintenence. The wires will create a horizontal field which links up with
ajacent lines to produce a mildly patterned horizontal field which will
throw the solar wind over the rim wall and allow some solar wind to reach
the attitude jets. One rim wall becomes magnetic north and the other
magnetic south. You position the jets where the wire is well away from the
wall and the wind can reach them.

Put the jets here
_______________________________ Rim wall
* *
___ ___ ___ ___
___/ \___/ \___/ \___/ 1 of 21 parallel wires

The above also works for your loops as the segment parallel to the rim
wall.

Stephen

<a style='text-decoration: underline;' href="http://www.cix.co.uk/~sforbesa" target="_blank">http://www.cix.co.uk/~sforbesa</a><!-- ~MESSAGE_AFTER~ -->

In article <414A1AD1.6BC1C423 RemoveThis @alcyone.com>, max RemoveThis @alcyone.com (Erik Max
Francis) wrote:

 > Dark2112 wrote:
  > > Some of you say that if a species could create a mostly-indestructible
  > > metal to fashion the Ringworld, and in fact to actually construct such
  > > a mammoth creation, that it should/would be child's play for them to
  > > engineer an automated system that would preserve said atmosphere.
 >
 > I don't recall anyone on the other side saying anything like that. On
 > the contrary, they didn't say that supertechnologies were required to
 > retain the atmosphere, they said _nothing additional_ was required to
 > retain the atmosphere, since the leakage rates would be utterly
 > trivial. It would take many times longer than the age of the Universe
 > for the Ringworld, as designed, to lose its atmosphere. The lone
 > detractor made up a figure of 100 yr for the timescale it would take for
 > Ringworld to empty itself, and then proceeded to claim the same thing
 > was happening to Venus, although curiously dodging the point that Venus
 > has had an atmosphere for longer than 100 yr.

Get your so called facts straight. I never said the same was happening to
Venus, somebody else said that. My reply to him was a partial explanation
as to why it wasn't happening. I have since discovered the real reason is
Venus has a protective magnetic field anyway, just not its own.

Stephen

<a style='text-decoration: underline;' href="http://www.cix.co.uk/~sforbesa" target="_blank">http://www.cix.co.uk/~sforbesa</a><!-- ~MESSAGE_AFTER~ -->