I like these ideas. About the magnetic field idea perhaps we could have a
flat plate magnet at the bottom. Instead of the entire fluid being charged
or magnetized, perhaps we could have a flexible metallic cover above the
fluid that would then apply a downward force.
Bob Clark
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wrote in message
...
hmm... meniscus. will if you have air pressure - which you could do, you
could put it in a pressurized container - i thing for sufficiently narrow
tubes, it's a sphere. not sure what happens in large tubes, though. i feel
it would be flatter in the middle.
another way you could create a sphere - two other ways - is using either the
electric or magnetic force.
somehow charge the liquid and have a charged ball at the desired focal point
or likewise for magnetic. though the ball at the focal point - you're not
going to have a spherical field.
but back to the meniscus thing - i'm reminded of a bubble. it forms
spherical between two gases because that minimizes gibbs free energy.
maybe instead of even spinning, you could just essentially blow a bubble,
then let it solidify.
On Sunday, May 22, 2016 at 9:35:03 AM UTC-5, Robert Clark wrote:
Found an interesting article after a Google search:
The shape of a liquid surface in a uniformly rotating cylinder in the
presence of surface tension.
http://maeresearch.ucsd.edu/~vlubard...s/Acta2013.pdf
This calculates the shape of the meniscus under both gravity and zero
gravity.
A topic I'm interested in is whether the method of making large parabolic
mirrors on Earth by rotating the glass in molten form to form a parabolic
meniscus then allowing it to solidify can also work in space.
This will have an advantage over transporting the already formed mirrors
into space because for large mirrors you have to concerned about the size
of
the rocket fairing. But in fact in zero g you would have an advantage in
that you wouldn't have to worry about the mass and cost of the support
structures and of the mirror deforming under it's own weight.
You could emulate the Earth's gravity during the formation stage in
space
by using either centrifugal force due to rotation around a second axis or
by
using linear acceleration. Rotation around a second axis though could
create
instabilities. On the other hand doing a linear acceleration for the weeks
of cooling time would require a prohibitive amount of propellant.
That is why I wondered if it is possible to do in zero gravity just using
a
rotation around a single axis as on Earth. In the article ther were able
to
only solve numerically the equations for the zero gravity case. So my
questions is, is it possible to set the starting parameters such that the
meniscus shape is a good approximation to parabolic? Note it would also be
sufficient to get a good approximation to a spherical surface since then
you
can use a combination of spherical mirrors to cancel out the distortions
due
to a non-parabolic surface:
Spherical Aberration.
https://starizona.com/acb/basics/equ...spherical.aspx
It may be possible to get it to work no matter the shape of the curved
meniscus by using a mirror of similar shape to cancel out the aberrations
due to the non-parabolic shape. For instance, the Hubble uses a
combination
of hyperbolic mirrors to cancel out aberrations.
Bob Clark
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