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As you read
from the previous page on the thermal
benefits of Dream
Cellular, LLC's engineered substrates you saw that they have
substantial thermal
advantages over monolithic
substrates. Now we will discuss their mechanical advantages. |
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When Dream Cellular,
LLC designs a cellular substrate we go through an iterative process
that lets FEA tells us what the actual mirror will do. Initial
designs are then modified until a design goal is met. On some
substrates this has gone through as many as 18 iterations.
There are two main
cases that we are analyzing: polishing and gravity displacements.
The former is an evaluation of how the blank will perform during
grinding, polishing and figuring. The latter is an evaluation
of how the finished mirror will perform in the completed opto-mechanical
system.
As stated from
the previous page on the thermal
benefits of Dream
Cellular, LLC's engineered substrates a lower mass will equalize
faster than a higher mass, all things being equal. The other
main benefit of lower mass is that the gravity displacements,
the movement of areas within the substrate itself, are lower
in the mounted, finished mirror. As the mass of the optic goes
up, so too do the self-weight deflection numbers. It is therefore
highly beneficial to have a low mass optic. The result is a finished
mirror that has substantial performance gains across the
board. |
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As the stiffness
of the finished mirror itself goes up, it becomes harder to distort.
This helps to reduce the complexity of the supporting structures
for such lightweight optics or conversely can allow tighter tolerances
to be reached. |
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Another benefit
to the lower mass of the finished mirror is that it sets up a
domino affect for the rest of the opto-mechanical system. The
mirror's supporting structure, mirror cell, for an optic that
is 60-85% lower in mass does not need to be as heavy. This in
turn means the main instrument structure does not need to be
as heavy, to achieve the same structural stiffness requirements.
This reduces the mass carried by the mounting and can lead to
greater performance or the use of less expensive mountings. The
performance gains can come in the form of greater pointing, tracking
and slewing capabilities. As the aperture size increases, so
does the amount of mass that can be saved by using Dream Cellular,
LLC's engineered substrates.
Another alternative
is to reduce the mass of the optical substrates but not reduce
the mass of the supporting and main instrument structure. This
will, through good design and implementation, lead to higher
stiffness in the opto-mechanical system. |
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