Re: Dyson spheres are not dark

siproj (
Thu, 26 Jun 1997 10:30:07 -0500 (CDT)

On Thu, 26 Jun 1997, Carl Feynman wrote:

> At 11:41 AM 6/25/97 -0500, Dejan Vucinic wrote:
> > o What is the minimal distance from Sun at which a (diamondoid?)
> > statite can preserve its crystalline structure?

Diamonds are not durable even under moderately high temperatures
and can revert back to carbon froms at 1000C to 2000C depending on
environmental conditions.

> The minumum distance is around 136 kilometers [not a typo!]. Allow me to
> quote from a not-yet-complete essay I have cluttering my hard disk:

> <p>The surface of the Sun is hotter than the boiling point of any known
> material. Indeed, it is hot enough to rip any known molecule into atoms.
> One might think this would preclude the direct exploration and
> exploitation of the Sun. However, this is not the case. It
> is possible to build a device that can operate for long periods of time in
> the atmosphere of the Sun. This can be done with plausible near-term
> technology, operating with known materials and entirely within the
> well-established laws of physics.

Like Silicon or Tungsten Nitride as my favorites. Silicon Nitride
is a wonderful material that allows you to make loaded bearings
without pesky hydrocarbon lubrication.

> <p>I call my design for such a device a <i>heliopter</i> (from the Greek
> <i>helios</i>, Sun, and <i>pter</i>, wing). It is essentialy a helicopter
> that can hover indefinitely in the Solar atmosphere, using solar energy as
> a power source.

Will this energy be utilized as heat to run a turbine, do
that standard p-n junction like photovoltaics or high temperature
based thermionics for electricity?

> <p>First I will discuss the environment of the solar atmosphere. This is
> well-established science. Then I will discuss how one might keep an
> object immersed in that atmosphere cold enough to remain solid. This is
> an application of well-established engineering thermodynamics. Finally, I
> will describe the heliopter as a whole. This is an excercise in wild-ass
> system engineering. There's nothing in the design that I know to be
> infeasible, but I certainly haven't worked out every stress and heat flux
> and confirmed that it will work. [end excerpt]


> > o Outgoing radiation doesn't have to have a blackbody spectrum.
> > Lasing comes to mind, or one could heat up relatively small
> > radiators to a very high temperature.


> Lasing in particular is very bad. You wouldn't know it to look at one, but
> laser beams are very cold, i.e. have very low entropy. Thermodynamically
> speaking, they're like a perfect crystal at very low temperature, and the
> process of producing one requires extracting lots of entropy from a lasing
> medium and dumping it in the environment. Trying to cool something by
> emitting a laser beam is like trying to cool your house by installing a
> powerful freezer, making lots of ice cubes, and throwing them out the
> window. (Hmmm... that has a certain surreal delight to it. Imagine a house
> with ice cubes flying out all the windows...)

There is an engineer that has conducted an experiment that actually
successfully used a 40 watt laser to cool a crystal in a surprising way.
As a matter of fact, the paper on the technique is something else to read.

> That's OK, I love giving answers. -- CarlF

A distant laser beam could potentially provide a remote cooling source to
optically relocate the entropy of the heliopter while it is very close to
the atmosphere of the Sun. The radiator would appear as black, but
actually could be reflective to the optical coupling to the remote
cooling laser array. Phase cooling is also valuable for nano-technology,
silicon semiconductor fabrication and in vacuum object thermal shunting. Creator of alt.inventors and keeper of the Official
alt.inventors FAQ despite what some alt.config
sysadmin/waste of time/bandwidth actions.