Re: Solar powered lasers in space

On Sep 20, 2:53 pm, Ian Parker <ianpark...@xxxxxxxxx> wrote:
Just one point. Could you explain why you would prefer a 4 wave mixing
system to a straight computational system?
Computational methods could work as well. They're more sophisticated,
and beyond my capacity to do experimental work with at present. So,
until I can actually do something with them, I don't feel competent to
talk extensively about them. But certainly, a sensitive imaging
device with adaptive optics that was affixed to a phased laser array
could figure out how to produce a beam from the main array that would
track the target.

You mentioned earlier
safety considerations, but is that really true?

Yes if the details are right.

If someone were to
shine a laser upwards they would get roasted.

Not if the originating laser were properly constructed.

This would in fact
constitute a powerful weapon.

Only if built to operate as a weapon. If built to operate as a power
transmitter, it would be perfectly safe.

Now, the 15 MW or 2 GW per square meter systems WOULD be weapons in
modern parlance - just as a 747 would be a dandy seige weapon in the
15th century - by crashing it into a castle. But that would be an
inconcievable waste of resource - oh, those in the 15th century would
certainly have no qualms about doing it - but a 20th century pilot
wouldn't do it easily.

So, lets be clear. I forsee;

(1) The construction of large terrestrial solar power arrays at less
than $1 per peak watt
(2) The conversion of those power arrays to IR lasersats operating as
400 W/m2 (less than sunlight)
(3) Increasing energy density to 1,000 W/m2 -and use in mobile
applications
(4) Increasing energy density to 1,000,000 W/m2 and use in flight
applications

Now, all these - over the next 25 years or so - involve power levels
that are not weapons. 1 MW per square meter by the way is equivalent
to the heating capacity of a hair dryer!! Once there is a long and
fruitful history of laser power from space - then we can contemplate
higher energy densities without fear of misuse

(5) Increasing energy density to 20 MW/m2 - and use in space flight
applications
(6) Increasing energy density to 2 GW/m2 - and use in laser light
flight applications

#5 permits a broad access to the solar system and the personal
spaceship
#6 permits interstellar flight and the personal interstellar ark

There is a correlation between income and per capita energy
consumption in an industrial society that suggests as our energy
intensity increases, the size and scope of our personal possessions
will also increase.

A computational system would be required to ensure that this did not
happen. Why not have a straight computer system and build safeguards
into the software.

There are mixed systems that are possible as well. That is, the same
nonlinear optics that implement 4 wave mixing also can implement
logical circuits with the same optics. That is an optical transistor
is possible since many nonlinear optical materials exhibit optical
hysteresis. So, a powerful beam can be switched in phase by a weak
beam digital fashion... when you do the math and some experiments -
there are some simple mixed mode solutions that are possible which are
satisfying and simple. These are subject of current research and
continuing IP work. Once that is completed I can talk more about it.

However, consider the two systems;

One consists of an imaging system looking at the surface of the Earth
for signaling beams from receivers. The beams location is noted and
the phased array of laser elements is controlled by software to
produce a counter propagating beam. The imaging system is equipped
with phase measuring equipment that allows it to determine the precise
conjugate character of the pilot beam - allowing it to undo
atmospheric distortion. The imaging system is also equipped with an
ablity to decode modulation of the beam so that the desired amount of
power is delivered and the customer is appropriately billed.

The second system consists of a phase conjugate mirror built into the
backside of the lasing cavity - in such a way that it carries out ALL
the functions just described. That is, there are logical layers in
the phase conjugate mirror that modifies the systems response or
eliminates it totally if certain things - such as digital access codes
- are not met.


In fact what you will have is a computer network
with (possibly) one 8 bit computer controling a laser.

You have that in both cases, except that in the case where its all
built into the phase conjugate mirror its far more reliable and safe
than putting the system together piecemeal. Also, the speed and
accuracy of the all optical system is far superior than light/
electrical/light system.

Consider an integrated circuit with 1 billion transistor elements
randomly connected into logical patterns and its abilit to respond to
digital signals. It consists of three varieties of crystalline
structure that responds differently to electrons (p-type, n-type,
neutral) - and dozens of conductive layers that interconnect them in
logical patterns.

Now consider an integrated optical system that has 10 billion optical
switches per square millimeter per in 10,000 layers. The optical
media consists of a continuously variable phase medium and a fixed
holographic layer. The optical media is the equivalent of the silicon
in an IC, and the holographic layer is the equivalent of the
conductive layer. This complex array of computing elements is backed
by a phase conjugate mirror. A 100 square meter mirror contains 1
million trillion logical elements all interconnected and capable of
doing whatever logical function the IC based system is capable of
doing - by operating directly on the incoming imaged light source.

Sites on the ground will ask for power. Air/space craft will give
their positions, velocities and accelerations using GPS/Galileo and
also request power.

Yes.

The main advantage of a straight computer is that the whole thing is
easilt simulatable on the ground.

This is still possible with an all optical system. I have written
software to simulate 1 micron square in 10,000 layers... which leads
naturally toward building working systems.

- Ian Parker


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Relevant Pages

  • Re: Solar powered lasers in space
    ... The construction of large terrestrial solar power arrays at less ... a powerful beam can be switched in phase by a weak ... The second system consists of a phase conjugate mirror built into the ... there are logical layers in ...
    (sci.space.policy)
  • Re: Solar powered lasers in space
    ... Increasing energy density to 1,000,000 W/m2 and use in flight ... a powerful beam can be switched in phase by a weak ... there are logical layers in ... built into the phase conjugate mirror its far more reliable and safe ...
    (sci.space.policy)
  • Re: Solar powered lasers in space
    ... a powerful beam can be switched in phase by a weak ... there are logical layers in ... built into the phase conjugate mirror its far more reliable and safe ... "whoever controls the past, controls the future" / George Orwell ...
    (sci.space.policy)