- First we had the space elevator madness, and then
microwaves beamed from space to generate power.
-
- Now it's lasers. It was just a matter of time that this
had to happen sooner or later. But we shall see that everything you can
imagine is wrong with this idea including safety, cost and efficiency.
-
- I'll swear that marketing people have so much BS that
when they dream at night their dreams are brown, not full color or black
and white. Having dealt with too many of them in my life, I speak from
experience.
-
- Astrium is the company with mad scheme to use sunlight
to power a laser in the 20KW class, and they claim it will be safe. (That
was also said about depleted Uranium, Aspartame, GM food, etc)
-
- SAFETY
-
- Mr. Perren of Astrium which is certain this idea is safe
proclaims the following:
-
- "We are concentrating on developing something that
is safe. While the laser beam will have some heat in it, we intend for
it to be safe for people to walk through unaffected." [1]
-
- "Something that is safe?" They better disconnect
their phones, faxes and shut off cell phones so they can concentrate enough
on this one. Let's take a closer look at their statement. Lasers excel
at concentrating high energy into a very small beam. If a satellite will
contain the laser, obviously the beam must be small. Standards to prevent
eye damage exist for a reason.
-
- The American National Standards Institute (ANSI) has
safe power standards for all types of lasers. These standards define exposure
limits to the human eye of less than 1 watt, and in some cases just thousands
of a watt for laser light.
-
- Here's a brief list of USA safety standards
for lasers:
-
- * ANSI Z136.1 - Safe Use of Lasers
- * ANSI Z136.3 Safe Use of Lasers in Health
Care Facilities
- * ANSI Z136.4 Recommended Practice for
Laser Safety Measurements for Hazard Evaluation
- * ANSI Z136.5 Safe Use of Lasers in Educational
Institutions
- * ANSI Z136.6 Safe Use of Lasers Outdoors
- * ANSI Z136.7 Testing and Labeling of
Laser Protective Equipment
-
- Near infrared light has a wavelength of about 850 to
900nm. Higher numbers (such as 1400nm) represent longer wavelengths in
the infrared. People cannot see this type of infrared but feel it simply
as heat. I have added some comments in the following text someone else
wrote using curly braces to help clarify a detailed statement on eye damage
taken from [2]
-
- "The coherence, the low divergence angle {that laser
light does not spread out very much over distance}of laser light and the
focusing mechanism of the eye means that laser light can be concentrated
into an extremely small spot on the retina [the back of the human eye.}
A transient {sudden} increase of only 10 °C can destroy retinal photoreceptors.
If the laser is sufficiently powerful, permanent damage can occur within
a fraction of a second, faster than the blink of an eye. Sufficiently powerful
visible {and ultraviolet}to near infrared laser radiation (400-1400 nm)
will penetrate the eyeball and may cause heating of the retina, whereas
exposure to laser radiation with wavelengths less than 400 nm {ultraviolet}
and greater than 1400 nm {far infrared or heat} are largely absorbed
by the cornea and lens, leading to the development of cataracts or burn
injuries.
-
- Infrared lasers are particularly hazardous, since the
body's protective "blink reflex" response is triggered only by
visible light. For example, some people exposed to high power Nd:YAG laser
{solid rod laser} emitting invisible 1064 nm radiation {heat} may
not feel pain or notice immediate damage to their eyesight. A pop or click
noise emanating from the eyeball may be the only indication that retinal
damage has occurred i.e. the retina was heated to over 100 °C {boiling
point of water, or 212 °F} resulting in localized explosive boiling
accompanied by the immediate creation of a permanent blind spot."
[2]
-
- Note that a temperature increase of just 10 °C causes
damage to the retina by destroying photoreceptors. Yet Astrium claims people
will be able to look up at the beam without eye damage? Perhaps they have
found a way to change the laws of physics!
-
- Let's look back at another Astrium statement "While
the laser beam will have some heat in it, we intend for it to be safe for
people to walk through unaffected." Ridiculous.
-
- It is well known that lasers with power levels less than
1 WATT can cause serious eye damage.
-
- "The U.S. Food and Drug Administration (FDA) requires
all class IIIb and class IV lasers offered in commerce in the US to have
five standard safety features: a key switch, a safety interlock dongle,
a power indicator, an aperture shutter, and an emission delay (normally
two to three seconds).[2]
-
- "Even a laser pointer which operates at about .005
watts or 5 milliwatts, can easily damage the eye. Yet parents think nothing
of giving one to their children.
-
- Note that lasers in class IIIb and class IV are only
a few milliwatts not 20,000 watts. With a satellite in orbit, there
would be no way for someone on the Earth to turn a key switch, trip a safety
interlock or hit a big red STOP button.
-
- For more on laser safety see Princeton University's training
information. [3]
-
- COST
-
- Astrium's laser power satellite will cost perhaps 300
million dollars to build, and many millions more to insert it into orbit.
All satellites expend fuel to reach their assigned locations, and in some
cases for station keeping operation. Station keeping prevents satellites
from plunging back to Earth, colliding with other satellites, losing orientation
and communication with Earth and drifting out of position. Also required
are a team of people who monitor and control the satellite around the clock,
365 days/year. Satellites only have about a 5 to 8 year lifetime in orbit
before solar cells have been degraded by full solar UV radiation and heat
to the point of no longer being efficient enough to be useful. In other
words, satellites slowly become 10 ton pieces of space junk. They are either
de-orbited with ground commands, or sent into the Sun for destruction.
Left in space a dead satellite becomes a serious hazard.
-
- Does all this seem worth the expense to generate a measly
20KW of power? If the cost to design, build and launch the satellite into
orbit is about $350 million, a simple calculation reveals that this "free"
energy from the Sun actually will cost about $17,500/ WATT - and
that figure doesn't even include the cost of the ground crew and ground
station to monitor and control it or the tens of millions of additional
dollars to build the laser power collection system on the ground. This
is what would collect the laser energy and convert it to regulated alternating
current.
-
- Even the most expensive system you could ever imagine
to generate electricity from ocean waves, is a tiny fraction of this cost.
Even if a sea wave power generating system was made out of the finest stainless
steel money can buy, it still wouldn't even come close to the laser power
system cost.
-
- 20KW is only enough power to supply the conservative
electrical needs of just FOUR HOMES. Laser light cannot power thousands
of homes, nor can the same light be used effectively at more than one location.
Laser light is very different than microwaves from television satellites.
These satellites distribute microwaves at a power level of about 36 watts
per transponder over an entire continent to provide television and telephone
service.
-
- EFFICIENCY
-
- Lasers are incredibly inefficient, with the best efficiencies
on the order of about 10 to 15%. This means to generate 20KW of power,
the satellite's solar panels will need to generate about 200KW of power
just to compensate for laser losses. Of course, this doesn't include additional
power required to operate the satellite's station keeping, computers and
communication systems.
-
- To put this into perspective, the 4 pairs of solar panels
on the Space Station generate only 32 KW of power. The Astrium satellite
will require a solar array at least SEVEN TIMES larger than the space station
has. It's hard to conceive that such a huge solar array could be carried
into space with just one launch.
-
- And we haven't yet considered how much of the 20KW of
laser light will actually reach Astrium's Earth power station. Although
infrared can pass through clouds there is still a loss factor for varying
weather conditions that must be accounted for when engineers calculate
power budgets and losses.
-
- With all these facts exposed, does it seem that Astrium's
power satellite makes sense or will be safe? Lasers are a wonderful solution
for a plethora of different technologies and problems - but are not practical
for beaming power back from space.
-
- Perhaps the entire scheme is just another stock-market
scheme to raise big bucks and make a few people rich. This wouldn't be
the first time.
-
- I think there's a whiff of a dead space elevator in the
air
-
- Ted Twietmeyer
-
- [1] - http://www.telegraph.co.uk/earth/energy/solarpower/7060015/
Lasers-to-beam-energy-to-Earth-from-space.html
- [2] - http://en.wikipedia.org/wiki/Laser_safety
- [3] - http://web.princeton.edu/sites/ehs/laserguide/sec3.htm#class3
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