Laser beams being aimed at airliners?

Recently, Happy Dog posted:

"Roger"
I really doubt a 5 Mw laser would cause a problem at a distance of
three miles. As I said previously, if it had been a theatrical
followspot, I doubt anyone would care much. It's the weird colour
of green that makes it
stand out.

You do have to be careful though. We sometimes use 30Mw lasers for
astronomical pointers on clear nights and you definitely do not want
to look into one of those. They cost a tad more (between $200 and
$300 USD) than the typical little one used for pointing as screens
and are a whole lot brighter. The green light also carries a bit
more energy than the red ones. But even at three miles it'd light
up most of the cockpit and wouldn't show as a moving spot inside.
I don't think the 30 Mw would do permanent damage at 3 miles, but
you'd need to turn up the cockpit lighting to read the instruments if
you looked directly at it.

You *might* see a bright flash. But it wouldn't likely have much
effect on vision. You need to get over 5Mw/cm before the eye can't
react quickly enough to avoid temporary blindness.

The difficulty that I'm having with this thread is that I haven't seen
mention of the windscreen. These are not optically transparent, and I
suspect that most would be sufficiently micro-scratched so that the laser
beam would be imaged on their surface and therefore diffused to the point
that retinal damage would be highly unlikely. However, I can imagine that
night vision may be affected by the glow, and that is not something one
would want to have happen on short final. I agree with Happy Dog's point
that someone using a follow spot would be far more detrimental, yet not
cause all this ruckus.

Regards,

Neil

Roger opined

On Sat, 8 Jan 2005 15:51:52 -0500, "Happy Dog"
wrote:


You do have to be careful though. We sometimes use 30Mw lasers for
astronomical pointers on clear nights and you definitely do not want
to look into one of those. They cost a tad more (between $200 and
$300 USD) than the typical little one used for pointing as screens and
are a whole lot brighter. The green light also carries a bit more
energy than the red ones. But even at three miles it'd light up most
of the cockpit and wouldn't show as a moving spot inside.
I don't think the 30 Mw would do permanent damage at 3 miles, but
you'd need to turn up the cockpit lighting to read the instruments if
you looked directly at it.

I hope you are talking about milliwatt, not Megawatt lasers.


-ash
Cthulhu in 2005!
Why wait for nature?

Marty wrote:

"Edward Green" wrote in message
oups.com...

Very loud music has recently been implicated in collapsed lungs.
This
occurs after a small tear in the lung sac allows air into the chest
cavity, which tear can be in turn be caused by gut thumping bass.


Sounds like a job for Myth Busters

Well, the evidence in fact seems to be anecdotal, but not entirely
mythological, and was published in a peer reviewed journal:

http://www.wired.com/news/medtech/0,...w=wn_tophead_8

I do retract my "mechanism" though. That's pure speculation.

As a sound tech, I have had the opportunity to stand in front of some
very
large sub cabinets. These buggers would blow your clothes similar to
having
your back to a 40mph+ wind.
They have left welts on my legs from my jeans snapping on my skin,
but I
never lost a lung tho.

wrote in message
oups.com...
Marty wrote:

"Edward Green" wrote in message
oups.com...

Very loud music has recently been implicated in collapsed lungs.
This
occurs after a small tear in the lung sac allows air into the chest
cavity, which tear can be in turn be caused by gut thumping bass.


Sounds like a job for Myth Busters

Well, the evidence in fact seems to be anecdotal, but not entirely
mythological, and was published in a peer reviewed journal:

http://www.wired.com/news/medtech/0,...w=wn_tophead_8


The four cases cited were all indoor or in a car. That may be the difference
as I have only done outdoor venues. They don't say but I would speculate
that there were additional strains on the lungs like yelling/screaming and
toxicology issues at the time. Again, thats only speculation.

Marty wrote:

wrote in message
oups.com...
Marty wrote:

"Edward Green" wrote

Very loud music has recently been implicated in collapsed lungs.

Sounds like a job for Myth Busters

Well, the evidence in fact seems to be anecdotal, but not entirely
mythological, and was published in a peer reviewed journal:


http://www.wired.com/news/medtech/0,...w=wn_tophead_8


The four cases cited were all indoor or in a car. That may be the
difference
as I have only done outdoor venues. They don't say but I would
speculate
that there were additional strains on the lungs like
yelling/screaming and
toxicology issues at the time. Again, thats only speculation.

Yes, but its very well-informed speculation. ;-)

Until we are able to run a controlled experiment randomly assigning a
test group to two cohorts, one required to become high and scream, and
the other distributed in a similar fashion in the sonic field at
selected entertainment venues but restricted to sober foot taping,
we'll never know.

Larry Dighera wrote:
On Wed, 5 Jan 2005 23:30:57 -0500, "Happy Dog"

wrote in : :

"Larry Dighera" wrote in message
.. .
On Thu, 06 Jan 2005 03:52:02 GMT, Jose
wrote in ::

There may not be that many photons involved, but
they are all coming from the same direction, and that does count
for
something.

If I'm not mistaken, coherent laser light is all in phase.
Doesn't
that cause it to have more energy?

No. The energy is measured in watts like any other kind of power
source.

I was referring to the phenomenon of light coherence. There's an
explanation of it he

http://whatis.techtarget.com/definit...4527%2C00.html

And my point was that because the light of a laser is coherent (in
phase), it will provide more energy than an equally bright light
source whose radiation is out of phase. At least this is what I was
told by an EE.

No, the differrence is in power vs power/area. A given power laser or
other light source will put out that same power level. But, at the
target, the laser will result in a higher received power density,
measured in watts/meter squared.

Some targets that may resonate with the laser light frequency would
absorb more power, but that's a separate issue as well.

-Malcolm Teas

On Sun, 9 Jan 2005 01:34:10 -0600, "Marty"
wrote:


"Edward Green" wrote in message
roups.com...

Very loud music has recently been implicated in collapsed lungs. This
occurs after a small tear in the lung sac allows air into the chest
cavity, which tear can be in turn be caused by gut thumping bass.


Sounds like a job for Myth Busters

As a sound tech, I have had the opportunity to stand in front of some very
large sub cabinets. These buggers would blow your clothes similar to having
your back to a 40mph+ wind.

I have an old Fender Super Twin Reverb concert amp with 395 watts of
peak music power out. 195 watts RMS. (6, 6L6s) I can guarantee when
it's cranked it'll snap your pant legs like a blast out of an air hose
when you pop a low E string.

No collapsed lungs after this many years, but it will give you an
upset stomach with too many low notes. At that power level I used to
wear headphones.

They have left welts on my legs from my jeans snapping on my skin, but I
never lost a lung tho.

What say?? Speak up.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


Marty

On 9 Jan 2005 8:45:26 -0500, "Ash Wyllie" wrote:

Roger opined

On Sat, 8 Jan 2005 15:51:52 -0500, "Happy Dog"
wrote:


You do have to be careful though. We sometimes use 30Mw lasers for
astronomical pointers on clear nights and you definitely do not want
to look into one of those. They cost a tad more (between $200 and
$300 USD) than the typical little one used for pointing as screens and
are a whole lot brighter. The green light also carries a bit more
energy than the red ones. But even at three miles it'd light up most
of the cockpit and wouldn't show as a moving spot inside.
I don't think the 30 Mw would do permanent damage at 3 miles, but
you'd need to turn up the cockpit lighting to read the instruments if
you looked directly at it.

I hope you are talking about milliwatt, not Megawatt lasers.

Don't know, but we lost three telescopes last week.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


-ash
Cthulhu in 2005!
Why wait for nature?

Marty wrote:
"Edward Green" wrote in message
oups.com...

Very loud music has recently been implicated in collapsed lungs. This
occurs after a small tear in the lung sac allows air into the chest
cavity, which tear can be in turn be caused by gut thumping bass.

I vaguely remember hearing that one too. Got any cites?

Sounds like a job for Myth Busters

Buster isn't equipped for that sort of test; they'd have
to go to pig parts again (remember the cola-pop rocks ep?).

As a sound tech, I have had the opportunity to stand in front of some very
large sub cabinets. These buggers would blow your clothes similar to having
your back to a 40mph+ wind.
They have left welts on my legs from my jeans snapping on my skin, but I
never lost a lung tho.

So blowing a lung may be dependent on a "convenient"
resonance inside the chest cavity, requiring the subject to
prestress everything by yelling etc. Gonna be hard to
model with pig parts...

Mark L. Fergerson

"Mark Fergerson" wrote in message
newsQwEd.4$bX4.2@fed1read03...
Marty wrote:
"Edward Green" wrote in message
oups.com...
SNIP
Sounds like a job for Myth Busters

Buster isn't equipped for that sort of test; they'd have to go to pig
parts again (remember the cola-pop rocks ep?).

Oh yea, I remember.
They don't always "recreate" accurately either. The other nite saw them
testing the "thawed vs frozen chickens" thing. Thru an airplanes windscreen
it may have been OK, but there would be (I think) a considerable difference
in a jet engine test just from the frozen bird being solid.
I have heard the "Myth" as the jet engine not a windscreen. That test may
have been cost prohibitive.
I still find them entertaining and thats probably their main goal.
Marty