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Preempting Hailstone Formation To Protect Cars
Makarand writes "Nissan has become the first automaker in the United States to start using
a device that suppresses hail formation to protect its fleet of new vehicles
from hailstorm damage. The device is a cannon capable of shooting sonic waves upto
50,000 feet in the air to keep hailstones from forming. The
device comes with its own weather radar and activates when it detects
conditions favorable for hail formation. The device can provide
hailstorm protection in an area with one-mile radius by firing
sonic waves every five seconds."
These fine people from "ke-bek"
Sponge!
This is common practice around my area (Christchurch, New Zealand) to protect pip fruit and grape crops from hail damage. I'm frankly surprised this is news.
Let me post this (ganked from another site):
[blockquote]Basically, the anti-hail cannon uses
acetylene to shoot cations into the
atmosphere at sonic speed, which creates
shock waves that interfere with the
crystallization of ice, thereby resulting in
rain or sheet, but not hail. It covers a
circular area of about 0.3 mile radius,
roughly 200 acres.[/blockquote]
This sounds like a bunch of baloney to me. "Shoots cations" is as ridiculous as when you hear hippies talking about "bad ions" and "good ions" with respect to some stupid lava lamp.
How would breaking it down from hail into say small ice crystals mess up the planet?
slashdot, news for crazed liberal socialist zealots
Related:
r ology/Weather_Modification/
. php
http://dir.yahoo.com/Science/Earth_Sciences/Meteo
http://www.weathermod.com/projects/hail/argentina
http://www.ametsoc.org/policy/wxmod.html
These guys have seriously been had. Anyone that knows anything about atmospheric physics can tell you that most atmospheric models neglect sound waves, and for a very good reason--because they are insignificant when compared with other phenomena present in the atmosphere, such as...surprise...wind. Anything on the scale of a severe thunderstorm strong enough to produce golf-ball sized hail or larger will have vertical air motions in excess of 40-50 m/s (100mph). Combine this with the tremendous amount of turbulence associated with such violent vertical motions, and a few piddly sound waves don't stand a chance.
Furthermore, hailstones of the size they're concerned with usually form miles from the location they actually fall in, and are held aloft for substantial periods of time--sometimes longer than an hour. Eventually, however, the updraft in the storm will weaken or reposition itself, and when it does, look out below. So even assuming this device could prevent hail from forming within a 1-mile radius of itself, your stuff is still gonna get the crap beat out of it anyway.
Whether the guy that sold them on this was a meteorologist or not, this sort of crockery is what gives meteorologists a bad name.
Hailstones form inside the thundercloud, and grow larger as they are suspended by the thunderstorm's updraft or recycled through it. Clear ice in a hailstone corresponds to growth in warmer regions of the cloud where the water has time to flow before freezing, cloudy ice corresponds to ice formation in colder regions of the cloud where the water freezes on contact.
Hail forms when a raindrop freezes inside a cloud, but shoots back up (due to massive updrafts), and falls back down, gaining more layers of frozen rain/ice. It continues this cycle until the ball of ice is too heavy to be lifted by the updrafts, at which point it falls to the ground as hail.
it only pays off for small volume cars. The first generations of Renault Espace for instance were made of fiberglass, as the Alpines or Matras, but Espaces sells so well that now it is less expensive to manufacture them out of steel. Steel necessitates big investments in terms of presses, that's why europeans cars only change every 5 or 6 years, then the factories are sold to 2nd or 3rd world countries, but has better performance overall notwithstanding what you mention. Chassis tend to be made of aluminium to save weight in new BMWs, the bodywork is still made of steel.
Google passes Turing test : see my journal
Jets are closer to 200dB.
not quite: Jet engine at 3m : 140dB
Seems you're off by a factor 1 million.
Still, it seems pretty unlikely to affect, let alone damage, an aircraft.
Also, I doubt lightning is THAT loud. Where did you get that number?
Be wary of any facts that confirm your opinion.
Daimler also have hail protection for their large car park of brand new Mercedes cars at Sindelfingen (by Stuttgart), but they don't use sonic booms. They have two Cessna pilots on standby, who will fly up and ionise the clouds or something like that, which stops the hail from forming. It seems to work well, too.
-- Steve
"Hailstones are formed and begin with a piece of dust in the clouds," he explains. "There is a lot of activity going on, and what we do is to de-ionize that activity in the clouds and keep those dust particles from collecting moisture out of the clouds in turn reacting and forming what we know as a hailstone."
I'm a professor of meteorology. If one of my students had written that drivel I would have flunked 'em!
The microphysics of clouds is very complex. I'd really like to know what mechanism they really are trying to stifle here. Here is a bit on how hail forms. First, some background:
In a rapidly growing cumulonimbus (thunderstorm) cloud, you have a strong updraft (air rising rapidly). This air is contains humid air, which condenses to form liquid cloud droplets as it cools (rising air expands and cools - basic thermodynamics). It is indeed true that cloud droplets condense upon pieces of dust/salt/gunk in the atmosphere, but ionization has very very little to do with it. Many of these so-called condensation nuclei are not ionized. Water will condense upon just about anything if cooled enough.
Eventually this rising, cloudy air reaches heights where temperatures are well below freezing - say -20 degrees C. Water actually does not have to freeze when it is below 0 degrees C, and in fact what leads to lots of hail is the fact that there is an abundance of supercooled (below freezing liquid) cloud droplets in this cloud.
Eventually some ice crystals form, either spontaneously (supercooled cloud droplets freeze at about -40 degrees C - this is called homogeneous nucleation of ice), or because they come in contact with an ice nucleus (something that has a similar crystal structure to water ice). These ice crystals fall and co-mingle with the supercooled cloud droplets. Due to the difference in saturation vapor pressures over ice and water at a given temperature, these ice crystals grow and grow at the expense of the cloud droplets without actually making physical contact!
Now the stage is set for hail. There is an abundance of supercooled cloud droplets, which freeze upon contact with ice crystals. Contact is made, and graupel is formed. Graupel is kind of an intermediate form of ice between snow and hail. The updraft of the storm keeps everything going, and in fact can suspend heavy hail particles for a while before they either become so heavy they fall through the updraft, or they are tossed horizontally to a part of the storm where they fall to the ground. The largest hailstones form with the strongest updrafts because the hail can acrete lots and lots of supercooled water (hail will melt and refreeze also as it rises and falls within the cloud).
Again, I simply cannot fathom what process they are trying to stifle with these sound waves. Hail suppression research has focused mainly on seeding clouds with silver iodide. Silver iodide is a powdery substance which has an ice crystal shape very similar to that of water ice. Overseeding a cloud with AgI, so the theory goes, will convert all that supercooled cloud water into small ice crystals, scavenging all the liquid so there won't be any "lucky" graupel particles growing to the size of hail stones.
The Russians claimed some success with this process during the cold war (launching AgI laced rockets into clouds) but frankly I think they were overstating their success. Hail suppression work reached its peak in the 70's but because of the lack of any real statistical success, funding for this kind of work has pretty much dried up.
Anyway, a sucker is born every minute.
Leigh Orf
A squid eating dough in a polyethylene bag is fast and bulbous, got me?
But since F-117s operate at night, they would be taking off at dusk, be in the air at night and return to base at dawn. Wouldn't that suggest that the planes were gone while the bats were coming and going?
Also, I'd imagine hangar doors are kept closed most of the time when occupied by (at the time) a highly classified aircraft.
Not to mention that radar waves are a much higher frequency than sound waves, sound waves would reflect differently than EM waves do.
A huge (glass) greenhouse for growing hydroponic tomatos near me (central Nebraska) has one of those annoying things. Whenever conditions are favorable for hail, the thing goes off, sounds like someone shooting a large shotgun every five seconds, which goes on for hour after hour. I can't think of anything more annoying. Everybody in town hates the thing, and in fact some redneck types (We are in Nebraska after all) think it's great fun to shoot their (real) shotguns in the air when this is going on, as the greenhouse blasts provide great cover.
Perhaps metal shielding on a conveyor system to be pulled over would be much better to deal with. Maybe more expensive, but this is fucking ridiculous.