Slashdot Mirror
Tsunami Warning From Space?
Peter bayley writes "Tell me I'm crazy or tell me someone has already done it — but wouldn't a satellite equipped with a laser be a great way to warn people of tsunamis? I was pondering how to warn people in remote coastal areas once evidence of a seismic incident has been received by the monitoring stations that have now been set up following the large Boxing Day tsunami. The idea is to illuminate the areas that are likely to be at risk with a bright (but not dangerous) light. People would be told to head to higher ground if such a light appears in the sky. Put the satellite in a geosynchronous orbit. Make it tunable so that different colors can convey different meanings. You would be able to warn anyone, anywhere they can see the sky. The laser could be directed to illuminate only those areas at risk, skipping unnecessary areas to save power. Power could be varied so that it is visible day and night and through cloud (raise the power where the satellite detects cloud cover). I emailed some people at NOAA about it but they said it would stand on too many toes by circumventing local emergency service organizations in the various countries. I replied that countries could easily opt out, in which case the laser would be turned off for those countries — but received no further reply. Anyway, I thought the massed minds of Slashdot would relish the chance to demolish my idea."
Better a shark with a fricken laser - they're right where the action is!!!
sudo mount --milk --sugar
I'm not an expert on tsunamis but I understood that tsunamis start as very low waves that roll over the face of the ocean for many many miles before reching land. Only where the sea gets less deep they turn into the ferocious waves that destroy everything. So even if you could see them then with a satellite you would still be warned late.
-- Cheers!
Wouldn't it be cheaper to hand out emergency radios that wait in a low power standby mode until a certain signal is received?
No, because the amount of energy, in the form of light, would be immense. You're talking at least 10 watts per square meter, much more during the daytime. Tsunamis can affect hundreds of miles of coastline.
By my impromptu math, you'd need at least a gigawatt of power to light up that kind of area. So a medium-size nuclear reactor in the sky.
How about, instead, we just use these devices that transmit sound and vision via lower-frequency light, aka radio and television? Cheap transistor radios are much, MUCH cheaper than launching a reactor into the sky.
This should be opt-in, not opt-out. As cool as the idea is, someone messing with your emergency services by lighting emergency signals from space on your country just isn't cool. The countries should sign that they agree to have such emergency warnings issued above their territory. And maybe should otherwise participate in the system. Such deals are much better done with opt in, not opt out.
Also, who runs the system? It should be multinational, otherwise someone might decide to run false warnings during a war, or to otherwise hurt an enemy nation through it. Also, how long before someone launches an amateur satellite that makes fake warnings as a prank? The last one is not a big deal, but also worth spending a second thinking about.
They used to use warning sirens for that sort of thing. Far more low tech, but quite cheap, and a single siren can be heard for quite a distance. Just put them near the shore. Now, it's not nearly as cool as the satellite, but it would work if people are indoors and not looking out the window.
if you need just 1W per square meter (very low for a visible light), 100 square miles (a tsunami danger zone would probably be bigger) would require >200MW.
I think we are currently 2-5 magnitudes away from feasability.
CU, Martin
If half the planet is at risk from a single tsunami, we've got bigger problems than just 'how do we power this satellite?'.
Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
Getting a laser from a sattelite to one place on earth so it could be seen would require a LOT of power, even at night. Illuminating an entire part of the earth would take more power than you could imagine...
Even measuring the ocean's height with a satellite would be challenging.
However, I think you've uncovered the real problem. It's not warning people that's the issue ( you could easily broadcast radio and pick it up with a small receiver ) it's that there's no desire to create such a system.
Usually, the authorities would prefer to be the only ones to know. Then they can make the decisions... Do they tell people in all areas? How do they handle the evacuations? etc.
Your heart is in the right place, but your idea itself presents a lot of problems... If you really want to help, then spend a few years teaching yourself world politics. Speak to experts in the field of emergency services and become one yourself. Don't wait for others to pick up your idea, make it work yourself and become an expert. Most experts are simply people who were driven for one reason or another to keep on learning about a particular field.
As a suggestion? The easiest way to address tsunami's might be without sattelites and high-tech... Perhaps just keep an eye on the situation by following the websites that publish that kind of information, then set up your own website to co-ordinate redistribution of it - Then people who are worried about it, such as yourself, can subscribe - perhaps you could even use SMS to notify them?
Big ideas are easy to implement and opt-in is the best system.
GrpA
Enjoy science fiction? "Turing Evolved" - AI, Mecha, Androids and rail-gun battles. What more could you want?
I don't think that this is a practical solution. Lasers are very focused and don't spread out like normal lights, if they were to spread out the power requirements would be huge. Also It would be walking a very fine line between delivering enough light to be noticed and too little to cause eye damage to people looking up. Lastly You would have to check the wording on the agreements banning weapons in space, even though it is not the intention this could be viewed as one. While this is an interesting idea I don't think it is very practical and there could be better solutions.
Planes? what if its night and everyone is asleep? Perhaps putting alarm systems in these areas that are run off solar power and get warnings via radio or satellite (the regular kind, not laser) would be better.
On one hand, as it may save lives, we shouldn't worry that much about the cost, but, on the other hand, if it just drains all the energy from the planet, that's another (big) problem to solve...
So, before deploying such a system, ideas on a less expensive way to power it, and discussions on that, are really important.
A warning system that requires GW of power (we are talking about making light visible over several km, right?) and people have to be looking at it (and having an unobstructed view to the sky)...
I suspect the power requirement would only be sort of manageable during night time, but that is when people sleep and a laser would not go far in waking them. Now, if it was SHARKS with lasers...
Violence is the last refuge of the incompetent. Polar Scope Align for iOS
The superscript "2" that was next to km was "eaten" by the slashdot comment engine, I was talking about the surface to be covered, although the distance is also a factor of the power requirement.
Violence is the last refuge of the incompetent. Polar Scope Align for iOS
My concern is with something like this is not everyone will see the warning light as a reason to leave. It would get many people out, but not all. Some would stay just for the sake of looting and something like this would only help. Telling people they need to leave with a big group behind you when your telling is one thing. Doing it alone (or unmanned) is worse. Think of all the looting that happened during the Hurricane Katrina. Now think about what people will due when they are left alone and have knowledge something bad is happening. A tsunami would literally 'wash' away the evidence. And looting might not be the only thing that could happen. People act crazy when mass danger is about to happen. The idea is a good one, but not everyone will use good ideas in positive ways.
Attention... all grammer nazi"s! Is they're anything; wrong with: my post,
Why not just get Superman to fly backwards around the world really fast thereby (somehow) turning back time? He could then fly under the country in danger and lift it up until the tsunami passed safely underneath.
Seriously - why is this crap get on the front page?
Connect them satellites to Google Maps and draw arrows on the streets in the safe directions.
Zap everybody that isn't listening.
While we're at it. If there is no water, there is no wave.
Use the lasers to evaporate the wave part of the sea before it hits the shore.
Privacy is terrorism.
...get killed when that thing fires off and people forget about a "Tsunami Warning System" and think that they are either 1) under attack from little green men from outer space OR 2) that the gods are angry with them?
"Be polite, be professional, but have a plan to kill everybody you meet." General James Mattis
True, but my point was that it wouldn't drain much power at all, unless the scale of the disaster is so huge that warning won't help anyway. With a few simple modifications (chiefly, the assumption that instead of constant illumination, it's better to make the light blink) the power requirements are easy to fulfill with a solar panel and a modest sized battery pack - say, one smaller than that used by the GM Volt.
Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
Yeah, now brainfarts... directly on slashdot... the only thing more stupid than anything following "Hey y'all watch this" are usually exposee introduced by a falsely humble "crazy idea" which in 90% of the case is totally retarded and in the 10% remaining already more common than water but the bragging genius was to dull to understand how it worked in the first place.
Seriously, keep this for april first or Digg...
You stupid twat!
I envisage this system as working something like in Wall-E when he follows the red light from the approaching spaceship. That would be cool - a little guide light showing you which way to run in an emergency. Or you could like shine it on some landmark that was a set height above the estmated wave and say "Try and get to this!". Or like a laser sight, shine it on someone running really fast in the right direction and say "Try and keep up". Man, look at those little ants scurry!
you seriously think that the battery used to power an electric car has enough energy to illuminate 100s of miles of coastline from orbit? I don't think you have a clear sense of how much energy it takes to get a beam of light to travel such a large distance.
And even if you had a satellite with enough energy, what is your warning system going to do when it is cloudy in the area where the tsunami is going to hit?
and even if you solved that problem too somehow, what if the people you are warning are asleep because it is night time? how are they going to see your warning system? what if they are awake but inside a building?
vastly more effective would be the systems that are already in place: a siren so loud that it is essentially impossible for people not to hear it unless they are deaf.
In a minute there is time For decisions and revisions which a minute will reverse. -T.S. Eliot
IMHO, this cannot work. Sunlight comes with approx. 1kW/m^2, the human eye detect changes in brightness if they exceed 30%, i.e. we'd need 300W/m^2 to be visible at daytime. OTOH, looking directly at the sun is harmful even with the sun having a diameter of 0.5 degrees. A light source with a third of the sun's brightness, but point-like would probably burn a hole right through the retina before the blink reflex can kick in.
Even the discussed 10W/m^2 (absolutely invisible unless one looks directly at the right point in the sky) would be dangerous (the eye's resolution is one angular minute, i.e. light from a point source would cover 1/900 of the sun's image's area, giving a retina burning power density of 9 suns).
Short wording: you can't see it unless it makes you blind.
April Fools was a few days ago...
Sounds great! Yes do it! No, I have no intention of focusing a laser that can be visible from tens of thousands of square kilometres onto a single city. None at all. Why do you ask dear?
Oops. Did i just break the stupid concept in another way?
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Although I don't really think it's a good idea given how much of my life I spend indoors, who is actually saying the satellite needs to illuminate 100's of miles of coastline all at once? Wouldn't it be more logical to pan the laser back and forward along the danger areas?
You don't need a huge amount of energy for a pencil beam to be visible, particularly at night, though obviously in the day time it'd require 11 on the dial.
Especially the idea of a continuous light.
There is no practical way to generate enough light to alert people on the ground of an approaching disaster. At best they would see a bright light if they looked in the right direction.
But.
Solar sails in orbit could be used to illuminate the surface of the Earth and I have seen proposals to use them to illuminate disaster areas where infrastructure has been destroyed. The idea was to give people light to work by until the sun comes up but I suppose you could illuminate the location of an anticipated disaster in advance and give people a warning of sorts.
But these days mobile phones are all over the place and can be used to warn people. If you want to predict the part of the tsunami then something which can get the Doppler shift from water a metre or so under the surface would be invaluable. Maybe a long wave radar, in orbit and pointing down.
http://michaelsmith.id.au
The article poster may get a better reception emailing advertising agencies - using orbiting lasers to beam down advertising to millions.
From a technical standpoint, as another poster on here already mentioned, the power consumption could be greatly reduced by illuminating only sections of area at a time instead of all at once in a strobe like fashion.
Or a more practical way, which is likely already feasible now, is to illuminate the sky instead of the ground.
As far as detecting tsunamis from space, while not what the article poster is suggesting, would be a better use of orbiting lasers - detection of small rise in sea-level over a large area would, presumably, be a phenomena easily spotted from space.
Ron
Look, we just need a bright flash of light. It doesn't have to be a laser.
Put up a large number of satellites, much like GPS or Iridium. Each one holds a 30 megaton nuke. When an area is affected by a tsunami, we set off all the nukes that would be visible above the horizon.
Tsunamis are rare enough that we can normally launch a replacement system fast enough, assuming we don't put spares in different orbits. Have replacements ready to launch.
Typically a better solution is to use radar or infrared, laser tends to have problems penetrating cloud cover and the like. Space based radar altimeters are nothing new, and yes you could theoretically set up a tsunami warning system in space. Radar technology has come a long way in terms of power and range. I work in the radar altimeter industry so maybe I am biased.
http://en.wikipedia.org/wiki/Space-Based_Radar
This is obviously absurd, as pointed out by plenty of the above posters. What I'm more concerned about, is why this got posted to the Slashdot front page. We have the Digital Economy Bill about to be passed without debate in the UK, various stories on the LHC's full power experiments, all sorts of lunacy in the US with patents, and we get a "hey guys, what about this idea" from a random slashdotter.
If this were coming from a noted astronomer, a major figure in disaster relief, or GWB, then it would be Slashdot-worthy. But seriously, what value did this Ask Slashdot add?
Also, the previous story on the sun-chandelier was such a non-story as to be shocking.
I've now started tagging stories: ohnoitskdawson
Why not just have a GSM/3g/4g signal that can be transmitted from the base stations? Either SMS or make all cell phones in the cell wake up and loudly tell the message.
Wow this story is almost as crazy as my idea to build a giant water tower in the ocean to lower sea levels, see http://izit.org/content/all-water-earth for more details.
In all seriousness the poster seems to be interested in using the laser to communicate, is that such a big problem ?. The world is a much smaller place than it used be, I suspect that simply activating the laser would take some time, possibly calling the local officials would be almost as effective.
I don't think its such a bad idea. I have to ask, would people really assume they are "under attack from little green men from outer space"? or "the gods are angry with them"? It's not first thing that would come to mind when I think of seeing the local area light up with bright light. That seems very 1950s, and extremely unreasonable.
Having the local area brighten suddenly, I would look around and then look up to search for the reason behind the sudden increase in luminance. what may be the reason for it before making assumptions like that. Measuring a tsunami is certainly feasible, even with low wavelengths, a tsunami is still a tsunami a excessively large mass of moving water in a series of waves. Instead of interfering with local emergency systems, a tsunami warning system as this could be used to complement local emergency systems by serving as primary warning.
Using different colours for the warning system would be pointless because until each you advertised each of the specific meanings to literally everyone, it would waste time for people to try to figure out what it meant. The biggest problem is powering such a system. (Perhaps you should get N.A.S.A.'s ideas for that part?)
On a point made by GrpA, if a person stopped to check a website to figure out if their area is about to be hit by a tsunami and one were on its way, then by the time they got outside, they'd be as good as dead.
"Do not go to look for a tsunami - if you are close enough to see one, you are too close to escape it unless above its level." (Wiseman, J (2004). SAS Survival Guide)
The idea that you can outshine the sun with a man made satellite is so absurd, you have to question the intelligence of the person asking this question. At night it would be easier, but still require an insane amount of power and be totally useless when there are clouds.
At first I thought the question might be about measuring the oceans for tsunami waves, but this kid wants to put up some kind of disco lights.
You already need binoculars to see the ISS and then you can only spot it if the light reflects of it in the right way. The idea that a man made satellite could light up the skies, that is the domain of 5 year olds.
But this is the reason most governments don't listen all that much to the voter. Because this is the kind of letters they get. Hard to take the voter serious when this is what they come up with.
MMO Quests are like orgasms:
You may solo them, I prefer them in a group.
Good old fashioned air raid sirens would be much cheaper and a hell of a lot more effective at getting the information to the people most likely to be in harm's way during a tsunami. The people who are most likely to be affected are the poor and uneducated, or tourists. The poor and uneducated are not likely to know what the "different colors in the sky" mean, no matter how hard you try to educate them. Tourists won't understand either unless they're from a place where such things are also a likelihood. People don't see colors in the sky as warnings (unless it's black when it's supposed to be daylight) because they'll just think it's some sort of plane or more likely a UFO. Furthermore, lasers are focused light, so it's not like it's going to illuminate the whole sky, just a specific spot. If people don't happen to be looking at the right angle to see the laser, or they're inside, or whatever, they're not going to see the laser.
Air raid sirens, on the other hand, have been used all over the world for decades and people already know what they mean. They can be understood without actively paying attention to searching for the sign, and while deaf people are not helped as much, they have a good track record of warning people of impending danger, of all types. They can also be complimented with some local lights for those who are deaf or for more specific suggestions of what to do in case of specific different types of emergencies.
"Growing old is inevitable; growing up is optional."
This. is the voice. of the Mysterons...
Sounds like a space-age version of the weather lights on top of the old Hancock building in Boston:
Steady blue, clear view.
Flashing blue, clouds due.
Steady red, rain ahead.
Flashing red, snow instead.
(During baseball season, flashing red means the Boston Red Sox game has been called off on account of weather.)
http://en.wikipedia.org/wiki/Berkeley_Building
If Slashdot were chemistry it would look like this:Cadaverine
"And when the unblinking star starts to blink.. Beware o evildoers... And when the star starts blinking red, Knoweth that thy doom is at hand Saints and sinners alike For the sea will come And seek you out of your lowly abode"
Who said this thing had to illuminate the entire damn planet in one go? Jeez, ever heard of raster scanning people?
Ok, as the post above stated above, it takes ~10 watts / m^2 to illuminate. Raster scanning does not fix the problem. if you only have a signal in a given place for say 1/1000th of the time, then the signal needs to be 1000 times stronger to be noticed by the naked eye. You have to remember that we are not talking about a transmission to dedicated hardware. The end result is that your power level required is the same no matter how fancy you get with your scanning system. Unless you are proposing that we attempt to shoot just the people with the laser, and skip everywhere else to save power, but I humbly suggest that this is impracticable...
So, it has to warn people in at-risk sections of coastline. That alone cuts the area to be illuminated by orders of magnitude. Then, it doesn't need to illuminate all of these areas simultaneously and permanently - it could sweep them repeatedly. Imagine that the laser was spread out along a line, say 20Km wide, and that then scanned the affected coastlines. So the people underneath might only see a bright flash lasting for say, 10th of a second every ten seconds. Brief, but maybe enough - better than nothing if you're out of range of a siren.
Say for the sake of argument that this was just 1 square mile of coastline. That is around 2.5 Million square meters, so again for just one square mile of coastline you need 25 Megawatts. This is roughly the power consumption of a small town. Good luck with that.
The whole idea is thoroughly unworkable, not necessarily because we cant build the tech, but because the cost would be prohibitive, and there are far cheaper and more effective solutions. The process you have witnessed here, is one I have seen countless times in engineering:
Step1: Clueless moron (usually management), says hay, lets build x to solve problem y.
Step: Engineer looks at solution x, and cringes at the raw stupidity of it, then looks at problem y, and realizes that there is a far cheaper solution, possibly even already in place.
Step 3: if this is government, the moron pushes ahead with solution x anyway because it is politically valuable, even though it has no practical value.
This whole thread has been an exercise in those who understand good engineering trying to pass some knowledge to those who are quite clearly ignorant and should stop trying to solve engineering problems with frikkin lasers
-=Geoskd
I wish I had a good sig, but all the good ones are copyrighted
Could be pretty soon then... You don't get free bags here (Belgium) anymore in super markets. You can get 1c bags made of corn, which are fully biodegradable. The process starts often before you get home... 10c will get you a proper reusable bag. Needless to say that you aren't inclined to throw those away. When this started I ended up forgetting my bags often, so now I have a stash of 20+ bags lying in my car...
1] I can't imagine the power source that would supply this amount of power. Maybe something with capacitators.
2] what about clouds? also, there's sometimes a sun-lightened atmosphere that you really can't see through (we call it 'day')
The problem is that this idea could NOT be made to work. Geostationary orbit is over 22,000 miles above the surface. Even highly precise lasers, (which themselves would be unsuitable for launching), spread out so that by the time they reach the moon (one order of magnitude further) they are approximately 2.5 miles wide.
What this means is that to visibly illuminate an area, not only are you dealing with the idea that you need to outshine local light sources, but you ALSO need to compensate for the fact that your energy is being spread out over an area of a quarter mile or so.
If you are talking about 10W/m^2, which is ludicrously low, you're talking over 1.6 MW per laser pulse just to make the light visible over a sixteenth of a square mile (a square one quarter mile on each side). This assumes NO efficiency problems and no loss due to interference, cloud cover or the atmosphere.
Why do you expect people to give an idea that is literally impossible with current technology, (even current LAB technology), a serious shake? This idea is good for a laugh, and nothing else.
FanFictionRecs.net
I still think it is an awful idea.
Either the laser light gets absorbed by the air, resulting in some non-focused emissions of non-laser light, but the problem is that the emissions start far away up in space, which means losing all energy before the beam hits the ground, or you somehow(I don't know how) use a laser which doesn't get disspelled as much, in which case the laser will not really illuminate an area, but just some spots or a line on the ground. And the coastline to be painted by such a laser might be really long, resulting in the laser passing by only every minute or so, so it would not be very noticeable.
Hey don't blame me, IANAB
Screw satellites. Sharks with frickin' laser beams attached to their head! ...Ah, would you remind me what I pay you people for, honestly? Throw me a bone here!
How you gonna get enough power to make daytime *brighter*?
Was the idea to cook people and see who notices?
How about bad stormy weather which the (visible light) laser can't penetrate?
You going to have geostationary satellites so far away as to multiply the power required and the tremendous power losses?
Or were you going to have low level satellites, and need thousands to make sure every inch of ground was within a few seconds of any satellite coming into position?
How about topography blocking line of sight?
There are so many FAILs all over this idea.
It's a comic book idea, should never have gotten past the hangover stage.
Infuriate left and right
It's nuclear weapons that are prohibited in space.
As well they should be. I mean, the detonation of a nuclear weapon in space might accidentally release General Zod and his minions from their eternal phantom zone prison.
I actually think people aren't afraid of the word nuclear. It's nucular that scares them. Mostly because they don't know nuclear is a real word and think nucular means big bad bomb go boom.
Ok, as the post above stated above, it takes ~10 watts / m^2 to illuminate. Raster scanning does not fix the problem. if you only have a signal in a given place for say 1/1000th of the time, then the signal needs to be 1000 times stronger to be noticed by the naked eye.
I'd dispute that. If the signal is, say, on for one second, then off for the next, does that make it less visible? You've just halved the average power requirement, and I'd argue the flashing makes it more visible if anything. I think you'd only need a very brief flash to make it visible, particularly if that flash was repeating periodically, so the average power requirement would fall correspondingly.
Say for the sake of argument that this was just 1 square mile of coastline. That is around 2.5 Million square meters, so again for just one square mile of coastline you need 25 Megawatts. This is roughly the power consumption of a small town. Good luck with that.
I had in mind a thin line, 20km long, but only 1 metre wide - one end of the strip at the beach, the other end inland (exact distance depending on gradient of coastline at that point). So that's 20,000 square metres, and I believe that 200kW is achievable with (really big) solar panels.
"Thousands killed from partly cloudy skies"
If you are talking about 10W/m^2, which is ludicrously low, you're talking over 1.6 MW per laser pulse just to make the light visible over a sixteenth of a square mile (a square one quarter mile on each side). This assumes NO efficiency problems and no loss due to interference, cloud cover or the atmosphere.
I'm not sure about this 10W/m^2 figure. Maybe I just have a different concept to the rest of Slashdot, who seem to be imagining a system that would light up the ground and everything around you. I was imagining a really bright flashing "star". Given that you can easily see satellites with a really small telescope, and that's just using the sunlight reflecting off their panels (say, 1kW per square metre, maybe 1-10 square metres), that I think the power requirements could be way lower than discussed, and still produce an easily visible light. Granted someone in the village would have to be looking up, but I think there's a fair chance of that?
Spending effort to make monumentally stupid ideas work is a waste of time.
How bout this: Install sirens instead, as has already been done in places like Hawaii. Cheap, effective, and doesn't cost all that much since the range of the sirens is pretty good.
Or at least keep them to yourself.
No that how they set them off and it's a good way to be able to have a under cover way of ......
http://xkcd.com/723/
Wasn't this the plot of at least 2 James Bond films?
You'd need a frakkin powerful laser to punch through clouds from geosynchronous orbit (about 36,000 km above the Earth).
What if it's a sunny day? How bright would the laser need to be to be noticeable in bright tropical sunlight?
Quidquid Latine dictum sit, altum videtur (anything said in Latin sounds important)
If Dr Evil got control of a satellite with a "big frick'n laser"...
Sounds like similar technology with similar issues raised:
http://en.wikipedia.org/wiki/Space_advertising
http://www.jhhuebert.com/articles/In%20Defense%20of%20Advertising%20in%20Space.pdf
I'm not entirely opposed to this kind of thing, as long as it is turned off most of the time :P But there has already been plenty of movement to ban sending visible messages from space since 1993.
It would be neat to be able to send text messages in the sky, even if it was just a little icon indicating that you really ought to turn on a radio to check for a news flash.
We already have a system that constantly covers the earth with multiple data streams. The GPS system. Many Cell phones are capable of receiving GPS signals. Seems like mostly a software issue to add a code that could provide localized warnings of many types of natural disasters. Your GPS personal navigator system could even respond by directing you to the nearest evacuation route. This would be an opt in system that you could use to protect yourself no mater what the local political issues may be.
I have 2-5 polystyrene bags full of these bags 300-400+ - I use them for everything as many times as I can, one day here they won't be free and I can start using all the cloth bags I've bought. I think Belgium is further ahead of the curve than many western countries like my own. A proper re-usable bag here costs a few dollars.
That said, I'm not dissing the idea of a Tsunamis warning from space, just pointing out how difficult it seems to be to get international agreement on anything. For my 2 cents I'd suggest it probably is a good idea - but instead of being a visual hey look up in the sky kinda Tsunami warning, it would carry data that powered alert systems would be able to detect and issue a simple alert, Tsunami intensity and eta.
This would allow local manufacture for local languages and conditions and reduce the cost of the satellite and education required to interpret the message.
One of the most telling stories of the Indian ocean Tsunami was that at a popular tourist resort only a 8 year old girl knew what it meant when all of the water from the beach went out to sea, she yelled and screamed at people to get to high ground immediately and was credited with saving tens of lives. If people don't know what it means when they are confronted with the most imminent warning of a Tsunami when it is in their face how are they going to know what that yellow and red flashing light in the sky means?
My ism, it's full of beliefs.
A light in the sky is not going to do any good when people are asleep.
A light in the sky is not going to attract any attention during the day unless it's a goodly fraction of the sun's brightness.
Let's see, how to put this... You want to build a laser that is powerful enough to be seen through cloud cover even when the beam is dispersed over hundreds, or even thousands of square kilometers of land area? OK, You know, President Reagan wanted to do that too... You see, if you just focus that puppy down into a nice tight beam you warning laser would be one of the nicest weapons systems ever built. When you were not using it to warn people about tsunamis you could use it to hold them hostage. You could could...
Well you get the picture. The sarcastic Dr. Evil posts are actually right on target. But, a reference to Star Wars is more accurate. IIRC the direct nuclear pumped laser was the design of choice. The reactor is the laser.
As far as I know such a device could be legally placed in orbit. But, most nations would rather their people die in a Tsunami that face having a nuclear battle star hanging over their heads.
Other than that, not a bad idea.
You could get about the same effect by installing a system of sirens and warning flares along coastal areas. They would cost much less and be much safer.
Stonewolf
...Is all fun and games until someone turns it up to 11 and pokes out a billion eyes.
The trip upwards can be assumed to have a very different attenuation from the downward trip. You can force the atmosphere to be optically nonlinear simply by making the beam powerful enough. It will then self-focus the beam. This effect is normally unwanted when you do laser experimentation, but here it could be perhaps used to minimize the losses. The high power beam can optically saturate the atmosphere, such that absorption will drop by a factor of magnitude or two. What I wonder about, though, is how one is supposed to defocus such a beam once it reaches the satellite "mirror" -- without vaporizing the said mirror.
A successful API design takes a mixture of software design and pedagogy.
Do it on the ground first. When you're satisfied with the optical output and visibility, multiply the power demand by a factor of 10 and start designing your, um, satellite. Good luck.
A successful API design takes a mixture of software design and pedagogy.
You are facing West.
> Look.
A Giant beam of light descends from the sky. You:
1. Pray
2. Run screaming
3. Assume Aliens are attacking and notify the authorities while arming yourself.
4. You realize that this is a Tsunami early warning beacon and promptly gather your things from the beach and head to higher ground helping old people on the way.
- Dan.
~ People that think they are better than anyone else for any reason are the cause of all the strife in the world.
I'd dispute that. If the signal is, say, on for one second, then off for the next, does that make it less visible? You've just halved the average power requirement, and I'd argue the flashing makes it more visible if anything. I think you'd only need a very brief flash to make it visible, particularly if that flash was repeating periodically, so the average power requirement would fall correspondingly.
What was discussed was using rastering to reduce the power need, but to reduce the power need to something manageable would require several orders of magnitude less on-time. You would be looking at 1 second on, 1 millions seconds off (scanning somewhere else). This would mean roughly two weeks between one second pulses. ?Or, you could have it on for only 1 ms out of every 1000 seconds (14 minutes), but a 1 ms pulse at 10 watts is too little to be seen against the daylight sky, so the power would have to be several kw to be seen, and once again you are back to unmanageable power again. The solution is unworkable plain and simple, there is just no real way to compete with the sun in this respect, unless your entire target is sufficiently small (a few tens of square meters at most).
I had in mind a thin line, 20km long, but only 1 meter wide - one end of the strip at the beach, the other end inland (exact distance depending on gradient of coastline at that point). So that's 20,000 square meters, and I believe that 200kW is achievable with (really big) solar panels.
Still no go, 10 watts / square meter is only bright enough to be seen as a light in the sky, reflected light will be non-existent, so it will be invisible for all intents and purposes. To "light up the sand" above daylight, you would need kws/square meter, and again it would be unworkable for anything larger than a few tens of square meters. Once again, you are failing to understand the truly colossal amount of power being output by the sun on a regular basis. The amount of power hitting the earth on Hawaii, in the form of sunlight, is greater than all of mankind's power consumption combined. You are simply not going to compete on any real meaningful basis.
-=Geoskd
I wish I had a good sig, but all the good ones are copyrighted
The same thing happened to me once when I was eight yrs old with respect to an idea i had involving magnets and trains. Don't let them tell you that you are insane...your simply ahead of your time! Now, get out there and raise some capital! hehe...
The main problem with tsunamis today is not how to warn people, it's how to detect them correctly at all. Seismic activity is correlated with them, but it's not a perfect correlation; a fair number of them are not caused by earthquakes at all, and a fair number of sizable earthquakes do not lead to tsunamis. There's both a fairly high false positive rate, and a fairly high false negative rate.
The situation is best in the pacific, where they have a network of deep sea buoys and alarm systems. I think the power necessary to illuminate vast areas of the world from space is much larger than a traditional RF signal, which is (I believe) the way this system works today. A factor in the devastation that occurred in Sumatra in 2004 was that there simply isn't any kind of tsunami detection network in the Indian ocean at all.
The cost of installing alarm systems at beaches is probably lower than the cost of installing the requisite sea buoys, and it's probably lower still than developing this kind of satellite too.
This is all a fantasy, then you do the math, and the math shows it's -- well, still a fantasy. The numbers just don't work out.
A decent laser pointer may have say 0.5mRad beam divergence. Assume we have better optics and improve the divergence by a factor of 500 to say 1uRad. That may be a long shot, I'd think 10uRad may be more practical without using a Hubble-sized mirror.
The nice thing about radians is that the length of the arc -- or, as it were, the diameter of our "pencil" beam -- is simply the angle times radius of the arc. The radius of the arc is the distance from source to Earth.
Geostationary orbit for Earth is 35.8 M meters. 35.8M*10u = 358. So our "pencil" beam is almost half a kilometer wide, and that's assuming it's all done in vacuum.
No we have atmosphere to cope with. Assume a red beam, that's around 700nm. At sea level, the optical transmission of the atmosphere at that wavelength is around 5*10^-2, or a factor of 50m.
So let's say we have a decently powerful 10kW laser up there. By the time we reach ground, it's 10kW*50m = 0.5W, illuminating an area of a quarter of a square kilometer. That's like looking at a 0.5W LED (bright sucker, mind you), with say 60 degree divergence -- that's 1 radian -- from ~400m away. That's an easy enough experiment to do. It looks rather unimpressive unless it's very, very dark out there.
So you'll definitely *see something*, but it'll look like a faint star, and that's about it. You won't see it if there is any sort of a cloud cover, and whether you'd see it during daytime is debatable at best. Maybe someone else can look up the brightness of equatorial sky mid-day and figure it out.
Now obviously, the beam has to be swept. Suppose it'll be swept along 1000km of coastline. Suppose that you want the pulse to last something reasonable - maybe 0.5s? So you have 500m per 0.5s, 1000m/s pan speed. It'll take only about a thousand seconds to pan your coastline, or about 20 minutes.
There goes your pencil beam. Still don't believe me? Well, assume you've ramped up your optical power output to 1MW (factor of 100), and got a better mirror -- 1MW laser and its power source will be big, so you may as well slap a big mirror. So assume we've improved power density by a factor of 1000 total -- 1MW laser + 1uRad divergence. Say you presume that you can then have 1000x shorter blips (0.5ms) still visible to the naked eye due to the integrator that our retina is. Your pan speed has made the blinks happen roughly once per second. And that's perhaps something that is still fantastically impractical -- it can be seen, at night and under clear skies.
So there goes the fantasy, full of glory and all.
A successful API design takes a mixture of software design and pedagogy.
Do you even know how much energy a laser would need, to become a bright light for a whole area, coming from *space*??
Please, do the calculations, and tell some scientists of what you came up with.
Also, if you do the calculations for the price, you already got something to pitch to country leaders. Maybe they see it as useful. If not, you can always tell that to their population. ^^
I replied that countries could easily opt out
I’m sorry, but you have to be pretty arrogant and egocentric, to make this opt OUT instead of opt IN like it should be.
Opt OUT, just like imperialism, am I right?
(Yes, I know your good intentions. It’s just very far from being polite. Be polite and humble, and you achieve more.)
Any sufficiently advanced intelligence is indistinguishable from stupidity.
How bout this: Install sirens instead, as has already been done in places like Hawaii. Cheap, effective, and doesn't cost all that much since the range of the sirens is pretty good.
I'm presuming this scheme was aimed at places like Indonesia, Papua New Guinea, rather than places like Hawaii, which are already well covered. How do you power these sirens in the absence of mains electricity? Would solar-panel-charged batteries still be able to keep a charge after say, 10 years?
10 watts / square meter is only bright enough to be seen as a light in the sky, reflected light will be non-existent.
So how is it then, then when you have something like the lights on a fire truck, these are clearly visible reflected off the walls of all the surrounding structures, even during broad daylight, even though there isn't anything close to 10W/sq metre incident on those surfaces? I don't envision competing with the sun - like you say, that would take ridiculous amounts of power. But to produce a bright flashing light in the sky? I think that can be done for a lot less power than people here assume.
If the root of the problem is notification of the event, then the solution can be had much more cheaply than launching a dedicated satellite, can't it? What about simply renting the transponder space on an existing satellite and installing simple receiving stations in coastal areas that are hooked to early warning alarms/sirens? Build the ground stations as passive listeners and you might even be able to run the thing from solar power alone.
... there are 12 different ways of skinning that cat. I think the real question is "who is going to pay for it?" Sat/transponder space/ground stations/engineering aren't free. I could see an international organization footing the bill for the NOC which transmits warnings and the specs for protocol ... that would make most sense I guess. Then leave it up to the central government or individual communities to buy receivers from 3rd party vendors? Is this an untapped business opportunity?
I don't think the problem is technical, however
"Glory is fleeting, but obscurity is forever." - Napoleon Bonaparte
This was invented by Shampoo.
Proverbs 21:19
I guess my concern would be, Earthquake at 2am? Everyone is indoors and asleep? How does some laser shining on their house wake them up? Seems like that is a pretty big gaping hole in the universality of the warning, and would create large doubts as to the efficacy and therefore need to spend probably billions of dollars developing and deploying such a system.
(Assuming it is practical and feasible to illuminate large swaths of the planet from space)
You just need to be looking right at it (or rather along it), the odds of which are vanishingly small.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Just think; The idiots who have all the money hire idiots like this idiot to implement such idiocy.
You're the reason behind Katrina and Haiti. I hope you get flattened in the next test run.
Idiot.
-FL
You've all just been turned into lab rats in a social experiment.
Everybody who pulled out their small man-parts to jump into the blood-bath crucifixion of this brave fellow, (who, on the surface, committed the ultimate crime of trying to start an interesting conversation on a slow news day), FAILED.
Jeez, people.
Are you all still strutting around in kindergarten trying to explain why everybody else's Lego creations are inferior? Still trying to "win" all the authority-figure love?
Grow Up. Think beyond the moment. A little pattern recognition please!
-FL
The amount of water affected by the wave is the same, and steadily diminishes over time. But over the open ocean, that effect is spread out horizontally (amount calculated by the inverse square law) and also vertically, from sea level to ocean floor. This vertical spread results in a wave that isn't very high at all and often passes unnoticed by ships at sea. Then, when the wave reaches the continental shelf, it cannot be spread out so far vertically. (Same amount of water affected by the event that caused the wave, or less, due to entropy, but less vertical room.) Having nowhere else to go but up, it rises up. So it doesn't actually grow in strength. Rather, it just gets taller in shallow water.
To detect a 1-meter rise in sea level by the timing of its laser light reflection would require detecting a 1/1,500,000 second difference in the round trip. That's 1/3,000,000 second sooner contact with the water on the down beam, plus 1/3,000,000 second sooner arrival by the reflection. That's a pretty small difference compared to the roughly 1/3 of a second it takes light to make that same round trip normally from geosynchronous orbit. Even if you can do it accurately enough, you would detect only position, not direction. (On the macroscopic level, that sort of Heisenberg-like uncertainty is very dissatisfying.)
That's why they use buoys instead. Not only is the change in sea level detected more accurately in the sea, where it happens, you can have lots of them, because they don't have to be launched into geosynchronous orbit. With lots of them, you can both detect position and infer direction.
To the original poster: It wasn't a bad idea, per se. It's good that you're thinking outside the box like that. It was just pretty impractical when you get down to the details.
exactly, if it is a pencil beam the chance that anyone will see it, assuming it is bright enough to be seen at all, is essentially zero. Which would make it the most expensive and most ineffective early warning system ever.
In a minute there is time For decisions and revisions which a minute will reverse. -T.S. Eliot
maybe the google engineers can use the google death ray for this in the 20% time. ;)
i was saying that because any other way of implementing would render the thing so inneffictive that it would end up warning fewer people than a 16th centery town crier. Moving a pencil beam across a 1000+ square mile area (100 miles of coast line up to 10 miles inland) slow enough for people to see it means the tsunami is going to hit land before you even had time to sweep once across the entire area. Moving it fast enough that it can sweep across the whole of the effected area in short enough time and it will be flipping by in front of people so fast that their conscious mind, even if they were looking right at it, wouldn't register that it had even occurred.
In a minute there is time For decisions and revisions which a minute will reverse. -T.S. Eliot
how is detecting a tsunami from space better than our current method? 1. seismometers detect earthquake, computers & scientists quickly determine possibility of tsunami generation and issue a warning. 2. buoys in the ocean and pressure sensors on the ocean floor detect passing tsunami energy wave, allowing warnings to be updated. This system works well in about 90% of cases where it's installed; it still isn't fully operational in the Indian Ocean(the Pacific system worked very well after the Chile quake in February), but should be soon. The only major gap that leaves is the places where time from wave generation to impact is only a few minutes -- that is, a city like Padang, Indonesia, or Seattle, which sit just a few miles from a huge fault. What do we do then? A satellite might be useful, but only if it can detect the formation and size of a tsunami and issue a warning *instantly*. Fortunately, those cities have a natural warning system in place: the earthquake itself. They're so close to the fault that inhabitants will certainly feel any tsunami-generating quake. So, spending tens (hundreds?) of millions of dollars on a satellite or satellites to monitor tsunamis probably isn't the best course when you can educated people about how to get out of harm's way for a tiny fraction of the cost.
It's easy, you fire the lazers at a ground based "difuser". NO I'm Serious.... but not in that literal translation. You know how you shine a green lazer on a plane and you go to jail right? You can't start infilltrating the earth with light that, to be visible in daylight would have to overcome the power than the sun. You would have an illuminated beacon, similar to a traffic light, that could get it's data via sattelite. It'd basically be a "recieving tower" on the ground which can then illuminate to whatever color you want. It's not a good idea to try and light up the sand. That won't work.
How much is your data worth? Back it up now.
Why do you think a rotating light won't put 10W/square meter on the wall? Those lights focus their light into a very narrow beam, I wouldn't be at all surprised if the spot they projected was in the neighbourhood of 10W/square meter. Say a 1/2 square meter patch from a 50W light at 10% efficiency?
I wasn't implying 'pencil width' in a literal sense, but rather an illumination footprint several meters across. Perhaps I used a bad choice of words. My background is in satellite communications - pencil beam obviously doesn't mean quite the same thing in the optical world I guess.
That sounds like a great way to deal with religious radicals. Right up there with projecting a whisper right next to their ears, except this can be implemented on a mass scale.
You'll just have to figure out how to make the light brighter than the sun, or are you under the impression bad things only happen at night?
*slaps forehead*
You're an idiot.
In order to make the "flashing light" appear as anything, it has to be several orders of magnitude brighter than whatever else it is around. If the sun is overhead, then it has to be brighter than the sun.
Go tell your local fire department to park their truck in a parking lot in broad daylight and tell me if the lights flash off the walls. They don't. Trust me.
In order to make it visible from the area affected by a tsunami (several thousand km of coastline, at least)....
my god this whole discussion is inane. You've OBVIOUSLY never done any experimental work with daytime lighting, or photography.
As a former professional photographer, in order to adequately light up an area (brighter than direct sunlight) with a flash in broad daylight, we're looking at a flash strong enough to have physical concussion on your hand. My bigger flash heads can give you an instant flash-burn if you were to stand directly in front of it, but will only give me about 20-30 feet of range in broad sunlight.
The absolute power of sunlight is profoundly stronger than most people realize. The amount of light in a shaded area in daylight is 8-10 times less than in direct sun. The amount of light during twilight is 20-30 times less than in broad daylight.
The efficiacy of illumination also follows the inverse square rule, where moving away from the source reduces the light in an exponential manner, not a linear one (obviously, this isn't quite the same for a laser, but regardless)...
Go take a pen laser outside and shine it on the sidewalk where the sun shining.
Try taking a maglight (which can be visible from hundreds of feet at night) and stand 40 feet away from someone who is not looking, and try to use it to get their attention. It simply won't work. The daytime is too bright.
And frankly, a warning system that requires people to notice a faint, flickering star in the sky that wasn't there the previous night might be problematic, especially many areas of the tropics (where tsunamis are most common) are cloudy almost 80% of some seasons.
This whole topic is just idiotic.
Are you assuming this would only work on cloudless nights?
How does a "warning system" that only works 15% of the time in some areas sound like a good idea to you?
Even providing you could produce enough power to make a "bright star" (which you can't), have you considered daytime (when you DO have to outshine the sun, indirectly at least) AND local weather.... during the monsoon season in some areas (or in places like British Columbia in winter), people don't see the open sky for weeks at a time.
It doesn't even seem worth thinking about, let alone expending significant effort on.
It's cloudy 80% of half the year in Indonesia (monsoon).
What about this system is remotely practical enough to even consider?
Radar is used for this purpose. It also penetrates clouds.
Using a laser from orbit for anything other than curiosity experiments is just inane.
Lighting up the daytime sky across the entirety of a major ocean coastline would cost a lot more than hundreds of millions of dollars. :-)
even several meters across, let's say 10 for simplicity, is 100 square feet of area illuminated at a time. If you had a 1000 square foot area to send the warning to, that means if you want to get the warning out in say 5 minutes, you would be able to send your signal to each location in your danger zone for 120 seconds. That is slow enough to give everyone a chance to see it, assuming that everyone in the warning zone has the habit of looking up at the sky in the direction of the satellite at least once every 120 seconds (not bloody likely).
In reality though 1000 square feet is actually a rather small. The way Tsunami's propogate out in a circular pattern from the point of the shock, 10000 square feet of area is more likely, in which case to get the warning out in 5 minutes to the entire area with a 100 square foot beam, you would be able to illuminate each area for only 0.5 seconds. That obviously isn't going to work.
That all sets aside the fact that it won't work when the weather is poor since visual light doesn't penetrate cloud cover, and also sets aside the other point that a warning system that relies on visual queues is utterly useless if people are indoors or asleep.
In a minute there is time For decisions and revisions which a minute will reverse. -T.S. Eliot
Now that the lasers from space idea has been suitably demolished, perhaps we can consider the other way around: Ground based lasers to write a warning on the moon! It will only work during new moon of course so lets forget about tsunami warning, lets put up commercial messages. I'm betting there a few companies willing to part with a few million dollars to have their logo written on the moon for a day. Great business plan. Publicity is instantaneous global and free. Endless debates in the press, Greenpeace is going to freak out. Technically feasible?
This sig is just as redundant as the rest of this posting
Considering they'll almost never be discharged, solar-charged lead-acid batteries should do just fine for a very, very, very, very, very long time.
Likewise, cloud cover shouldn't hurt because the batteries will almost never be discharged.
Unfortunately, as with most, this idea is not new:
/. story about this a few months ago? Maybe around the time of the last big Tsunami?
A google search for "satellite early warning tsunami":
http://www.google.com/search?client=opera&rls=en&q=satellite+early+warning+tsunami&sourceid=opera&ie=utf-8&oe=utf-8&safe=active
Comes up with the following results:
http://ec.europa.eu/world/tsunami/other-measures/early_warning.htm
http://www.drgeorgepc.com/TsunamiRWarningSystem.html
http://www.esa.int/esapub/bulletin/bulletin124/bul124h_martin_neira.pdf
I'm not picking apart your idea. Just you googleing (How the hell do you spell Googleing? Googling?) skills, I guess.
And, didn't I see a
- Zotdogg
In order to make the "flashing light" appear as anything, it has to be several orders of magnitude brighter than whatever else it is around. If the sun is overhead, then it has to be brighter than the sun.
So how is is that people have been able to use mirrors as a means of signaling?
My bigger flash heads can give you an instant flash-burn if you were to stand directly in front of it, but will only give me about 20-30 feet of range in broad sunlight.
Irrelevant. Not trying to take a flash photo of the land here. How far away is that flash visible from (and bright enough to attract attention) from in front of the camera? I bet it's a hell of a lot further than 30 feet.
Instead of trying to put such powerful lasers in orbit and dealing with the nightmare of servicing them, why not do the obvious: Transmit the data to the ground, and put the warnings on a group of web sites that can be checked by anyone.
Of course, most people in the world wouldn't be routinely checking that web site, especially when it goes for weeks without any tsunami warnings at all. Just as they wouldn't be routinely going outside every few minutes to check for a light in the sky that never seems to be there. What you'd also have to do is publicize your site with the relevant emergency and news agencies. If you could supply data accurate to the minute and danger estimates for various islands and coasts, I'd expect that the emergency and news people there would be interested, and would be happy to install software that pops up warnings on their screen when their coordinates appear on your site.
That way, you'd get the information widespread in a matter of seconds, and response wouldn't depend on people noticing a little light up in the sky. And the local emergency people wouldn't consider you competition. You'd just be a good source of information that would make them look like heroes to their local population.
You might also consider things like an RSS feed, a twitter account, and so on.
As I recall, there has been some research on the use of orbiting lasers to accurately measure sea-surface height. You might want to find what's been written about the topic. A quick google search for "orbiting lasers sea-surface height" gets about 84,000 hits right now.
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Why does it need to be continuous light?
What would a 10m x 10m "point" look like
raster scanning a swath of coastline?
How bright would it have to be to be noticeable
when everything around you briefly flashed red
from reflectance? And wouldn't the beam itself
be pretty visible from atmospheric backscatter?
Instead of a 5,000km x 5,000km area,
what about something that better matches
a coastline? Maybe 5,000km x 10km ?
And why orbit a gigawatt reactor?
It isn't like this would need to be switched
on continuously for days and days. Put up enough
batteries to run it for 15 minutes at a time.
After a few hours, the wave would hit and
at that point it doesn't really matter.
I don't know lighting well enough to
say whether 1w/m^2 "on the ground"
would be noticeable. The down side
there is you'd want enough of a flash
to get attention, but not enough to
blind / interfere w/evacuation.
Plenty of other problems, though.
As for the people writing "this is just
science fiction", lighten up.
Computer vision was science fiction not
that long ago.
*shrug*
This is an interesting idea; perhaps not
practical, but still interesting.
Some followup questions for the original poster:
what %ge of tsunamis would this actually be helpful?
(e.g. if it is too close, there won't be enough time
to get evacuate, and if it is coming from across the
pacific then there is enough time to save most people
with conventional tech).
How much would it cost?
Would that money be better invested in saving some
people from some tsunamis, or in saving all costal
area people from rising sea-levels / global warning?
My gut feeling is the global-warming thing would be
a better "net-good" for the planet.
But this is still an interesting idea :-)
Yes. RADAR is already being used, wonder if a Tsunami already is visible from space: http://www.osd.noaa.gov/ostm/
If you want to take the parent's suggestion of studying this stuff seriously, some pointers:
- Check out U of Colorado's Natural Hazards Center. They have info on the major disaster research mailing lists, and put out a very good bulletin on the latest and greatest of ideas.
- A tsunami notification system (via email or SMS) already exists; it has the same inherent flaws as any other automated tsunami warning in that it only activates for earthquakes (not landslides) and lacks in expert judgment on if an event is likely to occur.
As for the easiest, cheapest, and most effective means of reducing tsunami danger: let the mangroves regrow. Mangroves act as an absorbing buffer; the areas with the least destruction and deaths from the Boxing Day Tsunami were all where the mangroves were intact. Tourist destinations tend to pluck the mangroves (huge beaches are so much more attractive for hotels), removing that protection. For the ugliest enactment of this risk-increasing policy, check out the mudflats of Cairns, Australia.
What use is a laser if the average cloud coverage of the earth is 80 percent?
Remote sensing is not instantaneous or frequent enough to detect waves except after the fact
with a great deal of post processing. This is why a grid of in-situ sonar sensors and W.E.R.A.
radar are far more useful.
A mirror uses the power of the sun 100w/m2 to signal over a small area (maybe a few feet).
You're talking about matching that power over a hundred thousand square miles?
Wow.
You're just not understanding the scale, I think. My flash will burn your eyes out from 5 feet away, but from the upper level of a stadium, wouldn't even make the slightest dent in the illumination. From a mile away, I don't know if it would be bright enough to get someone's attention who wasn't already staring in the right direction.
From 30,000km, it wouldn't even be close to visible.
Understanding the power of the sun, the scale of distance and the scale of the target area... Go try some experiments with lasers. They're cool, but they're not that cool. 1Kw is a lot of output for a satellite. I would wager that even a fine-beam focus from a 1kW laser on just a few hundred meters of surface would have trouble penetrating the atmosphere and being strong enough to capture someone's attention in daylight from 30,000km.
How is this something that can be replicated over.. say... 10,000 square km? You're talking terawatts of power....
As someone pointed out earlier, the island of Hawaii receives more sunlight energy than the entire output of all human power production combined... How do you even remotely close to match this?
The benefit to Satellite-based early detection\warning systems would be the speed and dependability of the system (hopefully, one that would be able penetrate weather to always be able to see the sea). I think you are correct in assuming that it may be more expensive than some other alternatives though. However, when you talk about training civilians you have consider the recurring costs. I suppose the parents could teach the children who could teach theirs and so on but, it won't be something that just happens automatically. If you had a satellite always watching for abnormal changes in the oceans' surface topography\height it would be able to trigger alerts in seconds instead of minutes. Those alerts could be a combination of warning sirens, emails, Texts, Tweets or any other communication. That would allow an automated alert to be sent to all effected entities possibly under a minute after the tsunami has formed. As well, as alerting citizens, it would also give emergency responders an extra couple of minutes. A couple of minutes being a significant benefit in an emergency scenario.
What's wrong with satellite television? Any area that can receive a laser beam from a geosynch orbiting satellite can receive the Weather Channel, CNN or their non-corporate equivalents. And if it's not geosynchronous, you'll need a cluster of satellites to cover the appropriate areas like at the poles (Tsunami warnings for the Arctic Ocean?). If the satellite network isn't geosynchronous, you also get the mystery of "which satellite is currently visible, so where do I look"?
We are the 198 proof..
I can only imagine the potential for religious experiences from a giant light from the sky occurring for those who had no foreknowledge of the system. Is it possible Moses & the Jews were just out of the loop on the existing pharaoh/reptilian overlords communications technology?
To follow up with this, i did some research.
The full moon is quite visible during the day, but only if it's in the dark part of the sky. It has a stellar luminance of about -12 on the scale. I would figure you would need about -18 or so to have a "bright light" that would capture people's attention in broad daylight.
The approximate power required would be about 20 lux (lumens per square meter) incident on the surface, which is about 100mW per square meter.
The total coastline of places like Indonesia is hard to estimate, but it is somewhere around 60,000km. Assume 1/4 would be affected by a large non-localized tsunami and you're signaling to an area of coastline around 15,000km.
Presuming you can paint the coastline with a precise beam, say... all area within 500 meters from the water. Lets also say you're using a flashing with a 25% duty cycle (it's only on about 1/4 of the time), you're looking at 15000/8= 1800 square km or about 1.8 billion square meters "painted" at any given time.
With laser efficiency around 65% (in the best high output research lasers) and the power required around 100mW per meter incident on the surface and atmospheric losses around 40% (60% efficiency)...
((1.8b * .1) / (.65)) / .6 = 461.7 MegaWatts
Lets limit this to populated areas, say 10% of the coast. We're down to 46.2 MW.
Since the sun in space hits with about 1200W/m2, and given about 40% cell efficiency, we need about 96 square kilometers of solar cells, or about 100 4-ton steam turbines in a reactor (whether nuclear or otherwise).
Keep in mind, we're just looking at the coast of Indonesia....
Lets assume only 5% of the coast is occupied, that will reduce our power need to 23mW (only a few square KM of solar cells). But considering all the populated coastline in the Atlantic for an event like the proposed Azores landslide tsunami, lets multiply by 20.
Regardless, we're in the "entire power output of multiple massive reactors" sort of range, not the "strap it to a rocket and shoot it into orbit" sort of size.
To quote Mr Scott.
"WE SIMPLA DONT HAVE THE POWER KEPTIN"
Aside from this not working when it's cloudy, this also doesn't work when the sun is high in the sky. This is system is totally borked from 10am-6pm when the sun is up high in the sky and you won't see a flashing light against that backdrop, no matter how bright it is...
Oye...
To better address your question and lay a bit more clarity to it...
If a person were... say... flying... and they were up in the sky right next to the sun. Do you think a mirror in their hand would make them visible?
A mirror signaling is effective because it's done against the backdrop of the ground, which is not quite so bright as the sky, especially the sky immediately surrounding the sun.
How, dare say, do you propose to move the sattellite around when it happens to be directly in line with the sun, so as to be completely invisible.
Oye, there's so many parts of this that are just stupid.
I'm done... moving on...
good luck with your idea there, sparky.
Both of you should be executed for the good of the human race. You are disgusting.
Disgusting? That's an interesting word choice. Am I to understand that my being annoyed with cruel, mean-spirited people is disgusting to you?
Can you explain why that was your reaction, (that and your desire to see me exterminated)? Or if I'm reading you incorrectly, then can please explain what I'm mis-reading?
I'm not trying to hurt you, so don't worry. I'm really just curious.
-FL
Interesting analysis - in particular that you've come up with a figure of 100mW per square meter, which is two orders of magnitude less than most of the other postings assume. You don't make any mention of moving the beam around - surely that would cut power requirements? Signal one 1,000Km stretch of coast for a few seconds, then the next, etc, then return. Maybe enough to knock another order of magnitude off the sums? Which brings your final figure down to 2.3MW (for the Indonesia case, admittedly). Too high for direct power from (reasonable sized) solar panels, but surely the satellite would have some sort of stored energy system; flywheels or capacitors. Would reduce the allowable duty cycle further, but really only need a bright flash every few seconds. To answer your other point: if the satellite happens to be in front of the sun's disc (or even close) you obviously won't see it. But you're going to need a few of these things for coverage anyhow, even in geostationary orbit.
> If this were coming from a noted astronomer, a major figure in disaster relief, or GWB, then it would be Slashdot-worthy. But seriously, what value did this Ask Slashdot add?
No, then it might be newsworthy, at least in some news quarters. But one of the nice things about slashdot is that it's a bit more egalitarian. You get modded up or down based on your insights, not your credentials. Sometimes that results in sillyness, but we value it because we're nerds.
We can respect the work that goes into a Ph.D., but we'll never respect someone only because they have a Ph.D. In a community of nerds, an appeal to authority isn't required to make an argument valid.
-- IANAL, this isn't legal advice, and definitely isn't legal advice for you. Also, Squee!
You considered some "interesting" power sources:
100 km^2 solar panels - pretty expensive, check
4.5*10^8 kg of batteries - too heavy, check
8.2*10^11 kg of fuel cells - also too heavy, check
several hydrogen bombs - difficult, check
antimatter reactors - not invented yet, check
But why stop with antimatter? :-)
Why not: a naquada reactor?
Why not: a deathstar full of gerbil wheels?
Why not: unobtanium batteries?
Are we having fun yet?
So yeah, lighting up large land areas with
a space laser is a non-starter. I get that.
And there are more effective ways to solve
the advanced-warning problems that don't
involve space lasers. I get that, too.
Still, space lasers are kind of cool. It is
interesting to ponder, even if it is wildly
impractical.
*shrug*
By the way...
You missed my points about:
1) lighting up a single spot & scanning
that back and forth across the ground.
That drops the illumination requirements
a lot: from 25GW to 100W (using a 10m^2
"spot" at 1w/m).
How many "tons of hydrogen fuel cells"
would that require?
(I also wonder whether 1 W/m would even be
noticeable, but *shrug* it was just the
example Tibit used.)
And 2) Tibit's example assumes continuous operation.
I pointed out it wouldn't need to stay on for years
at a time - just a few hours at most. Does that trim
anything off the number of required batteries?
Anyway, thanks for coming out to play. :-)
p.s. I know you were just having fun with it.
My goal was wondering is there any possible way
to make it work at all, even if it isn't cost
effective. Out of all your ideas, the solar
array seemed least implausible.
Along those lines, shrinking the illumination
area and limiting the activation time seem to
make it a few notches even less implausible.
But that is, of course, still many many steps
away from practical.
I was already assuming a 25% duty cycle (flashing aka moving the laser). I don't think you can trim it more than that without increasing the power required to make it noticeable to the naked eye. But we're still talking about a faint flashing in the sky... Not anything that demands attention.. just something subtly noticeable.
The 100mW figure was based on the brightness of the moon in the daytime sky. Surely not bright, but at least visible. Maybe 10x more would be better for people to stop and notice it...
But 1kw lasers are considered pretty high power, so we're still off by a factor of 100 or 1,000...
I dunno... Just for indonesia...
Down with the herd mind.
What he can't kill, he has sex on. Trent.
What if we put the lasers on sharks? Would that help?
All of the posts calculating wattage per m*m and the weight of a nuclear reactor were impressive. But it seems to me there is a simpler reason why this will never work.
We are pretty much doing this already with the OSTM Jason 2 weather satellite, which measures the height of the ocean surface to an accuracy of 1 inch.
http://sealevel.jpl.nasa.gov/mission/ostm.html
Of course, this is not being being done with a laser, but rather radar.
You're probably right that clouds will interfere with the direct light beam. Also, I understand the power issues but feel they might be soluble using a ground-based light source and a space-based mirror. But if we can get enough light in pointing the right direction, wouldn't it illuminate the clouds which would act as a diffuser - a bit like a whole cloud lighting up when lighting occurs internally. I'm not saying we need the power of a lightning bolt - just that the light illuminating the cloud might still be sufficiently noticeable.