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."
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!
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.
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.
How about instead of assuming that we need to simultaneously light up hundreds of square miles of land, we assume that we only need to make the land 'blink'? Using your figure of 10 watts per square meter, and assume a 0.1 second flash every 3 seconds. That would require 1/30th the power, and it would only be necessary to transmit the warning for maybe 15 minutes at a time. A 10kWh battery pack should do the trick, and can trickle-charge from solar panels between tsunamis. In fact, the figures are even better because the tsunami would hit different pieces of coastline at different times.
Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
Does the laser have to be in the sky? Is ground-basing and bouncing it around okay? A laser cage would probably also help in asteroid defense someday.
Someone flopped a steamer in the gene pool.
Just give them cell-phones that can do that instead.
Make each cell phone have an emergency receiver.
The phone is more likely to be close to the person.
It has a greater chance of being charged.
People will not ignore it.
And the best part is that cellphones are spreading even in poorer countries.
Implementation costs would be minimal, just make sure every cellphone receives an emergency band.
(and being waterproof with a solar charger on the back would be nice too)
I reviewed a prototype for a mobile phone four days ago that would be perfect for this.
With mobile devices still pretty big and requiring something to stow them in, this company is trying to fill a niche market with a mobile device that's completely voice driven and pretty small as far as phones go. You don't actually stuff it in a purse or pocket, but rather pin it on your shirt like military insignia. They are offering integration with the audio system in your house for advanced features that require a computer. If your in the house you simple call up the system by saying a keyword (default is "Computer", which I think is too common a word, but hey, I'm no Vulcan). If you're not in the house you simply touch the phone on your chest and call up people by name.
I think this would be perfect since you would be wearing it the whole time. And somehow when I wear it I feel.... complete.
"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
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