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."
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.
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.
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?
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?
Wait a damn second here. You are against warning people about tsunamis because some might use it as a chance for looting? Personally, if there is a giant wall of watery death heading my way, I'd like to know about it. If some moron decides to stay behind to grab my stuff, I'll the aforementioned wall of watery death deal with him, wash away all evidence, including the moron himself.
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...
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.
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
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
I guess there's some misconception about what such a "light" would look like.
Everyone seems to react like this was going to be a streetlight type of a thing. You'd need a rather big nuclear powerplant to get that sort of power density on the ground. Assume we want 1W/m^2 on the ground, and a "square" area 5,000km on the side. That's 2.5E10 m^2, so you'd 25GW of optical power output for your illumination. How anyone sees that much power being generated in orbit using current technology -- I don't know. Even getting a 1MW generator in the orbit would be a big feat. You can't exactly put a chiller tower up there. Dissipating all the waste heat would be a huge fucking problem, no kidding.
For what's achievable with current technology, we're talking about a faint star that say can be red, green or blue. So beam forming to a point where "a country could opt-in" etc. is a fantasy at this point. How hard is it *not* to look up?
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