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."

Terrible idea, of course, which is why we don't

[Anonymous Coward]

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.

Re:Terrible idea, of course, which is why we don't

[burisch_research]

Correct.

This idea will never fly. Ten out of ten for style, but minus several million for good thinking.

Re:Cheaper solution

[will_die]

And easy in training people in what to do or what a laser from space would look like.
Just going with the old Communist fixed frequency radios or similar to the ones the US dropped during Korea or Vietnam would be cheaper and provide more and better information.

Re:Terrible idea, of course, which is why we don't

[HungryHobo]

no.
The testing of nuclear weapons in space is banned.
Nuclear reactors are fine.

The reason we don't see them on the ISS is the people who too terrified of anything with the word nuclear attached to think rationally.

Re:Terrible idea, of course, which is why we don't

[r00t]

Nope.

The USSR launched plenty of full-blown reactors, and RTGs are still popular.

You're not supposed to park ground-attack devices (like ICBMs) in space. Of course, if you imagine that Russia hasn't done that for decades, you're pretty gullible.

Re:Cheaper solution

[the_womble]

Living in one of the countries affected by the Boxing Day Asian Tsunnami, the problem was not lack of a way to reach people, but the lack of a mechanism to pass the message along. IN particular the people who had the warning, said they did not know how to contact the governments of some countries (which shows a worrying lack of resourcefulness, but that is another subject).

As you say, mobile phone penetration is easily high enough to work, but you will need to guard against hoax calls. A designated number of warnings would have to be well publicised.

Radio will work, but you hardly need to distribute them specially: just ask all radio and TV broadcasters to broadcast an emergency message. It may not work that well late in the night. For times like that vehicles with big speakers on them driving through towns with loud warnings should work well.

The laser idea is stupid: there are all kinds of lights in the sky to confuse people: I remember a huge number of people seeing "UFOs" in London in 1990 or 91 because someone said there was one on a popular radio station, so people started looking up and seeing all kinds of things they normally never noticed.

Re:Cheaper solution

[itoledo]

Here in Chile, everyone rushed to call their relatives when the earthquake came. The three main provides of GSM telephony collapsed, because of the huge number of people calling, oversaturating all the base stations. Also, the lights went off, and most towers shut down. Almost no one could place a call, and certainly not at the epicenter.

So I think that sat phones are a better idea for tsunami warnings.

Re:easier way to get the power

[tibit]

Even the rad-hardened stuff will be taken out in short order. They won't take a short burst of radiation (that's what they're designed for!) -- there'll be bazillions of particles trapped in Earth's magnetic field, pounding incessantly on everything up there. Remember that it's all in vacuum.

Rad-hardening works for short bursts of radiation coming *from Earth* -- from a ground or airborne nuclear explosion.

There's no rad-hardening for space-based explosions. We're several orders of magnitude away from being anywhere close to that.

Re:Terrible idea, of course, which is why we don't

[fractoid]

You're right about average vs. peak power, but you've got the wrong end of the stick. Specifically with semiconductor light sources (my particular experience was with high-intensity LEDs but should apply to diode lasers too) you overdrive them by ridiculous amounts as long as the average power stays the same. I've put half an amp through a 30mA LED for 50 microseconds without causing any damage.

Anyway the bulk of my argument was that you wouldn't need jigger-ma-whats of power because you wouldn't need to constantly illuminate the whole target area. Instead, you'd have a 100m x 100m illuminated spot scanning around the target area at 1km/sec. By my calculations, assuming that the original estimate of 1GW was accurate, a 100ms pulse every 3 seconds over the whole area gives a 1/30 duty cycle, or about 30kW sustained. That's well within the limits of LiPoly batteries. A 10kW battery pack can output 40kW for 15 minutes without too much trouble, most modern lithium batteries are designed for 10C or higher discharge rates.

So, how do we detect tsunamis from space, exactly?

[reillymj]

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.

Re:Cheaper solution

[DiegoBravo]

Exactly the same happened in Perú in our last big earthquake (2008). The epicenter was about 200 km south of the capital (Lima), but nobody in all the region could make a call after several hours (afterward there was a government investiagtion to the carriers, pure blah, blah..) Cell phones are useless at least in standard commercial installations or configurations.

Interestingly, the DSL services remained operative (at least in the capital) and it was the only way to communicate with peers.