Here's a Qassam rocket. When they're new they often paint them up all fancy, but you can see how simple they are without the paint. They're just a steel pipe with fins crudely welded to the side. The engine is a steel plate with nozzles drilled out. They use multiple nozzles because the rockets are so crudely made, they keep on going even if a couple fail. They're literally sugar rockets - the fuel is sugar and potassium nitrate fertilizer. The warhead is a steel shell which they stuff with whatever smuggled explosives they can get ahold of. The trigger is a bullet cartridge with a nail and a spring.

Teenagers competing in model rocket competitions build more advanced rockets than that.

Given how incredibly lame this missile's fuse is, you could literally defeat it by sticking a broomstick on the front end of your missile and rebalancing. That is, if the system even worked in the first place.

I had no idea that's how they triggered the Iron Dome warheads. Just a broken, angled light field triggering a central explosive a short time later on the premise that it'll be near the warhead at that point? That's so incredibly stupid. I don't know whether this guy's data about how effective the system is or not is accurate, but I can clearly see the glaring theoretical problems with such a system.

And this is ignoring the fact that they're using $50k missiles launched from $55 million systems to shoot down $800 rockets launched from pieces of drainage pipe. Even as poor as Palestinians are compared to Israelis, those are some pretty awful ratios. The Palestinians might as well save money and skip the warheads altogether, just shoot off as many empty rockets as they can to waste Israel's money.

Orders of magnitude are used for approximations of scale, not exact figures. And the Russian R-36 missile can take a 20MT warhead (although I think they've eliminated all of the R-36s in that configuration in favor of the MIRVed version, I'd have to check).

You're right, though, I think two orders of magnitude would be a more accurate figure.

I'm an atheist. But I am happy when terrorists die. I don't need to rationalize it.

Yeah, those damned terrorist children in their terrorist-loving hospital beds. Good riddance!

Oh, but Israel warned them, right? Yeah, great how that goes down!

Israel: Hey, just being nice and friendly and letting you know we're about to bomb!
Palestinains: Great, we're on our way!
Israel: Um, no... you can't come here.
Palestinians: So... you're going to open up the border crossing to Egypt?
Israel: Certainly not!
Palestinians: Okay... so I guess we're not leaving then.
Israel: Okay, your call, but don't say we didn't warn you!

Gaza has been since the beginning like a giant open-air prison camp. Where the heck are the impoverished people trying to flee the conflict supposed to go? And for that matter, for everyone criticizing Hamas for fighting and storing weapons in or near civilian areas... there is nowhere in Gaza not near a civilian area, certainly nowhere further than a stray tank shell can fly - it's one of the most densely populated places on Earth, over 5 times denser than Taiwan and 11.6 times denser than Japan. Israel forced as many people as possible into as little land as possible. And not accidentally. What little farmland there is can be overrun in a matter of minutes. Israel could fill the entirity of Gaza with tanks and artillery at a density of over 100 per square mile.

Of course, the old Orion design has been significantly surpassed by a number of newer designs. Medusa, for example, is much better than Orion - the bombs explode in front of the craft behind a gigantic "parachute", which captures far more of the energy and the long cords on the parachute allow for a much longer, smoother acceleration pulse. The bombs are also able to be detonated much further from the craft, and the craft may be made a lot smaller.

Nuclear thermal - the first version that was being developed called Nerva - allows for "clean" (to varying degrees) fission propulsion from the surface. Or if what you want is high ISP in space, then a fission fragment rocket goes much higher than an Orion or Medusa design (and scales down a lot better)

Decade or two to ramp up production for new vehicle sales. Plus a decade or so for consumer acceptance lag. Then two decades or more to phase out existing gas cars. We're talking half a century here.

Yes, at one point there were 5 cars per million people period. Around the year 1890. Today there's 0.15 cars per capita globally. It took over a century to scale up that much, so I don't think that's the sort of point you want to be making. Plus, not only do we have to scale up for existing car replacement, but also to handle the rapid growth of the third world, which will push that 0.15 cars per capita way up over the coming decades. It's simply something that will take decades to get the production capacity in place, and then decades at that level to phase out the existing vehicles on the road.

Biofuels are hardly a gap filler. Have you ever checked how much land they eat up even to meet today's tiny pathetic percentage of the market share? To meet the needs of the average American driver's 12k miles per year in an average 24mpg car (500 gallons) would require 3 million square miles of farmland dedicated to it, more than double the US total farmland for *all* crops - for human consumption, for animal feed, for clothing, for industry, everything combined. And that's just for passenger cars, let alone freight trucks, trains, airplanes, ships, etc.

It's not a gap filler. It's an environmental disaster on a greater scale than the oil it's trying to replace.

And for the literally 99.9995 percent of the world population who doesn't have a Tesla?

As much as I'm a fan of electric cars, it's simply an absurdity to pretend that everyone's going to have one any day now. The average car on the road in the US is 10 years old, implying an average US lifespan of 20 years - and many live on even longer, shipped to the third world. So even if every new car sold tomorrow was an EV, it'd still take decades to switch over. But of course, every new car sold tomorrow won't be an EV. Even if every consumer in the world was suddenly sold on the concept of EVs, it'd take a decade or two to be able to ramp up production that high. But of course every consumer in the world isn't sold on the concept of EVs, it'll take a decade or two of people getting to experience the technology and being satisfied with it for that to happen.

I wish this wasn't the case, but the majority of the cars in the world aren't going to be electric for many decades to come. So if your plan is to stop all oil production during that time... yeah, best of luck with the end of human civilization.

You think the boat is just going to sit in one place? They drag the sensors behind them while they travel across tens of millions of square kilometers. At the sort of pulse rate discussed and at typical ship rates of travel for a craft like this, the pulses would be about 100 meters apart, and the ship would be dozens of miles away an hour later.

There's no point to sitting in one area and pulsing the same place over and over.

France also has a much milder climate and 3.5 times the population density. They're also heavily dominated by nuclear power, which some people like but others truly hate, and which tends to be one of the more expensive generation sources per kilowatt hour and with a very long turnaround time from conception to commencement of generation.

And once again, we're talking about oil here, oil and electricity are not interchangeable. You need to be comparing oil consumption per capita. France's is a bit over half the US's, but with a population density 3.5 times higher, that's kind of to be expected.

Let me know how you managed to fit the sun or a fusion reactor into your gas tank.

Are we really going to keep pretending that oil and electricity are the same thing?

For the third time I have to point it out in this thread, underwater explosions are measured differently on the decibel scale than above water explosions, you need to subtract 61.5 from the decibel figures before comparing them with above-ground noise figures. That's over 6 orders of magnitude difference.

Also, when people talk about how the ships keep making pulses every ten seconds, they act like it's in the same spot. Which would be idiotic. "Okay, now that we know what's down here, what should we explore next? I know, let's keep exploring the exact same place!" The ships pulse every 10 seconds while moving across the vast survey area.

Lastly, see my comparison with lightning above, which strikes more frequently in the survey area, louder, and often hits the same area for hours on end.

Once again, people here at Slashdot seem completely unaware that underwater sounds are measured by a scale that's 61.5 db louder than sound in the air.

Nitrogen-based fertilizers generally come from natural gas, not oil, FYI. Of the three main sources of fossil energy (coal, oil, natural gas), oil is generally by far the most expensive per joule.

Also, I don't think your comparison is that simple that if yields decline, people die. If there was a global food shortage due to reduced yields per acre, the price spike would hit meat the hardest, practically driving grainfed meat off the market. A calorie of grainfed beef takes over 12 calories of grain to produce; all of that vast acreage dedicated to growing field corn for livestock feed would switch to the suddenly more valuable crops for human consumption. Meat from animals grazing on marginal lands wouldn't be more expensive to produce, although their profit margin would shoot up. The world's diet, although especially the poorer nations', would increasingly look more like it did in the past - calories primarily from plant sources with only the occasional meat supplementing it.

Also there's the fact that if price on food products skyrockets, all sorts of land that was previously considered marginal and uneconomical to produce on suddenly becomes economical.

Common screwup. Those are all atmosphere-rated decibel figures. Underwater decibel figures are listed at 61.5 dB louder than their atmospheric equivalents. 250 dB underwater is 188.5 atmospheric.

Adjusting your above examples to be underwater figures, we get:

271.5 dB 2.0 earthquake
296.5 dB 5.0 earthquake
309.5 dB atom bomb
371.5 dB loudest volcano

I'd think it obvious that an air cannon isn't going to produce sound levels equivalent to an atomic bomb. And actually one would expect an underwater atomic bomb to be much louder than a surface one, far more of the energy is going to go into creating a gigantic oscillating bubble. And lastly, your cited atomic bomb figure is only for the 16 and 21 kiloton bombs that were dropped on Hiroshima and Nagasaki. Modern thermonuclear weapons are generally three orders of magnitude higher yield than that. A large thermonuclear weapon in deep water will create a bubble on the order of magnitude of a kilometer in size, which will then oscillate in a series of collapses and reexplosions. The oscillating bubbles created by air cannons are practically microscopic by comparison.

286 db at source? Air cannons are 250 db at source, so 3 and a half orders of magnitude less powerful. Lightning in the ocean is 260 db at source and your average square kilometer of ocean gets two strikes per year. These ships will be covering tens of millions of square kilometers. With a pulse rate of once every 10 seconds (3.2 million pulses per year per ship, if they run constantly, which they almost certainly won't), you're looking at an order of magnitude less per ship than lightning (and I doubt there will be many ships, and they won't always be in operation). And lightning striking water is an order of magnitude louder. It even causes shock waves in the water by the same mechanism - rapidly creating an air bubble in the water (in lightning's case, by boiling the water) which then oscillates as it implodes and explodes repeatedly.

Now, one could say that this is different because it's all in one place at a given time, and thus animals would be tempted to flee instead of it being a one-off thing. But then again, lightning strikes aren't spread out evenly over space and time either, they come in thunderstorms which do the exact same thing, repeatedly hitting the same section of sea for hours at a time.

I'm not saying that I think these ships are harmless - not at all. I just think that I think people are overplaying it when they make these apocalyptic pronouncements on what effect they'll have on sea life. I mean, people have been detonating underwater *atomic bombs* - how do you think that compares to the sound of a pop of air? At 400 feet, a blue whale's own calls (188db @ 1m) are louder than the air gun.