Forgot your password?

Comment: Re:Yes, but... (Score 1) 337

by Rei (#47508393) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

Contary to popular belief, broomsticks can't fly and are not aerodynamic.

If 16th century India could do it... (why a person would believe that the warhead has to be the frontmost part of a rocket is beyond me, given that the interceptors themselves aren't built that way - yet the entire logic behind the interceptor's detonation system relies on that assumption)

In any case the missile will miss its intended target if it was hit by shrapnel.


Comment: Re:Maybe (Score 2) 337

by Rei (#47508237) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

1. A hit by a few pieces of shrapnel each weight no more than a few grams is not going to have a noticeable impact on something that's dozens of kilograms moving at roughly half their speed. It's simple physics.

2. The warhead is the whole point. A warhead-less rocket won't penetrate your roof. If you're out walking in the park and it lands on your head you might get seriously injured, but apart from that. no.

3. What are you talking about? The payload of the Tamir interceptors is is 11kg, that's no secret. And again, it's not designed to work by concussion, it's designed to work by shrapnel. The energy of the explosion is mostly spent in the process of creating high velocity shrapnel fragments.

Beyond that, the length of time of any exposure here to any explosive force is simply miniscule. The rockets pass each other at a rate of 1200 meters per second - nearly half the speed of the explosive shrapnel itself. Even if they passed directly past nearly grazing each other (which is grossly implausible), they'd only be within a meter of each other for less than two milliseconds. And even things that are right near explosions the whole time get surprisingly little push from blast shockwaves (Mythbusters did a full episode about this). Relevant push from explosions requires confinement of the gasses.

Comment: Re:But (Score 2) 86

The quickest numbers I could find say that at the scales of large power-plants, the generator is very efficient, but the turbine not so much, around 50%. This would put the system as a whole at around 40% efficency sunlight -> electricity. That's competitive with the best solar voltaic systems tested in the lab, and 50-100% better than practical systems on the market. Assuming their system really does scale up to power plant sizes, of course.

Comment: Re:5% 0%. (Score 1) 337

by Rei (#47507185) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

Israel's GDP is the equivalent of about US$250 billion. They can easily afford tens of thousands of intercept missiles if it keeps the population safe.

And Palestine's is 4B GDP. Yes, they're poor, but not *that* poor. They can afford to spot weld fins onto a piece of drainage pipe, drill holes into a bit of steel plate and spot weld it on, fill it with sugar and fertilizer, and attach onto the front end a hollow shell containing several kilos of smuggled or homemade explosives triggered by a bullet casing connected to a nail and a spring. That's literally all a Qassam rocket is.

Comment: Re:Maybe (Score 2) 337

by Rei (#47507075) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

Iron Dome isn't designed to hit rockets in the boost phase; when it hits them, the motor is not in operation. You could turn 90% of the rocket into swiss cheese, if you don't hit the warhead it's still going to explode when it comes down, and it's going to come down right where it otherwise would have (the Iron Dome interceptors work by shrapnel, not by concussive force that could push a rocket onto a different trajectory)

Comment: Re:"Patriot Missiles" (Score 1) 337

by Rei (#47507049) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

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.

Comment: Re:Yes, but... (Score 3, Informative) 337

by Rei (#47506969) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

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.

Comment: Re:Other loud noises (Score 1) 270

by Rei (#47506761) Attached to: White House Approves Sonic Cannons For Atlantic Energy Exploration

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.

Comment: Re: Here we go... (Score 5, Interesting) 337

by Rei (#47506103) Attached to: MIT's Ted Postol Presents More Evidence On Iron Dome Failures

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.

Comment: Re:Old dreams (Score 1) 108

by Rei (#47502111) Attached to: A Look At NASA's Orion Project

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)

Optimization hinders evolution.