This is the biggest, most ambitious, most expensive video I’ve ever made. And it’s also gonna be terrifying. We are strapping these giant metal weights to the belly of that helicopter, flying it up several kilometers in the sky and then dropping these weights, on a sandcastle city. I mean, we need luck. (dramatic music) Here we go.
– Oh my. YEAH! And this is all for a very good reason. So let’s do it.
In the late 1950s, the United States had a problem. The Soviet Union launched the first artificial satellite, Sputnik, into orbit around the earth on the 4th of October, 1957, but less well known is that just over a month earlier, they successfully tested the first intercontinental ballistic missile or ICBM. It could deliver a nuclear warhead from the Soviet Union to cities on the US East Coast, in around 30 minutes. Facing this threat, a researcher at Boeing named Jerry Pournelle came up with an idea for a space weapon. It could hit any location on Earth in half that time, just 15 minutes.
It could destroy targets buried 30 meters underground like the silos where the Soviet nukes were kept.
And theoretically it could intercept ICBM’s mid-flight. His concept was to put telephone pole sized pieces of tungsten in space, in orbit. So that these pieces of tungsten could drop on a target basically at any time. The idea was within a 15 minute window you would be able to release one of these tungsten rods and have it re-enter the atmosphere and strike a target in minutes.
And it would come in so fast, you know, in orbit things go about eight kilometers per second, and as it enters the atmosphere, it’s gonna slow down due to the atmospheric drag, but still on impact it’s still gonna be going like 10 times the speed of sound.
Mach 10 or about three kilometers per second. This is MOAB, which stands for massive ordinance air blast but it’s more commonly referred to by its nickname the Mother of All Bombs. It is one of the most powerful non-nuclear explosives on the planet. When it detonated, it released the equivalent of 11 tons of TNT.
Now, just one of these tungsten rods coming in would have the same energy as the largest conventional explosive ever detonated. They are not bombs, they contain no explosives but the amount of energy that they’re carrying in their kinetic energy because they are so heavy and they’re going so fast it is as big as any conventional bomb ever detonated. Pournelle called his weapon Project Thor after the Norse God who threw lightning bolts from the heavens. In the 1980s the kinetic missile interceptor idea was seriously considered by the Reagan administration. It was codenamed, Brilliant Pebbles but the project was abandoned.
In 2003 it was resurrected by the Air Force Transformation Plan which referred to this weapon as hypervelocity rod bundles. But colloquially, the weapon is known as Rods from God. The kinetic energy of an object is directly proportional to its mass and its velocity squared. So increasing the objects mass 10 times, increases its kinetic energy 10 times. But if you increase the velocity by a factor of 10 the kinetic energy grows by a factor of a hundred.
This is why even very light objects can carry lots of kinetic energy. This is what a 15 gram piece of plastic does to a block of aluminum when traveling at six kilometers per second. And this is a real problem for satellites because of the massive speeds on orbit, micro meteorites, small bolts, or even flecks of paint are serious risks for the astronauts living onboard the International Space Station.
This chip in the window of the ISS was caused by a tiny speck of dust. And a small piece of space junk punctured a hole in the robotic arm.
Imagine something that weighs 10 tons traveling that fast. Kinetic energy weapons appear in fiction including dozens of movies, video games and books. But how realistic are they? I mean, could this weapon ever become a reality? Well, that’s why we’re here in the middle of the desert.
We wanna see how damaging a Rod from God could be. And we really pulled out all the stops, even hiring a team of professional sandcastle builders to construct a city onto which we’ll drop the rods. I have all the respect in the world, for these sandcastle builders. – We are seven time US Open Sand Castle Champions. – That’s so cool.
It’ll endure the test of the highest weight at the highest drop with very little damage.
I’m really convinced of that. – The US Capital was great. – Yeah, isn’t that great? – Yeah.
– It’s one of our favorite. – I love all the buildings there. Who did the pickle? The Gherkin? – Yeah, the Gherkin right here.
– Very nice. This is beautiful. I mean, I feel bad for trying to hit it. I am just very concerned about aiming, the city is not that big. So before we get to that drop we’re gonna try to hit this swimming pool with a 100 kilogram or a 220 pound mass.
Probably go up about 500 meters. Try to drop a weight right into this pool. I don’t think it’s gonna work. I don’t think we’re gonna hit it. In fact, my main concern for the whole day is that we’re just not gonna be able to hit anything.
And then what was the point in coming out here in the first place? These are gonna be the questions that I ask myself. So the way we’re targeting is with GPS, we’re gonna take a GPS mark from like the center of the pool. Oh boy. We’ve also got GPS in the helicopter.
We’re gonna use that to try to line up square over the middle of the pool. So if we’re able to hit this pool from 500 meters then I think we’ve got a shot. (dramatic music) – Where’s your GPS? – My GPS is my phone. And I have the coordinates written on my arm.
We’re ready to go.
We’re professionals – First drop and it’s feeling shaky I gotta tell you. I’m surprised it can pull a load that heavy! – We’ve got another 700 feet to be at 1500. – Okay.
– I just dunno like why they’re circling up that high. Is that 500 meters? That seems really high. – Ryan to Rick, what’s your altitude? – 500 meters.
– We’re 1500 feet, that seems higher than 1500 feet. – They’re at 500 meters right now. – That is freaking crazy, okay. – Here we go. This is the one.
– This is the one. – It’s swinging around like crazy up there! – Yeah. Does it have fins on it? – Jesus.
No. No fins. Why didn’t we have this conversation a week ago? – Looking good? – We’re good left to right.
That’s good. We just need to go forward. – Oh geez. That does not look like they’re in position, right? Are you kidding me?
– It never will. – Its dropped. – Oh my. What the? What is that gonna hit?
Oh, it is going sideways. What did it hit? – Way past the sandcastle. – Oh geez. That was way more off than I thought.
– Oh my God. – I was right on. Was yours showing the same thing back there? – Yeah, we were right on it. – Yeah.
Good. Well that’s kinda weird. That’s just gonna show you what’s gonna happen at altitude. We both said we were right on it and we weren’t. – It didn’t look like you guys were moving, but.
.. – Yeah he’s telling me our horizontal velocity was zero. – And you were in the right spot? – We were exactly in the right spot.
– Oh wow. Oh wow! Look at that. – Oh Wow. – Totally, totally buried.
Falling from 500 meters, the rod accelerated for 10 seconds. And even accounting for air resistance it hit the ground going about 350 kilometers per hour.
At that speed, with a mass of a hundred kilograms it was carrying nearly half a million joules of kinetic energy. Our plan for the day is to drop something twice as heavy from six times higher. Then it’s energy on impact will be greater than the explosion of a kilogram of TNT.
Kinetic impacts are explosive. If you look at the craters on the moon and you look really closely you’re gonna see that they’re basically all circles.
I think no one stops to ask why are they circular? If you imagine when the moon gets hit by asteroids they’re gonna come in from all different directions. So shouldn’t you get these sort of oblong shapes where the asteroid comes in?
Well, the truth is, the asteroids come in with such incredible speed that it’s not like they’re pushing dirt out of the way and that’s what creates the crater. No, they’re coming in so fast that when they collide their kinetic energy is explosive. It heats up the ground, turns things into liquid and gas. They all get super hot and they spray outwards in a giant explosion. And this explosion is symmetric.
It doesn’t matter which angle or how shallow the asteroid was coming in, it’s gonna blow out everything radially because it is explosive.
Kinetic energy is explosive. And I think for me, that’s just the really surprising thing. It would be the exact same thing with dropping these rods going Mach 10, when they hit a target they’re gonna create an explosion as though they are the largest conventional weapon ever launched. And because it’s going so fast, it can penetrate around 30 meters of soil, enough to bust bunkers or silos.
And the explosion is therefore more localized. So it can be used for precise surgical strikes. Plus, unlike a nuclear weapon there’s no radioactive fallout to worry about or international laws. Do these ideas contravene any current laws or treaties? – No.
The only international agreement there is about putting weapons in space is about nuclear weapons. The only real prohibition is about putting nuclear weapons in space. – Man, like I thought targets would be hard to hit. Now I’m like super convinced they’re impossible to hit. – What we’re gonna do now, we’re gonna do a much lower altitude and we’re gonna do it visually.
– Yeah. Great. – So we’re gonna do it, you know, 300 feet visually. – I love it. We’re gonna do a cube drop.
Cube drop, is interesting cause I was like we shouldn’t do a cube drop. We’re here talking about Rods from God. They’re cylinders right? Now I’m so thankful we have the cubes because the cylinders, as Adam Savage told me, – Cylinders tend to fall on their sides, given enough chance. – Really?
Who would’ve thought I would’ve thought like, you know, a pencil type thing, it would tend to aim straight down. That still looks high. Is that a hundred meters? Does that? 30 second call, it doesn’t look like they’re over the pool.
It’s totally blowing around in the wind. It’s totally swinging. – GPS is spot on and I see it right below. – Still feels high. – We’re on it.
We’re on it. – Here we go. – All right. That wasn’t far off. – We’re off by 60 feet.
Oh wow. Did it look like we were right above it? – Looked like it yeah. – Wow.
‘Cause I still was right on it as well. – That’s something, from a hundred meters. I’ll take it. Okay, we’re setting up to drop this mass. 200 kilograms, 440 pounds.
What do you think? – Yeah, we’re gonna get there. – Are we gonna hit it this time? – I hope so. This is the moment of truth.
We’ve had two misses so far. So we’re going 50 meters or 150 feet above the pool which for me it’s pretty disappointing. But at this point I just want to hit something. – 30 seconds! 30 seconds!
– Oh boy.
The weight is swinging around on there. It’s getting blown around by the wind. I mean we need luck. There it goes, there it goes, there it goes.
I’m tracking, tracking. Got a hit of the pool! – (screaming) Yes! (crew all cheer) – It hit something. – Yes!
– It was like right on the edge. Right on the edge. – WOO! – This morning I was so worried that we weren’t going to hit anything. And like I think the footage is so shaky cause I was so excited.
But like seeing that from above was amazing. – Wow. It ripped right through the pool. – That’s crazy. – Unbelievable.
– Oh, look at the rubber duckies. – So, is the next target, the sandcastle? And you wanna go for a hundred meters? – I wanna double it.
– This will be amazing if we can actually hit the sandcastle from a hundred meters.
That’ll be something In all the different incarnations of Rods from God. The rods are made out of tungsten. And there are two reasons for this. The first is that tungsten is really, really dense. A cubic meter of tungsten weighs 19 tons.
That’s over twice the density of steel which is what we’re using here just because it’s a lot cheaper. But that means for a given amount of mass tungsten rods could be less than half the volume of steel and therefore encounter less resistance as they pass through the atmosphere. And importantly for re-entry, tungsten also has an incredibly high melting point.
The highest of any metal, at almost three and a half thousand degrees celsius. This is important because as the rod decelerates through the atmosphere a lot of heat builds up all around it.
And tungsten’s high melting point means the rods require much less shielding to prevent them from melting. The shape is also important. The goal is to hit the target with as much speed as possible. So a sleek, aerodynamic shape is best and rods are a great shape for that. Aerodynamics is why arrows and bullets and ballistic missiles all look the way they do.
It’s to minimize drag. Honestly one of the big mistakes we made was not welding fins onto our rods. We’re going up to about a hundred meters or 300 feet, before we drop.
We’re gonna hit the sandcastle city. That’s the goal.
– Any minute, any second. – There it goes, there it goes, there it goes. It’s going. Did it hit in front? – Just in font.
– Hit just in front. – We just missed it. – We were close. We were really close. So the tractor’s gonna dig the weight out right now.
– Yeah. – Just pick it up. – That’s how it landed. – So close to taking out the capital. – Yeah.
Look at that. – 30 seconds to drop. – Ah, that wind. – 20 seconds. – 20 seconds.
That wind is brutal. Oh boy. Oh boy. Oh boy. Hit something on the left?
But I don’t think it was the city. Seeing all the challenges we’re going through reminds me just how difficult it is to aim a kinetic projectile. 10 seconds. – Three, two, one , and drop. – There it goes.
Did they hit a building? Capitol’s still here.
What? What? – What?
– I cannot believe it. Direct hit on the building, but it only took down that side. – I find it unbelievable, that it hit right there – Look at the cracks. – Look at the cracks in the back – and like it created cracks but it didn’t make the whole – didn’t destroy the whole building. This is not what you would use if you wanted to cause mass devastation.
This is like if you wanted to pinpoint a target. Now if I’m honest, we did not manage to make a fair test of Rods from God, even on a small scale.
You know I wanted to drop 200 kilograms from three kilometers. But aiming was so hard that we got nowhere near that. So we didn’t get to see the explosive power of kinetic energy.
When we made one last ditch attempt to drop again from 500 meters. I was just terrified that we were gonna hit something or someone. Look out, look out, look out, look out, look out. Oh! Oh!
Caw! I was just happy to finish the day with everyone safe. I didn’t shoot that cause I was so terrified. Oh, I see it. Wow.
You’re right that it bounced out. But given the amount of time and money we spent on this video I would say it is my biggest failure of all time which as it turns out, is also something you could say about the actual weapon Rods from God.
I mean, just start with aiming. Steering a Rod from God is in theory possible you could use thrusters or adjustable fins or change the rod’s center of mass. But in practice it’s incredibly difficult to aim an object traveling at hypersonic speeds.
Not only that, communicating with the rod from the ground or from space would be nearly impossible due to the superheated plasma surrounding it. And there are other problems. You know, say you want to hit a target within 15 minutes you’d think the simplest thing would be to put a rod right above the target in geostationary orbit. But geostationary orbit is over 35,000 kilometers away. That’s almost a 10th the distance to the moon.
So from there a rod would take several hours to fall to the earth.
And if you put it in low earth orbit say around 350 kilometers above the earth the rod will move relative to the ground doing a revolution around the earth every 90 minutes. So between ordering a strike and the rod hitting the target that could take anywhere up to an hour and a half. Now you might think that you could get that time down to about 30 minutes by placing say 10 satellites in that orbit. But remember, the earth rotates so orbits drift, you would actually need hundreds of satellites to make sure there’s always a rod close by the target.
So let’s say you want to put a hundred rods into space. Well, the cost of launching them will be billions of dollars.
And over time the thrusters will break down and malfunction. So there are going to be ongoing maintenance costs. But what if you just want to use it for missile defense?
Well then you don’t need something that weighs 10 tons, a smaller rod would do. But even then it’s really, really tricky. And to successfully intercept an ICBM, you’ve gotta hit it during the boost phase, modern ICBMs split into a number of payloads after the boost some of which are decoys to overwhelm anti ICBM defense missiles.
To stop North Korean ICBM launches for example, the US would need around 400 rods spread among eight orbits to be able to intercept missiles in time. A global defense system would require at least a few times that amount.
And it’s been calculated that even a very limited system would cost around 300 billion dollars, which is nearly half of the US military annual budget. And even that wouldn’t work because enemies could evade the defense by launching several missiles at the same time. Since there’s only one rod in the right location at any time, a rod could intercept one of the missiles but the rest would pass through. So Rods from God turns out to be unfeasible to execute in reality. After his stint at Boeing, Jerry Pournelle who came up with the idea, became a science fiction writer.
And in his 1985 New York Times bestselling book, Footfall an alien race uses kinetic weapons to invade the earth.
And honestly, I’m pretty glad that this weapon is feasible only in science fiction. Engineering is all about trying, failing and sometimes blowing stuff up. And if you can’t drop giant steel rods in the desert well then the next best thing is Brilliant, the sponsor of this video. It’s the best tool I know for learning about physics, math, and engineering.
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