How Do You Shoot Down A House, Part 2

Last time, I covered some information about demolishing a house and then went wild with some rocket calculations that I hope I applied correctly. I should probably note that they also assume a single-stage rocket, not multi-stage rockets like the Saturn V or the new Atlas V. So my comparison of the ‘house rocket’ to the Saturn V was something like comparing oranges to ugli fruit – kind of related, but not really the same thing.

Also, all of that enthusiasm about giant rockets distracted me from doing a deeper dive into how you would actually demolish a house. So let’s get back to that. If you recall, it came from my son clarifying a question he’d asked by asking “How do you blowed a house up?” Last time, we established that it’s actually fairly unlikely that you would blow a house up (aka implosion), because houses usually aren’t big enough to make implosion practical. Instead, you’d be bringing in big machines and indulging in mechanical demolition.
excavator

Awesome Toys

For a look at the types of machinery that could be used, I ended up visiting ProMatcher, a sort of search engine that you can use to look for professionals in different fields. One of their subpages was Types of Demolition Equipment, which does exactly what it says it does. It describes broad categories of equipment that you might need for demolitions work. So, here we go.

First off are the demolition machines, which are the vehicles that you might see driving around the construction site. Broadly, they can be broken into trucks, loaders, excavators, and tractors – although you get some overlap on these.

  • Trucks. These are, well, trucks. They include the ubiquitous dump truck and the articulated truck – imagine a dump truck or similar with a joint connecting the cab and payload. The joint lets them turn in a much tighter area, making them more maneuverable.
  • Loader. This is a type of tractor with a scoop on the front, making it resemble a bulldozer – although their primary job is to scoop up or shove around loose material. They can have tracks or wheels, and may also have a rear-mounted tool (such as a backhoe or an auger).
  • Tractor. This is what you’re thinking of when you hear the word “bulldozer”. They’re used in much the same way as loaders, but for bigger and less loose object. Like, say, walls. They’re also pretty much universally tracked vehicles.
  • Excavators. When I was a kid, I thought these were called steam shovels. They’re tracked vehicles with a cab and an arm, and often a scoop on the end, and I don’t know any five-year-olds who don’t think they’re the coolest vehicles on earth. At least when they’re watching them.

These vehicles get the best toys, too.

  • Buckets. These are the scoops on the arm of the excavator, or on the front of the loader.
  • Grapples. Big robot claw hands for the arm of an excavator, and they’re used like big robot claw hands – they lift things, and they tear things apart. Like walls.
  • Hammers. Vehicle mounted jackhammers. Some are designed to go on the back of a loader or tractor, and others get mounted on an excavator arm.
  • Multi-processors. ProMatcher describes this tool as “an accessory that cuts, shears, and pulverizes.” After watching one in action(), I’d describe it as “big robot jaws”.
  • Pulverizers. This is another entry in the “big robot jaws” category, and it appears to be primarily used to reduce large chunks of things to much smaller chunks of things. So, pretty much what it says on the box.
  • Shears. ProMatcher describes this as “used for cutting steel, cable, and rebar.” Watching one in action makes me think of Fiddler crab claws.

Remember how I said that I don’t know any five-year-olds who don’t think excavators are te coolest vehicles on earth? Well, after watching those videos I am apparently still five years old myself. Because I really, really want to try my hand at one of those.

Wrecking stuff

But anyway, on to the actual demolition process. Sadly, there really isn’t a single way this is done – the actual methods vary from house to house. The general steps I described yesterday still stand, of course. But the House Demolitions page of Hometown Demolitions Contractors adds the following:

  • Demolish the house. This can take anywhere from a day up to several days. Home demolition generally involves a large, hydraulic excavator tearing down the house putting the unwanted house materials into the back of a truck or dumpster.
  • Remove all demolition debris from the site, leaving the site clean. Typically this means removal of everything “down to the dirt”, including removal of the house’s foundation.

In other words, it’s likely you’d see an excavator, a loader, and a truck if you demolished a house. And if you get the chance to see that happen, bring the kids. I’m sure they’ll love it.

Technically, however, I haven’t answered my son’s question. After all, he asked “How do you blowed a house up?” Not “how do you demolish a house?” The simplest way is to accidentally leave the gas on, but let’s go ahead and assume that you’re attempting to do it in a controlled and deliberate fashion.

implosion

I’m probably on a watch list, now

Strangely, simply typing “how do you blow a house up” into Google doesn’t get you many step by step instructions on how to blow a house up. It gets a few videos, and a few references to Oklahoma City, and the FBI paying attention to my search history. As a result, you won’t be getting details here. I don’t need a lengthy discussion with Agents Smith.

M4

How Building Implosions Work has a lot of  useful information on this subject. Specifically, the types of explosive you would use will depend on the nature of your load-bearing columns. Concrete columns are typically get holes drilled into them that are then stuffed with trinitrotoluene (TNT, aka dynamite) or plastic explosive. The explosion shatters the column, meaning (clearly) that it is no longer bearing the load.

Steel load-bearing columns are detonated with something called cyclotrimethylenetrinitramine, also known by the less tongue-twisting name of RDX because it was developed under the name Research Department Formula X. It is a white, crystalline solid that gets mixed with stabilizers and other explosives, and it only detonates with a detonator. If you set it on fire, it just burns. It’s considered to be far more powerful than TNT – if you’re curious about just how much more powerful, let me refer you to a US Army Armament Research And Development Command Contractor Report titled TNT Equivalency of RDX – I didn’t follow much of it myself, but the charts are impressive. Implosionworld.com states that it will cut through steel at “27,000 feet per second”, though, which certainly sounds impressive.

It’s also one of the key components of C4 plastic explosives, if you’re wondering.

Whichever explosive is used, they’re detonated remotely. They’re also frequently detonated in a sequence, instead of all at once, in order to control the direction and speed of the collapse of the building. Test explosions are typically performed on one or two columns, in order to confirm the necessary amount of explosives before trying to bring the building down. Failing would be both embarrassing and terribly dangerous.

61CA4B328Kind of like this, only with less humor…

Let’s be honest here, though. If you’ve got a house you’re trying to take down, you really don’t need to implode it. And you certainly shouldn’t try to do it yourself. Hire a contractor, and let them tear it apart with the big machines.

How Do You Shoot Down A House?

This was one of those utterly random five-year-old questions, really. I have no idea what triggered it at all. We were in the car last night, and I was talking to my wife, and he just tosses this question out: “How do you shoot down a house?”

“You mean, like a flying house?” I ask, trying to parse this question.

“No! How do you blowed a house up?”

So I [i]think[/i] he’s talking about demolitions. So, let’s look into it.

The Demolition Planning chapter fo The Architect’s Handbook of Professional Practice, Update 2006 gives three primary categories of building demolition: mechanical demolition, implosion, and special demolition. Mechanical demolition is the type of demolition that uses excavators fitted crushing and shearing tools.

excavator

Not all of the excavators are the huge ones, though. Small excavators are used for for interior demolitions. But the process is generally the same. The machines knocks down or pull down walls, cut trough metal, break up concrete foundations, and so on.

Implosion is the use of “highly specialized explosives to undermine the supports of a
structure so it collapses either within its own footprint or in a predetermined path”.

implosion

This demolition method is generally used for tall buildings or specialized structures like cooling towers and steel mills and bridges.

Special demolition is a catch-all category that requires ” specialized handheld
tools for cutting, chipping, drilling, and breaking small amounts of materials”. These tend to be smaller projects, like cutting a hole through concrete to install a door or window. The sledgehammer is a popular mental image for the type of tool used, but it’s far more likely to be a one or two man hydraulic or pneumatic tool these days.

Clearly, to “blow up” most houses, you likely wouldn’t blow them up at all. You’d approach it with mechanical demolition, and tear the house apart with a mechanical excavator or a bulldozer. You can read about some of the specific details here, but in brief you probably need to do the following:

  • Get a permit.
  • Have the house inspected for hazardous materials.
  • See if the house can be deconstructed (i.e. have parts salvaged intact) rather than just destroyed.
  • The big machines arrive and wreck the joint.

Clearly, that’s the serious answer to the question. For laughs, though, let’s see what it would take to make a house fly so that you could actually try to shoot it down. Be aware that everything past here is ludicrous and involves giant rockets.

According to HandCrafted Homes, a company that makes modular homes, they estimate 35 – 45 pounds per square foot for a ranch style home (depending on the specific model), plus 1,500 pounds for rigging. The Seattle Times Ask the Expert column came up with an estimate of 200 pounds per square foot for a single-level home, 275 for a two level home, and 350 for a three level home.

Picking a random home in my area, I found a single level 2,800 square foot house. HandCrafted Homes would estimate that at (40 * 2,800) + 1,500 = 113,500 pounds. The Seattle Times would estimate that at 200 * 2,800 = 560,000. Since it isn’t a modular home, let’s go with the heavier one – 560,000 pounds, or 280 tons. That’s big, but not undoable – it’s only (only?) about 50 tons heavier than an Airbus A340-500, an aircraft that is big but hardly the biggest in the world. So we could fly that thing. And most fighter interceptors and many shoulder-fired anti-aircraft missiles could shoot it down.

But let’s crank this up a notch and put it on a huge rocket and launch this house into Earth orbit. Turning to WolframAlpha, we’ll plug the details into the Tsiolkovsky rocket equation.

…wait. The what, now?

The Tsiolkovsky rocket equation, also known as the ideal rocket equation, is a formula that describes how rockets work. A rocket has to lift the mass of the payload plus the fuel, but it expends fuel and gets lighter as it moves. So, this equation works out how the changing mass impacts the velocity of the rocket.

So, with that in mind, back to our rocket and WolframAlpha. The rocket needs a final speed of 7.8 kilometers per second to hit low earth orbit, so assuming effective exhaust velocity of 5 kilometers per second the total mass of the loaded rocket is 1,335.3 tons. To achieve escape velocity, we’ll need a 2,855.2 ton rocket. Which seems big, right? But for comparison purposes a Saturn V – the rocket that sent men to the moon – weighed 2,520 tons and could lift 155 tons to low earth orbit.

saturnv-3_0

Why could it lift less than the house rocket? Because it was a real rocket with mass outside the fuel and the payload. Also, I have no idea what the effective exhaust velocity of the Saturn V was.

Let’s get crazier and put my house in orbit. I live in a condominium, with a total of 24 units on three floors. The condos run about 1,200 square feet each, so that’s 10,080,000 pounds or 5,040 tons. WolframAlpha and Tsilokovsky tell us that we’d need a 24,035 ton ideal rocket to get my condo building into low earth orbit, and a 51,393 ton rocket to achieve escape velocity.

NOw, could we shoot down a rocket heading for LEO or excape velocity? According to Air&Space, the answer is yes, in theory at least, but it’s really, really hard.

So cheer up. Your house might be vulnerable to interceptors if you have it on wings. But if you’re heading for [i]space[/i], you’re probably safe.