Original subtitles

In the movies, at least the ones I watch,

things are always blowing up.

People.

(high intensity rock music)

Cars.

(metal crashing) (glass breaking)

(high intensity rock music)

And houses.

(glass breaking)

But I want to know how is a real explosion

different to a movie explosion?

If there was a real explosion,

could I still walk away in slow motion

like an action movie hero?

I've always been fascinated with how the world works.

And I've got lots of questions

about why things happen.

To find out the answers, I'm gonna blow stuff up.

An explosion is a sudden and violent change of state

that produces a shockwave which can

sometimes destroy things if they're too close.

I'm gonna produce an explosion using

this large container of liquid nitrogen,

and the detonator in this hopefully-safe experiment

is this bucket of boiling water.

And when I add that to the liquid nitrogen,

you'll see that sudden violent state change

that I was talking about.

The boiling water instantly turns the

freezing liquid nitrogen into a gas.

But I wasn't blown to pieces because, in this case,

the change from a liquid to a vapor

was relatively slow.

So instead of a deadly shockwave we got

this lovely, gentle rolling fog.

But one way to increase the energy of explosion

is to constrain the reaction inside

a much smaller space.

I'm gonna use liquid nitrogen again,

a lot less this time,

but the reaction is going to be even more dramatic.

And that's because I'm constraining

the liquid nitrogen into this small plastic bottle.

(hissing)

And, uh, then we're gonna put that

inside this red plastic bin

with a thousand ping pong balls,

which means we're shaping and focusing all that energy,

which means a much more violent explosion.

Right, Des, arm the bomb.

(balls rolling)

(high intensity rock music)

The nitrogen has turned from a liquid into a gas.

It expanded to a size about 600 times bigger

than it's liquid state.

That change, and the fact that it was contained,

caused this explosion.

(dubstep music)

What determines the power of an explosion?

Well, basically, it's the rate of oxidation,

or combustion.

And that can happen in lots of different ways,

and a lot of different speeds.

In this incredibly exciting explosion, rust,

the rate of combustion is very slow.

It's just a few millimeters per century.

And really the only way to see that

is with time lapse photography.

Oxidation is a chemical reaction that releases energy,

and rust is no exception.

It's just really, really slow.

The next level of oxidation is fire,

and it combusts at a few centimeters per hour.

But we wanna go to the next level of oxidation

where things get faster and more dangerous.

So it's worth pointing out at this point

that over there we've got my explosives expert,

Martin Van Tiel, who has a PhD in chemistry,

and we've got a medic with truck loads of medical stuff.

They are overseeing everything that we do

so don't try this at home, ever.

When this liquid fuel hits the fire,

it's gonna oxidize considerably faster.

Slowed down, you can see that the fuel isn't exploding.

The vapor's oxidizing much more quickly than a wood fire,

but it's still at a slow enough rate

to be considered a fire.

It's still not technically an explosion.

For that we need an oxidation rate

of meters, or even kilometers, per second.

And for that I'm going to need

black powder,

an explosive made from sulfur, charcoal,

and with potassium nitrate as an oxidizer.

Martin Van Tiel has a license to make fireworks,

and he shows me how to grind and mix

the three components into a fine powder.

It's kind of like a cooking show,

but fun 'cause you're gonna blow stuff out with it.

All we need now is a bit of heat

to set off the chemical reaction.

(hissing)

It even smells like Guy Fawkes, too.

The black powder fizzles tamely.

To make it explode we need to contain it,

just like we did with the liquid nitrogen

and the ping pong balls.

And the speed of burning is gonna increase significantly.

Black powder probably originated in

China a thousand years ago,

so I wanna make an old school Chinese bamboo-cracker.

It will turn into needle-like shrapnel,

so the plan is simple:

light it and walk like hell.

(explosion) Oh!

There we go. Yes!

It exploded! Nice.

When I set fire to the black powder,

it starts off a chemical reaction

which is basically the potassium nitrate

stealing electrons from the charcoal and the sulfur.

And this rapid burning happens

at an explosive speed,

traveling at hundreds of meters per second.

Black powder, otherwise known as gunpowder,

is something that has changed the history of the world.

Possibly more than any other invention.

So you've got a cannon.

Of course I've got a cannon.

So what's the basic principle here, Martin?

Well it's a muzzle loading cannon, a Napoleon replica,

so we basically load everything from the muzzle in,

we put the powder in, put the cannonball in,

and we light the fuse.

Black powder is a low explosive,

so you don't say it detonates,

you say it deflagrates.

A clever sounding way of saying it burns quickly.

But when you get a breach or a cannon barrel

to confine that combustion, you get a real explosion.

And when people figure that out,

they've put the bow and arrow makers

out of business in a second.

Beautiful, that's all the way home.

So now we're loaded. We're loaded.

So, is it literally just light the fuse?

Light the fuse.

Well we'll aim it first, we'll make sure we hit the bucket.

Aiming is as basic as you get.

Happy with that.

Light the fuse.

(torch blowing)

It's getting close to it, put our fingers in our ears.

Whoa!

The slow motion shot shows

that aiming is a lot harder than we thought.

Skipped over the top.

We missed.

Thought we'd lined it up pretty well.

(laughing)

Good God!

If we slow it down some more,

you can see the cannonball zooming past

a few centimeters above the bucket.

We can't even aim it, then.

We have to put it right next to it.

Let's go forward, cause I wanna kill this bucket now.

It's become quite personal.

(hissing) (bouncy music)

We got it.

(laughing)

Got you, bucket!

(high intensity techno music)

That's what I call artillery.

(laughing)

Next,

it's time to try something even more explosive.

This is actual TNT. That's actual TNT.

And it's my turn to audition

to be an action movie hero.

I'm trying to find out the difference

between a movie explosion and a real world explosion.

Black powder explosions aren't that spectacular

by themselves, you need to suit them up,

and that's where fireworks come in.

(upbeat music)

Martin Van Tiel is a pyrotechnic expert

and we're building a firework,

adding different chemicals to the black powder.

So we need to load one side with some stars.

Martin's showing me how to build a Brocade Crown.

Then we'll add the burst charge.

A spectacular firework with a 150 meter burst radius.

And this particular one will feature in the finale

of a big show he's orchestrating.

That's what it looks like.

Over here, Nigel, we've got a mortar

especially for the finale.

Basically there's the lift charge at the bottom

of the shell, which you'll send this

out of this mortar about 300 kilometers an hour.

And then we'll just attach the igniter to this.

Then we just cover that up.

Make sure that no stray sparks land in that mortar.

(fast-paced music)

Do you get anxious at this point?

Yeah. (laughing)

Five, four, three, two, one, go.

(fireworks booming) (high intensity string music)

The extra chemicals we added earlier

to the gunpowder changed the colors of the explosions.

This red comes from strontium,

and magnesium makes this blinding white look.

Whoa!

That was my one!

And those dazzling silver sparkles

are created by the titanium.

So now we can add a firework element

to the movie explosion that we're going to make.

So fireworks are part of the low explosive family

and that's basically anything with black powder in it.

If you want your explosion to be even more powerful,

you have to find a way to mix the

oxygen and the fuel together at the molecular level.

And the first one to do that was Alfred Nobel

in the 1860s when he invented

the first high-explosive, dynamite.

This is black powder at a low explosive.

It doesn't have enough power to punch a hole in the tin.

All we've really done is made a loud noise

and left a black smudge.

Next is a few grams of sintex, a high explosive.

The fuel and oxidizer are mixed all in one molecule.

So firing in three, two, one.

(tin exploding)

Wow.

So, Martin, clearly high explosives are quite different.

Obviously we've generated a super high

pressure zone right in the middle here.

Part of that metal's just gone straight into the bank.

That pressure has just expanded

and basically peeled this metal backwards.

And how fast did this explosion go?

Eight kilometers a second.

This shows the true destructive

power of high explosives.

We've created a blast wave that has energy

speeding out at eight kilometers per second.

If there had been more sintex,

the air would've turned into a

supersonic blastwave, killing us all.

Now it's time to find out what happens

when explosions happen in the real world,

with real explosives.

Can I walk away in slow motion like an action movie hero?

We're going to blow up this small shed twice.

The first time is gonna be movie star,

so it's gonna look spectacular

but I should be able to stand quite close.

And then the second time is with high explosives

and we'll see what happens if I stand too close to that.

Okay so we'll be working with a variety of explosives,

everything from propellants

all the way up to high explosives.

Movie explosions are a mixture of

low explosives with a bit of firework flair.

They look amazing but they can be dangerous.

So what goes in here, Martin?

We've got a hydro-tab in fuel,

so we're basically burning enough fuel

that you can go from Auckland to Hamilton.

(laughing)

And each of them at about two seconds.

Right, nice.

Real demolition involves

high speed explosives, like the bit of sintex we used

to punch a hole in the sheet metal.

So change the volatility a little bit.

And black powder's used to lift and ignite the fuel.

Then fireworks are added.

So these little charges here

will produce a thirty meter ball of sparks.

So the explosive charge will go directly on that plate,

so we'll keep all nice and clear around it.

So we're almost ready to go.

Let me give you a quick tour of

my windy house in the quarry.

Out the front, a low explosive and two fuel bombs,

on the side here these two rather small

looking little white plastic containers

which will give me thirty meter diameter showers of sparks,

and out in the backyard, two fuel mortars

which will produce an enormous fireball.

So all we need to do now is push

the button and hopefully walk away unharmed.

I've had a last minute idea.

I want to put a cardboard me right

between the two mortars in the back garden

to see if I'll survive.

Right, we're all set.

The only thing left now is the

slow motion action movie walk away.

(bass music)

I'm finding out the difference

between a movie explosion and a real world explosion.

The windy house is now rigged to blow up

just like in the movies.

Right, we're all set.

The only thing left now is the

slow motion action movie walk away.

(bass music)

(house exploding)

You can clearly see the fireworks

attached to the side railings

sparkle in this replay.

The chemical element zirconium creates that effect.

(high intensity rock music) (explosions booming)

You can feel the heat.

Oh, exactly. But no shockwave, just heat.

No, no, just a loud noise.

Just a few little fragments here and there.

So this is what?

Is that just a plastic-

Yeah, a little bit of plastic from the bag tarp thing.

Little bit of fuel on the ground.

The house survives with just

the smallest amount of structural damage.

And so when we go to old Nigel around the back,

it looks like-

So the splatter, what's the splatter?

It's just a little bit of residue from the fuel.

So as the fireball develops,

a few little droplets will fall outside of the fireball.

Grab the end of that, Nigel.

So, this is basically the high explosive?

Yes, this is the high explosive charge.

So we're gonna do a 2.5 kilo charge in this hut.

What does it look like?

Let's open the box and find out.

So here's a charge, here.

That's it?

That's it.

There's two and a half kilos in there.

And it's kind of quite safe at this point, isn't it?

You can bang it.

Well see I should've asked you can you bang it

before I actually started banging it.

Yes, it's a very insensitive explosive.

It's still an explosive.

Right, so how do we initiate this?

We've got a booster.

So we've actually got TNT in this booster,

mixed with some other explosives.

So this is actual TNT?

That's actual TNT.

Can I bang this?

That's a different...

Yes, it's safe, but it's still a high explosive.

So... No.

(laughing)

I'll give you that one back.

Because the high explosive is so stable,

it needs a large blast to set it off.

So that's what the less stable TNT is used for.

And that TNT is set off itself by

a primary explosive, otherwise known as a detonator.

So Martin, that cardboard me survived quite well,

but I thought for the high explosive I wanted something

kind of a bit more substantial so

I've gone for the mannequin me.

High explosives are very dangerous.

So the team is putting up cardboard Nigels

to see what kind of damage the blast will do

and how far it will travel.

So I've redecorated my little villa in the quarry

for our real world explosion.

The first thing that you'll notice is

there's nothing outside, no paraphernalia at all.

Instead, I've gone for a bit of a minimalist look.

Just two and a half kilos of high explosives

all wired to blow.

So at this point I'm gonna close the door and run.

Ten, nine, eight,

seven, six... It's time for the real

world explosion, this time you'll notice

I'm a little bit further away.

So now the slow motion action movie walk away.

(high intensity rock music)

(ground booming)

Being so far away made the shot ho-hum

compared to the movie explosion,

but it was 1000 times more dangerous.

The house is kindling. (house exploding)

On the right side of the frame, you can see

cardboard Nigel ten meters from the explosives

being taken down.

The high explosive gets air molecules traveling

at supersonic speeds that would cause lethal damage

if you were close enough.

And in this angle you can see

mannequin Nigel hurled 20 or 30 meters.

This is the most dangerous part of an explosion.

Then, of course, there's the shrapnel to look out for.

This camera is taken out completely,

but you can see it go flying through the air in this shot.

There it is, that crate flying on the right.

I felt that.

You should've.

Like that was qualitatively different, wasn't it?

Oh, exactly.

You've got a very, very short duration and tense pulse here.

When that big boom went off as I was walking away,

I was expecting little bits of shed

to hit me in the back the whole time.

Which I didn't feel the first time around.

No.

But that time was like, you just...

(hand slapping)

you felt it.

Yes.

Okay we found the door!

(laughing)

So. That's the door.

Little bit of door.

Cardboard Nigel,

standing where I did my movie explosion walk away,

has debris flying past him.

So this is me at the point I was standing just before,

and... Exactly.

That's exactly what we're trying to avoid.

Imagine being struck by that.

You're lucky, you're extremely lucky it was right there.

This is about 10 meters.

Yup, I think you got your neck severed there.

I think your neck was the one that, yeah.

Yeah, he's gone.

And speaking of gone, our house is gone.

Gone. It's just bits.

Also missing in action,

is mannequin Nigel.

This camera angle shows that he's been thrown

30 meters by the blast wave into the side of the quarry.

This is huge.

So basically, it looks like something struck my face,

Gone straight through the back.

And has gone out and taken off the back of my head.

And then the rest of it is... God, look at that!

So we've actually got a bit of

shrapnel stuck into my liver, or something down there.

And we've got lots of holes. You've got puncture wounds.

All over the place.

And the back is just completely and utterly destroyed.

So all that movie stuff, that's movie stuff.

Real world stuff?

Results in holes in your head

and bits of wood in your liver.

Who's gonna clean it up?

(laughing)

(rock music)

Based on this evidence,

(house exploding)

you can casually walk away from a real explosion

like an action movie hero.

You just have to be a long, long way away.