Name: No-one knows how explosions work (yet)
Uploaded: 2026-01-17T17:00:17.000Z
Duration: 6 min 10 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

I thought that scientists understood how explosions work.

Now we're not going to see big orange fireballs going up into the sky.

I've done that before, I've filmed with a pyrotechnician.

We added a load of fuel to make the blast look like a Hollywood explosion.

Besides, these days Hollywood and scientists can simulate those sort of effects near perfectly in a computer.

There are industry standard ways of predicting blast waves.

They are very accurate once you're about half a metre away and there's clear air in between, which is good enough for most people because let's face it, if you're 5cm away from an explosion, you've probably got bigger problems.

But it turns out that's big picture stuff.

Right at the start in the detonation, in the first few instants of an explosion, as all that energy is released, that's where the simulations break down.

And solving that problem could save lives.

This bleak old World War II munitions site is now a university test laboratory and the research is close up.

Explosions are very difficult to measure.

We need something that's going to be rugged and strong enough to survive an explosion.

But we also need something that's sensitive enough to measure things that are changing over millimetre length scales and sub microsecond time scales.

The rig that we're going to be using today is called mace, which stands for Mechanisms and Characterisation of Explosions.

It's a bit of world leading kit where we can directly measure much closer than anybody worldwide can do gigapascals worth of pressures.

And that's a very, very complicated situation which we can't necessarily model or predict currently.

And we're going to use some high speed video cameras to film what's going on as well.

If you hit a metal bar the right way, it'll make a ringing sound, basically a musical note.

That ringing is made by the bar itself vibrating as the force from that initial hit bounces back and forth within the metal.

And the pitch of that note is really easy to measure.

The work the researchers are doing here is much more technical and much more precise, but

It's based on theory by a British physicist called Bertram Hopkinson 109 years ago.

And it's only now that the technology is catching up, where we can affix very, very small strain gauges and we've got data acquisition systems that can sample at the required rates and required frequencies.

The strain gauge is a tiny dot that we mount on the outside of our Hopkinson pressure bars.

Solid steel, 1 meter long, 4 millimeter diameter.

And we fix this strain gauge 40 millimeters from the loaded face of the bar.

We're going to set the explosive a little bit further away from the surface and so hopefully we can see that the fireball and the detonation products start to expand.

That's going to set up a blast wave that's going to propagate through the bar as a stress wave.

So the strain gauge records a change in voltage.

We can work out stress, which we can work out the pressure and the load on the end of the bar.

From there's a whacking great big steel plate that just acts as a shield and just deflects everything away.

So the pressure bars trap that pressure and send it downwards.

And then the arrangement of the mace rig that we're building towards is thin.

Today we've just got one just to focus on what's happening right in the most severe part.

So I asked the researchers, what's the use for this?

Their first answer was, well, for science, and that's fair enough.

But there are practical applications to start with.

If this works, building things that resist explosions will become a lot easier and cheaper.

In the 80s and the 90s, the big challenge was big truck bombs with tons of explosives.

Nowadays, explosive attacks are much more targeted.

They tend to be smaller devices and as a result they're located closer to the thing that they want to damage.

So that's why we've looked in this very extreme near field setting.

We're going to be doing some tests today.

With 100 grams of high explosive, it's around about tennis ball sized.

There are a lot of secondary reactions that go on.

It takes a while to develop, at least on our timescales.

And there are ongoing chemical reactions.

And that offers up the really interesting prospect of can we do something that's going to mitigate them or even turn them off?

Can we surround explosives in a particular type of material to manage those reactions?

Bomb proof luggage containers or storage containers on transport, that's a potential thing that could be done with this research.

If we can understand those first instances of an explosion, then maybe we can help keep it under control.

After all, this munition site is built to do that.

It was designed to contain anything that goes wrong by brute force, just using huge amounts of earth and concrete bunkers.

So can that be done with less materials and less cost?

We're about to take just one step towards finding out.

We've never been able to observe these features before, so we kind of don't know what we don't know.

That's what the group looks at, uncovering what we don't know about explosions yet.

So this is filmed at about a quarter of a million frames per second.

as it goes back up, see it reigniting, all that hot gas is getting churned back up.

It's mixing with the oxygen that's giving it that secondary kick that we see at these sorts of scale distances.

It's continually pushing the end of that bar and it's sending that information down because it's not one hit, it's a push that.

But you're recording that so quickly that.

That what you're actually getting is a push.