Good Afternoon and welcome to the Department of Chemistry, Welcome to the Cambridge Science Festival,
And Welcome to this lecture on Rocket Science
Now, every Rocket that has ever flown,
whether its a small firework rocket,
or whether its a giant rocket carrying people to the moon
every rocket is based on one simple principle.
So i thought i’d begin this lecture by demonstrating that principle
So this a beautiful reproduction, in miniature
of a Napoleonic Canon. But its a working model
And its actually capable of firing a live round: A Half inch diameter Lead Cannon Ball
Today we wont fire a live round, but im going to fire a blank round
and when we do, i want you to observe what happens to the cannon
Now the cannon’s really just a tube thats closed on this end (left side) and open at this end (right side)
This is called a muzzle
and theres a small hole we call a “touch hole”
that we use to transmit fire to the main charge
So im going to begin by taking a small slow burning fuse
And placing that in the “touch hole”
Then were going to charge this with gunpowder
So the gunpowder is in this nice powder horn
the way this works is: I put my finger over the brass nozzle, I press the valve and tip it upside down
And powder trickles into that brass spout
So I’m measuring a precise quantity of gunpowder
And I release the valve and turn it upside… right way up again
and we have a measured quantity of gunpowder in the spout
So I’ll place that into the barrel of the cannon
and I thought is since its “Science Week” we’ll use a double dose
Here’s a double dose of gunpowder going into the cannon
So that’s the gunpowder,
In the barrel; I’ll put this safely out of the way
Now to keep the gunpowder in the barrel and against the fuse
were going to use a bit of wadding
so this is some fireproof wadding which I’m going to put into the, into the muzzle of the cannon
and then use this “Ram Rod” to pack the wadding and the gunpowder tight up against the fuse.
Now at this point we would put our cannon ball in but were not going to do that today
so instead, we’ll, we’ll simulate that by adding a bit more wadding
so I’m going to put some more wadding into the barrel
and again just pack that down
and then finally, to, uh, to stop the ball rolling out, as it were,
we’d use a bit more wadding. So, why not, lets do a bit more wadding.
It is the science festival after all.
Okay, so we’ve got this wadding nicely pack down.
Our cannon, uh will be loaded, and it’s now ready to fire.
So I’m going to light the fuse
from where I’m standing, it’s quite noisy, so I’m going to be covering my ears;
if you’re near the front, you may wish to do the same.