Firing in 3, 2, 1

Day 5

Today, I followed Dr Yuan and a DHS student Li Ting to the High Speed Dynamics Lab where they investigate the properties and reactions of some materials under collision with a high velocity projectile. Today they were testing the effects of some ceramics under collision with high velocity projectiles.

No pictures will be included in today's post as certain information might be sensitive.

Setting Up

For the first time, I witness a firing (the process not the actual firing. A distance have to be kept during the actual firing so I could not actually see it fire).

First, the air gun has to be cleaned and set up, so that the velocity of the projectile obtained can be optimal, as well as to prevent accidents such as blockages that could potentially be dangerous. Dr Yuan allowed me to help out with the setting up of the air gun (rather minimally, but still a previllage). In the mean time, Li Ting was setting up her equipment (high-speed camera, lights) for her experiments (explained later).

There were many steps to the setting up (cleaning, assembling, ensuring vacuum, etc, etc.), so as to ensure the safety of everyone inside the lab, as well as to make sure that the experiment will go accordingly to plan.

Next, we went back to a room where it is safe to do firing, and where the launch button is located, as Li Ting explained to me what her experiment is all about.

Li Ting's Experiment

In order to accurately capture the motions of the projectile just before the impact and during impact, high speed photography have to be utilised. Dr Yuan have found that in some instances, the impact cannot be seen clearly due to the quality of the images. Hence, Li Ting is tasked to experiment with various lighting conditions to find the best lighting condition for which the photographs will turn out sharp and clear.

In the experiments conducted today, she used a lighting lamp and the high-speed lens. She angled the lamp at roughly 15 degrees on the left of the camera, and in the second experiment, roughly 35 degrees. The angle on the left is smaller to avoid the large shadows formed due to the target holder's position in the light, and with the shadows, the projectile may not be clearly seen.

In both experiments, there is a few steps to the recording. First, the trigger have to be set, and with Dr Yuan and another researcher, they counted down and fired the projectile. Afterwards, a programme will record and play back the impact for the researchers to analyse and evaluate. Since the images are not always clear, Li Ting will edit the photographs using the same software used to record the impact to attempt to make the quality of the images better.

She has found out that the images will differ from different position the lamps are placed, due to the shadows formed, and is still trying to determine the best position that it could be placed to obtain better results.

Problem: Fireball

One major problem that Li Ting has faced in the capturing of a good image is the formation of a "fireball" during impact. This "fireball" could cause the image to be totally obscured by a blinding white light, making sure that no image could be seen during that period of time.

The formation of the fireball seemed to be curious to me, as the target chamber would be vacuumed out before the experiment, and only inert gas would be used to pump the projectile forward - meaning that there is no oxygen available for combustion. So why could there be a fireball?

We have theoricised that it could be the heated fragments of the target and projectile.

As the projectile collides with the target, deformation of both will take place, a process which would produce heat. Since the time taken for the collision is very short, and the velocity very high, the compression takes place very quickly and by very much, possibly producing enough heat for the metal fragments to glow.

For the second experiment (the first experiment was only a target metal), where a ceramic plate is placed in front of a metal, the fireball is much smaller and it dissipates faster, it indicates that our hypothesis might be correct.

Li Ting has kindly allowed me to take some of her photographs of what she is analysing


Experiment 1 - Fireball effect

 Experiment 2 - Fireball effect

Only one way to prove it - experiments. Sadly I could not do it during this period of attachment.

It was really an interesting day, thinking of possible explainations for different phenomenons that occured. An insight to what research is about? Thinking of possible explainations for certain phenomenons then proving (or disproving) them?

Do leave your comments or questions on the chat box beside!