Liquid bomb easy to obtain, says expert

SEVERAL different kinds of liquid explosive may have been involved in the terror plot to blow up a number of transatlantic passenger planes, an expert said.

They are not difficult to obtain or make from raw ingredients, and can easily be hidden inside innocent-looking bottles or cans, said explosives technician Dr Sidney Alford.

One of the chemicals, nitromethane, is used as a fuel for model aeroplane engines.

The best known “liquid bomb” is nitroglycerine, commonly thought of as a deadly material that will detonate with the slightest movement.

This idea is a myth, said Dr Alford, chairman of the explosives company Alford Technologies.

In fact nitroglycerine, kept properly, is relatively stable and will not explode unless “you whack it quite hard”, he said. Usually mixed with another material, such as nitroglycol, it would have to be ignited with a detonator.

As well as powering model planes, nitromethane is used commercially, both as an explosive and an industrial solvent.

“It’s quite easy to get hold of in relatively small quantities,” said Dr Alford.

To be used in a bomb, nitromethane would have to be combined with another sensitising substance.

A similar alternative, nitroethane, is less well known but equally as effective. There are fewer restrictions on obtaining and transporting this chemical.

“Everyone in the business knows that nitromethane is an explosive, but many people, including some in the police and security services, haven’t cottoned onto nitroethane yet,” said Dr Alford.

A fourth candidate, methyl nitrate, is unusual in that it will explode as soon as it is combined with another substance. It does not need to be ignited.

“It can reliably be caused to detonate by mixing it with ingredient X,” said Dr Alford. He was not willing to reveal the name of the activating chemical.

He added: “The fact that you don’t need a detonator would be a great advantage. Methyl nitrate has been used as a component of an anti-personnel mine. When you step on the mine, you break a container which causes the substances to mix.”

Other substances belong to a group of explosives from the US called Astrolites. These are based on hydrazine, which is used to make rocket fuel. Several different varieties exist, all of which are very poisonous and require detonators.

Liquid explosives would not necessarily be picked up by “sniffer” type security scanners if placed in carefully sealed and cleaned containers, said Dr Alford.

Their chief advantage was that they could easily be disguised, and they also provided the element of surprise.

“Most people associate explosives with either solid materials or gases,” said Dr Alford. “You don’t expect an explosive to be liquid. If it’s in a baby’s bottle, or a clearly labelled bottle of gin or whisky, or cough mixture, how many security staff are going to question it?

“It’s right that they’re not allowing liquids to be carried onto planes other than milk for a baby, which the mother has to taste.

“I think a good move would be to ban all duty-free alcohol on planes. If I were a baddie then I would be very interested in who loads the trolleys before they go onto the aircraft. I might for instance have someone aboard, ideally a steward, who knows a bottle of gin isn’t a bottle of gin.”

A liquid explosive is thought to have brought down a South Korean passenger plane in 1987, killing all 115 on board.

According to a woman suspect’s confession, North Korean agents planted the bomb which was concealed in an alcoholic drink bottle and detonated it remotely. The plane crashed into the Andaman sea off Burma.

Q & A

What are liquid explosives?

The best place to start is with the term “high explosive”; these can be either solid or liquid. Of course, the most famous ones are solid, such as Dynamite and TNT.

One liquid explosive is a general use explosive that is used in quarries.

It would not be surprising if it is possible to produce solid explosives in liquid form.

How do they work?

Usually when something burns, it is subsonic and there is very little pressure effect.

With high explosives, the rate of burning is extremely rapid and exceeds the speed of sound. As a result, there is something called “overpressure” — pressure greater than the surrounding atmospheric pressure.

Massive overpressure is not needed to cause damage. An excess of 1% can break windows, and an overpressure of 10% can harm or kill people and cause structural damage to buildings.

An overpressure of just 2% could break the windows of the aeroplane, and 10% would wreck the aircraft and possibly kill the people in it before it reached the ground.

By the time the damage is caused, the chemistry has finished and physics has taken over.

How are they made?

There are such things as liquid explosives that are high explosives and they behave in exactly the same way as solid explosives, such as TNT.

But there are also explosives that are made by mixing a solid and a liquid — one being the oxidant and the other being the fuel. Unlike most high explosives, they do not contain the fuel and oxidant in the same molecule but they do contain them in sufficiently close contact to cause a blast.

Are the components difficult to obtain?

No, it is very easy. Ordinary household substances could be used.

If someone wanted to obtain a solid high explosive in a liquid form, it would not be difficult for a trained chemical technologist.

But if someone was using a backyard laboratory it is more likely they would go for the two component approach.

Not a lot of experience is needed, the principles are quite simple but it would be a hazardous process.

It has been known for schoolboys to go home and attempt this and blow their house up.

Could an explosive device be carried on to an aeroplane?

The size of a device necessary could be carried in hand baggage. Explosives in a toilet bag, certainly inside a shoulder bag would be enough to meet the terrorists’ needs.

They could be quite hard to detect because many of the explosives would not respond to x-rays. For example, a liquid hydrocarbon fuel could pass as mineral water.

The question is how does a terrorist get something packed into a bag so it does not look suspicious?