Bangalore: Terrorists can make an explosive out of ammonium nitrate, a commonly used fertiliser, according to a former defence scientist and explosives expert.
Saboteurs can also make a liquid explosive from the same ingredients (openly available in the market) that the Indian Space Research Organisation (ISRO) uses to make rocket propellant.
"Mixing the ammonium nitrate fertiliser with diesel oil makes it an explosive," Haridwar Singh, a former director of the Armament Research and Development Establishment in Pune, said.
Commercial grade ammonium nitrate is enough to make a crude bomb that has the consistency of a gel that can be hidden in a toothpaste tube, he added.
The liquid propellant used in rockets is also a potential candidate for liquid explosive.
"A terrorist need not steal it from ISRO," says Nambi Narayanan, who was a key figure in the development of ISRO's liquid fuelled rocket engines in the 1980s.
"You can buy its ingredients - nitric acid and uranyl dimethyl hydrazine -- from the market," Narayanan told IANS from Thiruvananthapuram. ISRO's technology for making both solid and liquid propellants has been licensed out to companies.
The ingredients are called "hypergolic" as they react only when mixed. Inside a rocket engine, the two are kept in separate tanks and mixing releases gases whose expansion through the nozzle pushes the rocket.
A terrorist can set off an explosion by allowing the mixing to take place in a sealed container from which the gases cannot escape, said Narayanan.
Liquid explosives have become a household phrase after the British government foiled a terrorist plot to allegedly blow up aircraft in mid-flight using such explosives and banned liquids in hand baggage of air travellers.
Any liquid that burns rapidly is potentially a liquid explosive, says Narayanan. He says a terrorist looking for a liquid explosive need not really go for rocket fuel.
"Even kerosene will do," he says. "It depends on what level of sophistication one is talking about. If aniline and nitric acid come in contact, the mixture catches fire."
Haridwar Singh doubts if nitroglycerine, a liquid explosive, would be involved in the alleged plot since it is so unsafe that even the impact of going through an X-ray machine will set the stuff off.
He also doubts if anyone can walk on to an aircraft with two ingredients and mix these two together to get an explosive liquid. "It will be very difficult," he said.
Haridwar Singh said his laboratory had developed a kit for detection of solid and liquid explosives based on simple colour test.
"The test kit costs just Rs.1,000 and we transferred the technology to a Mumbai firm two years ago," he said.
"During the time I was director, I had been telling Mumbai Police, without much success, to introduce this kit in their mobile squad. After my retirement I have not kept track of what happened to the test kit."