'Greener' missiles on the drawing board

Thomas Klapotke is looking for cleaner products of combustion

By BBC News Online's Helen Briggs

"Green" explosives are being developed by German scientists, in an attempt to reduce pollution caused by guns and military rockets.

Their ultimate goal is to produce explosives and fuels for missile launches that give off nothing more innocuous than a puff of hot air in their wake.

In the next 20 years, it should be possible to launch a missile either for military or for civil applications that works on a chlorine-metal-free basis

Thomas Klapotke, University of Munich

Exhaust plumes from missiles and space rockets contain pollutants linked to acid rain and damage to the ozone layer.

The researchers said fuels and explosives emitting greener gases would be "more environmentally acceptable". This might sound a bit bizarre given that the purpose of munitions is to destroy, but the scientists pointed out that the vast majority of missiles were fired in training over home ground.

Pollutants were likely to be concentrated around firing ranges, they added.

Acid rain

Rockets for launching missiles and spacecraft are powered by solid propellants made up of a mixture of chemicals and metals.

Modern day rocket fuels contain a number of chlorine-based compounds which react to produce a range of unpleasant chemicals

Upon combustion, these fuels give off hydrochloric acid and aluminium oxide, linked with acid rain, damage to the ozone layer and destruction of plants.

The researchers, who are working with the German army, are trying to develop alternative fuels and explosives that would give off less noxious fumes.

Thomas Klapotke, Professor of Chemistry at the University of Munich, said they were trying to replace conventional explosives containing chlorine and metals with ones that contain only nitrogen, oxygen and carbon.

'Hot air'

Such chemicals would be converted into "hot air" upon combustion, he said.

Speaking at the British Association Science Festival in Glasgow, Professor Klapotke said: "In the next 20 years it should be possible to launch a missile either for military or for civil applications that works on a chlorine-metal-free basis."

The research is being carried out in collaboration with the German Army. Two greener explosives have been developed and patented so far, he said.

One obstacle to the work is the cost. New fuels are 100 times more expensive than conventional fuels but should get cheaper in time, he added.