LETTER : Nukes may save us yet

Anita Roddick is still worried about Cassini's plutonium and thinks Bill Clinton should prevent nuclear power in space (25 May). Well I doubt if even he can switch off the Sun, which is a good thing because without that chunk of nuclear power in space, none of us would be here.

As for the Cassini mission, the sort of plutonium-powered radioisotope thermoelectric generators (RTG) it carries have been used many dozens of times on Nasa space missions over the last 30 years without any release of radioactive materials. Two of these had serious accidents - one was Apollo 13 - but the RTGs worked exactly as years of extensive and rigorous testing had predicted. There was no release of radioactive material.

The plutonium in RTGs is in the form of a ceramic - plutonium dioxide - which as well as being entirely unsuitable for weapon use has been chosen exactly because it makes the RTG extremely robust and the chances of a life-endangering release of radioactive material under extreme conditions, such as the failure of the launch system, about one in a million.

Ms Roddick could instead worry about the more likely event of a one- mile wide asteroid hitting Earth and causing the loss of up to 1 billion human lives. And then she might consider how such a catastrophe might be prevented without sending nuclear weapons into space.

Jim Mangles

Wortham, Norfolk