"Mir", apparently, means "peace". But the Russian space station of that name has had a troubled existence since its launch in 1986, and now seems set to make its final exit with one last dramatic disturbance of the peace. We may say of it, as they did of poor old Cawdor in Macbeth: "Nothing in his life became him like the leaving it."
How do you dispose of 140 tonnes of metal whirling around in space some 300 miles above the surface of the Earth? The answer is that it has to be "deorbited", or lowered gingerly into the atmosphere in such a way that the intense heat generated by the resulting friction causes it to vaporise and be no more. But this, in the case of Mir, is easier said than done. The complex exercise is scheduled for June next year, and space-Cassandras peering from the wings at the plans of the de-orbiters say that 10 per cent or more of Mir is likely to survive. This implies some 14 tonnes of debris showering down from space along an unknown track about 600 miles in length.
If Mir were spherical, the problem would be an easy one to solve. Its behaviour in the atmosphere would be predictable, and it could be arranged that the bits and pieces came to land in some lonely, deserted, uninhabitable spot. But Mir is not a sphere, or yet a cylinder; it is an irregular assembly of oddly-shaped modules, each comparable in size to a double-decker bus, with a huge array of solar panels that would act like sails. It is impossible to predict the path of such a complex shape were it to hit the atmosphere at 20,000 m.p.h.
There are, of course, alternative solutions, but all of them expensive. One is to dismantle the spacecraft before the operation, and then de-orbit each module in its turn. Not only would the behaviour of each element be easier to forecast than that of the spacecraft as a whole, but there is also a good chance that these smaller pieces would disintegrate entirely on re-entry, before doing any damage. Another strategy would be to attach large thrusters on to Mir and "punch" it into the atmosphere at such a speed that the process of disintegration was enhanced.
But the most imaginative idea comes from Arthur C. Clarke, that long-time chronicler of life in outer space. He suggests that Mir should not be de-orbited at all: the thrusters should be used to send it into retirement in a higher orbit than at present, there to remain until it becomes a major tourist attraction in the next millennium.