Sir - In his letter, Alan Mason says that, "mass times velocity says it all" (Flight International, 25 September-1 October, P55). Actually, it does not - he seems to be mistaking momentum for kinetic energy, which makes more than a slight difference when talking of speeds of 27,000kt (50,000km/h).
A given mass requires a velocity of about 1.7kt/s to achieve a kinetic energy equal to the explosive energy of the same mass of high explosive. Consequently, an object weighing about half a kilogram, travelling at around 7.5kt, would pack the punch of 8kg of dynamite. One can readily see how a fleck of paint might kill a space-walking astronaut.
That the French Cerise satellite survived a collision with a "briefcase-sized" fragment suggests that the closing speed must have been quite small, as would be the case if the orbits were roughly similar. It is crossing orbits and opposed orbits, which produce the worst situations.
DAVID MORRELL
Chelsea, London, UK
Make Heathrow American/BA
Sir - It was a splendid idea of American Airlines chairman Robert Crandall to open up London Heathrow to all the other US airlines by trading up to 50,000 slots (do that many exist?), so that the proposed American Airlines/British Airways alliance can have some "healthy competition" (Flight International, 25 September-1 October, P8).
Why not send all those unimportant "third-world and regional operators" off to the provinces and turn Heathrow into one huge American/BA hub so that Mr Crandall and Robert Ayling (chief executive of BA) can make even more money for their respective shareholders.
ANDREW ADAMS
Pevensey, Essex, UK
Christmas war anecdotes sought
Sir - We are preparing a book, to be entitled Christmas under fire, which will also be developed into a BBC radio programme and an exhibition in conjunction with the Imperial War Museum.
We are interested in any recollections of Christmas (military or civilian) in any of the world's trouble spots this century. We are particularly anxious to track down any Cold War aviation memories. Is there, for instance, anyone who has intercepted a Russian "Bear" bomber, or who flew a SAC mission over the Christmas season?
HUBERT von STAUFER
Christmas Archives
Kildoward House
Whitchurch
Ross-on-Wye HR9 6DN, UK
Source: Flight International
