Satgen543 Damage to Satellites by GM4IHJ (BID SGEN543) 1999-08-21 Satellites are expensive , not least because about 10% fail to reach their designated orbit. But once in orbit they are surprisingly sturdy and reliable , providing that the old ever present human failing of " not connecting the plugs properly etc " , has not occured. In the early days of artificial satellites the commonest cause of early death in orbit, was residual rocket fuel. Rocket fuels are by nature both highly corrosive and highly explosive. Putting up a rocket so that it uses its last drop of fuel just as it reaches its intended orbit is not practical. So most successful launches arrive in orbit with some fuel remaining. This has proved to be very dangerous, whereby the combination of corrosion and explosion , could and sometimes did result in a satellite blowing itself to pieces after several months or even years in orbit. This is now prevented by venting all excess fuel remaining when orbit is attained. A manouevre which has to be done very carefully , because fuel venting does introduce some thrust and risk of collision with satellites released earlier, as occured with Amsat Oscar Ten. Once in orbit with fuel succesfully vented , satellites can suffer damage from a number of other sources - Solar activity damage mostly affects geostationary satellites . In normal circumstances all satellites below 40,000 kms altitude , including geostationaries are protected from solar storms by the earths magnetic field. But big solar storms can push the magnetic field inwards towards the earth , thereby exposing the high flying geosats on the sunward side of the earth, to the full fury of the solar bombardment. In the past this has often resulted in geosats experiencing a massive build up of electric charge , which can eventually arc across , electrocuting the satellite with a local lightning flash. Today most geosats are shrouded in material which spreads out these dangerous charges thereby reducing their destructive potential. Though even with this protection there have been several recent incidents were geosats took several days to recover operational capability after a temporary knockout by a solar storm. Of recent interest to the news media, another potential satellite killer is meteor bombardment. Each year newspapers anticipate serious damage to satellites by either the Perseids or the Leonids meteor showers. In recent years the Perseids has seemed less of a threat because the changes in the orbit of parent comet Kegler-Swift-Tuttle caused by passing close to one of the big gas giant planets ( Jupiter , Saturn , Uranus, Neptune ) has split the meteor stream . Whereby a new stream comes past the earth roughly 8 hours before the old stream, with both streams being somewhat reduced in intensity compared with earlier this century. By contrast the Leonids of November 98 were quite strong but caused no serious damage. Though perhaps it is too early to discount meteor damage to satellites entirely . Noting that the November 99 Leonids may be a big shower producing some damage. PS. Iridium co in multi LEOsatphone trouble filed for Chap 11 bankruptcy protection in USA, last weekend.