Space Travel !

Perhaps the age of rockets taking us into space is coming to an end.  Research is now taking a serious look at one of the outcomes arising from the " Theory of Relativity " - which states that while light has no mass, it does have momentum !

This means that if a light is shone onto a mirror, the power of the light causes the mirror to move. It is reasoned that if a laser of adequate power was directed at a mirrored sail on a spacecraft it could accelerate that craft to about a third of the speed of light - achieving a speed of 80,000 kilometres a second.  It would become possible to reach other stars in months rather than years of travel.

The problems to be overcome to achieve success are daunting.  For a start, the power of the laser required to achieve these speeds would need to be about one Gigawatt - and a Gigawatt is a million watts.  Basically, it would take the entire output of a nuclear power station for several hours to generate the spacecraft to that incredible cruising speed, but the craft would need no engine of it's own nor fuel supply.

Science is scaling down this power need by using the magnifying principle employed by the telescope. If a light source is reflected to a central point by a number of mirrors the power is concentrated and enhanced beyond that of the original light source.   That works in similar manner to the solar farms where many mirrors reflect light to a central tower where sodium is heated to generate electricity.

There is one obvious disadvantage.  Such a spacecraft would have no brakes.At such speeds, reverse thrust from rockets would be impractical from both a weight and fuel point of view, but that only limits it's use for passenger travel.  A laser/sail propelled space craft to photo graph and explore distant space as an unmanned traveller could be a viable option.

Over a hundred million dollars has been earmarked for this project and it has the attention of those engaged on the " Search for Extra-terrestrial Intelligence. ( SETI ).   It could be a very cheap way of powering miniature space vehicles on missions to the far Cosmos to see if life exists other than on this planet. For well over a hundred years our discovery of radio waves have sent out signals into space and probes have gone to distant parts of the universe - without a reply.  Perhaps we should be grateful.   If others exist, they may be more scientifically advanced than us Earthlings - and they may not be friendly.

There is another aspect of this research that is troubling.  Several individual research projects are under way headed by scientists of various nationalities and in differing countries.  This would be better handled under the auspices of the United Nations as an international project with funding from the combined membership of sponsor nations.

A long time ago the balance of power on earth was under threat when the world's military considered what was termed " Star Wars " as new military technology.  Essentially, this involved the use of high power lasers reflecting off mirrors in space to direct death and destruction back to enemy targets below.  Fortunately, it was resolved by a treaty, but should research on space travel whet the appetite of an ambitious country with expansionist ambitions, this research could quickly return to military use.

Sometimes a little knowledge can be a dangerous thing !