ACCESS AND METHOD

Ask most people “How do you get into space?” and they would reply “by rocket”, not realising the fact that they are already “in space” on planet Earth, travelling in orbit

around the Sun. We are all “astronauts”, it’s just that most of us haven’t left the planet yet. For a lucky few though, leaving the planet has afforded them some of the most spectacular sights and experiences yet known to mankind. But there is more to it than simply “flying into space’’. There are various ways of doing this, depending on your mission and the type of spacecraft you have.

The atmosphere

Exactly where the atmosphere ends and space begins is a subject that has long been debated. Our atmosphere consists of roughly seventy-eight per cent nitrogen, twenty per cent oxygen, one per cent argon and trace amounts of other gases. It is not, however, uniform all the way up and has significant variations in temperature and pressure with increasing altitude. This defines the layers of the atmosphere. Our atmosphere can be divided into five regions of increasing altitude: the troposphere (0-16 km), the stratosphere (16-50 km), the mesosphere (50-80 km), the thermosphere (80-640 km) and the exosphere (640-10,000 km). Humans can survive with varying degrees of ease without assistance in the lower-most region, but require pressurised aircraft compartments or balloons up in the stratosphere. Above that is the realm of “almost space’’. The air here is much too thin to support an air-breathing engine, yet is sufficient to cause atmospheric drag on vehicles travelling through it. Above this, in the thermosphere, is where most of the spacecraft and satellites orbit the Earth, and the method used by most vehicles to travel in this region is by rocket thrust in the vacuum conditions.