Today we are likely to come across many news regarding to space travels, satellites, rovers, rockets, Space missions, space walks, etc. Recently, we heard about Sunita Williams, Akihiko Hoshide, Yurie Malchenko and their space walk. And how they repaired their space station. But actually the age of exploration began in 1957, when powerful rocket engines boosted Russian satellite ‘Sputnik 1’ free from the Earth’s gravity. This was the start of extraordinary series of adventures for mankind which has seen scores of satellites put in space, mans first steps on the moon, live broadcasts from Mars and space probes venturing past the outer planets of the solar system. These probes have not only beamed back the first pictures of new, previously unknown moons but have also provided remarkable insights into the nature of the universe. In early days manned spacecrafts could only be used once, within just a tiny capsule holding the astronauts falling back to the earth at the end of the mission. The US space shuttle was the first spacecraft that could be reused, landing back on the earth like an aeroplane. The rocket boosters that launched it into space are recovered.
Very powerful rockets are needed to push a spacecraft which is cleared from the earths gravity. But once clear, such power is no longer needed. So rockets are made in separate stages, each of which falls away when its fuel is spent. Unmanned space probes guided by computer, have now visited all the planets, but not Pluto which is the smallest and most distant planet. The probes have actually landed on Mars and Venus. Late in 1997, the Mars pathfinder beamed back the live pictures from the surface of Mars. The space probes voyaging to the planets used gravity to help them travel huge distances on very little fuel. As they pass each planet, their gravity pulls them in and hurls them onwards a slight different course like a sling shot. Thus space shuttle is launched with solid fuel booster rockets that fall away, but then recovered. Typical shuttle missions include launching and repairing satellites and performing scientific experiments.
Satellites stay in orbit along their orbital plane is already set. Satellite orbit is 22000 miles (35800km) above the ground, takes exactly 24 hrs- the same time taken by the earth to rotate once. So satellites on this orbit stay in exactly that same place above the earth are known as geostationary satellites.
Satellite that orbits with the Sun is called as sunsynchronus. The orbits precision is due to earth’s oblateness. The inclination of the orbit is measured by the angle formed by the orbital plane of the satellite and the equatorial plane. As the orbital plane will always maintain its position relative to the sun. The satellite will have constant illumination conditions throughout the year, useful for remote sensing operations. If launched in a due east direction, the latitude of launched site will be the inclination of satellites orbit. A sun synchronous orbit is also called retrograde orbit (as it is in the opposite direction to the earth’s rotation). The satellites orbital plane should be inclined away from true north south polar orbit and have an inclination of more than 90°, otherwise the satellite orbital plane would not complete a full rotation. Hence a Sun synchronous orbit cannot be precisely polar (with 90° inclination). But nearly polar, typically around 100°. In fact a sun synchronous orbit is invariably a polar orbit. But converse need not to be true.
In today’s era, aeronautical engineering and space science is an very beloved subject. The dream to become an renowned person in this field is an passion embossed on the minds of tomorrows generation.
Student: Sneha Magar
http://www.telegraph.co.uk/travel/destinations/northamerica/usa/10693321/Space-Camp-Alabama-how-to-be-an-astronaut.html
