# Eastward launch of a spacecraft- Reasons

## Eastward launch of a spacecraft- Reasons

Question:- The earth 's rotation helps in launching a satellite from the eastward direction. Explain this phenomenon.

- When viewed from the North Pole, the earth rotates anti clock wise which means from west to east. Surface velocity of rotation varies from one point to the other. Near the equator it is 1600 km per hour or 460 meters in a second. Velocity is seen to reduce towards the poles and is almost zero at the poles.

Reason for an eastward launch- Satellites launched from the sites near equator in the direction of east, they will get an initial boost equal to the velocity of earth's surface. This initial boost aids in reducing cost of rockets used to launch satellites. This is the major reason for launching satellites from the east, however this can be used only for satellites that are placed in geostationary orbit or that encircle the earth parallel to the equator. These are the communication satellites or those used in scientific research.

- Satellites launched to the east can make use of the earth's rotation as an extra propelling force, can take advantage of this momentum.

- The satellites used for mapping or spying are placed in polar orbits moving across equator and are launched in south or north ward direction hence cannot take advantage of earth's rotation. The launching stations are located near the eastern coast line so in case of a failure, the satellite does not fall on a built up area.

- On launching into the orbit, the spacecraft should end up spinning around the earth at such a speed that it should not be pulled back by the gravity of earth. However, spin of the earth too can give a push since anything on the surface at the equator id moving at 1670 kms per hour. The speed will help the spacecraft stay at a good speed in orbit.

- If launched from west, satellites will have to battle against the angular momentum of earth's rotation, implying more power in order to break earth's atmosphere. An eastern launch will yield this power and save on cost of fuel. The big rockets used in launching give a huge amount of thrust , enough to gain escape velocity.

Facts and figures:

- Sputnik was the first artificial satellite and was launched on on 4 October 1957.

- As of 2011, only three nations have flown manned spacecraft: USSR/Russia, USA, and China.

- The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963.