Speech on Space Research in India

Here is your speech on Space research in India!

SPACE research is no longer considered as a high-tech venture whose costs make it an irrelevant luxury for a developing country like India.Indeed, the benefits of space research have great relevance for developing countries—revolutionising communications, natural resources management, study of agricultural potential, weather monitor­ing, and disaster management. Furthermore, the spin-offs from space technology find applications in fields ranging from food storage to open- heart surgery, from fishing to automobiles.

Elements of Space Research and Technology

A spacecraft may make several kinds of trips into space. It may be launched into orbit around the earth, rocketed to the moon, or sent past a planet. For each trip the spacecraft must be launched at a particular velocity (speed and direction). The job of the launch vehicles is to give the spacecraft this velocity. If the spacecraft carries a crew, the spacecraft itself must be able to slow down and land safely on the earth.

Overcoming gravity is the biggest problem in getting into space. Gravity pulls everything to the earth and gives objects their weight. A rocket overcomes gravity by producing thrust (a pushing force). Thrust, like weight, can be measured in newtons or pounds.

To lift a spacecraft, a rocket must have a thrust greater than its own weight and the added weight of the spacecraft. The extra thrust accelerates the spacecraft. That is, it makes the spacecraft go faster and faster until it reaches the velocity needed for its journey.

Rocket engines create thrust by burning large amounts of fuel. As the fuel burns, it becomes a hot gas. The heat creates an extremely high pressure in the gas. The gas leaves the rocket engine at high speed through the rocket nozzle.

The reaction force created by the acceleration of the gas particles leaving the rocket engine causes the forward push on the rocket. This forward push on the rocket is the thrust, which is strong enough to lift the rocket from the ground.

Rocket fuels are called propellants. Liquid-propellant rockets work by combining a fuel, such as kerosene or liquid hydrogen, with an oxidiser, such as liquid oxygen (LOX). The fuel and oxidiser burn violently when mixed. Solid-fuel rockets use dry chemicals as propellants.

Engineers rate the efficiency of propellants in terms of the thrust that 1 kilogram of fuel can produce in one second. This measurement is known as the propellant’s specific impulse. Liquid propellants have a higher specific impulse than most solid propellants. But some, including LOX and liquid hydrogen, are difficult and dangerous to handle. They must be loaded into the rocket just before launching. Solid propellants are loaded into the rocket at the factory, and are then ready to use.

Space Shuttle

The primary vehicle for research and exploration in the United States space programme is the space shuttle. The space shuttle takes off like a rocket, orbits the earth like a spacecraft, and lands like an aeroplane. It consists of an orbiter, an external tank, and two solid rocket boosters.

The orbiter resembles an aeroplane. It carries the crew and the payload (cargo). The orbiter has three liquid rocket engines near its tail. Propellants are fed to the engines from the external tank.

The external tank holds the propellant, which consists of liquid hydrogen and LOX. The orbiter’s engines, combined with a solid rocket boosters, provide the thrust to launch the space shuttle. After two minutes of flight the boosters separate from the orbiter. The orbiter continues into space and releases the external tank just before entering orbit.

Returning to the earth involves problems opposite to those of getting into space. The spacecraft must lose speed instead of gaining it. The space shuttle orbiter has two smaller engines that are fired to slow down the spacecraft and modify its orbit for the return to earth. These engines are also used for manoeuvring during orbit.

The orbiter enters the earth’s atmosphere at a speed of more than 25,800 kilometers per hour. As the spacecrafts slows down, friction with the air produces intense heat. The temperature of the wings may reach over 1500 °C. A thermal protection system shields the orbiter from this heat.

The thermal protection system consists of more than 25,000 ceramic tiles bonded to the body of the spacecraft. About an hour after the shuttle’s engines are fired to bring it out of its orbit the spacecraft glides down, using its wings to manoeuvre and lands on a runway. The shuttle touches down at a speed of about 320 kilometers per hour.

Artificial Satellites

An artificial satellite is a manufactured ‘moon’. It circles the earth in space along a path called an orbit. An artificial satellite may be designed in almost any shape. It does not have to be streamlined, because there is little or no air where it travels in space. A satellite’s size and shape depend on its job.

Artificial satellites stay in space for varying lengths of time. The lifetime of each satellite depends on its size and its distance from the earth. Whenever a satellite swings close to the earth, it runs into many air particles that slow it down.

To stay in orbit, a satellite must keep a certain speed. If it slows below this speed, it plunges into the atmosphere and burns up because of friction with the air. The slowing of a satellite by air is called decay. Large satellites in low orbits decay rapidly. Small ones in high orbits decay slowly.

Most satellites carry some type of radio transmitter and receiver. One kind of transmitter is called a radio beacon. It sends signals that enable engineers to track the satellite. Tracking means finding the satellite’s exact position in space.
Another kind of transmitter sends to the earth the scientific information gathered by the satellite’s instruments. This sending of information is called telemetry. Telemetry transmitters usually serve also as beacons. A satellite’s receiving equipment is turned on and off by means of signals beamed from the earth.

Most satellites stop working long before they fall into the earth’s atmosphere. Their batteries go dead, or their electronic equipment breaks down. They become “silent” and of no further use.

Artificial satellites may be classified according to the jobs they do as (1) weather satellites, (2) communications satellites, (3) navigation satellites, (4) scientific satellites and (5) military satellites.

Orbits

Selecting the orbit is one of the first steps in planning the launch of an earth-orbiting spacecraft. Early manned spacecraft usually orbited less than 320 kilometers high. In this way, they avoided the radiation in the Van Allen belts. A communication satellite may orbit at a much greater distance in order to serve many ground stations.

Most orbiting spacecraft do not stay the same distance from the earth all the time. Their orbits have the shape of a flattered circle called an ellipse. One end of the ellipse comes closer to the earth than the other. The point closest to the earth is called the orbiting spacecraft’s perigee. The farthest point is called the apogee. Many scientific satellites follow orbits that have a low perigee and a very high apogee. These satellites can explore a wide range of space.

Satellites may also be launched in various directions around the earth. They may circle in an east-west direction, in line with the equator. Or, they may travel north and south, passing over the earth’s poles. Most satellites travel in a direction between these extremes.

The low-earth-orbit (LEO) satellite operates in an elliptical orbit usually at a range of 200-600 km. Most of the current satellites are in LEO.

An inclined orbit forms an angle with the equator. Because the spacecraft does not pass over the same points on earth during each orbit, the path of the spacecraft appears as criss crossed lines on the earth.

A polar orbit carries a spacecraft over the north and south poles. As the earth rotates, the spacecraft passes over different points on the earth during each orbit. A polar orbit is useful in scientific satellites which, by orbiting almost directly over the poles, can photograph the entire earth once a day.

A synchronous orbit carries a spacecraft around the earth once every day. As mapped on the earth, the path is a figure eight, because the orbit is slightly inclined. If the craft were launched directly in line with the equator, it would stay above one spot on the earth without moving north or south.

It would then be geo-synchronous, with a period of 23 hours, 56 minutes, 4.1 seconds, that is equal to the earth’s period of rotation on its axis. If the orbit lies in the equatorial plane and is circular, the satellite will appear from earth to be stationary, and the orbit and orbiting body are termed geostationary.

A geostationary orbit has an altitude of about 36,000 km (35,786 km to be exact). Satellites in such orbits are used for communications and navigation, etc. Most commu­nication satellites are now geostationary. INSAT class of satellites come under this category.

Sun-synchronous—as opposed to geo-synchronous equatorial satellites-means that the orbital plane of the satellite will always be at the same constant angle relative to the sun-earth during all reason. These satellites operate in a near-circular polar orbit running nearly north to south at a fixed altitude ranging from 500- 1000 km.

Every time the satellite passes from north to south, it has a consistent and constant sunlit view of a swath (around 150 km) of earth’s surface. Indian remote sensing satellites (IRS) come under this kind. The son-synchronous mode also enables the satellite to cross above a given place on the earth a; the same local time so that repeated observations of a given area car be compared as well as conjoined.

Another type of satellite is one of long-elliptical Molniva-orbit (for example, Molniya 1-73 satellite with 504 and 39,834 km altitudes at perigee and apogee respectively).