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# SPACE SCIENCE (B) ROCKETS AND ARTIFICIAL SATELLITES

1. Explain the principle of rockets.
It is based on the law of conservation of momentum which states that ‘the total momentum of a system is conserved when the net external force acting on the system is zero.
During firing of a rocket the fuel burns and is converted into gases at high pressure. The gasses escape from the nozzle of the rocket with a high velocity. The rocket acquires an equal momentum in the opposite direction.
2. Draw a neat diagram of single stage rocket and label the parts.

3. What is orbital velocity? Give the expression for orbital velocity of a body circling round the earth, near its surface.
The velocity of the body along the circular path is called orbital velocity.
Expression for orbital velocity of a body circling round the earth, near its surface is
vo = √ Rg
Here Vo = orbital velocity, R = radius of earth, g = acceleration due to gravity.
4. Define escape velocity? Give the expression for escape velocity. What is thevalue in the case of the earth?
Escape velocity is defined as that minimum velocity with which a body must be projected so that it escapes from the gravitational field of the earth.
Expression for escape velocity is given by
ve = √ 2Rg
Here Ve = escape velocity, R = radius of earth g = accelaration due to gravity.
In the case of the earth, escape velocity is 11.2 km/s.
5. What are the factors that decide the value of escape velocity?
The factors are (1). Mass of the earth and (2). Radius of the earth
6. What is a multistage rocket? How is it advantageous?
Several rockets are joined together one on top of the other, to provide the necessary power. Rockets built in this way are called multistage rockets.
a) The demand on fuel consumption can be slightly reduced.
b) This increases the efficiency of the rocket.
c) Speed & Direction of motion can be controlled easily.
7. Make a list of the uses of artificial satellites
Uses of artificial satellites
a) It is used in communication
b) Survey of earth’s natural resources
c) Weather watching and remote sensing
d) Monitoring air, water, sound and thermal pollution.
8. Write an essay on Indian space programme.
The organization Indian Space Research Organisation (ISRO) was established in 1969, for the progress of space research and technology. Indian space programme was started in 1963 with the launching of an American research rocket, from Thumba. India entered the scene of satellite technology in the seventies. The fore-thought of Dr. Homi. J. Bhabha and Dr. Vikram A. Sarabai, put our country in the front line. The programme has been furthered by Prof. Satish Dhavan, Prof. U.R. Rao and Dr. Kasturi Rangan with the launching of various types of satellites. The first rocket was launched from Thumba, in Kerala as early as in november 1971. This rocket was a sounding rocket used for atmospheric studies. The rocket Rohini RH-75, had a single stage with only one instrument. Now multistage rockets are being used. The first satellite Aryabhata, weighing 360kg was launched in 1975. Launch vehicle called CI intercosmos of the former USSR, put it into orbit at a height of 550km. It worked efficiently for 6 months. Bhaskara was the first among the Remote sensing satellites (IRS); It went into orbit in 1979. After Bhaskara, sophisticated IRS satellites are being launched. The monitoring of the behaviour of the satellites is achieved at the Master control facility at Hassan. Technological advancement has made it possible for us to successfully build satellite launch vehicles. Four launch vehicles namely Satellite Launch Vehicle-3 (SLV-3), Argumented Satellite Launch Vehicle (ASLV), Polar Satellite Launch Vehicle (PSLV) and Geo Synchromes Satellite Launch Vehicle (GSLV) have been built and successfully tested. The Polar Satellite Launch Vehicle, PSLV-C5, placed the heaviest ever satellite into orbit on 17th October 2003. The satellite weighing 1380kg was put into orbit at a height of 821 km from Sri harikota range. The satellite is IRS-P6 (Indian Remote Sensing Satellite). The launch vehicle PSLV-C5 is dependable and can be used in all weather conditions. The geostationary satellite : APPLE, went into orbit in 1981. It was launched by a space vehicle called Ariane from French Guiana. The INSAT series of geostationary satellites have revolutionised our communication capabilities. Satellite INSAT-A was put into orbit on 19th April 2003. India’s latest communication satellite INSAT-3E was successfully launched from French Guyana, on 28th September 2003, using Ariane space vehicle. The 27 tonne INSAT 3E has an operational life time of 15 years. The satellite will provide telecommunication
and TV transmission services for the Indian subcontinent.
Today various sophisticated satellites are being utilised in various fields such as communications, agriculture, flood forecast, identifying geological mineral resources, identifying underground water sources, monitoring air, water, sound & thermal pollutions. The various application centres of ISRO are located at Bangalore, Tiruvananthapur, Thumba, Ahmedabad, Lucknow, and many other cities. Indian Space Programme has placed India in a prominent position at the international level.

II. Choose the right answer .
1. Fuel and oxidant are together called
a. fuel mixure b. combustion mixure
c.propellants d.propulsions
2. In the expression RVex = Ma , R stands for
a. resistance b.rate of fuel consumption
c.rate of change of velocity d.rate of change of mass
3. Communication satellites are also referred to as
a. polar satellites b.geostationary satellites
c. launch vehicle d. projectiles
4. The value of escape velocity on earth is
a. 11.2 KmS-1 b.11.2 KmS-2 c.10.2 mS-1 d.11.2 mS-2
5. The first Indian built rocket was launched from
a. Bangalore b.Sriharikota c. Tumba d.Trivandrum

III. Fill in the blanks with right answer
1. The ratio of payload mass to fuel mass is known as ---- (payload ratio)
2. The scientific instrument or the satellite which is carried by the rocket is called ----(payload)
3. The substance that provides oxygen to burn the fuel is called -------(oxidant)
4. The velocity of the body along circular path is called ------(orbital velocity)
5. The first Indian satellite is -----(Aryabhata)

IV. Match the followings
1. Orbital velocity – mv2 /2
2. Escape velocity - √ 2Rg
3. Centripetal force on satellite – mve2 / (R+h)

1. Give the relation between escape velocity and orbital velocity.
Relation between Orbital Velocity and Escape Velocity
Orbital velocity, vo = √ Rg ......................................... (1)
Escape velocity, ve =√ 2Rg ........................................( 2)
\ve = √2 X vo
2. A jet air craft cannot be used to put satellites into orbits. Explain why.
A jet air craft cannot be used to put satellites into orbits because it does not propellants to travel in space
3. Explain briefly the launching of a satellite.
Most of the rockets used to launch space vehicles, have a massive first booster stage and two smaller stages. Multistage rockets are used to launch artificial earth satellites. At start the rocket must be given sufficient velocity to rise to the desired height. When it has ascended the required height, the satellite (last stage) is placed in to orbit with sufficient horizontal velocity. If the velocity is greater, the satellite moves into a larger orbit or escapes from earth’s gravity. If the velocity is lesser than the proper value, the satellite falls back to the earth.
4. What is a geostationary satellite? Explain.
A satellite which has same period of revolution & period of rotation is called geostationary satellite. Geostationary satellite appears to be stagnt with earth. it should be located at an height of 36000km from earth. only three geostationary satellites can communicate the whole earth.
5. Write a short note on IRS satellites.
Bhaskara was the first among the Remote sensing satellites (IRS); it went into orbit in 1979. After Bhaskara, sophisticated IRS satellites are being launched. The monitoring of the behaviour of the satellites is achieved at the Master control facility at Hassan.
6. Write a short note on INSAT series satellites.
The INSAT series of geostationary satellites have revolutionised our communication capabilities. Satellite INSAT-3A was put into orbit on 19th April 2003. India’s latest communication satellite INSAT-3E was successfully launched from French Guyana, on 28th September 2003, using Ariane space vehicle. The 27 tonne INSAT 3E has an operational life time of 15 years. The satellite will provide telecommunication and TV transmission services for the Indian subcontinent.
7. What area Propellants? Name some rocket propellants.
Both fuel and oxidant are together called propellants.
Some rocket propellants are
1. Liquid hydrogen and Liquid oxygen
2. Kerosene and liquid oxygen
3. Hydrazine and Nitric acid
4. Synthetic rubber or Cellulose base compounds and liquid oxygen
5. Polybutadiene and Acrylic acid with oxidiser such as aluminium percolate.
8. Name the first Indian artificial satellite?
Aryabhata.
9. Expand the followings: INSAT, IRS, PSLV, SLV, ISRO, and ASLV.
INSAT = Indian satellite. IRS = Remote sensing satellites.
PSLV = Polar Satellite Launch Vehicle. SLV = Satellite Launch Vehicle.
ISRO = Indian Space Research Organisation.
ASLV = Argumented Satellite Launch Vehicle.
GSLV = Geo Synchromes Satellite Launch Vehicle.