# Rockets and Artificial Satellites

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Rockets and Artificial Satellites

Module Objectives Rockets Satellites Indian Space Programs Principle
Working Single-stage and Multi-stage Rockets Satellites Orbital velocity and Escape velocity Launching of a Satellite Geostationary Satellites Satellite communications Indian Space Programs 10th - Physics

Momentum(p) = mass(m) X velocity(v)
Recap Momentum = Mass in motion All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion The amount of momentum depents on how much stuff(mass) is moving and how fast the stuff(velocity) is moving Momentum(p) = mass(m) X velocity(v) Newtons third law of motion Newton's Third Law : For every action, there is an equal and opposite reaction Variation of Gravity Acceleration due to gravity g is a variable quantity and it varies with altitude Above the surface of earth, it decreases as the height / altitude increases 10th - Physics

Recap (cont.) Centripetal Force
An external force required to make a body move along circular path with uniform speed is called centripetal force It acts along radius and towards the centre of circular path Where m is mass of body, v is velocity and r is radius of path along which body moves. In case of planets and satellites centripetal force is the gravitational force 10th - Physics

Introduction to Rockets
A Rocket can be a missile, spacecraft , aircraft or other vehicle that obtains thrust (or push) from a rocket engine Chemical rockets are the most common type of rocket and they typically create their exhaust by the combustion of rocket propellant. The propellants are carried within the rocket Rocket engines work by action and reaction. Rocket engines push rockets forward simply by throwing their exhaust backwards extremely fast Rockets are used for fireworks, weaponry, ejection seats, launch vehicles for artificial satellites, human spaceflight, and space exploration Image: STS-1 Launch The April 12 launch at Pad 39A of STS-1, just seconds past 7 a.m., carries astronauts John Young and Robert Crippen into an Earth orbital mission scheduled to last for 54 hours, ending with unpowered landing at Edwards Air Force Base in California. Image source: 10th - Physics

Principle of operation
Rockets, be it small as the firework or large as the launch vehicles, operate by the same principle. Rocket propulsion can be explained well with two fundamental laws of physics: Newton's third law or conservation of momentum Newton's Laws of Motion - The third law states that For every action there is always an opposite and equal reaction When an action takes place, like gases escaping from the rocket, a reaction follows - the rocket rises in the air 10th - Physics

Principle of operation (cont.)
The Conservation of momentum In the absence of external forces , the total momentum of the body is conserved Any quantity, such as momentum or energy, that must remain constant is ‘conserved’ On interaction with an external impulse(burning of fuel incase of rockets) Momentum before interaction = Momentum after interaction Or Momentum of Rocket = Momentum of Exhaust but in opposite directions 10th - Physics

Conservation of momentum - illustrations
Example1 : When a bullet is fired , it moves in the forward direction and the gun kicks backward. It is because before firing total momentum of system constituted of barrel and gun is zero. When bullet is fired it gains some momentum(due to velocity acquired by it) but to nullify this momentum gain, gun moves in backward direction such that it has momentum equal in magnitude to momentum of bullet with opposite direction Example2 : Same can be seen when releasing an air filled balloon, the air rushes out of the balloon providing the thrust, which propels the balloon forward and it flies Click here to see a simple demonstration of conservation of momentum using air filled balloon Can use a balloon to demonstrate the same 10th - Physics

Rocket - Components The structural system or frame
made from very strong but light weight materials, like titanium or aluminum to form the basic shape of the rocket coated with a thermal protection system to keep out the heat of air friction during flight and to keep in the cold temperatures needed for certain fuels and oxidizers Fins are attached to some rockets at the bottom of the frame to provide stability during the flight 10th - Physics

Rocket – Components (cont.)
The payload system depends on the rocket's mission – explosives, satellite launches, human passengers, guidance system The Guidance system may include very sophisticated sensors, on-board computers, radars, and communication equipment to maneuver the rocket in flight must also provide some level of stability so that the rocket does not tumble in flight 10th - Physics

Rocket – Components (cont.)
The Propulsion system Propellant = fuel + oxidant Types of propellants, Liquid-propellant systems, The fuel and oxidizer are pumped from separate tanks into the combustion chamber Solid-propellant systems, These carry the fuel and oxidizer, already mixed together, in a solid state The various rocket parts described above have been grouped by function into structure, payload, guidance, and propulsion systems. There are other possible groupings. For the purpose of weight determination and flight performance, engineers often group the payload, structure, propulsion structure (nozzle, pumps, tanks, etc.), and guidance into a single empty weight parameter. The remaining propellant weight then becomes the only factor that changes with time when determining rocket performance. 10th - Physics

Rocket – Components (cont.)
Types of propellants (cont.), Gas-propellant systems Involves some form of compressed gas Hybrid-propellant systems usually have a solid fuel and a liquid or gas oxidizer Gel propellant systems Research has been done on gelling liquid propellants to give a propellant with low vapor pressure to reduce the risk of accidents. Gelled propellant systems behaves like a solid propellant in storage and like a liquid propellant in use. The various rocket parts described above have been grouped by function into structure, payload, guidance, and propulsion systems. There are other possible groupings. For the purpose of weight determination and flight performance, engineers often group the payload, structure, propulsion structure (nozzle, pumps, tanks, etc.), and guidance into a single empty weight parameter. The remaining propellant weight then becomes the only factor that changes with time when determining rocket performance. 10th - Physics

Working of Rockets A rocket works by burning fuel that is exhausted out of one end of the rocket at a high speed. Since momentum is conserved, the momentum carried away by the fuel results in the rocket moving forward. Click here to see a demonstration of this. Rocket mass (Mass of payload + Mass of structure + Mass of propellants) - M Velocity of exhaust - Vex Rate of fuel consumption – R Accelleration due to gravity - a The thrust or the product mass of the rocket is Thrust = RVex= Ma Points to note: The rocket consumes fuel, so mass keeps decreasing The accelleration due to gravity keeps changing with the altitude gained by the rocket 10th - Physics

Multi-Stage Rockets Rockets use the thrust generated by a propulsion system to overcome the weight of the rocket. The weight of the payload is only a small portion of the lift-off weight Most of the weight of the rocket is the weight of the propellants As the propellants are burned off during powered ascent, a larger proportion of the weight of the vehicle becomes the now empty tankage and the structure that was required when the vehicle was fully loaded In order to lighten the weight of the vehicle to achieve orbital velocity, most launchers discard a portion of the vehicle in a process called staging And these rockets are called multi-stage rockets An animated video demonstrating staging can be seen by clicking here Image illustrates stage separation of a two stage rocket 10th - Physics

Types of staging There are two types of rocket staging, serial and parallel. Serial staging There is a small, second stage rocket that is placed on top of a larger first stage rocket. The first stage is ignited at launch and burns through the powered ascent until its propellants are exhausted. The first stage engine is then extinguished, the second stage separates from the first stage, and the second stage engine is ignited. The payload is carried atop the second stage into orbit. Serial staging was used on the Saturn V moon rockets. The Saturn V was a three stage rocket, which performed two staging manoeuvres on its way to earth orbit. The discarded stages of the Saturn V were never retrieved. 10th - Physics

Types of staging continued…
Parallel staging Several small first stages are strapped onto to a central sustainer rocket At launch, all of the engines are ignited. When the propellants in the strap-on's are extinguished, the strap-on rockets are discarded The sustainer engine continues burning and the payload is carried atop the sustainer rocket into orbit. Parallel staging is used on the Space Shuttle The discarded solid rocket boosters are retrieved from the ocean, re-filled with propellant, and used again on the Shuttle 10th - Physics

Types of staging continued…
Hybrid Some launchers, like the Titan III's and Delta II's, use both serial and parallel staging The Titan III has a liquid-powered, two stage Titan II for a sustainer and two solid rocket strap-ons at launch After the solids are discarded, the sustainer engine of the Titan II burns until its fuel is exhausted Then the second stage of the Titan II is burned, carrying the payload to orbit. The Titan III is another example of a three stage rocket 10th - Physics

Orbital velocity Orbital Velocity can be defined as
the velocity which is given to an artificial earth's satellite a few hundred kilometers above the earth's surface so that it may start revolving round the earth. It is denoted by Vo Expression for orbital velocity m = Mass of satellite, r = Radius of circular orbit of satellite h = Height of satellite above surface of earth. R = Radius of earth Vo = Orbital velocity M = Mass of the earth. G = The Gravitational constant The Centripetal force (mv2/r) required by the satellite to keep moving in a circular orbit is produced by the gravitational force between the satellite and earth Therefore hence When h is sufficiently small compared to R, h can be neglected. Then Where 10th - Physics

Escape velocity Escape Velocity can be defined as
The minimum velocity needed for a celestial body to escape the gravitational pull of another, larger body and not fall back to that body's surface. In our case, satellites escape earth’s gravity Escape velocity is determined by the mass of the larger body and by the distance of the smaller body from the larger one's center Depending on its initial trajectory, a smaller body traveling at the escape velocity will either enter a periodic orbit around the larger body or recede from the surface of the larger body indefinitely Expression for orbital velocity Relation between Orbital velocity and Escape Velocity The escape velocity at the Earth's surface is about 11.2 kilometers per second (25,000 miles per hour). The escape velocity on the Moon's surface is 2.4 kilometers per second (5,300 miles per hour). The escape velocity within the event horizon of a black hole is higher than the speed of light; since nothing can exceed the speed of light, nothing - even light can escape from within the event horizon of a black hole. 10th - Physics

Orbital and Escape Velocity - illustrations
Newton’s Illustration Newton's Mountain Newton illustrated orbital behavior for a simple idealized situation where a powerful cannon is placed on top of a high mountain on the Earth. Since both the distance from Earth's center and the direction of initial flight is fixed, the cannonball follows an orbit that depends only on the muzzle velocity of the cannon as shown in the image. The gravitational force of a spherical body like the Earth acts as though it originates from the center of the sphere, so elliptical orbits have the center of the Earth at one focus. 10th - Physics

Launching a Satellite Artificial Satellites
A satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon. Image is of Delta II to launch the Air Force’s Global Positioning System IIR-20 on March 24 from Cape Canaveral Florida, called GPS IIR-20M, this is the seventh modernized NAVSTAR Global Positioning System Block II R-M military navigation satellite to launch. Some interesting facts The world's first artificial satellite, the Sputnik1, was launched by the Soviet Union in 1957. Some satellites, notably space stations, have been launched in parts and assembled in orbit. Artificial satellites originate from more than 50 countries and have used the satellite launching capabilities of ten nations. A few hundred satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn and the Sun 10th - Physics

Launching a Satellite(contd.)
Multi-Stage rockets are used to carry Satellites, providing the necessary velocity to rise the desired height Greater the velocity – Satellite escapes the earth’s orbit Lesser the velocity – Satellite falls back to the earth Click here to see a short demo video of how Satellites are launched An example of Multi-Stage rocket used for launching Satellite Image is of Delta II to launch the Air Force’s Global Positioning System IIR-20 on March 24 from Cape Canaveral Florida, called GPS IIR-20M, this is the seventh modernized NAVSTAR Global Positioning System Block II R-M military navigation satellite to launch. Some interesting facts The world's first artificial satellite, the Sputnik1, was launched by the Soviet Union in 1957. Some satellites, notably space stations, have been launched in parts and assembled in orbit. Artificial satellites originate from more than 50 countries and have used the satellite launching capabilities of ten nations. A few hundred satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn and the Sun 10th - Physics

Satellites – Uses Satellites are used for a large number of purposes.
Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways Well-known (overlapping) classes include low Earth orbit, polar orbit, and geostationary orbit Satellites are usually semi-independent computer-controlled systems Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control and orbit control Image : A full-size model of the Earth observation satellite ERS 2 10th - Physics

Geostationary Satellites
Geostationary Earth Orbit (GEO), is a circular orbit 35,786 kilometres (22,236 mi) above the Earth's equator and following the direction of the Earth's rotation. A geostationary satellite is an earth-orbiting satellite, placed at the geostationary orbit an altitude of approximately 35,786 kilometres (22,236 mi) directly over the equator, that revolves in the same direction the earth rotates (west to east) At this altitude, one orbit takes 24 hours, the same length of time as the earth requires to rotate once on its axis It is called geostationary since the satellite appears nearly stationary in the sky as seen by a ground-based observer Communications satellites and weather satellites are often given geostationary orbits, so that the satellite antennas that communicate with them do not have to move to track them, but can be pointed permanently at the position in the sky where they stay Geostationary orbits (top view) 10th - Physics Geostationary orbits (side view)

Indian Space Programmes
The Indian Space Research Organisation (ISRO) is the primary space agency of the Indian government. ISRO was Established in 1969, ISRO's headquarters is located at Antariksh Bhavan in Bangalore ISRO took the place of the previous Indian National Committee for Space Research (INCOSPAR), which set up Thumba Equatorial Rocket Launching Station (TERLS) at Thumba on the southern tip of India Click here to see an interesting article with old photos of this first launch The Indian National Committee for Space Research (INCOSPAR) was set up in 1962 by the Indian Government under Dr. Vikram Sarabhai to formulate the Indian Space Program. At the time, the committee was part of the Tata Institute of Fundamental Research, led by M. G. K. Menon. The committee took over the responsibilities of the Department of Atomic Energy in Space science and research. The then director of the DAE, Dr. Homi Bhabha, was instrumental in creation of the Committee. Dr. A. P. J. Abdul Kalam (former President of India) was amongst the initial team of rocket engineer forming the INCOSPAR. Note: The image in the bottom-right corner is the logo of ISRO 10th - Physics

Frist Indian Satellite - Aryabhata
Mission Scientific/ Experimental Weight 360 kg On board power 46 Watts Communication VHF band Stabilization Spinstabilize Payload X-ray Astronomy Aeronomy & Solar Physics Launch date April 19,1975 Launch site Volgograd Launch Station (presently in Russia) Launch vehicle C-1 Intercosmos Orbit 563 x 619 km Inclination 50.7 deg Mission life 6 months Spacecraft mainframe active till March,1981 Orbital Life Nearly seventeen years (Re-entered on February 10,1992) Aryabhata was India's first satellite, named after the great Indian astronomer of the same name. It was built by the Indian Space Research Organization (ISRO) to gain experience in building and operating a satellite in space. The 96.3 minute orbit had an apogee of 619  km and a perigee of 563  km, at an inclination of 50.7 degrees. It was built to conduct experiments in X-ray astronomy, aeronomics, and solar physics. The spacecraft was a 26-sided polygon 1.4 m in diameter. All faces (except the top and bottom) were covered with solar cells. A power failure halted experiments after 4 days in orbit. All signals from the spacecraft were lost after 5 days of operation. The satellite reentered the Earth's atmosphere on 11 February The satellite's image appeared on the reverse of Indian 2 rupee banknotes between 1976 and 1997 The satellite provided ocean and land surface data. One of two onboard cameras malfunctioned, however it sent back more than two thousand images. Housekeeping telemetry was received until re-entry in 1991 10th - Physics

Frist Indian Remote Sensing Satellite - Bhaskara

India’s Moon Mission (22 October 2008)
In Sanskrit (language of Ancient India) "Chandrayaan" means "Moon Craft". Moon has always fascinated Indians from ancient days and now 21st century India is ready to land on moon! Chandrayaan-1 is the first mission towards the dream. In Chandrayaan-1, the lunar craft would be launched using Polar Satellite Launch Vehicle (PSLV) weighing 1304 kg at launch and 590 kg at lunar orbit. Lunar craft would orbit around moon 100 km from moon surface. ISRO invited international space organization to participate in the project by providing suitable scientific payloads (instrument for experiments). ISRO selected 3 (C1XS, SIR-2,SARA) payload from ESA (European Space Agency) 1 (RADOM) from BSA (Bulgarian Academy of Science), 2 (MiniSAR, M3) from NASA (National Aeronautics and Space Administration) 10th - Physics

‘SARAL’ : Latest satellite launch – India (Feb 25 2013)
Sriharikota: Indo-French oceanographic study satellite ‘SARAL’ and six foreign mini and micro satellites were successfully launched today by ISRO’s PSLV-C20 rocket from this spaceport. Indian Space Research Organisation’s (ISRO) workhorse Polar Satellite Launch Vehicle (PSLV) lifted off from the first launch pad of Satish Dhawan Space Centre at around 6.00pm at the end of the 59-hour countdown and placed in the orbit the satellites about 22 minutes later. The 410-kg SARAL with payloads—Argos and Altika—from French space agency CNES is meant for study of ocean parameters towards enhancing the understanding of the ocean state conditions. SARAL was injected first into the space about 18 minutes after the lift-off followed by other satellites in the space of about four minutes. 10th - Physics

Indian Current Programmes
ISRO satellite systems ISRO has successfully operationalized two major satellite systems Indian National Satellites (INSAT) for communication services and Indian Remote Sensing (IRS) satellites for management of natural resources; ISRO Launch vehicles Polar Satellite Launch Vehicle (PSLV) for launching IRS type of satellites Geostationary Satellite Launch Vehicle (GSLV) for launching INSAT type of satellites. Satellite Applications SatCom Applications Remote Sensing Applications VRC Click here to see a comprehensive list of Indian satellites 10th - Physics

India - Future Programmes
Forthcoming Satellites INSAT-3D, an exclusive meteorological satellite ASTROSAT is a national multiwavelength space borne astronomy observatory, would be launched by PSLV from Satish Dhawan Space Centre, Sriharikota GSAT-6 The spacecraft weighs 2200 kg at lift-off GSAT-7 is a multi-band satellite.The configuration of the satellite has been finalised and the design of new payload elements is completed GSAT-9 The satellite is planned to be launched during by GSLV GSAT-11 is under advanced stage of development. It consists of 16 spot beams covering entire country including Andaman & Nicobar islands, to be realised in orbit in 2013 time frame GSAT-14 is intended to serve as a replacement for EDUSAT and is planned to be launched by GSLV with indigenous cryogenic upper stage Indian Regional Navigational Satellite System (IRNSS)-1, the first of the seven satellites of the IRNSS constellation, and is designed for a nominal mission life of 7 years. The first satellite of IRNSS constellation is planned to be launched onboard PSLV in 2013 while the full constellation is planned to be realised during 2014 time frame 10th - Physics

India - Future Programmes

Extras Difference between a rocket and a missile
Missile is also a rocket but the difference is that, it hold explosive for mass destruction. a rocket is just use to propelling vehicle like in satellites etc. Missiles are self guided by the help of inertial navigation system. Tipu Sultan, the king of Mysore, is also referred as father of modern missile technology when he first used the 2 k.m. missiles against the British troops in the Third Anglo-Mysore war at the end of 18th century 10th - Physics

References Rockets - http://en.wikipedia.org/wiki/Rockets
Principle and Components of Rockets - Satellites - Indian Space Programmes - Instructional videos – 10th - Physics