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Knowledge in ROCKET SCIENCE
Orbit: The Path To Follow
Hello reader!! I will be discussing Orbits in this article. If you are new to space science, I would like to recommend you to go through the previous article for a better understanding.In the last article we got a new term, ‘Orbit’. What is an orbit?... How does it look like?... You may arise many more questions. So, let’s find out.What is an Orbit?An orbit is a path that is repeatedly followed by an object to move around another object in space. As you know, the earth rotates around the sun and the moon rotates around the earth. Each of them follows a particular path. These paths are called orbits.How does an Orbit look like?An orbit is a path to be followed. So, it can be considered as an imaginary line. Now, what is the shape of this path??.... It is elliptical (flattened circle) in shape. In some cases, it is nearly a circle, and sometimes it is highly eccentric. Comets have highly eccentric orbits. The object that follows the orbit is called a Satellite. It may be natural (Moon) or Artificial.How does an object stay in Orbit?If an object is in motion in an orbit it remains in the same orbit unless it is pushed or its motion is disturbed.Now we are in a good position to discuss earth’s orbit.You know about the Universal Gravitational Law, proposed by Sir Isaac Newton. Yes… I am talking about that theory which started with that Apple Incident. According to that theory, every object attracts another object with a certain amount of force. This force is termed as Gravitational Force.What happens if you push a ball in Direction 1???.... It tends to move in the same direction...But, what happens if you push the ball in both directions 1 and 2 at the same time??...... Yes, the ball tends to move in another direction between directions 1 and 2 as shown in the picture. This Motion is called Resultant Motion as it is the combined result of these two acting forces.Now, when an object is in motion, it tends to move in the straight path. But Earth attracts the object with some force which tends the object to move towards the earth. So, the resultant motion will be in a direction between these two motions. This resultant motion makes the object to stay in the same orbit. Without any push, it will always remain in the same orbit.Types of earth's orbit: Any path that can be followed to move around the earth, is Earth's Orbit. They can be classified depending upon their orientation & distance from the center of the earth.The angle between the orbit & the earth's equator is termed as Orbital Inclination The plane on which the orbit lies is termed as Orbital Plane.If the orbital inclination is nearly 90 degrees, the orbit passes almost above both the poles of the earth. This orbit is termed as Polar Orbit.If the orbital inclination is 0 degree, the orbit lies on the equatorial plane of earth. This orbit is termed as Equatorial Orbit.Now, we know, the earth rotates on its own axis and it takes 24 hours to complete one rotation, which is termed as Solar Day.But the actual time period is a little lesser, to be precise it is 23 hours 53 minutes 4.091s. This time period is termed as Sidereal Day. Now imagine, if you can place an object in an orbit whose orbital period is exactly the same as sidereal day, it will be stationary with respect to a particular longitude on earth. As the rotation of the object in this orbit is synchronized with the earth's rotation, this orbit is known as Geosynchronous Orbit.If the Geosynchronous Orbit lies on the equatorial plane, it is known as Geostationary Orbit. The height of the Geostationary Orbit is approximately 35,786 km from the earth's surface.To move an object from an orbit to a larger orbit in the same plane, the object needs to be pushed by some means. The intermediate orbit is termed as Transfer Orbit.Do you know about the GSLV and PSLV?? Those are Launch Vehicles operated by the Indian Space Research Organisation. GSLV stands for Geosynchronous Sattelite Launch Vehicle and PSLV stands for Polar Satellite Launch Vehicle.Now you have some idea about the significance of the words Geosynchronous and Polar. That's enough for this article.If you ever witnessed any Launch, you have heard of these phases :- "First Stage Separation Complete" "Second Stage Ignited" "Second Stage Separation Complete" Ever thought about their meanings??
KRISHNENDU GHOSH
Liquid Propulsion System(UNIT -1)
Hello readers!! Welcome to another article on Rocket Science. In this article, I will discuss another type of propulsion system, Liquid Propulsion System. In the last article, I discussed the Solid Propulsion System. But there are some problems in using Solid Rocket Motor in the Upper-stages of a Launch Vehicle.Liquid Propulsion Systems are a little complicated with respect to the Solid Propulsion System. But we will keep our discussion simple. If you are new to this domain, please go through the previous articles for a better understanding.What is Liquid Propulsion Rocket?Liquid Propulsion Rockets are those rockets that use fuels and oxidizers in liquid form to propel in a particular direction.A liquid Propulsion system is generally termed as Liquid Propulsion Engine as it has moving parts.Advantages of Liquid Propulsion Engine over Solid Propulsion Motor:In the case of Solid Propellent rockets, the generated thrust can not be regulated after the ignition of the solid propellant grain. The thrust requirement is calculated before designing the propellant grain. So, they can not be throttled or restarted.But in the case of an upper stage rocket, the thrust may not be calculated in advance.For example, in the case of a satellite, the position and orientation always may not be perfect. Thrusters are required to bring them to a suitable position and orientation. The required thurst for this job varies and depends upon the satellite. Here Liquid Propulsion Engine comes into action. They can be throttled and restarted to produce thrust when required.How does Liquid Propulsion Engine work?In liquid propulsion systems, the propellants are stored in tanks and they are carried to the combustion chamber by some means. Then the propellants are injected into the chamber using an injector. There may or may not be an ignitor in the chamber. The propellants are combusted in the chamber and hot gasses are produced. These hot gasses are exhausted through the nozzle with high velocity. This generates thrust which propels the rocket in the desired direction.Different parts of Liquid Propulsion Engine:The liquid Propulsion system consists of four major parts: Propellant Tanks Feed System Combustion Chamber Nozzle CONTINUING...
Liquid Propulsion System(UNIT-2)
CONTINUE WITH 1...1. Propellant Tanks: In the case of Liquid propulsion, the propellants are stored in propellant tanks in liquid form. The tanks are specially designed to handle propellants in the state of weightlessness. 2. Feed System: Propellants are carried to the chamber from the propellant tanks with the help of the Feed system. For small rockets, Gas controlled feed system is used. For large rockets, a pump feed system is used where high-speed pumps are employed. To run these high power pumps a turbine is installed in the system.Propellants are injected into the chamber with the help of an Injector. Different types of injectors are used for different engines.3. Combustion Chamber:Propellants are injected into the combustion chamber with the help of injectors. Then the mixture of fuel and oxidizer is ignited with the help of a spark ignitor.In the case of some propellant, when the fuel and oxidizer come in contact, they ignite spontaneously. They are termed as Hypergolic Propellants.The propellants are ignited to produce hot gasses. 4. Nozzle: The generated hot gasses are exhausted through a Convergent-Divergent Nozzle with a high velocity. In GSLV, 4 Liquid Propulsion Strap-Ons are augmented with the 1st stage. These powered by VIKAS engine. In the second stage, the same engine is used.In the second stage of PSLV, the same engine is used. VIKAS Engine:Vikas engine is a liquid propulsion engine designed by Indian Space Research Organization in India. It is named after Indian Physicist VIKram Ambalal Sarabhai (Father of ISRO).This engine uses UDMH as fuel and N2O4 as an oxidizer.In the third stage of GSLV, a special type of engine is used, named Cryogenic Engine.These engines are much more complicated than normal Liquid propulsion engines.In the next article, we will discuss this type of engine and the story associated with it.That's all for this article. See you at the next one when we discuss Cryogenic Engine.
History of Cryogenic Engine
Hello readers!! Welcome to another article on rocket technology. In the last article, I discussed the Liquid Propulsion System. In this article, I will focus on a special type of liquid propulsion engine, Cryogenic Engine.You may have heard of this term before. If not, don’t worry, we will keep our discussion very simple and knowledgeable as well. But, if you are new to this topic, please go through the previous article for a better understanding.What does the term Cryogenic mean?The term “Cryogenics” is associated with the branch of physics that deals with the effects and behavior of materials in very low temperatures.Here a question may be raised, is there any bordering temperature for Cryogenics??..... No, there is no specific bordering temperature for cryogenics.Scientists assume a gas to be cryogenic if it can be liquified at or below -150°C.IAs an example, Hydrogen is a cryogenic fluid and it can be liquified at -253°C.What is a cryogenic rocket engine?A Cryogenic Rocket Engine is an engine that uses cryogenic fluid as fuel and oxidizer. Both the fuel and oxidizer are liquified gases and they are stored and handled at very low temperatures in the cryogenic rocket engine.So, maintaining the temperature that is far less than 0°C and execute the operations at that temperature is a challenge for rocket engineering. This challenge leads to a much-complicated structure of a cryogenic rocket engine than the structure of a usual liquid propulsion engine or a solid propulsion motor. Importance of Cryogenic Rocket Engine:In the choice of fuel and oxidizer, Oxygen is the simplest oxidizer and Hydrogen is the simplest fuel. So, we can consider hydrogen-oxygen combination is one of the most preferable propellants for rocket engines as they release a high amount of energy when combusted and generate high thrust to propel a rocket.But the problem with the hydrogen-oxygen combination is both of them are gas at normal temperature. It is possible to store them as pressurized gas, but this would require large and heavy storage tanks, which would make spaceflight almost impossible.So, these gasses are cooled to sufficiently low temperature and liquified and then stored in tanks. They are handled at that temperature and used as the propellant in the Cryogenic engine.Various fuel-oxidizer combination has been used as propellent of the cryogenic engine. But generally, the hydrogen-oxygen combination is used as they are easily and cheaply available.History of Cryogenic Engine:he world's first cryogenic engine, RL10, was developed in 1962 in the United States of America by Marshall Space Flight Centre (NASA) and its first successful flight took place on 27th November 1963. It was mainly developed for Lunex Lunar Lander. On the first flight, it was used in the upper stage of Atlas Launch Vehicle.This RL-10 engine was one of the most important weapons of NASA’s space exploration.On 26th February 1966, another cryogenic engine, J-2, developed by NASA, completed its first flight successfully. This engine is considered as one of the main factors of the success of SATURN-V Launch Vehicle in many different missions including the Appolo-11 mission ...IMPORTANT NOTE:-(A) In GSLV Mk-I, Russian cryogenic engine, KVD-1 was used in the third stage of the launch vehicle. In GSLV Mk-II, KVD-1 was replaced by India’s CE-7.5 engine. In GSLV MK-III, it is further replaced by India’s CE-20 engine.(B) In India, Liquid Propulsion Systems Centre (ISRO) developed the first Indian Cryogenic Engine, CE-7.5 under Cryogenic Upper Stage Project (CUSP).(C) Unfortunately, the first flight of the CE-7.5 engine ended with a failure in 2010. Later in 2014, this engine completed its first flight successfully.(D) In 2017, Liquid Propulsion Systems Centre (ISRO) developed another cryogenic engine, CE-20. It completed the first successful flight on 5th June 2017. (THE END )