Rockets are mostly known as vehicles used to transport spacecraft into other planets and people into the international space station. In the past rockets where used primarily for long range warfare but now they have been used to expands mankind presence in the solar system.
Rockets require huge amounts of thrust to enable it to travel fast and high enough to get into orbit and escape earth's gravity.
Rockets engine work in space because they are self-contained system. Unlike jet and combustion engines, rocket engines do not require oxygen from the atmosphere. They carry their own oxygen source.
Rockets work based on Newtons third law of motion Action and produces equal and opposite reactions.
Ironically, rockets are the most inefficient means of transport on earth. The require a large amount of fuel compared to the mass of the payload they carry. To get into space, they are currently the best and only option
To compensate for this, modern rockets are built in stages. A multi staged rocket is a rocket with two or more stages. Each stage contains its own fuel and engine. A multi staged rocket can be taught as a rocket of rockets. When a stage uses up all its fuel, it is dropped off and the rest of the rocket carries on to its destination.
For a trip to the moon, a rocket will need 3 stages. The first stage will be used to get it to an ideal altitude, the second stage will be used to get it to a desired orbital trajectory and the third stage will be ramp up the speed and put it in a trans-lunar orbit. The Saturn V rocket used to go to the moon by the US Apollo program, the rocket reached an altitude of 67 kilometres and fired for 2 minutes and 42 seconds. The second stage took the rocket to 185 kilometres and burned for approximately 6 minutes. With the third stage, the rocket reached an altitude of 191 kilometres and a speed of 28,000 kilometres per hour.
To reduce the cost of space travel, Manufacturers are currently making use of reusable first stage rockets. Space X rockets have reusable first stage and have been successful with resupply missions to the international space station.
History of rockets
Rocket technologies can be traced back to 2000 years of inventions, tinkering, failed experiments, improvements, explosions, more explosions and even some more explosions. All this has led up to the current systems we have today.
Below are some of the major innovations that have been the inspiration for modern rocket technologies.
Archytas, 428 – 347 B.C.
Constructed and flown a small bird shaped device propelled by a jet of steam. The bird revolved around a pivot suspended by a wire on the end of a bar. This is mankind's intro into rocket propulsion.
Hero Engine A.D. 10 - 70
This consisted of a copper vessel heated by fire beneath and a hollow sphere. The sphere was connected to the copper vessel via two conduits. From the sphere where two L shaped cylinders. The pressure from the copper vessel was forced into the sphere and out the l shaped cylinder. This caused the sphere to rotate along its axis. Although it's not a rocket, this principle demonstrated rocket propulsion. Its potential was not realised for a thousand years.
Chinese Fire Arrow A.D. 1232
Gunpowder was packed into bamboo tubes and closed off at one end. The powered was then ignited and produced thrust from the gases escaping at the open end of the tube. This propelled the tubes. These were used attached to arrows and used to in the battle of Kai-Keng. The rocket was born, and its uses was demonstrated in warfare.
Roger Bacon 1214 - 1292
Worked on improved forms of gunpowder to greatly increased the range of rockets.
Wan Hu, 16th Century
According to legend, A Chinese star gazer living sometime in the middle of the Ming dynasty constructed a chair and attached 47 gunpowder's rockets to its base. After the explosion produced by the ignition, He was gone. Some say he was launched into space and you can see him as the Man in the Moon.
Joanes de Fontana 1420
In Italy, Joanes invented the surface running torpedo that was supposed to set an enemy ship on fire.
Jean Froissart
Discovered accurate flight could be achieved by launching rockets through tubes.
Kazimierz Siemienowicz 1600 - 1651
A polish-Lithuanian commander and expert in rocketry and artillery. Kazimierz published a paper on the design of multi stage rockets that became fundamental in the design of rockets for space travel. He also proposed delta wings stabilisers and batteries to replace guiding rockets for use in the military.
Galileo Galilei 1564 – 1642
Galileo proved that objects in motion tend to remain in motion without need for continuous application of force. This he called inertia. This is one of the principles for rocket propulsion.
Isaac Newton 1642 – 1727
Isaac condensed all rocket science into 3 elegant scientific laws. His laws were published in Philosophiae naturalis Principia Mathematic and provided the foundation for all modern rockets.
Colonel William Congreve 1772 – 1828
Colonel William took charge of the British military rocket companies. He invented case shot rockets that sprayed the enemy with carbine balls and incendiary rockets for burning ships and buildings. He also invented the first off shore launch pad and was launching rockets from a ship. The phrase “by the rockets' red glare” was attributed to his rocket.
Jules Verne 1828 – 1905
In his De la Terre á la Lune, Verne used a cannon to fire a manned projectile at the moon. The projectile was called Columbiad contained a crew of three and was launched from Florida. The Apollo 11 capsule had a crew of three and was launched from Florida. He accurately predicted that the crew will experience weightlessness during their trip.
Konstantin E. Tsiokovski 1857 – 1953
Son of a polish forester, Konstantin taught about human space travel and was considered the father of cosmonauts and human space flight. His rocket equation relates the rocket engine exhaust velocity to the change in velocity of the vehicle itself. He supported the idea of liquid propellant engines, orbital space stations, solar energy and colonisation of the solar system.
Robert H. Goddard 1882 -- 1945
American professor Robert built and flew the world’s first liquid propellant rocket on March 16th, 1926. It reached a height of only 12.5 meters. He improved on his design and developed a gyroscope system for in flight rocket control instrumentation compartment and parachute recovery system. He is often referred to as the Father of modern rocketry.
Hermann Orberth 1894 – 1989
Hermann a German citizen but Romanian by birth, His dissertation for the university of Heidelberg was rejected and became a book called Die Rakete zu den Planetanraumen. The book inspired many rocket societies that lead to the V2 rocket. He worked on using liquid fuelled rocket motor and multistage rockets.
Rocket Experimenters 1920s – 1930s
Rockets were used on air planes, racing cars, boats, bicycles and every that could be dreamt off. Most of these experiments failed but improved the reliability and power of the rocket.
Flying Bombs World War 2
Rockets were used to propel German fighter planes and Japanese Kamikaze pilots with bombs into ships.
Vergeltungswaffe 2 – V2 1930s
The German Verein fur Raumschiffart Society for Space Travel evolved and built V2 rocket. The most advanced rocket ever made. Under Werner von Braun an intern of Hermann, they created an alcohol and oxygen powered rocket with a range of 200 miles and max altitude of 55 miles. It could deliver a 1 ton explosive war head.
Bumper project 1948
300 trainloads of V2 rockets and parts were shipped to the United states. This became the basis for the intercontinental ballistic missile program and eventually the manned space program. The initial launch of the Bumper took place on May 13, 1948.
Sputnik 1957
The first man made object in orbit was launched in October 4, 1957. It weighted 83.6 kilogram. It was launched by R-7 rocket a byproduct of the V2 rocket. The R-7 was 25 times bigger than V2 weighting in at 7,000 tons. It featured a multi stage design, multi engine propulsion system 20 main chambers 8 steering thruster on its four boosters of the first stage and a single core booster for the second stage. It burned kerosene instead of alcohol. This began the space race.
Yuri Gagarin 1961
Yuri became the first man in orbit aboard the Vostok 1 space capsule. The Vostok 1 was the first manned space craft every made. The Vostok 1 was an improvement and derivative of the R-7 rocket. It was designed to enable to for the human space flight program. Yuri was in orbit for 1 hour and 48 minutes and reached a maximum altitude of 315 kilometres. Upon reentry he ejected from the capsule at 20,000 feet.
Project Mercury 1961
The US program to launch humans into low earth orbit. The Atlas rockets was derived from the Atlas missile and was upgrade to human worth. It had a One and half stage configuration and capable of carrying 1.3 tons into low earth orbit and generate 1,517 KN thrust. Astronaut Alan Shepard Jr board the rocket with the mercury space capsule on May 5 1961. The rocket didn’t have enough power to reach its designated height and Shepard made a suborbital flight reaching 187 kilometres before the mercury capsule splashed down in an ocean 15 minutes and 22 seconds later.
Apollo Program 1969
Neil Armstrong set foot on the moon on July 20, 1969. This was one of the greatest achievements of mankind. The 2000 years of rocket experiments led to this. A rocket had been designed capable of taking humans beyond earth orbit. The Apollo mission was done using the Saturn V rocket. A 3-stage liquid fuelled super heavy lift vehicle. The Saturn V remains the tallest, heaviest and most powerful rocket ever used. It can carry a payload of 310,000 lb with a thrust of 35,100 KN at the first stage. The Saturn V was also used to launch Skylab into orbit.
Space X 2015
Prior to Space X all rockets used to launch spacecrafts into orbit were destroyed during reentry and a new rocket was made from scratch for a new mission. But in December 2015, Space X achieved a successful landing and recovery of the first stage with their reusable launch system. This technology led to a drop in the cost of space travel. Reusable rockets have become a norm in the space industry.
Working Principles of Rocket
Rockets operate based on 3 laws of motion propagated by Isaac newton.
The first law states, an object at rest tends to remain at rest and an object in motion tends to remain in motion unless acted upon by an external force.
If an object is at rest, it will take an additional force to set it in motion. If the object is moving it will taking an external force to stop it, change its direction or alter its speed.
For rockets, while it's on the launch pad, the rocket is at rest. It will require an external force to start moving. This force comes from the and expulsion and combustion of the rocket fuel. When the rocket is blasting into orbit, it is acted upon by the force of gravity.
The thrust generated from the engine keeps the rocket in motion and travelling upward, when all the fuel is expended, the rocket falls back to earth due to gravity.
The second law states, the force on an object is proportional to its mass and acceleration
This law of motion is essentially a statement of a mathematical equation. The three parts of the equation are mass (m), acceleration (a), and force (f). Using letters to symbolise each part, the equation can be written as follows:
F = ma
Applying his principle to rockets, the pressure created by the controlled explosion taking place inside the rocket's engines is a force called thrust. That pressure accelerates the gas one way and the rocket the other.
The largest mass on the rocket is the propellant hence the due to the fuel of the rocket being burnt up, mass of the rocket reduces during flight. For the equation to remain balanced, the acceleration of the rocket increases as the mass decreases. Therefore, rockets look slower as they leave the launch pad and faster the higher it goes.
A rocket must reach escape velocity 40,250 km/hr. to leave earth and travel into deep space. To each this, the rocket must achieve greatest trust possible to in the shortest amount of time. The rocket must eject and burn a large mass of fuel as out its engine as possible.
Newton's second law can be restated in the following way: the greater the mass of rocket fuel burned, and the faster the gas produced can escape the engine, the greater the upward thrust of the rocket.
Newton's third law states every action produces an equal and opposite reaction
A rocket can lift off from a launch pad only when it expels gas out of its engine.
The rocket pushes on the gas, and the gas in turn pushes on the rocket. With rockets, the action is the expelling of gas out of the engine. The reaction is the movement of the rocket in the opposite direction. To enable a rocket to lift off from the launch pad, the action, or thrust, from the engine must be greater than the mass of the rocket. In space, however, even tiny thrusts will cause the rocket to change direction.
Rocket Engines
Rockets move forward by expelling hot gases downward. These gases are produced by the combustion of a fuel and an oxidiser in its combustion chamber.
Due to lack of oxygen in the vacuum of space, rockets must carry their own oxygen in order to make space travel possible
Rockets use 3 kinds of Rocket Engines.
Solid Rocket Engine
A solid rocket engine packs the fuel and oxidiser together into a cylinder. A hole at the base of the nozzle acts as the combustion chamber. When the mixture is ignited, a flame front is created which burns the mixture. This combustion produces high pressure gases at high temperature. The area of the flame front determines the amount of gases produced. Rocket manufactures have designed hole shapes for different burn rates and purposes. The gases are then expelled through a nozzle which gives the rocket its lift.
Solid rocket engines are used in missiles and as rocket boosters for satellite launch. They are the fuel used in many model rockets.
A solid rocket cannot be stopped once it is turned on and will burn till completion.
Liquid Rocket Engine
Liquid rocket engines rocket uses high pressured fuel and oxidiser pumped into a combustion engine where they are mixed and burned. This produces high temperature and pressured gases that exit through a nozzle which produces thrust for the rocket according to newtons third law of motion. The amount of thrust is proportional to the mass flow rate of the fuel, the exit velocity of the exhaust and the pressure at the nozzle exit.
Cryogenic engine is a type of liquid rocket engines using gaseous fuel and oxidiser stored at very low temperatures which liquefies the gases. The extreme cold liquid is also used to cool down the combustion chamber and prevent them from melting due to the high temperatures of the exhaust gases that can reach about 3500k
When the fuel and oxidiser mixture reaches the combustion chamber, they are ignited using an electric spark, pyrotechnics or hypergolic reaction. One advantage of hypergolic reaction is that two liquids ignite when mixed together and not needing an extra ignition system.
Hybrid Rocket engine
The fuel and oxidiser in a hybrid rock are stored in two phases. The liquid or gaseous fuel is pumped into a combustion chamber containing a solid oxidiser.
Rocket Parts
A rocket is composed on 4 main parts. The structure is the entire structural part of the rocket. That is the outer shell. Could be made from aluminium or titanium. The structural system includes the nose cone frame and fine.
The guidance system is the computers on board that guide the rocket to its destination. It also contains the command system for the rocket stages to break up. It is the brain of the rocket.
The Propulsion system is the largest part of the rocket and is composed of 90% of the rocket. It has the fuel, the oxidiser, the pumps and nozzle.
The payload system depends on the mission of the rocket. The payload is either be a satellite to be deployed into orbit or humans and cargo that will be delivered to the ISS.
So far, we have explored basics of rocketry tracing its history from the early days of rocket arrows till reusable rockets, we have looked at the working principles, types of rockets and the rocket sub assembly. In the coming weeks we look at rockets made by the various manufacturers from the Atlas family till Vulcan.