Read Online How to Destroy the Universe by Paul Parsons - Free Book Online
Authors: Paul Parsons
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ice reserves to give running water. It has even been proposed that an asteroid laden with the greenhouse chemical ammonia could be steered into Mars. Others regard such ecological tinkering on other worlds with dismay. Then again, if we cannot fix the climate of our own planet sometime soon we may well have no choice.
CHAPTER 8
How to launch yourself into space
⢠Early ideas
⢠Rocket science
⢠How much fuel?
⢠Beating gravity
⢠Multi-staging
⢠Atmospheric re-entry
⢠Space tourism
Space is just an hourâs drive away, 100 km (60 miles) above your head. And yet only a few hundred humans have ever been there. Thatâs because, while possibly the most alluring destination for the intrepid traveler, itâs also one of the most difficult places to reachâdemanding the ride of a lifetime aboard a giant firework traveling at 25 times the speed of sound. If that doesnât put you off then check your bags and climb aboard the orbital express â¦
Early ideas
Going into space is one of humankindâs oldest dreams. The idea began to edge its way closer to reality in 1903, when Russian space scientist Konstantin Tsiolkovskypublished
The Exploration of Cosmic Space by Means of Reaction Devices
. In it, he described how human explorers could escape Earthâs gravitational field to enter orbit around the planet and possibly even venture further afield. Tsiolkovsky imagined that we would use rockets to get there.
Rockets had already enjoyed a long, if less than peaceful, history within the confines of the planetâs atmosphere. In the 9th century, Chinese scientists invented gun-powder and were quick to use it as a power source to hurl projectiles at their enemies. Ever since, rockets have been used in conflicts around the world, right up to the war in modern-day Iraq.
Rocket science
Rockets work by ejecting fuel exhaust at high speed, which accelerates the body of the rocket in the opposite direction. This is based on Newtonâs third law of motion, which says that for every force there is an equal force pushing in the opposite directionâwhen I fire a rifle the bullet is accelerated forward out of the barrel, while the stock of the gun kicks back against my shoulder. Newtonâs third law means that as the rocket fuel burns, expands and is forced out of the rocket engine, an equal and opposite force is exerted on the rocket itself, which accelerates it forward.
The increase in speed is given by a principle known as the conservation of momentum. Momentum can be thought of as the impetus that a moving object has. Physicists calculate the momentum of a moving object simply by multiplying together its speed (measured in meters per second) and its mass (in kilograms). Fast, heavy things carry more momentum than slow, light thingsâwhich is why getting hit by a lorry hurts more than being bumped by a shopping trolley. The conservation of momentum says that the total momentum in any physical process must always stay the same. So if two billiard balls collide, the sum of both ballsâ momentum before the collision must equal the sum of their momentum after the collision. If one ball starts at rest, and is hit by a second ball which is stopped dead in the collision, then the first ball must carry away exactly the same momentum that the second came in with. And if they are both of equal mass then the second ball must leave with the exact same speed too.
How much fuel?
In rocketry, the conservation of momentum says that the rocket must gain momentum at the same rate as momentum is being carried away by the exhaust gas vented from the back. For example, say a small rocket spits out a kilogram of exhaust gas at 2,500 m/s. If the rocket body weighs 10 kg, that means the rocket will be moving forward after the burn at 250 m/s. Themomentum of the rocket must be the same as that of the exhaust, which is just the speed of the exhaust (2,500) times its mass (1). The
CHAPTER 8
How to launch yourself into space
⢠Early ideas
⢠Rocket science
⢠How much fuel?
⢠Beating gravity
⢠Multi-staging
⢠Atmospheric re-entry
⢠Space tourism
Space is just an hourâs drive away, 100 km (60 miles) above your head. And yet only a few hundred humans have ever been there. Thatâs because, while possibly the most alluring destination for the intrepid traveler, itâs also one of the most difficult places to reachâdemanding the ride of a lifetime aboard a giant firework traveling at 25 times the speed of sound. If that doesnât put you off then check your bags and climb aboard the orbital express â¦
Early ideas
Going into space is one of humankindâs oldest dreams. The idea began to edge its way closer to reality in 1903, when Russian space scientist Konstantin Tsiolkovskypublished
The Exploration of Cosmic Space by Means of Reaction Devices
. In it, he described how human explorers could escape Earthâs gravitational field to enter orbit around the planet and possibly even venture further afield. Tsiolkovsky imagined that we would use rockets to get there.
Rockets had already enjoyed a long, if less than peaceful, history within the confines of the planetâs atmosphere. In the 9th century, Chinese scientists invented gun-powder and were quick to use it as a power source to hurl projectiles at their enemies. Ever since, rockets have been used in conflicts around the world, right up to the war in modern-day Iraq.
Rocket science
Rockets work by ejecting fuel exhaust at high speed, which accelerates the body of the rocket in the opposite direction. This is based on Newtonâs third law of motion, which says that for every force there is an equal force pushing in the opposite directionâwhen I fire a rifle the bullet is accelerated forward out of the barrel, while the stock of the gun kicks back against my shoulder. Newtonâs third law means that as the rocket fuel burns, expands and is forced out of the rocket engine, an equal and opposite force is exerted on the rocket itself, which accelerates it forward.
The increase in speed is given by a principle known as the conservation of momentum. Momentum can be thought of as the impetus that a moving object has. Physicists calculate the momentum of a moving object simply by multiplying together its speed (measured in meters per second) and its mass (in kilograms). Fast, heavy things carry more momentum than slow, light thingsâwhich is why getting hit by a lorry hurts more than being bumped by a shopping trolley. The conservation of momentum says that the total momentum in any physical process must always stay the same. So if two billiard balls collide, the sum of both ballsâ momentum before the collision must equal the sum of their momentum after the collision. If one ball starts at rest, and is hit by a second ball which is stopped dead in the collision, then the first ball must carry away exactly the same momentum that the second came in with. And if they are both of equal mass then the second ball must leave with the exact same speed too.
How much fuel?
In rocketry, the conservation of momentum says that the rocket must gain momentum at the same rate as momentum is being carried away by the exhaust gas vented from the back. For example, say a small rocket spits out a kilogram of exhaust gas at 2,500 m/s. If the rocket body weighs 10 kg, that means the rocket will be moving forward after the burn at 250 m/s. Themomentum of the rocket must be the same as that of the exhaust, which is just the speed of the exhaust (2,500) times its mass (1). The
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