school energy&environment

Three… two…one… Go!

How is a probe launched into space? In order to succeed in sending any object into space, or even simply making it orbit around the Earth, it must be given a thrust that can lift it off the ground, and accelerate it up to a speed of approximately 36000 km/h, about 40 times the speed of the airlines’ aircraft. For this purpose, special rockets known as launchers are used. These release a thrust that is sufficient to win their own weight. The technique is very simple: the gas, produced by combustion of the so-called propellant in the engine, is expelled at a speed of approximately 16000 km/h downwards, and in turn, due to the recoil, the rocket is pushed upwards. Obviously in order to produce such a thrust, a very large amount of gas must be expelled, and therefore many dozens of tonnes of propellant must be used. The more propellant is burnt, the greater the thrust that is generated, but at the same time the total load to be lifted and transported to the higher altitudes increases. It must not be forgotten that not only the satellite needs to be lifted but the entire structure, including the tanks full of propellant.
For example, the European launcher Ariane 5 can lift off and put a satellite that weighs approximately 6 tonnes into orbit. But the total mass of Ariane 5 is 750 tonnes, 120 times greater than its pay load!
It is possible to avoid this problem of the load, allowing a greater weight, by simply choosing the area where the rocket will be launched carefully. In fact, not all the locations on the Earth are equivalent. Our planet behaves like a top that spins around itself in approximately 24 hours, and since it is not a perfect sphere, places at different latitudes travel around a circumference that increases progressively as we move from the poles to the equator. And since all the points of the Earth take the same amount of time to complete a full circle, a point that is on the equator will move at a greater speed. So the solution has been found: if the launch takes place on the equator, the Earth’s rotation shall behave just like a sling, thus a large amount of fuel is saved.