Space Rockets are Big

Scientists in America who are planning to explore space may build a rocket which will stand as high as a tall building, like St. Paul's Cathedral. Why is it necessary for rockets to be so large when it is much harder to lift a heavy weight than a lighter one?

The rocket which carried the American astronaut, Colonel John Glenn, into his orbit round the world, weighed 120 tons and was 80 feet high as it stood on the launching pad at Cape Kennedy (formerly Cape Canaveral). But the most important part of the rocket, the capsule, in which the astronaut travelled, held all the delicate instruments, radio, oxygen and safety equipment and weighed only a small fraction of the total-not more than one and a half tons. This part of the rocket is known as the payload. The rest of the weight was taken up almost entirely by fuel.

The fuel, and the material which supplied the oxygen to burn it, made up over one hundred tons of the total weight, while the rocket itself weighed no more than twelve tons.

The amount of fuel is heavy in itself; therefore it needs a lot of energy to lift it, which again means more fuel. Most of it is burned during the early stages of the flight when the earth's pull is strongest.

A lot of fuel needs large tanks to hold it, and, since empty tanks are only useless weight, some rockets have fuel tanks which fall away when empty.