Page 9 - Curriculum Visions Dynamic Book

 Stage 1 of a launcher falls away, its fuel having been used up.
The science behind what has to be done is very straightforward in principle. But changing the science into technology that works—now that’s a very different matter, and one that has challenged people for over a century and is still challenging them today.
The nature of launch vehicles
A rocket is really a simple all-in-one projectile. Modern spacecraft are much more sophisticated, consisting of a number of separate items connected together. A launch vehicle (or launcher) is what most of us think of as a rocket. It is the propulsion system that allows its cargo to orbit the Earth or to leave the Earth altogether. It is by far the biggest part of the whole assembly and may weigh well over 90% of the total.
The payload of the launcher is the spacecraft. The spacecraft may be a satellite, or it may be a manned spacecraft. If an unmanned spacecraft is going to travel long distances across the solar system or beyond to newly explored areas, it may be called a space probe.
The job of the launcher is to get the payload either into orbit around the Earth or to send it beyond the gravity of the Earth.
Getting a payload into space requires twice as much fuel as putting it into orbit, so the payload for a space journey can only be half as heavy as the payload on the same launcher going into orbit.
It takes much more fuel to go directly into space than
to go first into orbit and then leave orbit for space. So
all spacecraft follow a curving path, or trajectory, that first takes them into orbit. The least a launcher must do, therefore, is be able to lift its payload into an orbit around the Earth. To do this, the launcher must achieve a velocity of 7.5 kilometres a second. That was not possible until 1957.
friction The force that resists two bodies that are in contact.
gravity/gravitational pull The force of attraction between bodies. The larger an object, the more its gravitational pull on other objects.
launch vehicle A system of propellant tanks and rocket motors or engines designed to lift a payload into space. It may, or may not, be part of a space vehicle.
orbit The path followed by one object as it tracks around another.
payload The spacecraft that is carried into space by a launcher.
probe An unmanned spacecraft designed to explore our solar system and beyond.
projectile An object propelled through the air or space by an external force or an on-board engine.
propellant A gas, liquid, or solid that can be expelled rapidly from the end of an object in order to give it motion.
propulsion system The motors or rockets and their tanks designed to give a launcher or space vehicle the thrust
it needs.
rocket Any kind of device that uses the principle of jet propulsion, that is, the rapid release of gases designed to propel an object rapidly.
satellite A man-made object that orbits the Earth.
thrust A very strong and continued pressure.
trajectory The curved path followed by a projectile.
velocity A more precise word to describe how something is moving, because movement has both a magnitude (speed) and a direction.
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