Newton’s Laws in Space Technology

A space shuttle or a rocket is definitely one of the most complex structures one can ever build. You need the best engineers to build one successfully, for if anything goes wrong, then lives and billions of dollars will be lost. Physics comes into play here. In fact, it plays a major role in making sure everything is up to pa. Many laws of physics are used but we shall look specific into one important one, the Newton’s Law of Motion. There are three Laws provided to us by Sir Isaac Newton: The first law states that a body will remain at rest or in motion in a straight line unless acted upon by a force. The second law states that change in motion is proportional to the applied force and parallel to it. The third Law states that to every action there is an equal and opposite reaction.

By Newton's first law, two things are really cheap: Coasting and sitting still. Out in space, sitting still is a little hard to define - do I mean compared with the Sun, or Mars? Also, most of the time we are in an orbit of some sort, so sitting still doesn't really make sense. What we need to think about is how to change from one kind of orbit to another kind of orbit. Newton's Third Law contains the "secret" of rocket propulsion for space travel. See the figure below. If A exerts a force on B, then B exerts an equal and opposite force on A. Or, in the case of space travel, if a mass (m) of fuel is pushed out the exhaust of a rocket, then the rocket will accelerate in the opposite direction the direction the exhaust fuel went. What happens to the spacecraft immediately after the rockets are turned off?

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It slows down like an airplane does here on Earth until it comes to a complete stop. However, unlike an airplane that must contend with Earth's gravity, the spacecraft will keep going in the same direction as it slows down. The astronauts will simply have to fire the rocket engines again to keep moving. The spacecraft will keep coasting at the same speed and in the same direction. The spacecraft will slow down until it comes to a complete stop. Also, the ship will veer off course in the process of slowing because the astronauts can not use the flaps on the spacecraft's wings to steer.

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While the engines are firing, the spacecraft accelerates. When it has reached its planned speed, the rockets are turned off. This means it is now in some sort of orbit around Earth or around the Sun. It will stay in this orbit until its rockets are fired again. Its speed will be constant except for very slow changes that are part of its orbital motion. After you have worked through the question above, you should now see that coasting, as a result of Newton's first law, is a vitally important aspect of space travel. The reason this is the case is because it means that astronauts only need to fire their engines for a brief time to then coast their way to a planet. But what happens when they get to a planet? If they don't slow down they could crash their ship into the planet. The easy answer to the last question is that a spacecraft must use fuel to slow down as well as tospeed up. When a spacecraft is moving forward, using Newton's laws again, the astronauts must fire their rockets in that direction to create an opposing force. In a later unit we will look at this in more detail, but for now: To get to another planet, we need to use enough fuel to get us into a big orbit that reaches all the way to the planet. Once we arrive at the planet we will need to use more fuel to slow down again. In general, the faster we get from Earth to the other planet, the more fuel we will need at both ends.

Speed And Velocity

One of the words that appears in this discussion, "velocity," is a special word to which you should pay careful attention. In everyday English, the word "velocity" is used as another way of indicating speed. Therefore, "high velocity" means "high speed." But in the context of Newton's laws, it is important to keep in mind the technical definition of velocity. Velocity is a vector indicating both speed and direction of motion. So, what are the implications for moving around in space? By Newton's second law, a force is required in order to change the direction of motion of a spacecraft, even if its speed stays constant.

Rocket Physics – Equations Of Motion

To properly analyze the physics, consider the figure below which shows a schematic of a rocket moving in the vertical direction. The two stages, (1) and (2), show the "state" of the system at time t and time t+dt, where dt is a very small (infinitesimal) time step. The system (consisting of rocket and exhaust) is shown as inside the dashed line. The principal of impulse and momentum is used here, governed by calculus to show us how certain equations are derived. It is important to note that once in space, there is no resistance or drag for there is no gravitational force acting on the rocket.