When discussing the launch and re-entry of rockets why do we need to consider gravitational force?

Question

The term g force expreses an astronauts apparent weight divided by the true weight ( that is the weight of the person on earth ).

Answer 1

Simply? Gravity is the force responsible for accelerating you towards the earth's center. Thus, when considering the forces exerted during launch, there is a constant m(9.8m/s^2) force directed straight down to the center of the earth. Dividing all forces out by mass, then no matter what acceleration into the heavens the rocket is given, it will face a near-constant 9.8m/s^2 (~ closer to 8.6 at altitude (not that much different from on earth)). What this means pertains to energy.

The rocket must get form one level to another, so the energy well decreases, in the sense of its kinetic energy must at least be (GMm/r1 - GMm/r2), where r1 is on the ground and r2 is at altitude. If you didn't factor in gravity, no force would be acting downwards on the rocket. Technically, this means any acceleration could place it at any altitude; i.e., flicking it would put it in orbit.

Answer 2

To launch a rocket with the least amount of fuel, you need to accelerate it as much as possible, unfortunately this is hard on the crew. 4g is like being 4 times your normal weight. Imagine accelerating very gently away from Earth; in an extreme case you'd just hover, use a huge amount of fuel and get nowhere. When you re-enter, you rely mostly on air friction to slow you down. If you re-enter at too steep an angle, you could be subjected to up to 200g, which would kill you. You only get one shot; if your angle is too shallow, you shoot off into space again, and you've already used all your fuel to drop out of orbit. Your re-entry path has to be correct to within about one degree. If the Earth's gravity was just a little bit stronger, then space travel would be impossible with today's chemical rockets. We'd have to wait for nuclear-powered rockets, which have got some obvious disadvantages when used in the atmosphere.

Answer 3

Because it is the G force that hold every thing to earth. So if a rocket has to escape it G force is considered. On re entry th G force will pull the rocket faster and it could burn up so the G force is again to be considered

Answer 4

G rigidity is regularly properly-referred to as "gravitational rigidity", it truly is the rigidity of gravity it truly is exerted on each and every merchandise on earth. even as it really is linked with rocketry, scientists favor to calculate the end result that the g-rigidity could have on the rocket. A rocket should be able to conquer the g-rigidity with the intention to fly upwards. Upon get perfect of entry to diminish back to Earth, the rocket will accelerate because of the g-rigidity appearing on it. Gravitational rigidity is an acceleration. it really is extra or less 9.80 one m/(s^2). once you hear 2g's or 3 x the g rigidity, it purely ability two times or 3 circumstances the rigidity of gravity. in words of the burden of an astronaut, someone's weight is measured in Newtons (N) and is dependant on the gravity or g-rigidity. If there is not any gravity, there is not any weight. If there is extra gravity than Earth (say if an astronaut were on a better planet), the burden of the astronaut will be extra. Please do not confuse weight with mass.

Answer 5

because gravity takes all things down. you underestimate gravity and the rocket will not launch. you overestimate it and you waste rocket fuel. during reentry you overestimate gravity and rocket wont enter Earth. you underestimate it and you have tons of burnt metal raining on Earth.