About satellite launching and satellites in orbits

1. Aug 29, 2014

PhysicsStudnt

Dear Experts,

When we launch a satellite, we launch it from earth which is spinning, so the tangential velocity component of the point on the surface where the rocket is launched from will be acquired by it. Is that the only horizontal velocity or is the rocket accelerated at an angle upward? How is it practically done?

2. Aug 29, 2014

Staff: Mentor

The rocket starts out going vertically upwards, then the engines are "steered" so as to make the flight path curve into a "horizontal" (actually tangential) one.

3. Aug 29, 2014

PhysicsStudnt

Thank You. I still have a little doubt regarding this. Even if i dont impart it any horizontal speed,i guess it will still have a horizontal speed resulting from the fact that it is sent from a plane that is spinning. So why do i need to impart more horizontal speed? is there any technical or practical side to it?.

4. Aug 29, 2014

JasonGodbout

Orbital speed

From wikipedia the earth radius is 6371.0 Km it take 24h for one turn: 463m/s

depending on your altitute there is different Obital speed but it is multiple time the earth rotation.
V=$\sqrt{\frac{GM}{r}}$

Last edited: Aug 29, 2014
5. Aug 29, 2014

PhysicsStudnt

So i guess it is arguably less compared to the orbital velocity.

6. Aug 29, 2014

JasonGodbout

I just find a good example geostationary orbit occur when the satellite speed equal earth rotation it is at 36 000 km everything below that need more horizontal speed.

7. Aug 29, 2014

A.T.

The geostationary orbit requires more horizontal speed too. Geostationary means same angular speed, not same tangential speed. But there is an orbit beyond the geostationary that has the same tangential speed as the surface at the equator, so it doesn't require any tangential acceleration.

Last edited: Aug 29, 2014
8. Aug 29, 2014

rcgldr

If there was no atmoshpere, you'd want to launch horizontally as soon as possible to make efficient use of fuel, since the goal is to increase velocity, not climb vertically which has to oppose the force from gravity. With an atmosphere, drag presents another opposing force, and it's a compromise made to accelerate both vertically and horiztonally, reducing thrust if needed until the astmosphere is thin enough that you don't stress the launch vehicle. Most of the change in speed occurs after a launched aircraft is nearly horizontal, well into the very thin upper fringes of the atmosphere. The thrust may be completely horizontal, but the space craft continues to "climb" since the increase in speed results in an outwards spiraling path.

9. Aug 30, 2014

PhysicsStudnt

When i send a projectile up, the height attained clearly relates to the angle of projection. But quite differently, when i launch a satellite, the height it attained is independent of the angle of projection. In fact, i guess, both the horizontal and vertical components in a launch contribute to increasing the distance from the surface of the earth. But how can i explain this more quantitatively and mathematically.

10. Aug 30, 2014

Staff: Mentor

Don't be thinking just about the height - you also have to consider the shape of the orbit, how elliptical it is.

11. Aug 30, 2014