# Homework Help: Launch speed to reach a given orbital altitude

1. Oct 19, 2011

### horsecandy911

1. The problem statement, all variables and given/known data

[EDIT: My first statement of the problem was wrong.]

1. The space shuttle releases a satellite into a circular orbit 720 km above the Earth. How fast must the shuttle be moving (relative to Earth) when the release occurs?

2. Relevant equations

F=GmM/r^2

Fc = mv^2/r

3. The attempt at a solution

Cannot figure out how to do this. I can solve for the orbital velocity (the speed at which the satellite will move around the Earth), but what does this have to do with the speed at which the space shuttle is moving relative to the Earth?

Last edited: Oct 19, 2011
2. Oct 19, 2011

### cepheid

Staff Emeritus
When the satellite is released, it will be moving at the same speed as the shuttle is. Therefore, the shuttle had better have the right speed in order for the satellite to end up in the desired orbit. In other words, the shuttle basically also has to be in that orbit at the time of release. That's all.