Changing Orbits (1 Viewer)

[Roobs]

I think i might have seen a post like this on here a while ago...but i searched like a biatch for it and couldnt find it:

If a sattelite accelerates to get to a higher orbit (obviously) then why, according to the formula for orbital velocity, does its velocity decrease?

this has got me really stumped.....

 

[rama_v]

I think i might have seen a post like this on here a while ago...but i searched like a biatch for it and couldnt find it:

If a sattelite accelerates to get to a higher orbit (obviously) then why, according to the formula for orbital velocity, does its velocity decrease?

this has got me really stumped.....

This might be counter to your intuition but it is true. The reason lies in the fact that as a spacecraft is falling in orbit, it is converting the gravitational potential energy it stores into kinetic energy. Now, since GPE actually increases as you move away from the earth and drops as you move closer to the earth, then this energy must be used up somewhere - in this case it is used in the kinetic energy of the satellite. So as the satellite reduces its altitide, it's speed increases (the change in GPE is equal to the increase in kinetic energy). Similarly when it increases in altitude, its speed must reduce to compensate for the increased GPE it carries.

 

[Roobs]

ok so just clarifying for my own sake:......So the energy produced by the engines is used not to increase the orbital velocity of the craft, but to increase the crafts GPE, moving it away from the earth, and its velocity decreasing as it does so. this kinda meakes sence (correct me if im wrong) as the earth is the Perigee of the elliptical path the sattelite will take to the higher orbit?

 

[rama_v]

ok so just clarifying for my own sake:......So the energy produced by the engines is used not to increase the orbital velocity of the craft, but to increase the crafts GPE, moving it away from the earth, and its velocity decreasing as it does so. this kinda meakes sence (correct me if im wrong) as the earth is the Perigee of the elliptical path the sattelite will take to the higher orbit?

Yes. You don't have to worry about elliptical motion too much. Always remember, that velocity determines the period of orbit, and the period determines the radius of the orbit.