# Question regarding artificial satellites

• Declan McKeown
In summary, the conversation discusses the relationship between velocity, radius, and force on artificial satellites in orbit. It is mentioned that decreasing the velocity will result in a lower orbit, but the force and acceleration also increase, causing confusion. It is explained that this is because the period is not constant and that circular orbits are not the only possibility. The conversation concludes by mentioning the need to fire the engines to return to a circular orbit.
Declan McKeown
Hey guys,

I just had a question regarding artificial satellites:

From what I understand, satellites are able to enter into a lower orbit by reducing their velocity, which makes sense because of V=2*pi*r/T

However, decreasing radius should also increase Fg and thus acceleration and thus velocity because of Fg=GMm/r^2 and also directly if you make Fc=Fg, then v^2=GM/r

I am quite confused with this because It seems that the velocity and radius of a satellite are both inversely and also directly proportionate at the same time. Could someone please explain to me how this works?

Thanks a tonne :)

The period is not a constant, it depends on radius. So you first equation does not mean what you think.
Actually, for circular orbits, the speed is highest in low orbit and decreases for higher orbits. As shown in your last equation.

But circular orbits are not the only possible ones. If the satellite is in circular orbit and you decrease the speed the orbit will became elliptic. The ellipse will be tangent with the original orbit in the point where you change speed so on this elliptical orbit the satellite will move closer to Earth.
To go back to a circular orbit but closer to Earth you will need to fire the engines one more time.

Declan McKeown

## 1. What are artificial satellites?

Artificial satellites are man-made objects that are placed into orbit around the Earth or other celestial bodies. They are used for various purposes such as communication, navigation, weather forecasting, and scientific research.

## 2. How are artificial satellites launched?

Artificial satellites are launched into space using rockets, which provide the initial thrust needed to escape the Earth's gravitational pull. Once in space, the satellite uses its own propulsion system to reach its designated orbit.

## 3. How do artificial satellites stay in orbit?

Artificial satellites stay in orbit by balancing the force of gravity with the centrifugal force generated by their orbital speed. This allows them to continuously circle the Earth without falling back to the ground.

## 4. How are artificial satellites controlled and powered?

Artificial satellites are remotely controlled by ground stations using radio signals. They are powered by solar panels, which convert sunlight into electricity to operate their systems and instruments.

## 5. Can artificial satellites fall back to Earth?

Yes, artificial satellites can fall back to Earth if they run out of fuel or encounter atmospheric drag. Most satellites are designed to eventually re-enter the atmosphere and burn up, but some larger ones are equipped with propulsion systems to move them to a higher orbit or bring them back to Earth safely.

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