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That is the highest we are going with manned spacecraft technology at the moment.

Obviously, 40 years ago we were taking people out 250,000 miles.

Unmanned is a different story. The "highest" unmanned probes are the Voyagers and Pioneers 10 and 11.

BarnatosGhost said:

annodomini2 said:

SystemParanoia said:

isnt geo-sync orbit 26,000km ... not 200km

Geostationary is 35786Km.Geosynchronous varies depending on the required position and can be elliptical.

The mass only has an impact for the launcher and orbital maintenance.

annodomini2 said:

BarnatosGhost said:

annodomini2 said:

SystemParanoia said:

isnt geo-sync orbit 26,000km ... not 200km

Geostationary is 35786Km.Geosynchronous varies depending on the required position and can be elliptical.

The mass only has an impact for the launcher and orbital maintenance.

I ask because that doesn't seem intuitive to me. Swinging a 1kg weight on a 1m string around my head at 60rpm requires a different input of energy to a 2kg weight on the same string at the same speed, doesn't it?

Or doesn't it?

The energy required to get that object to the stable orbit will have been set by the mass of the object. That is why a 7.5 million pound thrust Saturn V was needed to launch 100 tons into a low earth orbit whereas the much less powerful Atlas was required to put 1.5 tons into the same type of orbit.

BarnatosGhost said:

I ask because that doesn't seem intuitive to me. Swinging a 1kg weight on a 1m string around my head at 60rpm requires a different input of energy to a 2kg weight on the same string at the same speed, doesn't it?

Or doesn't it?

A string isn't gravity. While swinging a 2kg weight on a string will put more force onto the string than a 1kg one will, gravity 'automatically' puts more force on a 2kg mass than a 1kg one.Or doesn't it?

The two important equations you need to know to work it out are:

Force due to gravity F=GMm/r^2 ( G=universal gravitational constant, M=mass of Earth, m=mass of object, d^2=sqaure of the distance between the centre of gravity of the two objects )

'Centrifugal Force' ( I know, it doesn't really exist ) F=mv^2/r (m=mass of object, v=velocity ( parallel to planet surface ) r=radius of the orbit )

For something to be in a stable orbit the centrifugal force must equal the force due to gravity, so the equations simplify to GM=rv^2 i.e. the radius of the orbit multiplied by the square of the velocity equals the mass of the Earth multiplied by the gravitational constant. Notice that the mass of the satellite doesn't appear in this equation, as it doesn't affect the result

BarnatosGhost said:

But why does a 1 ton satellite have a geosynchronous orbit at the same distance as a 2 ton satellite?

Isn't there a difference? It 'feels' like there should be.

If you had two 1 tonne satellites tied together with string, do you think they would be in a different orbit to a 2 tonne satellite ?Isn't there a difference? It 'feels' like there should be.

( incidentally, it's this concept that Galileo used to show that objects of different mass fall at the same rate )

MartG said:

BarnatosGhost said:

I ask because that doesn't seem intuitive to me. Swinging a 1kg weight on a 1m string around my head at 60rpm requires a different input of energy to a 2kg weight on the same string at the same speed, doesn't it?

Or doesn't it?

A string isn't gravity. While swinging a 2kg weight on a string will put more force onto the string than a 1kg one will, gravity 'automatically' puts more force on a 2kg mass than a 1kg one.Or doesn't it?

The two important equations you need to know to work it out are:

Force due to gravity F=GMm/r^2 ( G=universal gravitational constant, M=mass of Earth, m=mass of object, d^2=sqaure of the distance between the centre of gravity of the two objects )

'Centrifugal Force' ( I know, it doesn't really exist ) F=mv^2/r (m=mass of object, v=velocity ( parallel to planet surface ) r=radius of the orbit )

For something to be in a stable orbit the centrifugal force must equal the force due to gravity, so the equations simplify to GM=rv^2 i.e. the radius of the orbit multiplied by the square of the velocity equals the mass of the Earth multiplied by the gravitational constant. Notice that the mass of the satellite doesn't appear in this equation, as it doesn't affect the result

Now the crucial test-your-understanding second question:

So if the moon were to be geosynchronous, it too would have to orbit at 37,000 (or whatever the figure was) km?

Eric Mc said:

BarnatosGhost said:

But why does a 1 ton satellite have a geosynchronous orbit at the same distance as a 2 ton satellite?

Isn't there a difference? It 'feels' like there should be.

"Feelings" aren't very scientific.Isn't there a difference? It 'feels' like there should be.

Or did you know exactly what I meant and were 'feeling' a little supercilious?

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