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Author: Subject: Throwing objects down from satellites - would it work? Why not?
blogfast25
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[*] posted on 28-5-2015 at 05:50


Quote: Originally posted by SupFanat  
Geostationary satellites would have the same speed as the atmosphere at such altitude. Ideally it would orbit the Earth as if it were bound to Earth surface but in the practice the orbit isn't as precious.


That's basically word salad.

Geostationary orbits are orbits too. AAHD's derivation holds perfectly for such orbits too.




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blogfast25
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[*] posted on 28-5-2015 at 05:58


Quote: Originally posted by SupFanat  
About re-entry... Adiabatic compression can produce high temperatures.
But what about adiabatic expansion which gives low temperatures? How low are the reachable temperatures?


I don't know. The braking force due to air-drag is given by (IIRW) F<sub>drag</sub> = k v<sup>n</sup>, as explained high up.

The braking force performs mechanical work acc.:

dW = F<sub>drag</sub> dx

That work is converted to heat energy, at least in part, causing both the air (around the object) and the object itself to heat up. Very hard to calculate, I think...

It's obvious that the heat shields of the Apollo capsules and space shuttles heated up very strongly upon re-entry. Shooting stars are meteorites burning up in the higher atmosphere, due to entry heat.

[Edited on 28-5-2015 by blogfast25]




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SupFanat
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[*] posted on 28-5-2015 at 06:33


Quote: Originally posted by blogfast25  
Quote: Originally posted by SupFanat  
Geostationary satellites would have the same speed as the atmosphere at such altitude. Ideally it would orbit the Earth as if it were bound to Earth surface but in the practice the orbit isn't as precious.


That's basically word salad.

Geostationary orbits are orbits too. AAHD's derivation holds perfectly for such orbits too.

If the atmosphere still exists on such altitude and rotates around the Earth with the same speed as the satellite then the satellite doesn't move relative to atmosphere.
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blogfast25
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[*] posted on 28-5-2015 at 07:20


Quote: Originally posted by SupFanat  

If the atmosphere still exists on such altitude and rotates around the Earth with the same speed as the satellite then the satellite doesn't move relative to atmosphere.


True but that doesn't change anything, fundamentally. Air drag is ZERO at 35,786 kilometres above earth.

http://en.wikipedia.org/wiki/Geostationary_orbit




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SupFanat
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[*] posted on 28-5-2015 at 07:49


The zero speed relative to atmosphere means the air drag would be zero even if the atmosphere were dense at such altitude?
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[*] posted on 28-5-2015 at 07:59


Quote: Originally posted by SupFanat  
The zero speed relative to atmosphere means the air drag would be zero even if the atmosphere were dense at such altitude?


Yes but it's a nonsensical question: orbital period and orbital radius (and Earth's mass) are tied to each other by Kepler's Law. No low altitude geostationary orbits, for instance.




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[*] posted on 28-5-2015 at 08:24


I hope they make better geostationary weather satellites which show as many color channels as they want for some scientific purposes but they don't forget about "true color" version as well.
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[*] posted on 28-5-2015 at 08:25


Quote: Originally posted by SupFanat  
I hope they make better geostationary weather satellites which show as many color channels as they want for some scientific purposes but they don't forget about "true color" version as well.


Colour is in your mind. Not important...




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[*] posted on 28-5-2015 at 08:38


I hope it's thinkable. I want to view Earth from great altitude but I can't reach even low earth orbit, a fortiori such high orbit that the Earth appears as disc. So the only chance is...virtual trip.
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[*] posted on 28-5-2015 at 11:12


Quote: Originally posted by SupFanat  
I want to view Earth from great altitude


Source: https://en.wikipedia.org/wiki/Pale_Blue_Dot

You're welcome.
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[*] posted on 28-5-2015 at 20:07


Thank you but billions of kilometers/miles is too tall. I prefer thousands of kilometers/miles.
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