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European space truck the Johannes Kepler successfully docked with the International Space Station this afternoon. The Johannes Kepler approaching the ISS earlier today The Automated Transfer Vehicle (ATV) made initial contact with the orbiting outpost at 15:58 GMT without the need for human intervention, and is now clamped to …

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Coat

We need to get the space freight off space trucks;

and back on to space trains!

Also, I thought that 56mph (90km/h) was less than escape velocity? Has this truck had its limiter removed? ;)

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Anonymous Coward

Uh, what?

"the ISS does indeed lose altitude due to skimming the Earth's outer atmosphere, rather than as a result of gravity."

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Boffin

Orbital mechanics for dummies

The orbit of the ISS is due to it's speed. Basically it is always "falling" towards the Earth because of gravity, but because of it's speed it "misses"; If the Earth was not there, it would be travelling in a straight line, but the gravity of the Earth "bends" it's path around the Earth.

The height of the orbit depends on how fast the ISS is travelling; the faster it is going, the less curved it's path (in other words a larger circle, and hence further from the Earth's surface). You can also think of swinging a brick on the end of a piece of string; the faster you swing the brink, the harder it pulls outward, and this pull is what counter-acts gravity's attempt to make the ISS crash into the ground.

The atmosphere of the Earth does not just stop at a certain point, it keeps on going far far out into space (although the higher you get, the less there is). As the ISS passes through this atmosphere, it suffers from drag, which slows it down. Slowing it down causes it's path to be more bent by gravity, so it's orbit is lower.

The ATV is used to compensate for this by speeding the ISS up. (You can't just push the ISS away from the Earth to raise it's orbit, it would just fall back; you need to speed it up so that it's orbit is less curved.)

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Boffin

Er No...

It is Definitely due to gravity!

The atmosphere will slow the ISS causing its circular orbit to decay into a spiral.. now the one crucial thing required for an orbit to exist let alone be circular or spiral ...is GRAVITY.

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Go

Youve all miss understood...

The statement says "that the ISS does indeed lose altitude due to skimming the Earth's outer atmosphere, rather than as a result of gravity."

If there was no atmosphere, there would be nothing to slow down the ISS and so it would NOT lose ALTITUDE. Gravity alone (without atmospheric intereference) would maintain the ISS in its orbit and therefore as stated would NOT cause the ISS to lose ALTITUDE.

The statement is correct as written.

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HMB

Top picture

I was reading through the digits and letters when I realised that O_Failure had occurred. I hope O wasn't important. :P

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Joke

re: Top picture

The picture was probably taken from freeview, and so the left-hand side was chopped off where it says "N".

(Probably also the top and bottom as well, so the copyright message is gone, it's now an orphan and you can do what you want with it)

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Go

False alarm

That image is cropped -- it actually says NO_FAILURE.

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Alien

Insert obligatory Deep Purple song title here

Space Truckin'

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