will my space station over time fall from 320km back to earth?

[gazn1]

Just built a medium-large sized space station over kerbin for housing my kerbals and refueling but will it eventually fall back down?

[togfox]

No. It won't.

Ever.

[Sirine]

Earth？ No. Never.

[Monger]

Nope. The atmosphere really stops at around 100km. The orbit calculations might vary due to floating point calculation errors, but they will never add up enough to actually change the orbit. Also, there are no tidal forces implemented, so Kerbin will NOT lose momentum, even in a billion years.

[blizzy78]

The atmosphere really stops at around 100km.

You mean ~69 km.

[vexx32]

As long as its entire orbit path is outside of the atmosphere (i.e., above ~69km), it'll stay there till you bring it back or knock it out of the sky.

[FuzzyLlama]

If you do not focus on your space station, it can pass as close as ~26,000 m to Kerbin's surface without its orbit becoming altered, or the station being deleted. Parts and vehicles greater than 2.3 km away from the currently focused craft are automatically deleted when they pass through > 1% of a planet's atmosphere. For Kerbin, 1% ends around 26 km. However, if you focused on your space station while its altitude is below 69 km, you are performing physics calculations which include atmospheric drag and thus will lower its orbit terminally.

So you can get away with a little bit, but you want a circular orbit outside of the atmosphere for ease of rendezvous and docking.

[Kasuha]

There are no atmospheric effects (drag) outside the atmosphere (<70 km on Kerbin).

If you stay in physics mode for really long time, orbital simulation errors may sum up to a measurable change of your orbit. But as far as I know, these errors tend to raise your orbit rather than lowering it.

If you leave the ship unattended, it will stay on its precise orbit without any change for any time interval.

The limit below which unattended objects disappear in Kerbin's atmosphere is 23 km.

[blizzy78]

If you stay in physics mode for really long time, orbital simulation errors may sum up to a measurable change of your orbit. But as far as I know, these errors tend to raise your orbit rather than lowering it.

How long would you have to wait in Earth days to see a significant change in orbital parameters?

[Redhotita1]

I had a huge Space Station orbiting at 73km, 300km is way to high imho

[vexx32]

How long would you have to wait in Earth days to see a significant change in orbital parameters?

Depends how significant you mean. If you left the game in 4x P-Warp mode for long enough, you might end up in orbit around the Sun, or deorbiting entirely. That might take weeks, though, I don't know.