In and out of orbit: Difference between revisions

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Above 6km or so becomes impractical for people to breathe enough oxygen.
Above 6km or so becomes impractical for people to breathe enough oxygen.


Up to 10km or airplanes with jet engines get some increase in fuel efficiency from less drag - above that it starts getting less efficient/practical for engine related reasons.
Jet planes cruise around 12km because the decreased drag makes for better fuel economy, and not much higher for a mix of reasons (more than one of them related to pressure).
: Though the record of trying really hard is rather higher, order of 35km.  
The record of trying really hard is rather higher, order of 35km.  


The same 35km-ish is also the highest recorded balloon flight{{verify}}
The same 35km-ish is also the highest recorded balloon flight{{verify}}


Above 100km or 200km the gas is thin enough that it would barely slow you down.
Above 100km or 200km the gas is thin enough that it would barely slow you down.
The likes of sputnik, MIR, ISS, and Hubble are somewhere in the 200 to 600km range.
The likes of sputnik, MIR, ISS, and Hubble are somewhere in the 200km to 600km range.


You can detect some tiny amount of gas ''at all'' up to order of 10000km{{verify}}, but you'd only care when you want your vacuum to be ''really'' empty.
You can detect some tiny amount of gas ''at all'' up to order of 10000km{{verify}}, but you'd only care when you want your vacuum to be ''really'' empty.
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On that scale, 100km away is comparatively close, and gravity is still roughly 95% of that at the surface.
On that scale, 100km away is comparatively close, and gravity is still roughly 95% of that at the surface.


Even at 2000km, far above the ISS, it's still roughly half.
Even at 2000km, far above the ISS (at ~400km), it's still roughly half.




While mathematically you could pretend it never quite goes to zero, in practice there is a distance at which the force becomes easy to counteract with small amounts of energy.
While mathematically you could pretend it never quite goes to zero, in practice there is a distance at which the force becomes easy to counteract with small amounts of energy.


This guides our understanding of '''microgravity''' (which has no exact definition - it's basically 'little, but not nothing').
This also guides our understanding of '''microgravity''' (which has no exact definition - it's basically 'little, but not nothing').




Revision as of 17:25, 10 July 2023


How high up is space?

How hard is it to get to space?

How hard is it to stay in space?

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