> The denser dayside region of hydrogen is still rather sparse, with just 70 atoms per cubic centimeter at 60 000 kilometers above Earth’s surface, and about 0.2 atoms at the Moon’s distance.
At the distance of the moon: 200000 per cubic meter so I think it's a bit higher than you think... of course you don't explicitly mention a height for the spacecraft surfaces...
For reference, lead in drinking water is actionable at a 10^8 factor, but beyond that — say 10^12 — we largely talk about it not being there.
There’s basically no case we refer to something attenuated by twenty orders of magnitude as qualitatively the same.
Edit:
For fun, I looked up what it meant as energy differences — twenty orders of magnitude is the difference between you jumping and the total energy from the sun that strikes the face of the Earth each day.
https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(energy)
https://en.m.wikipedia.org/wiki/Vacuum
Poster was completely correct that this accounts for only minuscule interactions such as surface oxidation and teensy drag over prolonged interactions, and nothing like the “atmosphere” behaves.
Leaves me wondering if it varies in size much, because electron flow is quite easy.