Where do all the Ki blasts that missed and sail off into space go?

[Speedster]

Outer space in not perfect vacuum - it contains a few hydrogen atoms per cubic meter as well as (though to a much lesser extent) atoms of helium, carbon, oxygen, and nitrogen.
https://en.wikipedia.org/wiki/Interstellar_medium

That might not seem much to slow down ki attacks but it actually is enough to attenuate anything over large distances as the solution of the governing differential equation is an exponential decrease.
https://en.wikipedia.org/wiki/Attenuation_coefficient

What is more is that the further we move away from our galaxy, space itself (with all the galaxies etc it contains) expands faster and faster – even faster than the speed of light. We don't know the speed of ki blasts but even if they weren’t slowed down by the interstellar matter there would come a point that their speed would be surpassed by the speed of space’s expansion. So they would go nowhere really.
https://en.wikipedia.org/wiki/Metric_expansion_of_space

[Gog]

They either destroy a planet, or like everything they slowly get weaker and weaker until the blasts dissipate harmlessly in the infinite void.

But how can anything get slowly in space?

Sorry, I incorrectly phrased myself. I was referring to the fact that the blasts would slowly break apart and eventually disappear in space.

[saunasolmu]

What is more is that the further we move away from our galaxy, space itself (with all the galaxies etc it contains) expands faster and faster – even faster than the speed of light. We don't know the speed of ki blasts but even if they weren’t slowed down by the interstellar matter there would come a point that their speed would be surpassed by the speed of space’s expansion. So they would go nowhere really.
https://en.wikipedia.org/wiki/Metric_expansion_of_space

It doesn't work like that. Space itself expands, it doesn't expand any faster further away from us - there's just more space to expand itself.

[Speedster]

It doesn't work like that. Space itself expands, it doesn't expand any faster further away from us - there's just more space to expand itself.

Speeds are relative. The universe's expansion is like inflating a balloon - the farther apart two points on it are, the faster they move away from each other.

[dragonballer]

z-fighters seems to have some control over their ki blasts even after they were fired,then I think they can erase the ki attacks in the outer space.