Learn Croatian: Baza će biti u svemiru. - The base will be in space.

In Croatian, short helper words called enclitics, like će, naturally want to be in the second position in a sentence. Because the noun Baza takes the first spot, će steps in right after it, followed by the infinitive biti. If we dropped the word Baza and started the sentence with the verb, it would be Bit će u svemiru.

How would I change this to say "I will be in space"?

You would use the "I" form of the future helper verb, which is ću. With a subject, it is Ja ću biti u svemiru. If you drop the pronoun Ja, the verb comes first and drops its final "i", becoming Bit ću u svemiru.

Why does the word for space (svemir) end with an -u in this sentence?

The preposition u means "in" and triggers the locative case when you are describing a static location (where something currently is). Because svemir is a masculine noun, we add the locative ending -u to the end of it, making it u svemiru.

Can I use svemir to talk about having enough space in my house or car?

No, svemir specifically means outer space or the universe. If you are talking about physical room or an empty area, you should use the word prostor instead.