Quote from : Star Trek II: The Wrath of Khan Movie

Kirk: Kirk to Enterprise.
Spock: Spock here.
Kirk: Captain Spock, damage report.
Spock: Admiral, if we go "by the book". like Lieutenant Saavik, hours could seem like days.
Kirk: I read you captain. Let's have it.
Spock: The situation is grave, Admiral. We won't have main power for six "days". Auxiliary power has temporarily failed. Restoration may be possible, in two "days". By the book, Admiral.
Kirk: Meaning you can't even beam us back?
Spock: Not at present.
Kirk: Captain Spock, if you don't hear from us within one hour, your orders are to restore what power you can, take the Enterprise to the nearest star base, and alert Starfleet Command as soon as you're out of jamming range.
Commander Nyota Uhura: Sir, we won't leave you behind!
Kirk: Uhura, if you don't hear from us, there won't be anybody behind. Kirk out.