What is a Spaceman Word™?

Question

_{In the spirit of the What is a Word™/Phrase™ series started by JLee, a special brand of Phrase™ and Word™ puzzles.}

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If a word conforms to a special rule, I call it a Spaceman Word™.
Use the following examples below to find the rule.

Spaceman Words™	Not Spaceman Words™
FAMILY	FRIENDS
TABARD	TUNIC
TAIPAN	MOGUL
CLAVUS	CALLUS
CEILIDH	SHINDIG
REMORSE	REGRET
DEMOLISH	ESTABLISH
COBALAMIN	RIBOFLAVIN
REBUKABLE	COMMENDABLE
UNREBUKED	DISCIPLINED

In case you want it in CSV:

Spaceman Words™,Not Spaceman Words™
FAMILY,FRIENDS
TABARD,TUNIC
TAIPAN,MOGUL
CLAVUS,CALLUS
CEILIDH,SHINDIG
REMORSE,REGRET
DEMOLISH,ESTABLISH
COBALAMIN,RIBOFLAVIN
REBUKABLE,COMMENDABLE
UNREBUKED,DISCIPLINED

The puzzle satisfies the series' inbuilt assumption, that each word can be tested for whether it is a Spaceman Word™ without relying on the other words.
These are not the only examples of Spaceman Words™; many more exist.

What is the special rule these words conform to?

Answer 1

A Spaceman Word™

contains a national capital spelled backwards. This is hinted by the fact that SPACEMAN spelled backwards is NAMECAPS i.e. "names of capitals."

The listed examples include

FAMILY $ \rightarrow $ F (LIMA)< Y (capital of Peru)
TABARD $ \rightarrow $ (RABAT)< D (capital of Morocco)
TAIPAN $ \rightarrow $ T (APIA)< N (capital of Samoa)
CLAVUS $ \rightarrow $ CL (SUVA)< (capital of Fiji)
CEILIDH $ \rightarrow $ CE (DILI)< H (capital of East Timor)
REMORSE $ \rightarrow $ R (ROME)< SE (capital of Italy)
DEMOLISH $ \rightarrow $ D (LOME)< ISH (capital of Togo)
COBALAMIN $ \rightarrow $ C (MALABO)< IN (capital of Equatorial Guinea)
REBUKABLE $ \rightarrow $ REB (BAKU)< LE (capital of Azerbaijan)
UNREBUKED $ \rightarrow $ U (BERN)< UKED (capital of Switzerland)