What does ‘nominal’ mean when Spacex mission control says it?

I love watching Spacex live streams of their missions. But I am super confused at what they mean when they say ‘speed is nominal’, or ‘mission proceeding nominally’.

I initially thought nominal was a negative word. So I probably just don’t know the definition or how they are using it.

So I looked up the trusty Internet Dictionaries for the definition. (Side note looking stuff up in a real dictionary used to take forever.) The first couple definitions… were not helpful.

One definition was being small or low in amount when compared with the actual value’. That didn’t seems to make sense in Spacex usage.

Another was ‘being such in name only’. Like a nominal head of state is in charge in name only. Again doesn’t make sense in Spacex usage.

There was a definition of ‘pertaining to, or constituting a name or names or nouns’ but that seemed to be only referencing grammar.

Finally I found a definition that makes sense.

nominal — Aerospace

performing or achieved within expected, acceptable limits;
normal and satisfactory;

Example The mission was nominal throughout.

So when the rocket performance is ‘nominal’ is it within expected and acceptable limits.

Thanks Internet Dictionaries

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