I agree that it is acceptable but, as I'm sure you noticed, your dictionary definition comes from the American Heritage Dictionary and my point was that whilst it is used in America, it is not a term or phrase that an English person would use. Not least because we don't have a space program, whereas the only time I've actually heard the phrase is in Hollywood movies about NASA or the military.
Also, 'let's go' can mean 'lets get on with it' in England, informally.
The only thing the poster needs to think about is whether he wishes to learn English or American English, and I only intended to put the English perspective forward.