His Falcon Heavy vehicle is designed to have more than twice the lifting capacity of any existing launcher.
Because of the historic high failure rate of maiden flights, the rocket will only carry a dummy payload, however.
Mr Musk has decided this should be his old cherry-red Tesla sports car. A mannequin wearing a space suit will be strapped to the driving seat.
The entrepreneur says David Bowie's classic hit Space Oddity will be looping on the radio in the roadster as it is hurled into an elliptical orbit that stretches out to Mars' orbit around the Sun.
"[The car will] get about 400 million km away from Earth, and it'll be doing 11km/s," he told reporters in a briefing on Monday. "We estimate it will be in that orbit for several hundred million years, maybe in excess of a billion years."
Three cameras attached to the car would provide "epic views", Mr Musk added.
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