Elon Musk says traditional concrete and steel blocks are too 'boring' for use as a dummy payload in the first rocket test.

Elon Musk has posted pictures showing a Tesla Roadster prepped for launch in SpaceX's inaugural Falcon Heavy flight.

The idea was recently floated in a Twitter post claiming the first test flight would carry Musk's midnight cherry Roadster to play "Space Oddity" and put into a Mars orbit.

"Will be in deep space for a billion years or so if it doesn't blow up on ascent," he said, however it was unclear if the comment was a tongue-in-cheek joke or a serious plan.

Images now show an original Roadster shrouded by the Falcon Heavy's massive payload fairing. Musk has also explained his motivation for sending Tesla's first EV into space.

"Test flights of new rockets usually contain mass simulators in the form of concrete or steel blocks," he said on Instagram. "That seemed extremely boring. Of course, anything boring is terrible, especially companies, so we decided to send something unusual, something that made us feel."

The new Falcon Heavy rocket combines three first-stage booster cores, strapped side by side. Thrust consequently triples compared to the single Falcon 9 rocket core that has served SpaceX customers so far.

Falcon Heavy is designed to deliver astronauts to the International Space Station, take humans back to the Moon and eventually carry a crewed capsule to Mars.