SpaceX is planning to launch its Falcon Heavy rocket Tuesday. CEO Elon Musk tweeted Sunday night it "remains go." If it is successful it will be the biggest, and most powerful rocket to go into space over thirty years. Phil Plait, author of The Bad Astronomy blog, explains challenges facing Tuesday's lift-off.

"This is the most powerful rocket that will have been launched since the Saturn 5," says Plait. "In this case we are having a new generation of rocket that will be able to hopefully take people to Mars."

Tesla's roadster will be in the cargo when this rocket goes to space, along with what Elon Musk is describing as a Starman pressure suit. "It's a publicity stunt," says Plait. "You need to launch something in there. There's got to be some mass in there to test the rocket, and he chose this for sentimental reasons."