SpaceX Starship will fly nine miles into the air later this week according to Elon Musk, who says it has a one in three chance of landing safely.

The massive Starship two-stage-to-orbit heavy lift vehicle has been in development since 2012 and is designed to bring the cost of launch down by being reusable.

Musk says the first ‘high-altitude test’ of the rocket will see it fly nine miles up above the Boca Chica facility in Texas at some point this week — possibly tomorrow.