The SpaceX Falcon 9 rocket and Dragon spacecraft break apart shortly after liftoff from the Cape Canaveral Air Force Station in Cape Canaveral, Fla., on June 28. SpaceX CEO Elon Musk said Monday the failure of a steel strut likely caused the rocket to explode. John Raoux/AP hide caption

itoggle caption John Raoux/AP

Musk with the Tesla Model S in Fremont on Oct. 1, 2011. Stephen Lam/Reuters/Landov hide caption

itoggle caption Stephen Lam/Reuters/Landov

A rendering of a Hyperloop pod. Courtesy of Elon Musk hide caption

itoggle caption Courtesy of Elon Musk

Elon Musk's "Hyperloop" vehicle. Elon Musk hide caption

itoggle caption Elon Musk