Mr. Musk now concedes that was not a viable business plan.
Mr. Musk’s tweets suggest that the giant rocket has slimmed to a diameter of 9 meters, or about 30 feet. The original design was 12 meters in diameter, with 42 individual engines powering the booster stage. His reference to “some unexpected applications” could be how SpaceX expects to generate enough revenue to pay for the rocket’s development.
SpaceX also will not be getting to Mars as quickly as Mr. Musk originally forecast. The company had planned to launch one of its Dragon 2 capsules without people, to Mars in 2018. (The capsule is under development for taking astronauts to the International Space Station.) This mission, called Red Dragon, was intended to demonstrate that SpaceX’s technique of using thrusters at supersonic speeds to slow down a spacecraft — essentially the same technology it uses to land the boosters of its Falcon 9 rockets — would work on Mars as well. The Red Dragon capsule was to be bigger and heavier than anything NASA has landed on Mars.
But in February, the launch date slipped to 2020. In July, Mr. Musk acknowledged that landing thrusters had been removed from the capsule design, and that appeared to mark the end of Red Dragon.
SpaceX is not the only company with proposals for the red planet. A few hours before Mr. Musk’s talk on Friday, Lockheed Martin will provide an update of its own Mars mission vision, called Mars Base Camp. Compared to Mr. Musk’s ambitions, the Lockheed Martin plan seems quaint and slow. It would not head to Mars until 2028, it would take only six astronauts and the first trip would not even land on Mars but instead circle the red planet for a year before returning to Earth.
From Mars orbit, astronauts could control robotic explorers like rovers more easily.
Mars Base Camp is…