The U.S. space agency's heavy-lift Space Launch System, which is scheduled to make a test flight as early as September 2018, will be able to lift 154,000 pounds to low-Earth orbit in its initial configuration. Future versions are planned to provide a 286,000-pound lift capacity.
Musk also alluded to a roomier Dragon spaceship for human missions to Mars.
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SpaceX next year plans to debut a passenger version of its Dragon cargo ship, which currently ferries supplies to the International Space Station for NASA.
Dragon Version 2, or Crew Dragon, is scheduled to fly for the first time in May and make a test flight to the station with NASA astronauts aboard before the end of 2017.
A Dragon V2, flying without crew, also will be used for SpaceX's initial journey to Mars, which is targeted to launch in 2018.
"I wouldn't recommend (people) traveling to Mars in that because it has the interior volume of a large SUV. The trip for Dragon would be on the order of six months. It's a long time to spend in an SUV," Musk said.
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"It also doesn't have the capability of getting back to Earth," he added.
Musk said he will release details of the SpaceX Mars project in September at the International Astronautical Congress in Guadalajara, Mexico.
"The basic game plan is that we're going to send a mission to Mars with every Mars opportunity from 2018 onwards," Musk said.
Mars and Earth favorably align for interplanetary travel about every 26 months.
"We're establishing cargo flights to Mars that people can count on ... and I think if things go according to plan we should be able to launch people probably in 2024, with arrival in 2025," Musk said.