Musk posted an eye-catching photo late Sunday showing the Crew Dragon inside an anechoic chamber.
Sound-absorbing anechoic chambers have been described as the quietest places on Earth and can simulate the environment in space. The Crew Dragon is tucked inside one for electromagnetic interference testing, which is done to make sure a spacecraft's electrical systems will work properly.
This current round of testing is a precursor to moving the capsule to NASA's Plum Brook Station facility in Ohio, home to the world's largest vacuum chamber. The space agency built the vacuum chamber to test its Orion crew vehicles, but it will work just as well for SpaceX's Crew Dragon.
"Dragon's first manned test flight is expected to take place as early as 2018," SpaceX says. Musk is still targeting 2024 for a mission to take both crew and cargo to Mars. But first, Crew Dragon will need to prove itself by acing its tests on the ground.