Still to come are lithium hydroxide (LiOH) canisters to scrub carbon dioxide from the atmosphere, along with humidity control and high-pressure air to maintain pressure in case of a leak.

The primary external difference between the cargo version of the Dragon and the crew version will be a pusher-type launch-abort system mounted in four pod-like bulges around the circumference of the capsule. They will be powered by four redundant pairs of SpaceX-designed SuperDraco hypergolic engines that have been test-fired to full thrust and duration, says Musk.

A mockup of the crewed Dragon has the abort-system pods mounted at 90-deg. intervals around the capsule (see photo, p. 47), but Musk says that is being redesigned with an asymmetric configuration to address heating concerns.

Crew seats are “pretty close to the flight design,” he says, with individually molded liners able to accommodate astronauts as tall as 6 ft. 6 in. While docking will be autonomous using the NASA system in development at Johnson Space Center, pilots in the seven-member crews will be able to take control in emergencies or for special-purpose maneuvers such as inspection flyarounds, says Musk.

Although some of the companies building the next generation of crew vehicles are experiencing difficulty obtaining components from a dwindling aerospace supply base in the small lots they require (see p. 44), Musk says his company's philosophy of building as much as possible in-house mitigates the problem. Workers are currently reconfiguring the factory floor for efficiency and to keep activities requiring cleanliness away from heavy machining and other dirty areas.

“As far as engines and primary structure go, raw metal comes in and engines and rockets come out,” Musk says. “We do have suppliers of smaller components, but all major subsystems are made at SpaceX. It's harder and more painful in the beginning, but it pays off long term.”