NASA believes its previous and upcoming commercial cargo missions to the International Space Station give Space Exploration Technologies Inc. (SpaceX) the best chance of transporting a human crew to the space station first, but the brash startup is not a sure bet to win the commercial crew race.

While company founder Elon Musk says he will fly a crew to the station before the end of 2015—earlier than any of his competitors—his main NASA customer is a little more cautious.

“There are some systems that are acceptable in cargo that may not be acceptable in crew,” says William Gerstenmaier, associate administrator for human exploration and operations. “There's obviously a lot of stuff that needs to be added in terms of life support; there's some cooling that needs to be there, humidity control, atmosphere monitors. There are a lot of other little subtle things that have to be there. So they've got the good basic capsule design, but I think there's still a little bit of work for them to do in those other areas.”

Still, in his formal source-selection document, Gerstenmaier found that the SpaceX proposal for the Commercial Crew Integrated Capability (CCiCap) program “provides the earliest crewed demonstration flight under a credible schedule at the lowest development cost.” On that basis, NASA awarded the Hawthorne, Calif., company $440 million in federal seed money to continue work on the crew version of the Dragon capsule that reached the ISS in May, and is scheduled for at least one more return trip before the end of this year (AW&ST May 28, p. 35).

“I think there are advantages of having flown cargo, but then there's a statement in the document where I caution that we need to know how they're going to transition from cargo to crew,” says Gerstenmaier.

That will not be too big a problem, Musk says with typical bravado. A lot of the work has been done, he says, and the rest can be completed within the time constraints laid out in the company proposal.

“We actually already have much of the [environmental control and life support] system working, even for cargo missions, because we are required to take biological cargo to and from the space station,” Musk says of the $1.6 billion commercial resupply services NASA contract his company entered after demonstrating Dragon's ability to dock with the ISS. “And some of the experiments actually have very tight temperature requirements, so we have very good thermal control of the Dragon interior. It's accurate to within about 1C.”

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.”