Contractors under NASA's commercial crew development (CCDev) programme have completed a number of technical milestones marking significant progress towards access to the International Space Station (ISS) and low Earth orbit (LEO).
The series of announcements also pave the way for a third round of grants, called commercial crew integrated capability (CCiCap).
SpaceX has completed the design phase of the crewed Dragon capsule, which will be launched atop the company's Falcon 9 launch vehicle. An uncrewed version of the capsule has already been selected to deliver cargo to the International Space Station (ISS). In May, the Dragon capsule became the first private vehicle to dock with the ISS.
SpaceX has a single remaining milestone under the CCDev agreement. The company was unable to respond to questions by press time.
Sierra Nevada has completed tests on the nose gear of its orbital vehicle, the Dream Chaser, in advance of drop tests, to include approach and landing, at Edwards AFB, California.
"The landing gear system must perform flawlessly, just like the space shuttle orbiter's did, for the safe return of the crew" says Ed Mango, NASA's commercial crew programme manager.
Sierra Nevada declined to comment on upcoming flight tests, saying the company was waiting for the CCiCap announcement before elaborating on the programme.
Fellow awardees Boeing and Blue Origin were unavailable for comment by press time, but count few remaining items on their milestone lists. All milestones were initially planned for completion in mid-to-late 2012, and all companies have more or less remained on schedule.
ATK announced completing all milestones under its unfunded CCDev award, involving designs and plans for the company's Liberty launch vehicle, as did Excalibur Almaz for its former Soviet equipment.
Many of the companies have entered bids for the CCiCap awards, the outcome of which is scheduled to be announced in late July or early August.
Most companies are adopting a wait-and-see approach to their programmes, leaving open the possibility of cancellation or slowdown should CCiCap awards not go as hoped. With only two full awards and one partial award possible, companies are anxious to see who will be cut from the competition.