Boeing is making progress on the CST-100 capsule, intended to fly astronauts to the International Space Station.
"Our next milestone we've got planned is in July, for the orbital manoeuvring and control engine developed by Rocketdyne," says John Mulholland, Boeing's programme manager. "We've already done some early demonstration tests of that, this would be the final demonstration before their critical design review, which is later in the fall."
In addition to orbital manoeuvres, the engines will be used for emergency aborts during ascent aboard the Atlas V launch vehicle, and retrofiring to slow the capsule from orbital velocity to initial re-entry speed.
Ground operations tests are also ongoing. Tests have been conducted to ensure good communications in all phases of flight, with satisfactory results.
"We've got two critical milestones coming up focused on that. The first will be mission control center interface testing," says Mulholland. A pilot-in-the-loop test is expected in the near future.
"In December this year we'll have a full demonstration of the integrated software system, leading up to the critical design review (CDR) in March, all in support of the integrated system [CDR] in April."
NASA has scheduled the first operational resupply mission to the International Space Station in 2017, though the agency is likely to cull at least one of the three companies currently funded - Boeing, Sierra Nevada and SpaceX - to save money.