The private space company has had problems with its human habitation Crew Dragon capsule, with one exploding on a test stand at a Florida Air Force station moments before firing thrusters in April. Monday’s comments were a fresh sign the scheduled human launch milestone could slip into 2020. “I’m pretty optimistic at this point in time because we have a good path forward,” Hans Koenigsmann, SpaceX’s vice president of Build & Flight Reliability told reporters on a conference call as the company provided fresh details from the investigation.
“But like I said, still not quite done.”
Mr Koenigsmann added: “My emphasis is really on making sure this is safe by the end of this year, I don’t think it’s impossible, but it’s getting increasingly difficult.”
SpaceX are currently investigating the possible cause of a fiery explosion in April that destroyed one of the capsules that will ferry astronauts into space.
Crew Dragon was slated earlier this year to carry US astronauts to the International Space Station (ISS) in a first manned test mission in July, although that date slipped until November following the explosion and some other hitches in the vehicle’s design.
SpaceX said its accident investigation was pointing to a leaky valve as the likely cause of the April explosion.
NASA is paying SpaceX $2.6billion (£2.08billion) and Boeing Co $4.2billion (£3.36billion) to build rocket and capsule launch systems to return astronauts to the International Space Station from US soil for the first time since America’s Space Shuttle program went dark in 2011.
Mr Koenigsmann, who sits on an investigative board convened by SpaceX just after the April explosion, said the probe is nearing completion and that the space company will need to make some changes to Crew Dragon’s design before it can be trusted to send humans to space.
SpaceX said evidence shows that a leaking check valve allowed nitrogen tetroxide (NTO) to enter high-pressure helium tubes during the April test.
SpaceX said on its website: “The failure of the titanium component in a high-pressure NTO environment was sufficient to cause ignition of the check valve and led to an explosion.”
Steps were being taken to reduce such risks within the launch escape system, the company said.
This includes replacing check valves, which typically allow liquid to flow in only one direction.
These valves employ burst disks that seal completely until opened by high pressure.