The flight of the Falcon 9 has once more been rescheduled, with a new launch date of 19 May, as Elon Musk's SpaceX decided to tweak the software one more time.
The first commercial craft to restock the International Space Station, a Dragon capsule strapped to a Falcon 9 rocket, has seen more than its fair share of push-backs for the test flight, but it will all pay off if the cargo ship can dock with the station.
SpaceX has already shown it can release and retrieve the Dragon, but getting it to motor alongside the fast-moving ISS and accurately berth with it is no mean feat and the firm has tested and retested the necessary software in the hopes it won't end up with egg on its face.
The commercial space company has a multimillion-dollar contract with NASA to replace the Shuttle as America's cargo-runner for the ISS. So far, SpaceX has gotten $381m out of the Commercial Orbital Transportation Services (COTS) agreement for hitting 37 out of 40 milestones, and that will hit $396m if the private space firm gets all the way.
Providing this test flight is successful, the Dragon will start to fulfil the contract for a minimum of 12 flights to resupply the ISS. Since the ship is reusable, it will be the only spacecraft capable of bringing cargo back with it as well. And, ultimately, SpaceX hopes that a version of the Dragon will be its first manned spaceship as well.
However, the company has been careful to keep expectations low, constantly emphasising that this is a test flight as well as only the third blastoff for the Falcon 9 and the second flight of the Dragon.
This mission was originally only supposed to be a launch and orbit test, so attempting to connect with the ISS is actually ahead of schedule. If it doesn't happen this time, SpaceX and NASA have both said they'll figure out why and make sure the rendezvous happens on the next demonstration flight.
The launch is set for Saturday, 19 May at 8.55 GMT, with coverage starting on NASA TV at 7.30 GMT. ®