Watch the Next SpaceX Falcon 9 Launch the CRS-17 Mission

Watch the Next SpaceX Falcon 9 Launch the CRS-17 Mission

The company has concluded, meanwhile, that the smaller, simpler cargo version of the Dragon capsule is safe to fly to the International Space Station.

The capsule is packed with 5,500 pounds research, crew supplies and hardware, on top of a Falcon 9 rocket.

The April 20 accident occurred at Cape Canaveral Air Force Station as SpaceX was about to test eight emergency thrusters created to propel the capsule, dubbed Crew Dragon, to safety from atop the rocket in the event of a launch failure. SpaceX confirmed for the first time since the incident that the "anomaly" did, in fact, cause an explosion in which the capsule was destroyed completely. SpaceX coverage begins about 15 minutes prior to liftoff at 1:30 a.m CDT.

"We have no reason to believe there is an issue with the SuperDracos themselves, those have been through about 600 tests", Koenigsmann said, adding that "it is too early to confirm any cause".

On 20 April, SpaceX was performing tests on its new reusable astronaut taxi, Crew Dragon, in Cape Canaveral, Floridaahead of its launch which is scheduled to take place later in the year.

Because the April 20 accident occurred so close to SpaceX's landing site at Cape Canaveral Air Force Station, the booster for the cargo launch can not return there following liftoff.

But just as SpaceX was activating the SuperDraco thrusters, which are used for emergencies to push the capsule away from the rocket, something went wrong.

The SuperDraco thrusters are created to let the Dragon spacecraft land with pinpoint accuracy.

Meanwhile, Boeing's Starliner is also gearing up for test flights this year, and the two private commercial space companies are competing to win large NASA contracts to ferry as many as four astronauts into space at a time.

"We have no reason to believe there is an issue with the SuperDracos themselves", Koenigsmann said, adding that the engines have been tested almost 600 times in the past. "That said, we're looking at all possible issues and the investigation is ongoing".

The cargo Dragon does not feature a Super Draco abort system and NASA managers agreed with SpaceX engineers that the launching could proceed.

Today's delay is the latest in a series of slips that saw the launch move from April 26 to (now) May 4.

The next chance to launch the capsule is Saturday at 2:48 a.m. ET and there's about a 70% chance of favorable weather.