The SpaceX Falcon 9 rocket with the manned Crew Dragon spacecraft on launch pad 39A.
After a day of suspense, SpaceX's landmark launch to the International Space Station -- the first crewed mission to blast off from US soil in almost a decade -- was scrubbed Wednesday due to fears of a lightning strike.
With NASA astronauts Bob Behnken and Doug Hurley strapped into the Crew Dragon capsule, the launch pad platform retracted and rocket fueling underway, SpaceX made the call to abort.
"Unfortunately, we are not going to launch today," launch director Mike Taylor said, with about 17 minutes to go until takeoff.
"We had just simply too much electricity in the atmosphere," NASA chief Jim Bridenstine said later.
"There wasn't really a lightning storm or anything like that, but there was a concern that if we did launch it could actually trigger lightning," he added.
This was the case for the Apollo 12 mission, which was struck twice shortly after launch -- losing the use of some non-essential instruments but completing its mission nonetheless.
A rocket and its plume ascending through clouds act as conductors and can trigger lightning at lower levels of atmospheric electricity than what is required for natural lighting.
The delay means a wait of at least a few more days for the first crewed launch on an American rocket since the space shuttle program ended in 2011. They will try again on Saturday.
If successful, the launch will be the first time the feat has been performed by a privately owned company.
A live video feed showed Behnken and Hurley -- in their futuristic white uniforms adorned with the US flag and the logos of NASA and SpaceX -- waiting as propellant was unloaded from the reusable Falcon 9 rocket after the launch was postponed.
The emergency ejection system remained armed until the fuel tanks were emptied, in case of an accidental explosion.
The launch had been scheduled for 4:33 pm (2033 GMT) from the Kennedy Space Center's Launch Pad 39A. Neil Armstrong and his Apollo 11 crewmates lifted off from the same spot on their historic journey to the Moon.
SpaceX win over Boeing
Founded in 2002, Space Exploration Technologies Corp. has torn up the rules to produce a lower-cost alternative to human spaceflight that has gradually won over skeptics.
The project has experienced delays, explosions, and parachute problems -- but even so, SpaceX has beaten aerospace giant Boeing to the punch.
Boeing's NASA entry, the Starliner, is still not ready.
Ending dependence on Russia
A decade on, it was Trump who was present for the launch.
The Republican is trying to reaffirm American domination of space, militarily but also by ordering a return to the Moon in 2024.
NASA hopes to entrust "low Earth orbit" space travel to the private sector in order to free up dollars for its more distant missions.
Crew Dragon is a capsule like Apollo, but updated for the 21st century. Touch screens have replaced switches. The interior has more subtle lighting.
It looks entirely different from the huge winged space shuttles that carried astronauts into space from US soil from 1981 to 2011.
When the mission eventually goes ahead, Crew Dragon will catch up with the space station, and will probably remain docked there until August.
'I'm so excited that we finally get to share what we have been working on for the past year!' the 29 year-old Bouman said.
NASA have made it clear they want astronauts back on the Moon in 2024, and now, they are zeroing in on the Red Planet -- the US space agency confirmed that it wants humans to reach Mars by 2033.
NASA's Mars Helicopter has successfully completed a series of tests and is ready to take flight over the Red Planet, the US space agency said. "The next time we fly, we fly on Mars," MiMi Aung, Project Manager for Mars Helicopter at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement.
Talks with North Korea should not be for political show but contribute to establishing peace, South Korean President Yoon Suk-yeol said on Wednesday, just hours after the North test fired two cruise missiles into the sea.
For the Aug. 29 mission, called Artemis 1, the Orion capsule will launch atop the Space Launch System without any humans and orbit the moon before returning to Earth for an ocean splashdown 42 days later.
Noeleen Heyzer's visit to the crisis-wracked country, which began on Tuesday, "will focus on addressing the deteriorating situation and immediate concerns as well as other priority areas of her mandate," the UN has said.