WATCH: Vulcan rocket blast upsets ULA space travel plan

A rocket launch by United Launch Alliance (ULA) which was scheduled to lift off from the NASA launch facility on May 4 suddenly exploded while preparations for the flight jeopardised the plans of space travel.

The ULA rocket was under construction since 2014.

ULA Chief Executive Tory Bruno shared a video on his Twitter handle in which a closer look was taken into the explosion that marred the flight's first debut scheduled for next month.

Precisely informing his followers about the incident, he said: "[Hydrogen] accumulated inside the stand. Found an ignition source. Burned fast. Overpressure caved in our forward dome and damaged the rig."

The Colorado-based company was pressurising the upper stage of the Vulcan rocket when the explosion occurred. The massive fireball was produced after the spark ignited a significant accumulation of hydrogen fuel.

After the explosion, CO Burno wrote on Twitter that "This is why we thoroughly [and] rigorously exercise every possible condition on the ground before flight. The investigation is underway."

He also added: "Vulcan will fly when complete."

The company initially intended the launch Vulcan in 2020 which was delayed to 2022. Later on, it was decided that the rocket will be launched the next month. There had been also a four-year-late delivery of BE-4 engines by billionaire Jeff Bezos’ Blue Origin.

After the incident, it is not clear whether Vulcan can lift off as per the schedule.

According to CO Burno, ULA will get access to the first stage on Friday, recovering it for analysis.

He further said on Twitter: "Don't know yet whether the leak was in the test article [the rocket] or the test rig."

The 62-meter tall rocket will replace ULA's Atlas V and Delta IV rockets, used for the past two decades. The under-construction rocket is capable to lift 27.2 metric tons to low Earth orbit and 6.5 metric tons to geosynchronous orbit. SpaceX’s Falcon 9 has the capability to carry 22.8 metric tons to LEO.

Following ULA’s successful mission, it decided to another Vulcan launch this year for Sierra Space’s Dream Chaser mission.

In order to get clarification to launch US military and intelligence satellites for the Space Force, the Colorado-based company needs to conduct two Vulcan flights.

US Space Force has given the contract for the next five years to Burno’s company to deliver 35 missions to the force. Vulcan will also be launching more satellites for Amazon's Kuiper satellite project.

The launch of the rocket is crucial as it has to deliver payloads to space missions. The rocket is ready to deliver Astrobotic’s Peregrine lunar lander that will attempt to provide 11 payloads to the lunar lander on behalf of NASA. The rocket will also deliver the first two Amazon Kuiper internet satellites to low Earth orbit, which are owned by Blue Origin's Bezos.