Isaacman said he understood “that people are disappointed by this development”, after almost 50-hours of checks on Thursday revealed no faults.
The agency felt almost certain that its “wet rehearsal” had been a success, leading the team to announce that the launch could take place as soon as 6 March.
But overnight on Friday, engineers observed an interruption in the flow of helium required for launch operations.
Disruption to helium, which is used to pressurise fuel tanks and cool rocket systems, is treated as a serious technical issue, according to Nasa.
The test was the scientists’ second attempt at a practice run at the Kennedy Space Center in Florida, having fixed earlier issues with filters and seals that had led to hydrogen leaks.
The rocket was fuelled with around 730,000 gallons of propellant over several hours on Thursday, with the team stating that the simulation felt like “a big step in us earning our right to fly”.
But space missions are often fraught with setbacks, Isaaman said, highlighting that Neil Armstrong’s 1966 Gemini 8 mission ended prematurely due to a technical issue, before his historic moon landing three years later.
Three US astronauts, Reid Wiseman, Victor Glover and Christina Koch, and Canadian astronaut, Jeremy Hanse, are due to take off in the mega Moon rocket, which will allow them several hours to study the moon’s surface up close.
It is hoped that the mission, if successful, will pave the way for Artemis III, which will see astronauts set foot on the Moon for the first time since 1972.
Nasa says the landing will happen by 2028, but accepted this could be an ambitious time frame.
