Why NASA’s Solar Probe launch was stalled

[dropcap]T[/dropcap]he launch controller shouted “hold, hold, hold” with just one minute, 55 seconds remaining for NASA’s Parker Solar Probe to lift off. Reason was the red pressure alarm for the gaseous helium system had gone off.

Rocket maker United Launch Alliance said it would try again on Sunday, provided the helium-pressure issue can be resolved quickly.

Engineers are taking utmost caution with the $1.5 billion Parker Solar Probe, which Thomas Zurbuchen, head of NASA’s science mission directorate, described as one of the agency’s most “strategically important missions.”

NASA wrote on its Twitter page that the launch was postponed from 3:33 am ET to 4:38 am ET. It later updated that the launch was “scrubbed” and a second attempt will be made on Sunday morning.

Thousands of spectators gathered in the middle of the night to witness the launch.

(With inputs from agencies)