Last-minute technical problem delays NASA’s flight to sun

CAPE CANAVERAL, Fla. (AP) — A last-minute technical problem Saturday delayed NASA's unprecedented flight to the sun.

The early morning launch countdown was halted with just one-minute, 55 seconds remaining, keeping the Delta IV rocket on its pad with the Parker Solar Probe.

The probe was expected to launch early Saturday morning but was delayed twice, once at 3:53 a.m. and again at 4:28 a.m., during the 65-minute launch window that began at 3:33 a.m. ET. It was then scrubbed by NASA and the teams will attempt a launch on Sunday morning. If the teams investigate the issues that delayed Saturday's launch and it can't be resolved in time for a 24-hour turnaround, the next attempt won't happen until Monday.

But if all goes according to plan, the probe will launch at 3:31 a.m. ET Sunday from Cape Canaveral, Florida, on a United Launch Alliance Delta IV Heavy rocket, one of the world's most powerful rockets.

If the probe doesn't launch on Sunday, the window for a successful launch doesn't close until August 23.

Rocket maker United Launch Alliance said it would try again Sunday, provided the helium-pressure issue can be resolved quickly. As soon as the red pressure alarm for the gaseous helium system went off, a launch controller ordered, "Hold, hold, hold."

Once on its way, the Parker probe will venture closer to our star than any other spacecraft. The $1.5 billion mission is already a week late because of rocket issues. Saturday's launch attempt encountered a series of snags; in the end, controllers ran out of time.

Thousands of spectators gathered in the middle of the night to witness the launch, including the University of Chicago astrophysicist for whom the spacecraft is named. Eugene Parker predicted the existence of solar wind 60 years ago. He's now 91 and eager to see the solar probe soar. He plans to stick around at least another few days.