Orbital Sciences, one of two firms hired by NASA to ferry cargo to the International Space Station, has been trying since December to get its first operational mission off the ground.

First, the company stood down while NASA dispatched spacewalking astronauts to repair the station’s cooling system. This week, it was the record cold weather that prompted a delay, followed by perhaps the most unusual reason ever for a scrub: a massive solar flare.

ANALYSIS: Solar Boom: Sun Blasts X-Class Flare Right At Us

“We concerned about mission failure,”  Antonio Elias, Orbital Sciences chief technical officer, told reporters.

The issue is whether the charged-up radioactive space environment could mess with the rocket’s gyroscopes, avionics or other systems. The flare erupted 24 hours before the scheduled 1:32 p.m. EST liftoff of Orbital’s Antares rocket from a commercial spaceport on Wallops Island, Virginia.

The company may try again on Thursday.