Atlas rocket launch delayed by pad hydrogen leak

Launch of a United Launch Alliance Atlas 5 rocket carrying a DigitalGlobe high-resolution commercial surveillance satellite was scrubbed Friday because of a “very small” hydrogen leak in a ground system that caused an unusual “ice ball” to develop on an umbilical.

ULA rescheduled launch the WorldView-4 satellite from complex 3 at Vandenberg Air Force Base northwest of Los Angeles for Sunday at 2:30 p.m. EDT (GMT-4; 11:30 a.m. local time).

The countdown had just entered a planned 30-minute hold at the T-minus 4-minute mark Friday when ULA CEO Tory Bruno tweeted the launch would be delayed. The announcement followed the apparent resolution of an earlier problem that delayed the start of liquid hydrogen loading.

“Scrub,” Bruno tweeted. “Very small ground side LH2 (liquid hydrogen) leak. Forming an ice ball on the umbilical. Outside our history. Standing down attempt today to resolve.” He then added: “Always better to be on the ground, wishing you were in the air than the other way around.”