“The reduced Delta launch tempo is certainly a factor.”

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• The Mobile Service Tower rolls back from the United Launch Alliance Delta IV Heavy rocket carrying the NROL-44 mission on Wednesday, September 30.
• The Delta IV Heavy rocket is seen on the launch pad Wednesday night during the webcast at 1 minute, 33 seconds before planned liftoff.
• The rocket, shown with a flare stack.
• Starting to get hot at the business end of the rocket at T-10 seconds.
• At T-7 seconds the starboard engine ignites, to be followed by the center and port engines at T-5 seconds. In this case, the abort was triggered just before ignition.
• So the engines didn’t fully ignite.
• And so the engines slowly …
• And then, so did the webcast.

Late on Wednesday night, United Launch Alliance’s large Delta IV Heavy rocket again came within seconds of lifting off from its Florida launch pad. But once again, the launch was scrubbed.
Following the automated abort of the rocket at T-7 seconds, both the booster and its valuable National Reconnaissance Office payload were said to be safe. Because the abort was triggered just before the rocket’s main RS-68 engines had begun to ignite, the delay before the next launch attempt may be less than a week.
“The terminal countdown sequencer rack identified an unexpected condition prior to the engine start sequence,” the company stated about an hour after the scrub. “The TCSR, which controls the final 10 seconds of the countdown, performed as intended and safely initiated a hold at T-7 seconds. The team is currently reviewing all data and will determine the path forward.”
Wednesday night’s abort of the NROL-44 mission, coming just six minutes before midnight in Florida, is just the latest setback in the attempt to get this mission off the launch pad.
Although it is not clear whether the scrub’s root cause lay on board the rocket or with the ground systems, United Launch Alliance has been having difficulties with the launch pad infrastructure at Space Launch Complex-37, which supports the Delta IV Heavy booster.
This launch has been scrubbed three times, leading to more than a month’s worth of delays, due to separate ground systems issues: a regulator that delivers high-pressure helium on board the rocket; the launch pad’s swing arm retraction system, which pulls back fuel lines and other connections from the rocket just before liftoff; and a hydraulic leak in the Mobile Service Tower.
Ars reported on Wednesday that a combination of aging infrastructure at the launch pad, which is now nearly 20 years old, and a relatively low flight rate of about one Delta IV mission a year may be contributing to these delays.
The Colorado-based launch company has already retired the single-core Delta IV rocket and plans to fly the Delta IV Heavy rocket just four more times after the NROL-44 mission before its retirement in favor of the more cost-effective Vulcan-Centaur booster. Only two of those four flights will take place from Space Launch Complex-37.
In response to an inquiry about these issues before Wednesday night’s scrub, United Launch Alliance chief Tory Bruno told Ars, “The reduced Delta launch tempo is certainly a factor. We will be changing our operations readiness process for the remaining Delta IV Heavy missions in order to avoid the type of issues seen here.”