Late on Wednesday evening, the United Launch Alliance’s large Delta IV Heavy rocket returned within seconds of its lift off its launch pad in Florida. But once again the start was scrubbed.
After the missile automatically aborted at T-7 seconds, both the booster and the National Reconnaissance Office’s valuable payload were considered safe. Since the abort was triggered shortly before the rocket’s RS-68 main engines began to fire, the delay before the next attempt at launch can be less than a week.
“The terminal countdown sequencer rack encountered an unexpected condition prior to the engine starting sequence,” the company said about an hour after the scrubbing. “The TCSR, which controls the last 10 seconds of the countdown, has performed as intended and safely initiated a hold at T-7 seconds. The team is currently reviewing all data and will determine the way forward.”
The cancellation of the NROL-44 mission on Wednesday night, which occurs just six minutes to midnight in Florida, is just the latest setback in trying to get this mission off the launch pad.
While it’s not clear whether the main cause of the peeling was on board the rocket or with the ground systems, the United Launch Alliance had problems with the launch pad infrastructure of Space Launch Complex-37, which supports the Delta IV Heavy Booster.
That launch was scrubbed three times, which resulted in delays of more than a month due to problems with separate ground systems: a regulator delivering high pressure helium on board the missile; the launch pad’s swing arm retraction system, which retracts fuel lines and other connections from the missile just before liftoff; and a hydraulic leak in the Mobile Service Tower.
Ars reported 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 per year could contribute to these delays.
The Colorado-based launch company has already retired the single core Delta IV missile and plans to fly the Delta IV Heavy missile just four more times after the NROL-44 mission before retiring in favor of the lower-cost Vulcan Centaur booster goes. Only two of these four flights are operated from Space Launch Complex-37.
In response to a request about these pre-peel issues Wednesday night, Tory Bruno, head of the United Launch Alliance, told Ars, “The reduced Delta launch pace is certainly a factor. We will be in our readiness process for the remaining Delta IV Heavy missions in the correct order to avoid the kind of problems that arise here. “