WASHINGTON — United Launch Alliance expects to conduct a static-fire test of its Vulcan Centaur rocket in several days, but the timing of the vehicle’s first launch will depend on the outcome of an ongoing investigation of a test anomaly.

ULA rolled the Vulcan rocket from the pad at Space Launch Complex 41 at Cape Canaveral, Florida, back to its Vertical Integration Facility (VIF) building on May 15. The vehicle had been on the pad for several days to conduct a tanking test and practice countdown.

Tory Bruno, president and chief executive of ULA, said in a May 15 tweet that the company needed to “adjust a handful of parameters and set points” for the vehicle before performing what the company calls the Flight Readiness Firing (FRF), a static-fire test of the booster’s BE-4 engines on the pad. That work would be done while the rocket is back in the VIF.

In a May 16 interview after a speech at the Humans to Mars Summit here, Bruno said that work involved a combination of minor adjustments to both pad infrastructure and the vehicle. The former includes adjusting set points in a hydraulics system and changing the rate of liquid oxygen flowing into the rocket to top off tanks after recycling the countdown. Those adjustments, he said, could be done in software.

On the booster, he said there was an issue during the pad tests with flowing gas through spark torch igniters used to ignite the BE-4 engines. The gas is intended to make sure that the igniters are dry and can light, but the timing was off. That could involve some combination of adjustments on the rocket and ground infrastructure.

“There’s nothing wrong with the engines,” he added. “We’ve lit the engines a zillion times on the test stand at Blue,” a reference to test stands by engine manufacturer Blue Origin.

That work is done more easily inside the VIF, he said, where there is protection from the weather and where work can continue when other range operations might cause a halt to work on the pad.

Once those fixes are complete, Bruno said the vehicle will roll back out to the pad for the FRF. “It’ll be a few days,” he said of the timing of the test, which will depend on both when the work is complete and getting approval from the range for test, which is required since it is considered an “energetic” event.

Assuming there are no problems with that firing, the last major obstacle before launch is completing an investigation into a March 29 incident during testing of the Centaur upper stage. Hydrogen leaked from the structural test article and ignited, creating a fireball.

Bruno said the investigation was delayed because it took time to remove equipment on top of the Centaur, such as a payload adapter and mass simulators for the payload and payload fairing. Only in the last week and a half was ULA able to get access to the dome section of the Centaur where the leak was located.

Engineers have isolated a small region on that dome where they believe the leak came from, as well as the likely ignition source. “I’m pretty confident that we’re going to find the leak, and once we find the leak we’ll know if we have to take corrective action or not on the flight vehicle,” he said.

If ULA doesn’t need to modify the Centaur, that would allow the Cert-1 launch to take place in early summer, he said. “If we do, it could take longer, but I don’t expect it to get out of the year.”

Complicating launch scheduling is the requirement for the primary payload, the Peregrine lunar lander from Astrobotic, which has a launch window that is open only for about four to five days per month. Before the Centaur test anomaly, ULA had been working towards a May 4 launch, which Bruno said in February was the start of a window about four days long.

“In the big picture, it’s a steel pressure vessel and it had a leak,” he said. “We’re going to understand it and we’re going to fix it. It’s not like other things that go wrong on rockets like engines that blow up. It’s just a piece of structure. We’ll fix it.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...