United Launch Alliance (ULA) is now targeting Q4 of 2023 for the inaugural flight of Vulcan, its new family of rockets set to replace both Delta-IV Heavy and Atlas V launchers. During a media event held on July 13, 2023, Tory Bruno – ULA CEO and President – gave significant updates on the current testing status and anomalies of the past months.
Vulcan is the last iteration of ULA launchers. It features a dual Blue Origin BE-4 MethaLox engine configuration in the first stage, with the supplement of up to six Solid Rocket Boosters (SRBs) for enhanced thrust at liftoff. The second stage, Centaur V, is instead powered by two Aerojet Rocketdyne RL-10c HydroLox engines.
Centaur V Anomaly
On March 29, 2023, a Centaur V upper stage exploded while undergoing testing at NASA’s Marshal Space Flight Center. Specifically, it was the 15th test run for that article whit the aim of qualifying the structure.
Outside of the test rig/ stand. Test article is inside (you can’t see it). Hydrogen leak. H2 accumulated inside the rig. Found an ignition source. Burned fast. Over pressure caved in our forward dome and damaged the rig. pic.twitter.com/0d0KpI1ggj— Tory Bruno (@torybruno) April 13, 2023
In the space domain, when dealing with a satellite or rocket qualification process, engineers intentionally apply higher-than-expected loads on the system to validate its design process. In this specific case, Centaur was experiencing a mix of all possible mission scenarios for which it was developed.
The anomaly occurred halfway through the test; a hydrogen leak developed in the front part of the stage and continued for about four minutes until it found an ignition source. The resulting explosion and the fire that erupted afterward seriously damaged the testing facility and Centaut itself; the overpressure ruptured the LOx tank sitting below filled with nitrogen.
The analysis revealed that the leak started from a welding in the forward dome of the H2 tank. Corrective action includes the addition of stainless steel reinforcements near the leakage site; as Bruno said, this won’t significantly impact the rocket’s performance, with Centaur V version three already being updated.
BE-4 Failing Acceptance Test
Contrary to qualifications, acceptance tests are performed with lower loads on the model (inside the design criteria) and run for a lower duration. The aim is to exclude any human error in the system assembly.
On June 30, 2023, a BE-4 engine, scheduled to fly on Cert-2 mission, exploded 10s into the firing leading to the destruction of the stand and the engine itself. This was the second attempt at completing the acceptance for this particular unit; Blue Origin is already working on remedial actions.
This issue, however, shouldn’t affect Certification 2 Mission as the production of BE-4 is currently two engines per quarter, with the following one ready in six to eight weeks. Cert-2 is currently scheduled for no earlier than Q1 2024.
Before flying, Vulcan and Centaur V still need to pass a series of qualification runs. Certification 1 Mission is expected to fly in late 2023, carrying Astrobotic’s Peregrine lander to space. If everything goes well, the second Certification Mission is planned for a few months after and will launch Sierra Nevada Corporation’s Dream Chaser spacecraft.
With Cert-1 and Cert-2 on the books, Vulcan will start the National Security Space Launch manifest by delivering the USSF-106 satellite to geostationary orbit in late 2024.