United Launch Alliance (ULA) says despite recent anomalies involving their Centaur V upper stage and the BE-4 engines built by Blue Origin, Vulcan should still fly this yr, although behind schedule.
Vulcan is ULA’s successor to the Atlas V and Delta IV heavy-lift rocket families, each of that are scheduled to be retired. The brand new vehicle uses liquid natural gas and liquid oxygen in its first stage, which is powered by two BE-4 engines. The upper stage, meanwhile, uses liquid hydrogen and liquid oxygen to propel satellites to their deployment orbits.
Centaur Anomaly
Tory Bruno, the CEO of ULA, says all components of the corporate’s next-generation Vulcan rocket have been certified for flight apart from the upper stage, often called Centaur V. The corporate currently uses an upper stage with an identical name, Centaur III, which is flown on Atlas V.
The major difference between the 2 is the dimensions, during which Centaur V is sort of double the dimensions of its predecessor.
During a propellant loading and tank pressurization test at NASA’s Marshall Space Flight Center on March 29, 2023, a test article of the Centaur V upper stage was destroyed after a hydrogen leak ignited. Until this point, the primary launch was scheduled for May 4 from the Cape Canaveral Space Force Station in Florida, carrying the private Peregrine lunar lander and two prototype Amazon Kuiper satellites.
Outside of the test rig/ stand. Test article is inside (you may’t see it). Hydrogen leak. H2 gathered contained in 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
More recently, following testing on the launch pad, the Centaur upper stage that was attached to and able to fly aboard the inaugural Vulcan launch has been sent back to the corporate’s manufacturing facility in Decatur, Alabama following the explosion.
In a teleconference on July 13, Bruno outlined what went flawed with the Centaur test in March. Throughout the fifteenth test of the stage, he explained that a leak formed near the highest of the tank dome, releasing hydrogen for 4 and a half minutes into an enclosed space. Bruno says it then found an ignition source, causing a big fireball.
Bruno noted the region where the crack formed is in an area near a door toward the highest of the stage, noting it has a singular shape.
“We’d expect to have a certain load profile across that dome, but right in that narrow region, the hundreds went way up for this reason complicated geometry,” Bruno said.
The answer involves adding an additional stainless-steel ring to assist strengthen that specific area. It is going to, nevertheless, add an extra 136 kilogram (300 lbs) of mass to the stage.
In consequence, the Centaur originally scheduled to fly on Vulcan’s third flight — currently on the factory in Alabama — will probably be modified with this recent ring and can now launch on the rocket’s inaugural flight. The stage that was sent back from the Cape will then be retrofitted with this fix and fly in the longer term. Finally, the Centaur set to fly on the second flight will now be used on the test stand to finish the certification needed for Vulcan to fly by the fourth quarter of this yr, Bruno said.
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/07/49720321573_d864ee3187_o-scaled.jpg)
The Centaur V (right), which can fly on Vulcan, in comparison with the currently-used Centaur III (left). (Credit: ULA)
The welding procedure used to construct Centaur V may even change. Up to now, these recent upper stages have been built using automated laser arc welding. SpaceX’s Starship also employs this welding technique.
Nonetheless, following the leak, Bruno says the welds weren’t as strong as they were expecting — the truth is their effort to avoid wasting time with this recent construct technique actually takes longer.
“These seams are 12 feet long, and the time that we were saving with the faster speed on this welder was actually greater than offset by the point it has been taking to establish the panels on the fixture before the robot is available in,” Bruno explained.
As a substitute, the corporate will revert back to the strategy used on Centaur III called gas tungsten arc welding. Bruno says it’s a wider weld which might be more forgiving, regardless that it is finished manually.
BE-4 Engine Anomaly
The CEO also addressed a recent explosion involving the first-stage BE-4 engines. During a test firing on June 30, Bruno confirmed considered one of the engines exploded at a Blue Origin testing site in West Texas.
Throughout the fifteenth acceptance test procedure (ATP), the engine being tested — which had previously failed an earlier ATP
– experienced a burn-through. While conducting tests, waiting to liftoff on the pad, and in the course of the flight, computers monitor all instrumentation to see in the event that they exceed a “red line limit.” This limit is a set mark where if any of their vehicle constraints go over that red line number, either an abort is named on the bottom or a command to shut down an engine occur mid-flight.
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/07/50947042873_151856616b_k.jpg)
Two BE-4 engines are seen at the bottom of the Vulcan vehicle that may fly the primary certification flight. (Credit: ULA)
Bruno admitted that the red line limit was set barely too high, leading to an explosion while the engine was attempting to shut itself down. The edge will probably be lowered on all future missions and tests.
Bruno emphasized failures like these are a part of the method, claiming to have seen similar test failures on engines currently in service reminiscent of the RL-10 and RD-180.
“The 2 engines on flight one have passed this test, as have a dozen BE-4 rocket engines, all of which have been hot fired and in total have gathered over 26,000 seconds of operation,” Bruno said. “We’re very confident within the design and the workmanship of the assets which have passed acceptance. This isn’t unexpected. It won’t be the last. And there will probably be other components on the rocket that also fail acceptance testing.”
STATIC FIRE! Vulcan conducts its first ignition of its BE-4 engines in the course of the Flight Readiness Firing (Cert-1).https://t.co/6FHkldnYri pic.twitter.com/SpZAWLgl0T
— Chris Bergin – NSF (@NASASpaceflight) June 8, 2023
A test of the vehicle often called the Flight Readiness Firing was accomplished successfully on June 7, which saw the primary stage ignite and fire its two BE-4 engines at flight power for about seven seconds. Bruno says those are among the many engines that passed their ATP.
The Path Forward
Based on Bruno, the primary certification flight of Vulcan will occur in either the late third or early fourth quarter of this yr, but no specific date was given. Full vehicle certification is anticipated to be accomplished in the primary quarter of 2024. The corporate expects to have the opportunity to fly military payloads later in that very same yr as a part of the US Space Force’s National Security Space Launch program.