ULA Prepares Vulcan For 1st Mission

While the Vulcan has not yet been approved for US National Security launches, and the investigation into the solid rocket booster failure isn't complete, United Launch Alliance has continued preparations for the first such launch "before the end of the year."  A bit optimistic but, the first rocket assembly milestone, "Launch Vehicle On Stand," took place Monday at Cape Canaveral Space Force Station in Florida.  

The first stage of ULA's third Vulcan rocket sports a different paint scheme than the first two missions, with solid red replacing a red flame pattern. Image credit: United Launch Alliance

Space Force officials say they expect to issue the approval without requiring another test mission.  The Vulcan has flown two certification missions, with the first in January and second at the start of October. The Cert-1 (first) mission was essentially flawless, while the second had an anomaly on one of the two strap-on Solid Rocket Boosters, with what appeared to be large sections of the engine's bell breaking off.

The rocket's twin BE-4 main engines, made by Blue Origin, corrected for the asymmetric thrust from the two strap-on boosters. Vulcan's Centaur V upper stage also fired its engines longer than planned to make up for the shortfall in performance from the damaged strap-on solid motor. Ultimately, the rocket reached its planned trajectory and delivered a dummy payload into interplanetary space.

Col. James Horne, who oversees launch execution for Space Systems Command, called the test flight a "successful launch" in an interview with Ars. The nozzle failure caused a "significant loss of thrust" from the damaged booster, he said.

The Vulcan rocket's ability to overcome the dramatic nozzle failure, which was easily visible in video of the launch, "really demonstrated the robustness of the total Vulcan system," Horne said.

Horne went on to note that he thought it might have been, "...probably one of the most accurate orbital insertions that I've seen them fly yet." Since the certification depends on them placing the payload in the claimed orbit, "one of the most accurate orbital insertions" is optimum. Horne considers the mission successful. 

As a side note, any control system designer will tell you there is a range of errors that can be adjusted out and systems typically have a point at which they lose control ("lose lock"). I think that it could be argued that this mission might have had a lot of spare ability in the corrections it could apply that won't always be there.  On a bigger payload with a bigger error injected by the SRB, it might lead to mission failure. The fact that Vulcan's systems corrected the SRB issue shouldn't mean they let the whole thing be forgotten about.

Investigation into the SRB problem is paramount.  

“I think, when folks zoom in on the video, they see thrust, hot gas burn-through, potentially, in the bottom of the rocket section," Horne said.

Tory Bruno, ULA's chief executive, posted on X shortly after the October 4 launch that initial findings suggested the rocket casing itself did not suffer a burn-through, which would allow super-hot gas to escape the booster. However, there were visual indications of a plume of hot exhaust appearing just above the bell-shaped nozzle, possibly near where it was bolted onto the booster's main body.
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Horne said the Space Force is "assessing schedule impacts" to the next couple of Vulcan launches as engineers probe the booster malfunction. Military officials hoped to launch the first two national security missions on the Vulcan rocket by the end of this year. That's still the hope, Horne said, but he expects there will be "some impact" on the schedule for the next two Space Force missions, named USSF-106 and USSF-87.

The Vulcans that will be used for those next two launches will have four of those strap-on SRBs instead of the two the Cert-2 flight had. Does that double the chance of the kind of SRB nozzle failure seen on Cert-2?

Don't forget that ULA has a backlog of these National Security Missions.  Under existing contract, they're to launch a little more than half of the military's national security space missions over the next few years, (SpaceX is booked for the rest of the missions).  In the contract talked about two days ago, SpaceX won all the missions.

Tory Bruno has said they're targeting 25 launches a year but it may take a couple of years to get there. Next year, they're speculating "up to 20 launches," including the Vulcan and using up the last of the Atlas V missions.