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Forum:Commercial Space - Military Space
Topic:%5BDiscuss%5D ULA Vulcan Certification-2 flight test
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Robert PearlmanFrom United Launch Alliance (ULA):
To recap, the United launch Alliance rocket departed Space Launch Complex-41 at 7:25 a.m. EDT.

The countdown started at 7:40 p.m. EDT under the guidance of ULA Launch Conductor Dillon Rice. The pad crew completed final preps at the complex and then cleared the area for fueling. The "go" for cryogenic tanking was given at 12:28 a.m. Tanking operations were successfully performed as a million pounds of cryogenic propellants were placed into the rocket.

At T+plus 2 minutes, 14 seconds, both solid rocket boosters jettisoned as planned.

At T+plus 5 minutes, 30 seconds, staging, ignition of the Centaur V upper stage and payload fairing jettison was confirmed.

At T+plus 16 minutes, 15 seconds, the first main engine cutoff, or MECO-1, was confirmed for the Centaur V upper stage. The Vulcan rocket reached a preliminary Earth orbit where it coasted above the globe until the next burn.

At T+plus 31 minutes, 10 seconds, the Centaur V's two RL10C-1-1A engines ignited again to climb from its initial parking orbit into an Earth-departure trajectory.

At T+plus 35 minutes, 3 seconds, the second main engine cutoff, or MECO-2, was confirmed for Centaur V, for a course into deep space where the upper stage and non-deployable inert payload will orbit the sun for the rest of time.

olyIt appears one of the solid boosters experienced an issue. It seems that a large amount of debris was shed from the booster during operation.
BlackarrowThat ULA statement seems to have been very carefully contrived, indicating that "...at T+2m14s both SRBs jettisoned as planned."

It's obviously true that they jettisoned, and the action of SRB jettison was obviously planned, but was it really the case that SRB jettison was planned to be at T+2m 14s? According to the clock on the video, I suggest that jettison was actually at T+2m 10s which makes the ULA statement seem oddly imprecise for the world of "rocket science."

But a more important point arises from a comparison between the first Vulcan certification flight and this second test. During both tests, the SRB "burnout" calls were at the same time (T+1m 27s). On Cert. 1, the boosters visibly separated at T+ 1m 50s. It's reasonable to ask why SRB jettison took place a full 20 seconds later on Cert. 2 compared with Cert. 1.

Is SRB jettison automatic, or can it be delayed manually (and if so, why)?

It is also pretty obvious, comparing both launches, that one of the Cert. 2 SRBs had a problem. The SRB plumes were definitely asymmetric, and sparks and debris were seen. Could the SRB exhaust nozzle have fractured or melted through?

GACspaceguyI saw this SRB anomaly and noticed the asymmetric plume. Also, the commentator announced SRB sep should be occurring but it was noticeably delayed. An indication of some sort of off nominal performance?

Robert PearlmanULA CEO Tory Bruno acknowledged on X that an anomaly occurred but it did not prevent Vulcan from reaching its intended orbit. He also noted that the cause was still unknown.
Bullseye chart coming. I imagine some of you are especially curious: orbital insertion was perfect.

All missions have propellant reserves. We add to that additional propellant margins based on the mass and the configuration of the rocket. Because this was compensated for within reserves, this anomaly was "invisible" to the rocket.

An update from Bruno on X:
Nozzle anomaly. Case and grain fine. Reduced, asymmetric thrust. Compensated for by booster.
BlackarrowOn reflection, this launch provided a far better test of the Vulcan Centaur's capabilities than a completely nominal launch. It reminds me a little of Apollo 6, which made it into orbit in the most trying circumstances.

On yesterday's launch, the vehicle itself seems to have performed perfectly and was able to demonstrate its ability to cope with an alarming failure of one SRB. (Photos I have seen show what appears to be part of the SRB nozzle falling away. I somehow doubt if ULA planned for that!)

Robert PearlmanYes, this should give ULA's national security customers even more confidence to certify Vulcan for use.

The nozzle fell away (as now confirmed by Bruno) but the casing remained intact, so the SRB did not fail. There was no burn through and, according to Bruno, the SRB was never close to blowing up.

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