Vulcan VC2S V001 - Peregrine Lander - CCSFS SLC-41 - 8 Jan 2024 (07:18 UTC)

[whitelancer64]

(snip)
Tory Bruno has also confirmed that VC0 has to be short fueled to lift off at an acceptable T/W ratio.  This may indicate that the dry mass of the booster is greater than originally planned. 
(snip)

@Jim
IIRC, you once said that rockets, at least certain rockets, could not be partially fueled.
Have special accommodations been made to enable this on Vulcan?

ULA is developing a LEO-optimized variant of the Centaur V, with shorter tanks / less fuel. Presumably that would be used in any VC0 launch.

[deltaV]

ULA is developing a LEO-optimized variant of the Centaur V, with shorter tanks / less fuel. Presumably that would be used in any VC0 launch.

My impression is that there are two different circumstances where Vulcan reduces the amount of propellant in a stage to improve thrust to weight ratio. You appear to be conflating these two circumstances. The first circumstance is for LEO missions a Centaur V with smaller tanks can improve performance by improving thrust to weight ratio during the Centaur burn. The second circumstance is in VC0 missions less first stage propellant is used to improve thrust to weight ratio at liftoff.

[whitelancer64]

ULA is developing a LEO-optimized variant of the Centaur V, with shorter tanks / less fuel. Presumably that would be used in any VC0 launch.

My impression is that there are two different circumstances where Vulcan reduces the amount of propellant in a stage to improve thrust to weight ratio. You appear to be conflating these two circumstances. The first circumstance is for LEO missions a Centaur V with smaller tanks can improve performance by improving thrust to weight ratio during the Centaur burn. The second circumstance is in VC0 missions less first stage propellant is used to improve thrust to weight ratio at liftoff.

Ah, I see.

Source: https://www.reddit.com/r/ula/comments/17wos9u/tory_bruno_ceo_of_ula_vulcan_ama/

[deltaV]

My impression is that there are two different circumstances where Vulcan reduces the amount of propellant in a stage to improve thrust to weight ratio. You appear to be conflating these two circumstances. The first circumstance is for LEO missions a Centaur V with smaller tanks can improve performance by improving thrust to weight ratio during the Centaur burn. The second circumstance is in VC0 missions less first stage propellant is used to improve thrust to weight ratio at liftoff.

On second thought VC0 would tend to have a lower staging velocity which makes upper stage T/W more of an issue so VC0 may benefit from propellant offload from the upper stage for lower energy orbits than VC6 does. So the clean separation in my previous message was probably over simplified.

[seb21051]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

[whitelancer64]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

[seb21051]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Another thing I was not able to discern directly was at what altitude and speed the booster separated from the Centaur (L+05.05). The last reference I heard to speed and altitude was at L+03:98 of 47 miles (75 km) and 5,500 mph (8851 kph). I was curious if anyone had more specific information?

[whitelancer64]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Another thing I was not able to discern directly was at what altitude and speed the booster separated from the Centaur (L+05.05). The last reference I heard to speed and altitude was at L+03:98 of 47 miles (75 km) and 5,500 mph (8851 kph). I was curious if anyone had more specific information?

As of now, I don't think that information is publicly available.

[seb21051]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Another thing I was not able to discern directly was at what altitude and speed the booster separated from the Centaur (L+05.05). The last reference I heard to speed and altitude was at L+03:98 of 47 miles (75 km) and 5,500 mph (8851 kph). I was curious if anyone had more specific information?

As of now, I don't think that information is publicly available.

I'm sure there must be some opinions out there amongst the alumni?

[Newton_V]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Another thing I was not able to discern directly was at what altitude and speed the booster separated from the Centaur (L+05.05). The last reference I heard to speed and altitude was at L+03:98 of 47 miles (75 km) and 5,500 mph (8851 kph). I was curious if anyone had more specific information?

As of now, I don't think that information is publicly available.

I'm sure there must be some opinions out there amongst the alumni?

Your velocity off by about 100%?   (could be I'm confusing units here, but seems way too slow)

[seb21051]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Another thing I was not able to discern directly was at what altitude and speed the booster separated from the Centaur (L+05.05). The last reference I heard to speed and altitude was at L+03:98 of 47 miles (75 km) and 5,500 mph (8851 kph). I was curious if anyone had more specific information?

As of now, I don't think that information is publicly available.

I'm sure there must be some opinions out there amongst the alumni?

Your velocity off by about 100%?   (could be I'm confusing units here, but seems way too slow)

Could be, but feel free to check out the launch video. I thought I noted what the commentator was saying pretty carefully. These are my notes. Times are not exact, but close as I could get them:

L+01:10  Transonic
L+01:50  MAXQ followed by SRB Jettison very soon after - 17 miles (27 km) Alt. reported.
L+03:11  Alt/Vel Report: 33 miles (53 km), 4,000 mph (6,347 km/h)
L+03:98  Alt/Vel Report: 47 miles (75 km), 5,500 mph (8,851 km/h)
L+04:16  Passing through Karmann Line - 60 miles (100 km)
L+04:59  BECO
L+05:05  Booster Separation
L+05:15  MES-1
L+05:23  PLF Jettison (Fairings)

[FutureSpaceTourist]

twitter.com/fasthawkpottery/status/1754539173078536345

@torybruno If I may ask.  Did actual ascent data from Vulcan get sent to the ATF in Ohio for Dream Chaser's shakedown test?

https://twitter.com/torybruno/status/1754619335295840611

No updates to predictions were necessary

[catdlr]

This post has a video.

https://twitter.com/ulalaunch/status/1755595039323861299

It's been 1️⃣ month since the inaugural flight of #VulcanRocket! We sat down with ULA's Vulcan #Cert1 Launch Conductor Dillon Rice. Watch as Dillon takes us behind the scenes!

Vulcan: Behind the Scenes with ULA's Launch Conductor Dillon Rice
Watch on YouTube:

[Hog]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Bold emphasis mine.

...due to SRB disposal considerations?

[Vettedrmr]

I was reviewing the launch and noticed that the commentator mentioned the SRB separation and MAXQ at about the same time (L+01:50), at an altitude of 17 miles (27km). So the question I have is whether the vehicle reached MAXQ before or after the separation?

Before. Max Q was a few seconds before SRB burnout. The SRBs remained attached for about 25 seconds after burnout.

Bold emphasis mine.

...due to SRB disposal considerations?

Back on page 70:

Both SRB separation and fairing sep seemed to be later than usual:
- SRB sep ten seconds after burnout. Shuttle separated them as soon as thrust had dropped below a T:W of 1:1 for the booster.
- fairing sep 5 minutes into the flight, compared to F9 which separates its fairing after 3 minutes.

Not really.  Common practice

A.  They may have had to wait until they were over a drop zone
B.  They want the SRMs to be completely non propulsive before separation

Fairing separation is after 2nd stage ignition and upon reaching steady state.  See Delta II, Delta IV, Atlas V 4XX,

[PahTo]

Per SRM sep, once we get closer to launch of Dream Chaser on VC4L, I'll post a couple of questions/notes in that thread, but for consideration given ongoing comments in this thread:  it'll be interesting to see how long the SRMs are carried on a launch that is inclined [Edit:  51.6] degrees given the different ground asset/drop zone considerations.  Corollary is that I assume launch on an ascending node trajectory.

[spacexplorer]

Post-launch final trajectory (attached both pre- and post-).

https://win98.altervista.org/space/exploration/3d/space-explorer-tracker.html?orbiter=pere&body=@399&start=2024-01-08%2008:08&stop=2024-01-18%2021:01&step=200&3dzoom=1

[edkyle99]

I just now got around to reading Aviation Week's write up on Cert-1 by Irene Klotz.  It noted that the Centaur 5 second stage was not fully filled with propellants on this flight.  It also said that  the BE-4 burn was a "split second" shorter than planned, which caused Centaur's first burn to run 10.7 seconds long.  The second Centaur burn, according to the story, was 5.9 seconds shorter than expected, but a precisely on-target orbit was achieved.  ULA described the differences as "normal variations", especially for an inaugural flight.

Irene was not allowed to release the exact Centaur propellant loading for "proprietary reasons".

The story stated that ULA plans to fly 9 of its remaining 17 Atlas V rockets this year, along with up to 5 more Vulcans.  It expects 28 launches next year.

 - Ed Kyle

[Robert_the_Doll]

I just now got around to reading Aviation Week's write up on Cert-1 by Irene Klotz.  It noted that the Centaur 5 second stage was not fully filled with propellants on this flight.  It also said that  the BE-4 burn was a "split second" shorter than planned, which caused Centaur's first burn to run 10.7 seconds long.  The second Centaur burn, according to the story, was 5.9 seconds shorter than expected, but a precisely on-target orbit was achieved.  ULA described the differences as "normal variations", especially for an inaugural flight.

Irene was not allowed to release the exact Centaur propellant loading for "proprietary reasons".

The story stated that ULA plans to fly 9 of its remaining 17 Atlas V rockets this year, along with up to 5 more Vulcans.  It expects 28 launches next year.

 - Ed Kyle

There are better details given in Will Robinson-Smith's article for Spaceflight Now:
https://spaceflightnow.com/2024/02/12/cleanest-first-flight-ula-president-reflects-on-inaugural-vulcan-launch-and-future-of-program/

The underburn was not anything due to the BE-4s themselves, but rather the last of the propellant moving through the feedlines was warmer than thermal modeling suggested it should be and so the engines shutdown 1.2 seconds. A possible solution will be to adjust the propellant reserves to account for this.