Author Topic: LIVE: Ariane 5 Flight VA239 - Intelsat 37e & BSAT-4a - September 29, 2017  (Read 56034 times)

Offline Mapperuo

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- Aaron

Offline Steven Pietrobon

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Had an aborted launch. Satellites are fine. Apologising for the abort. Will return to flight as soon as possible.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Steven Pietrobon

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Webcast ending.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Space Ghost 1962

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Engine start did not look typical to me. Subjectively, seemed subdued and not stable.

Offline northenarc

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Wow, first ever abort for Ariane isn't it?

No. To my knowledge, there's been two others: one in December 2002, which included the first failed Ariane 5ECA; and one in March 2011, which included a previous Intelsat satellite.
Thanks, that was probably just before I started watching them on a regular basis when the shuttle program ended, looks kind of similar to a shuttle abort at that.

Offline Rik ISS-fan

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I watched from ~T-4:00. My impression is the following:
Umbilical retraction was late @ T-0:05 instead of T-0:07.
As consequence, the Vulcain 2 engine started late and wasn't running stable at the check-point before the solid are ignited. (@T+0:07 if I'm not mistaken.)

They have to roll the launch table back to BAF to reconnect the umbilical arms and connectors.
And to replace igniters on the Vulcain2 engine.
« Last Edit: 09/05/2017 10:08 pm by Rik ISS-fan »

Offline russianhalo117

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From Memory: minimum 5 day recycle is required for reconnecting the separated umbilicals alone.
Day 1 vehicle safing, De-arming/servicing prior to rollback.
Day 2 Table disconnect from pad, Rollback, connect table in BAF
Day 3 Umbilicals reconnect
Day 4 Table disconnect from BAF, Rollout, connect table in Pad
Day 5 Launch day
« Last Edit: 09/05/2017 10:10 pm by russianhalo117 »

Online ZachS09

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From Memory: minimum 5 day recycle is required for reconnecting the separated umbilicals alone.
Day 1 vehicle safing, De-arming/servicing prior to rollback.
Day 2 Table disconnect from pad, Rollback, connect table in BAF
Day 3 Umbilicals reconnect
Day 4 Table disconnect from BF, Rollout, connect table in Pad
Day 5 Launch day

If that's the case, then this recycle sequence places the second try on September 9.
« Last Edit: 09/05/2017 10:09 pm by ZachS09 »
Liftoff for St. Jude's! Go Dragon, Go Falcon, Godspeed Inspiration4!

Offline russianhalo117

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Engine start did not look typical to me. Subjectively, seemed subdued and not stable.
Prestart seemed slow and did not reach flight thrust in time of check point. the mixture ration kept the flame orange instead of the normal blue with Mach diamonds.
« Last Edit: 09/05/2017 10:34 pm by russianhalo117 »

Online DT1

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I watched from ~T-4:00. My impression is the following:
Umbilical retraction was late @ T-0:05 instead of T-0:07.
As consequence, the Vulcain 2 engine started late and wasn't running stable at the check-point before the solid are ignited. (@T+0:07 if I'm not mistaken.)

They have to roll the launch table back to BAF to reconnect the umbilical arms and connectors.
And to replace igniters on the Vulcain2 engine.

From my point of view, Vulcain 2 was up and running at H0+5,5 s - as it should.
The nominal ignition sequence only starts at H0+1 s (in contrast to Vulcain 1 at H0) and chamber ignition itself only happens at around H0+2 s.
« Last Edit: 09/05/2017 10:14 pm by DT1 »
---------------------------
Ralf
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Online Chris Bergin

Last time this happened - thanks to Matt Hughes‏ @hughesm02

« Last Edit: 09/05/2017 10:23 pm by Chris Bergin »
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Offline Rik ISS-fan

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I watched the start sequence of VA238.
Umbilical disconnect also @T-0:05
From the two video's I got the impression that vulcain2 of VA239 started much harder than VA238.
Ignition of vulcain is always a bit violent, but normaly after one flash you can see mach diamond's at roughly T+0:06. With this launch the flame stayed bright, this indicates that vulcain didn't run stable (jet).

Online Chris Bergin

Anyway, let's see what they come out with on the reasons.

Thanks to all, especially Steven, for the coverage!
« Last Edit: 09/05/2017 10:36 pm by Chris Bergin »
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Offline AncientU

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I watched from ~T-4:00. My impression is the following:
Umbilical retraction was late @ T-0:05 instead of T-0:07.
As consequence, the Vulcain 2 engine started late and wasn't running stable at the check-point before the solid are ignited. (@T+0:07 if I'm not mistaken.)

They have to roll the launch table back to BAF to reconnect the umbilical arms and connectors.
And to replace igniters on the Vulcain2 engine.

From my point of view, Vulcain 2 was up and running at H0+5,5 s - as it should.
The nominal ignition sequence only starts at H0+1 s (in contrast to Vulcain 1 at H0) and chamber ignition itself only happens at around H0+2 s.

Where do the solids ignite?
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Online ZachS09

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The SRBs ignite at H0+7.3 seconds (or T0, as I see it).

The SRBs, however, never ignited because during the brief health check of the Vulcain 2 engine, the startup problem was detected and the engine shut down.
« Last Edit: 09/05/2017 11:45 pm by ZachS09 »
Liftoff for St. Jude's! Go Dragon, Go Falcon, Godspeed Inspiration4!

Offline Rocket Science

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Could be a turbopump, but without the data it's just conjecture on my part...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Lars-J

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From Memory: minimum 5 day recycle is required for reconnecting the separated umbilicals alone.
Day 1 vehicle safing, De-arming/servicing prior to rollback.
Day 2 Table disconnect from pad, Rollback, connect table in BAF
Day 3 Umbilicals reconnect
Day 4 Table disconnect from BAF, Rollout, connect table in Pad
Day 5 Launch day

I've never understood why they disconnect the umbilicals before launch commit. It has always seemed very optimistic.

Offline russianhalo117

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From Memory: minimum 5 day recycle is required for reconnecting the separated umbilicals alone.
Day 1 vehicle safing, De-arming/servicing prior to rollback.
Day 2 Table disconnect from pad, Rollback, connect table in BAF
Day 3 Umbilicals reconnect
Day 4 Table disconnect from BAF, Rollout, connect table in Pad
Day 5 Launch day

I've never understood why they disconnect the umbilicals before launch commit. It has always seemed very optimistic.
Same. They are like launchers in Russia and China.

Offline woods170

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From Memory: minimum 5 day recycle is required for reconnecting the separated umbilicals alone.
Day 1 vehicle safing, De-arming/servicing prior to rollback.
Day 2 Table disconnect from pad, Rollback, connect table in BAF
Day 3 Umbilicals reconnect
Day 4 Table disconnect from BAF, Rollout, connect table in Pad
Day 5 Launch day

I've never understood why they disconnect the umbilicals before launch commit. It has always seemed very optimistic.
The umbilicals that are retracted 5 seconds before Vulcain ignition are the LOX and LH2 propellant umbilicals for the upper stage (ESC-A). These don't need to be T+7 (= launch commit) umbilicals given that they only transfer propellant into the ESC-A stage. It is OK to stop topping-off the ESC-A propellant tanks several seconds before ignition of the main engine.
Purging the ESC-A propellant tanks after a pad abort is done via several T+7 "pull-out" umbilicals that carry-away gaseous oxygen and gaseous hydrogen.
« Last Edit: 09/06/2017 06:55 am by woods170 »

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