Author Topic: LIVE: Ariane 5 Flight VA239 - Intelsat 37e & BSAT-4a - September 29, 2017  (Read 14077 times)

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.

Online 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 »

Offline bolun

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September 5, 2017

Anomaly causes interruption of the countdown for Arianespace Flight VA239

During the final seconds of the launch countdown for Arianespace Flight VA239, the checkout process detected an anomaly on the launcher as the Vulcain cryogenic main stage engine was being ignited. As a result, the final countdown was interrupted.

The Ariane 5 and its Intelsat 37e and BSAT-4a payloads immediately switched to a safe mode. Analysis of data is underway to determine the cause of the anomaly. In parallel, the launcher will be transferred back to the Final Assembly Building at the Spaceport in French Guiana – where it is to be returned to a flight-ready condition.

Arianespace will set a new launch date as soon as possible.

http://www.arianespace.com/mission-update/anomaly-causes-interruption-of-the-countdown-for-arianespace-flight-va239/

Online Ben the Space Brit

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Any word from ESA on how quickly VA239 can be turned around? I imagine that, if nothing else, the Vulcan will need to be thoroughly checked.
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Offline DT1

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From the French Forum:
http://www.forum-conquete-spatiale.fr/t18803p50-ariane-5-eca-va239-intelsat-37e-bsat-4a-05-09-2017

Il s'agirait d'un problème SEL (systèmes électriques et logiciels).

I do not know the source, but if this is correct that does not sound Vulcain 2 related to me: "Electrical and Software Systems"
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Online Ben the Space Brit

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I know but the engine was ignited so they will want to make sure that it hasn't been affected by that.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Offline DT1

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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).

As with gas generator cycle engines like the Vulcain 2, they are ignited in two steps: chamber and gas generator.
The first flash you can see is the chamber ignition. And the mach diamond is nominally coming very late. Yesterday the camera switched away from the engine before the nominal time of formation of the mach diamond.
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Offline DT1

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I know but the engine was ignited so they will want to make sure that it hasn't been affected by that.

Yes, of course.
The engine is also "polluted" by the pyro residuals...
« Last Edit: 09/06/2017 01:30 PM by DT1 »
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Ralf
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Offline TrevorMonty

What happens if one of the SRBs ignites and the other one doesn't.

Offline timverhoeven

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What happens if one of the SRBs ignites and the other one doesn't.

Are the SRB bolted down and can these bolts hold the upward forces from the SRBs? If yes I guess they would the one burn out. If not, then there will be a lot of fireworks  :P
« Last Edit: 09/06/2017 05:55 PM by timverhoeven »

Offline Flying Beaver

What happens if one of the SRBs ignites and the other one doesn't.

Something similar to this wonderful quote from Chris back in 2007 about the shuttle (Nothing beats google for searching NSF 8)).

They did a simulation apparently, and depending on which SRB doesn't light, it'd lift off and cartwheel into the ocean, or into the LCC. If you were at the press site, you'd be toast.

« Last Edit: 09/06/2017 05:50 PM by Flying Beaver »
Saw OG-2 Booster Land in person 21/12/2015.

Offline AS_501

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Imagine the heart attacks if this shutdown had occurred during the JWST launch!  JWST's ride to orbit and final insertion will be especially nerve wracking.

Online Chris Bergin

What happens if one of the SRBs ignites and the other one doesn't.

Something similar to this wonderful quote from Chris back in 2007 about the shuttle (Nothing beats google for searching NSF 8)).

They did a simulation apparently, and depending on which SRB doesn't light, it'd lift off and cartwheel into the ocean, or into the LCC. If you were at the press site, you'd be toast.





I was just about to go looking for that post until I noticed you had already quoted it! ;)

Offline bolun

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Booster electrical issue was the cause:
http://www.arianespace.com/press-release/interruption-of-the-va239-countdown-results-of-preliminary-analysis/

As soon as the analysis of the anomaly has been completed, Arianespace will announce a new launch date. The objective is to launch around the end of September 2017.

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.
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.

I understand that the umbilicals are not required for the last seconds before a launch, but that misses my point. It is still not very smart (as highlighted by this very scrub) to disconnect them before you absolutely have to.

Online LouScheffer

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

I understand that the umbilicals are not required for the last seconds before a launch, but that misses my point. It is still not very smart (as highlighted by this very scrub) to disconnect them before you absolutely have to.
Perhaps they are worried about the opposite - the vehicle takes off and the umbilicals do not detach.   This might be even worse than a pad abort.   So detach, then verify, then launch.  If they are wrong, it's only a few days, not loss of mission.

Online Jdeshetler

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Can they drained the fuels normally without reattaching the umbilicals? Is't the tanks refilled with helium?

Online woods170

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Can they drained the fuels normally without reattaching the umbilicals? Is't the tanks refilled with helium?
The umbilicals that are detached at T-5 seconds are the umbilicals for carrying LOX and LH2 INTO the ESC-A upper stage. So, these are umbilicals for propellant LOADING.
There is second set of "hung" umbilicals, of the "pull-out/pull-off" type for UNLOADING of gaseous Oxygen and Hydrogen. Those umbilicals detach when the launcher rises off the launchpad during launch.
When a pad abort on a Ariane 5 ECA takes place the propellants in the ESC-A are allowed to simply boil-off with the gaseous Oxygen and Hydrogen being carried away via the UNLOADING umbilicals.

From the top of my head: returning the ESC-A to launch-ready condition requires re-attaching the umbilicals for propellant loading as well as check-out of all attached umbilicals. Additionally all tanks and propellant lines are purged again to get rid of possible contaminants. Helium supply (for propellant tank pressurization) is topped-off as well as all electrical circuits re-checked. Reloading of the propellant tanks naturally takes place only after the launcher is returned to the launch site.

Offline bolun

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