BeechTalk - BT - Delta IV Heavy; Hot Fire Abort (this morning)

Username Protected · **Posted:** 29 Aug 2020, 09:24

I hope to attend the next launch attempt:

[youtube]https://youtu.be/P3f-rFA5Wp8[/youtube]

Username Protected · **Posted:** 29 Aug 2020, 09:29

Tory said it was a GSE issue.
But ripples back some other launches that were this weekend.

Username Protected · **Posted:** 29 Aug 2020, 09:31

Glad they didn't lose the vehicle. I would not want to be one of the first people out to the pad.. :bugeye:

--paul

Username Protected · **Posted:** 29 Aug 2020, 09:43

I used to work on that vehicle. Specifically on the engine start sequencer (ESS) and the other component that is there to take over for aborts, which is the emergency safing and control system (ESCS).
In working around 25 launches, ESCS was never used in anger. This may be the first. Glad to see it appears to have worked as designed.

Oh, and by the way, there's no human intervention inside of about a minute or two in the launch sequence countdown. Lots of parameters have to hit their windows or the system aborts...right up to the hold-down arm retraction.

Username Protected · **Posted:** 29 Aug 2020, 09:50

Username Protected wrote:

Glad they didn't lose the vehicle ...

... and the payload. NRO payloads are exceptionally precious.

Username Protected · **Posted:** 29 Aug 2020, 10:18

I don't know what the recycle sequence involves for that vehicle, but I assume detanking and drying out the engines somehow. They'll have to replace the hydrogen burn pyros as well.

Username Protected · **Posted:** 29 Aug 2020, 10:29

Why the Delta 4 starts with a fireball and runs ROP:

[youtube]https://youtu.be/i-zmptK7PDE[/youtube]

Username Protected · **Posted:** 29 Aug 2020, 10:30

Username Protected wrote:

I don't know what the recycle sequence involves for that vehicle, but I assume detanking and drying out the engines somehow. They'll have to replace the hydrogen burn pyros as well.

I don't know either...but I can tell you it will be A LOT of work.

to abort at that phase is most likely one of the engines not hitting its performance target. That in itself is going to be a pain to sort out.

Username Protected · **Posted:** 29 Aug 2020, 10:33

I haven't watched your video Doug, so I don't know if they talk about it...but I was involved on the analysis (mostly CFD) to see about reducing the fireball. Just because the govt. customers didn't like the look of it.

We came up with a staggered start on the Heavy. That is, one engine started about 1.5 seconds before the other two, under the theory that it would get the flame trench moving. It worked...sort of.

Username Protected · **Posted:** 29 Aug 2020, 10:35

Username Protected wrote:

I don't know what the recycle sequence involves for that vehicle, but I assume detanking and drying out the engines somehow. They'll have to replace the hydrogen burn pyros as well.

Tory was quoted in one media report saying, “at least a week.”