Author Topic: F9 Block 5 Updates and Discussion  (Read 323825 times)

Offline Nomadd

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Re: F9 Block 5 Updates and Discussion
« Reply #560 on: 04/03/2018 11:34 pm »
 I'm still trying to grasp taking an engine that's flown close to 500 times without an issue and still looking for ways to increase reliability. The gigantic gulf between airline and space operations is getting smaller.
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Online matthewkantar

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Re: F9 Block 5 Updates and Discussion
« Reply #561 on: 04/03/2018 11:57 pm »
I'm still trying to grasp taking an engine that's flown close to 500 times without an issue and still looking for ways to increase reliability. The gigantic gulf between airline and space operations is getting smaller.

There was the one issue one time, too bad it was before the bad engine could be returned home for analysis. 

Offline JH

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Re: F9 Block 5 Updates and Discussion
« Reply #562 on: 04/04/2018 12:20 am »
That was a Merlin 1C, not a 1D.

Offline Robotbeat

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Re: F9 Block 5 Updates and Discussion
« Reply #563 on: 04/04/2018 12:40 am »
Yup, and SpaceX didn't even make the turbopump for the Merlin 1C.
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Online docmordrid

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Re: F9 Block 5 Updates and Discussion
« Reply #564 on: 04/04/2018 12:57 am »
Yup, and SpaceX didn't even make the turbopump for the Merlin 1C.

Wasn't it Barber-Nichols?
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Offline IanThePineapple

Re: F9 Block 5 Updates and Discussion
« Reply #565 on: 04/04/2018 01:00 am »
Yup, and SpaceX didn't even make the turbopump for the Merlin 1C.

Wasn't it Barber-Nichols?

Yep! They brought it in-house for the 1D IIRC

Offline IanThePineapple

Re: F9 Block 5 Updates and Discussion
« Reply #566 on: 04/04/2018 01:05 am »
Most issues of a launch related to Merlin engines weren't directly caused by the engine itself. Only exception was on Falcon 1 Flight 3, but that was more of a timing issue rather than an engine failure.

Offline niwax

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Re: F9 Block 5 Updates and Discussion
« Reply #567 on: 04/04/2018 07:45 am »
I'm still trying to grasp taking an engine that's flown close to 500 times without an issue and still looking for ways to increase reliability. The gigantic gulf between airline and space operations is getting smaller.

Including all pre-flight tests that's still only one or two days of total runtime.
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Offline Robotbeat

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Re: F9 Block 5 Updates and Discussion
« Reply #568 on: 04/04/2018 11:24 am »
Unlike slow subsonic aircraft, rocket engines donít need to run for hours just to get you somewhere.
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Offline livingjw

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Re: F9 Block 5 Updates and Discussion
« Reply #569 on: 04/04/2018 11:56 am »
Its usually not the time, but the number of starts that kill engines.

John

Offline meekGee

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Re: F9 Block 5 Updates and Discussion
« Reply #570 on: 04/04/2018 02:37 pm »
Its usually not the time, but the number of starts that kill engines.

John
Yup, which is why the number above (>500) is more significant than the accumulated minutes.

... And is still too small, so needs to be coupled with demonstrated low impact of failure, something SpaceX demonstrated once with F9 1.0

-----
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Online ValmirGP

Re: F9 Block 5 Updates and Discussion
« Reply #571 on: 04/04/2018 03:07 pm »
Its usually not the time, but the number of starts that kill engines.

John
Yup, which is why the number above (>500) is more significant than the accumulated minutes.

... And is still too small, so needs to be coupled with demonstrated low impact of failure, something SpaceX demonstrated once with F9 1.0

-----
ABCD: Always Be Counting Down

Not to mention that they are started for testing prior to integration, tested after integration, tested pre-flight and then during flight... that's a lot of starts!
« Last Edit: 04/04/2018 03:08 pm by ValmirGP »

Online acsawdey

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Re: F9 Block 5 Updates and Discussion
« Reply #572 on: 04/04/2018 03:12 pm »
Its usually not the time, but the number of starts that kill engines.

John
Yup, which is why the number above (>500) is more significant than the accumulated minutes.

... And is still too small, so needs to be coupled with demonstrated low impact of failure, something SpaceX demonstrated once with F9 1.0

I have to believe that spacex does extensive qualification of M1D start up -- In all the recent landings we have only seen a couple fail due to an engine not starting, and (I think) those have all been bleeding-edge marginal 3-engine burn cases that may or may not have actually had enough fuel on board. Also we have not recently seen any issues with aborted starts of static fire or for launch.

Offline HMXHMX

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Re: F9 Block 5 Updates and Discussion
« Reply #573 on: 04/04/2018 03:13 pm »
Its usually not the time, but the number of starts that kill engines.

John
Yup, which is why the number above (>500) is more significant than the accumulated minutes.

... And is still too small, so needs to be coupled with demonstrated low impact of failure, something SpaceX demonstrated once with F9 1.0

-----
ABCD: Always Be Counting Down

Not to mention that they are started for testing prior to integration, tested after integration, tested pre-flight and then during flight... that's a lot of starts!

This is why, even for expendable ICBM/IRBM engines in the late 1950s, the USAF specification required 12 starts.

Another critical factor is rate of onset of thermal shock in the turbine.  As I recall, the SSME was about 7,000 degrees F/second, while jet turbine engines are maybe 5x less.  Slower starts waste propellant but have big effects on life.
« Last Edit: 04/04/2018 03:14 pm by HMXHMX »

Offline CuddlyRocket

Re: F9 Block 5 Updates and Discussion
« Reply #574 on: 04/05/2018 12:13 am »
I'm still trying to grasp taking an engine that's flown close to 500 times without an issue and still looking for ways to increase reliability. The gigantic gulf between airline and space operations is getting smaller.

There's no Merlin 1-D engine that's "flown close to 500 times" - there's a big difference between 500 engines that have flown   once and a single engine that's flown 500 times!

Offline rockets4life97

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Re: F9 Block 5 Updates and Discussion
« Reply #575 on: 04/05/2018 12:19 am »
I'm still trying to grasp taking an engine that's flown close to 500 times without an issue and still looking for ways to increase reliability. The gigantic gulf between airline and space operations is getting smaller.

There's no Merlin 1-D engine that's "flown close to 500 times" - there's a big difference between 500 engines that have flown   once and a single engine that's flown 500 times!

I wonder how many times they've test fired the same engine on the test stand.

Offline Asteroza

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Re: F9 Block 5 Updates and Discussion
« Reply #576 on: 04/05/2018 05:41 am »
Unlike slow subsonic aircraft, rocket engines donít need to run for hours just to get you somewhere.


Not yet anyways...

Offline jpo234

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Re: F9 Block 5 Updates and Discussion
« Reply #577 on: 04/05/2018 09:05 am »
Unlike slow subsonic aircraft, rocket engines donít need to run for hours just to get you somewhere.


Not yet anyways...

If we are talking about chemical rocket engines, then the Merlin-1D has an engine flow rate of 273.6 kg/s. An hour of operation of a single Merlin-1D requires about 1000 mT of fuel.
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Offline OnWithTheShow

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Re: F9 Block 5 Updates and Discussion
« Reply #578 on: 04/05/2018 01:57 pm »
I wonder how many times they've test fired the same engine on the test stand.

I dont remember how many post-landing firings there were on JCSAT-14's core but those engines probably have the most firings of anything other than dev units.

Individual Engine Test
McGregor Static Fire
Cape Static Fire
Launch
Entry Burn
Landing Burn
Numerous subsequent firings at McGregor

Online rsdavis9

Re: F9 Block 5 Updates and Discussion
« Reply #579 on: 04/05/2018 02:14 pm »
I wonder how many times they've test fired the same engine on the test stand.

I dont remember how many post-landing firings there were on JCSAT-14's core but those engines probably have the most firings of anything other than dev units.

Individual Engine Test
McGregor Static Fire
Cape Static Fire
Launch
Entry Burn
Landing Burn
Numerous subsequent firings at McGregor

8 was the number I remember
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