Author Topic: SpaceX: Merlin 1D Updates and Discussion Thread 2  (Read 289982 times)

Offline alang

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #620 on: 08/15/2016 08:00 AM »
Probably discussed many times but I can't find it: is there any likelihood that sea level Merlin will burn redirected turbo pump exhaust in future?

Offline mfck

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #621 on: 08/15/2016 09:22 AM »
Probably discussed many times but I can't find it: is there any likelihood that sea level Merlin will burn redirected turbo pump exhaust in future?
IANAE, but it does not seem worth the trouble at this point in engine design cycle all for a couple of seconds of ISP on an SL engine. They probably want to be done with R&D on this engine.

Offline cuddihy

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #622 on: 08/15/2016 10:27 AM »
Well it's already ducted into the after part of the nozzle to provide cooling. That probably lets you burn the engine hotter overall, which means better MR, which gives you more Isp. So I think it's already maxed out in that regard.

Offline hkultala

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #623 on: 08/16/2016 05:04 AM »
Well it's already ducted into the after part of the nozzle to provide cooling.

Only in vacuum version of the engine. The 1st stage version has separate nozzle for the turbopump.

Offline Dante80

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #624 on: 08/16/2016 06:15 PM »
Probably discussed many times but I can't find it: is there any likelihood that sea level Merlin will burn redirected turbo pump exhaust in future?

I think I read somewhere that the actual turbopump exhausts pay a role (due to their position and use) on some aspects of the octaweb assembly performance.

Offline russianhalo117

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #625 on: 08/16/2016 09:34 PM »
Probably discussed many times but I can't find it: is there any likelihood that sea level Merlin will burn redirected turbo pump exhaust in future?
That was a planned feature for Merlin-2 LRE before Raptor Development became a thing and Merlin-2 work was shelved indefinitely. Any Merlin-2 improvements they decide to move over to the Merlin-1 family would likely become Merlin-1E although there are no present plans for Merlin-1E LRE development.

Advancements in 3-D Printing and other new/next generation manufacturing technologies will make these LRE advancement options easier to produce and cut dry mass and manufacturing complexity (turbo pump exhaust reuse was one of the manufacturing issues that came up with the ABMA/NASA MSFC development of the Rocketdyne F-1 LRE's and is the main reason why the F-1 LRE Family has never been selected for a project other Apollo Saturn V series).
« Last Edit: 08/17/2016 03:34 AM by russianhalo117 »

Offline kaoru

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #626 on: 08/17/2016 03:05 AM »
Probably discussed many times but I can't find it: is there any likelihood that sea level Merlin will burn redirected turbo pump exhaust in future?

I think I read somewhere that the actual turbopump exhausts pay a role (due to their position and use) on some aspects of the octaweb assembly performance.

The answer is, quoting "Generator gas flows through a heat exchanger which heats up Helium gas for tank pressurization in flight before being dumped overboard through an exhaust.", obviously plays an extremely important role.  That role requires plumbing that has to have high tolerances/pressures (read heavy).  Moving the heat exchanger and adding mass for a diffuser of cooler and slower gas/exhaust is not practical.  The F1 did it only to provide cooling to the nozzle extension so it was worth it in that regard.

Kaoru

Offline deruch

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Re: SpaceX: Merlin 1D Updates and Discussion Thread 2
« Reply #627 on: 08/17/2016 07:23 AM »
It's not like it hasn't already been done -- sort of.

I wish I could recall exactly which mission it was, but I recall quite well an occurrence where the Falcon 9 engines started up, then shut down just prior to the hold-downs coming off.  After a short analysis and quick fix, the count was recycled and the launch proceeded that night (IIRC), late but still within the launch window.

I believe the F9 sequence you are describing was prior to subcooled LOX...

Yes, I'm positive it was.  I'm also pretty sure it was a Falcon 9 v1.1, prior to the current FT version that, we are told, should just be called Falcon 9... :)

Anyone remember which mission it was?  I'm pretty certain it wasn't a CRS flight, they have very short launch windows.  Maybe Cassiopeia?  It was definitely pre-stage-recovery days.

SES-8, though based on a perusal of the "SpaceX launch log" thread, I think your memory may be playing tricks on you a bit.  SES-8 got through start-up, but didn't release.  They then recycled and attempted a second countdown.  But that second countdown was scrubbed due to contamination of the ground side TEA-TEB.  It then launched successfully a few days later.  So, the gist of your point was still valid.  They got through engine start-up, held the launch, and then recycled to try again within the same window.  But it didn't launch on the second attempt either.  That's the only launch that I could find that might fit your memory.  It's also possible that the log didn't catch this somewhat unusual type of attempt.



Somewhat interestingly, SES-9 did pretty much the same thing.  On the launch attempt with the wayward boat.  They recycled after the range fouling and got through start-up but held for low thrust.  They then considered another attempt in that same window, but couldn't because of the subcooled LOX warming too much.  But if they hadn't had to worry about the warmer LOX, I think they would have recycled and tried again.  I remember them taking a fair bit of time after the low thrust hold to finally scrub the attempt.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd


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