SpaceX: Merlin 1D Updates and Discussion Thread 3

[Boost]

Yes indeed, it is visible. What's the purpose of the grids at the exit of the nozzles ?

[jpo234]

One more question that remains unclear to me: in the following video:


The gas generator exhaust is clearly (or darkly ) visible, but I have a hard time observing them in any of the SpaceX flights. Where are these GG nozzles located in the octaweb ?

I think it's visible during landings when only the center engine is active.

[Lars-J]

Yes indeed, it is visible. What's the purpose of the grids at the exit of the nozzles ?

Presumably to prevent debris from entering and blocking the exhaust during re-entry and landing. (not many rockets fly backwards, so it is not necessary for those) But there could be another reason.

[John Alan]

If you watch an F9 launch, and fixate on the area in and around the nozzles...
From about T+ 0:50 to T+1:20 or so... on CRS-12 for example
The open area right under the GG exhausts back to the rocket nozzle faces...
You see random flames that dance and flicker in that area...
Mostly hidden by the nozzles... 
But seen as a dull orange fire ring above the white hot rocket plume...

I have come to think these flames are the carbon rich exhausts from the GG exhausts catching fire and burning.
The radiate heat from the hell storm below the nozzle faces catches the carbon dust smoke afire and away it goes.
Is it hurting anything?... Nah, I don't think so... 

Much later edit... added pic of above

[cambrianera]

Yes indeed, it is visible. What's the purpose of the grids at the exit of the nozzles ?

Metal wire grid can act as flame stopper, preventing ignition of the flow upstream.
This is the case of safety lamps for mines.

[docmordrid]

SpaceX ✔ @SpaceX
The SpaceX team recently completed production on our 400th Merlin 1D engine—the latest iteration of SpaceX’s rocket engine that powers Falcon 9 to space → http://instagram.com/p/Bc8lfJ0l2X3/
9:17 PM - Dec 20, 2017

https://twitter.com/SpaceX/status/943666709189160962

[vaporcobra]

The aforementioned image of Merlin. Bantered with another proud employee crossposting it and he confirmed that it was indeed Block 5.
https://www.instagram.com/p/Bc8pqAng9rH/

[nacnud]

Can anyone talk through the differences with this engine? I guess block 5 would all be about reuse with minimum refurbishment.

From my ill informed perspective the gas generator exhaust looks shorter and is now actively cooled. Anything else obvious?

[woods170]

Can anyone talk through the differences with this engine? I guess block 5 would all be about reuse with minimum refurbishment.

That and it has a completely re-designed turbopump.

[nacnud]

That and it has a completely re-designed turbopump.

I forgot about that, that is fairly substantial! I was thinking more might be spotted from the picture that we don't already know.

[stcks]

The aforementioned image of Merlin. Bantered with another proud employee crossposting it and he confirmed that it was indeed Block 5.
https://www.instagram.com/p/Bc8pqAng9rH/

205k lbs thrust? That's more than expected, right?

[nacnud]

I think 205k lbs for the Merlin Vac was announced in May 2016. 190k lbf for the ground start version

Next question, is the pic above of a Merlin Vac?

[ugordan]

Next question, is the pic above of a Merlin Vac?

It's a booster Merlin. MVac looks substantially different, see https://forum.nasaspaceflight.com/index.php?topic=41014.msg1617897#msg1617897

[MikeAtkinson]

I think 205k lbs for the Merlin Vac was announced in May 2016. 190k lbf for the ground start version

Next question, is the pic above of a Merlin Vac?

https://www.instagram.com/p/Bc8pqAng9rH/

todomevaleThis is one of the Merlin 1D engines I help assemble at work, this one is M1D #400. Each engine produces 205,000 pounds of thrust, 9 engines gets our F9 rocket to 17,600 mph or 4.9 miles per second. Put your seatbelt on.

He clearly talking about the Merlin 1D (not Merlin 1D vac).

Not sure how to resolve the discrepancy, perhaps difference between maximum possible thrust and what it will be used at. 

[ugordan]

Not sure how to resolve the discrepancy, perhaps difference between maximum possible thrust and what it will be used at. 

Or just thrust in vacuum.

[OneSpeed]

205k lbs thrust? That's more than expected, right?

205,000 lbs = 912 kN

For nine SL engines, that is 8,208 kN, just under the 8,227 kN quoted by SpaceX.

[woods170]

Next question, is the pic above of a Merlin Vac?

It's a booster Merlin. MVac looks substantially different, see https://forum.nasaspaceflight.com/index.php?topic=41014.msg1617897#msg1617897

Yeah, it looks different for two reasons:

1. Expansion ratio from the nozzle throat downwards is much greater on MVac.

2. The exhaust from the gas generator is fed into the MVac nozzle extension by a tapered manifold; this relatively cool gas forms a film which protects the nozzle extension from the hot exhaust gas coming out of the main combustion chamber. The linked picture shows an MVac with the manifold but minus the (huge) nozzle extension.

[stcks]

205k lbs thrust? That's more than expected, right?

205,000 lbs = 912 kN

For nine SL engines, that is 8,208 kN, just under the 8,227 kN quoted by SpaceX.

Only if that is vacuum thrust. I was interpreting it as sea level thrust, which would be more than the 190k on their website.

[AncientU]

205k lbs thrust? That's more than expected, right?

205,000 lbs = 912 kN

For nine SL engines, that is 8,208 kN, just under the 8,227 kN quoted by SpaceX.

Only if that is vacuum thrust. I was interpreting it as sea level thrust, which would be more than the 190k on their website.

Weren't these new Merlins tested up to 245klbf?  Could be the 190,000 has been supplanted by a higher rating in the Block 5s... been a while since the 190k has been repeated.

Correction:  The 5.1Mlbf number from EM this week is 27 x 190,000lbf, so that's still the baseline... modulo whatever the meaning of the 92% that the first mission will run.

https://twitter.com/elonmusk/status/943590152181448704

[Ictogan]

205k lbs thrust? That's more than expected, right?

205,000 lbs = 912 kN

For nine SL engines, that is 8,208 kN, just under the 8,227 kN quoted by SpaceX.

Only if that is vacuum thrust. I was interpreting it as sea level thrust, which would be more than the 190k on their website.

If it's vacuum thrust, it matches the thrust listed on SpaceX's website with just a small rounding error(500lbf). Seems much more likely as an explanation to me than a further thrust upgrade.