Author Topic: SpaceX: Merlin 1D thread  (Read 204438 times)

Offline MP99

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Re: SpaceX: Merlin 1D Updates thread
« Reply #450 on: 10/03/2012 07:11 AM »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

If you look in the background you will see a flex below the turbo pump.  Notice the dark streaks in the exhaust.  Compare it to the F-1 and the only conclusion is the turbo pump exhaust is pumped into the nozzle.

Isn't the turbo-pump exhaust shown at the left of the pic, rather than being diverted into the nozzle? This would need to remain separate if v1.1 us is going to use the same roll control as v1.0.

cheers, Martin

Offline modemeagle

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Re: SpaceX: Merlin 1D Updates thread
« Reply #451 on: 10/03/2012 10:15 AM »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

If you look in the background you will see a flex below the turbo pump.  Notice the dark streaks in the exhaust.  Compare it to the F-1 and the only conclusion is the turbo pump exhaust is pumped into the nozzle.

Isn't the turbo-pump exhaust shown at the left of the pic, rather than being diverted into the nozzle? This would need to remain separate if v1.1 us is going to use the same roll control as v1.0.

cheers, Martin
I could be wrong, been know to happen from time to time.
« Last Edit: 10/03/2012 10:26 AM by modemeagle »

Offline MATTBLAK

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Re: SpaceX: Merlin 1D Updates thread
« Reply #452 on: 10/03/2012 10:20 AM »
A rare admission around here!
"Those who can't, Blog".   'Space Cadets' of the World - Let us UNITE!! (crickets chirping)

Online ugordan

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Re: SpaceX: Merlin 1D Updates thread
« Reply #453 on: 10/03/2012 11:14 AM »
Isn't the turbo-pump exhaust shown at the left of the pic, rather than being diverted into the nozzle? This would need to remain separate if v1.1 us is going to use the same roll control as v1.0.

Not necessarily. F9 US has to have cold gas RCS anyway for coast period attitude control, prop settling, etc. You don't need GG exhaust for roll control if you're confident the engine operation itself won't introduce large roll torques (although this assumption can bite you in the rear), bigger than RCS can handle and/or deplete the propellant.

MVac already demonstrated that any roll torques it produced were fairly small and yet the lower regen part of the nozzle was tube-wall design which makes the exhaust swirl a little. M1D flavor should be free from even that effect so it should impart very little roll torque.

Offline Crispy

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Re: SpaceX: Merlin 1D Updates thread
« Reply #454 on: 10/03/2012 11:43 AM »
How does the shape of the regen channels affect the motion of the exhaust? I can understand how acceleration of propellant flow through the channels can create a torque, but how can it influence the exhaust?

Offline corrodedNut

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Re: SpaceX: Merlin 1D Updates thread
« Reply #455 on: 10/03/2012 11:58 AM »
...the lower regen part of the nozzle was tube-wall design...

I'm not sure about that. It seems that both Merlin C and D Vac are solely channel wall. Although the new MvacD extension has yet to be seen, assuming they are the same, there's no active cooling on the nozzle extentions, aside from the new GG exhaust injector.

edit: wrong picture, fixed.
« Last Edit: 10/03/2012 12:03 PM by corrodedNut »

Offline meekGee

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Re: SpaceX: Merlin 1D Updates thread
« Reply #456 on: 10/03/2012 02:51 PM »
I could be wrong, been know to happen from time to time.

I don't think you're wrong this time. There's what appears (to me) to be insulation on the lower conduit. My guess is that this is done to prevent cooling of the flowing gasses, which would have created unrealistic test conditions.

Online cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #457 on: 10/03/2012 07:21 PM »

If you look in the background you will see a flex below the turbo pump.  Notice the dark streaks in the exhaust.  Compare it to the F-1 and the only conclusion is the turbo pump exhaust is pumped into the nozzle.

I agree with you; for sure the manifold has sensors (thermocouples?) for something flowing inside.
Also it seems tapered from left of the image to the right.

I second also Ugordan's conclusions about roll control, considering that SpaceX has data from three flights to validate their models.

Online ugordan

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Re: SpaceX: Merlin 1D Updates thread
« Reply #458 on: 10/03/2012 07:40 PM »
It seems that both Merlin C and D Vac are solely channel wall.

Hmm, you're probably right.

Offline iamlucky13

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Re: SpaceX: Merlin 1D Updates thread
« Reply #459 on: 10/03/2012 08:57 PM »

If you look in the background you will see a flex below the turbo pump.  Notice the dark streaks in the exhaust.  Compare it to the F-1 and the only conclusion is the turbo pump exhaust is pumped into the nozzle.

I agree with you; for sure the manifold has sensors (thermocouples?) for something flowing inside.
Also it seems tapered from left of the image to the right.

I second also Ugordan's conclusions about roll control, considering that SpaceX has data from three flights to validate their models.

I agree on the roll control...requirements could certainly be within the limits of a reasonable cold gas system.

I can't say the "only conclusion" however is that they're mixing the turbopump exhaust in the nozzle extension. That was the answer that jumped out at me most immediately when seeing the big ring and the darker exhaust but a couple things surprise me about this;

1.) The current nozzle extension is apparently fine just being radiatively cooled niobium.

2.) It's a relatively substantial difference between the vacuum and atmospheric configurations of the -1D.

3.) It doesn't taper around the circumference like the scrollcase manifold on the F-1, which isn't necessarily required, but would help distribute the exhaust evenly.

4.) I haven't previously heard any rumors about switching to cold gas roll control on the upper stage, except in connection with brand new engines like Raptor. On the other hand, I briefly forgot the 2nd stage already has a cold gas system, so it's not like it would be completely new...

Online cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #460 on: 10/03/2012 09:08 PM »
@iamlucky 13
It seems to me that the manifold does taper around the circonference; right side is smaller, and we can't see behind.
About nozzle extension maybe (maybe!) they could change material; titanium is 50% lighter than niobium with not so smaller high temp strenght.

Online simonbp

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Re: SpaceX: Merlin 1D Updates thread
« Reply #461 on: 10/04/2012 12:47 AM »
South Africa after 1977 was fully metric only, so this is the measument system environment in which Elon Musk grew up. He left South Africa in 1988. The default "ton" definition to someone who used only metric and very little English measurments would be the metric ton.

http://ukma.org.uk/south-african-experience

So the interpretation of metric ton for this tweet has a foundation.

Except there isn't such a thing as a "metric ton" of force, just a metric tonne of mass (1000 kg precisely). Force/mass confusion is a common deficiency of American engineers...

He almost certainly got the number from his engineers, most of whom are American, and would have expressed it in US short tons of force (2000 pounds-force), so the thrust is about 160,000 pounds-force or 711 kN.

Ed Kyle's estimate of the mass of v1.1 the upper stage is 78.1 tonnes = 86.1 short tons. So, what Elon's tweet really says is that the upper stage has a thrust/weight just less than one at ignition. That's all it needs to be, and you don't want it too much higher or the burnout acceleration will be too high for the crew.

Offline QuantumG

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Re: SpaceX: Merlin 1D Updates thread
« Reply #462 on: 10/04/2012 01:15 AM »
Except there isn't such a thing as a "metric ton" of force, just a metric tonne of mass (1000 kg precisely). Force/mass confusion is a common deficiency of American engineers...

It's not a confusion, it's shorthand.. and it's not just American engineers.

When someone is wishing for a pony, there's little to be gained by suggesting a unicorn would be ever better.. ya know, unless it's sarcasm.

Online bocephus419

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Re: SpaceX: Merlin 1D Updates thread
« Reply #463 on: 10/04/2012 02:30 AM »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

This is a totally random uneducated guess, but would the ring make sense as a mounting point for a retractable nozzle?

While we're making uneducated guesses, I bet they chose to dump the turbo pump exhaust into the main nozzle in order to make it sleek enough to be retractable.  I don't see an exhaust nozzle in spacex's reusability video nor do I see where they would put one: http://spacex.com/multimedia/videos.php?id=2

Online cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #464 on: 10/04/2012 06:38 PM »
Except there isn't such a thing as a "metric ton" of force, just a metric tonne of mass (1000 kg precisely). Force/mass confusion is a common deficiency of American engineers...

It's not a confusion, it's shorthand.. and it's not just American engineers.


+1

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